Long Life Dairy, Food and Beverage Products

Transcription

1 Long Life Dairy, Food and Beverage Products White Paper

2 Table of Contents Executive Summary....3 Introduction to SPX FLOW...3 Vision and commitment...3 Customer focus....3 Introduction to long life dairy, food and beverage products Microbiology...5 Bacteria...5 Spores...6 Enzymes...6 Moulds...7 Yeast...7 Bacteriophages...7 Toxicity...7 Process classification....7 Pasteurisation...7 Extended shelf life...8 UHT treatment...8 Sterilisation...9 EU classification...9 Process evaluation The logarithmic reduction of spores and sterilising efficiency...10 Terms and expressions to characterise heat treatment processes...10 Residence time...11 Commercial sterility...12 Chemical and bacteriological changes at high temperatures...12 Raw material quality...12 Shelf life...13 Choosing the right process The heat treatment processes...14 Plate heat exchangers...14 Tubular heat exchangers...15 Corrugated tubular heat exchangers...15 Steam injection nozzles...16 Steam infusion...16 Scraped surface heat exchangers...17 Various aseptic UHT systems Indirect Plate Steriliser...17 Indirect Tubular Steriliser...19 Steam Infusion Steriliser...20 High Heat Infusion Steriliser...21 Instant Infusion Pasteuriser...22 Steam Injection Steriliser...23 Scraped Surface Heat Exchanger Steriliser...24 Pilot UHT Plant...24 Sterile Tank...25 Deaerator...26 Extended shelf life/esl The Pure-Lac TM process...26 Comparison between different systems Process controls Filling and packaging Product development About SPX FLOW...30 Contact us

3 Executive Summary Introduction to SPX FLOW There are a number of important microbiological factors that need to be addressed in the production of long life dairy, food and beverage products. The presence of microorganisms in the milk must be reduced to a safe number in order to ensure sufficient shelf life under appropriate storage conditions. This can be achieved by a variety of thermal processes. The efficiency of these processes is a factor of temperature and holding time and can, if not properly controlled, lead to adverse effects on flavour and appearance. A number of systems of relevance to the dairy, food and beverage industries are discussed and advice is offered on how to achieve the best quality product at a reasonable cost, taking into account safe and trouble-free operation. Efficient aseptic processing is an important factor in development of new products. The SPX FLOW Innovation Centre in Denmark offers Pilot Plant Testing and application solution guidance services to help customers maximise the performance of their plant. Pilot Testing can also be conducted on customers own premises based on rental equipment and, if required, with support from SPX FLOW experts. VISION AND COMMITMENT SPX FLOW designs, manufactures and markets process engineering and automation solutions to the dairy, food, beverage, marine, pharmaceutical and personal care industries through its global operations. We are committed to helping our customers all over the world to improve the performance and profitability of their manufacturing plant and processes. We achieve this by offering a wide range of products and solutions from engineered components to design of complete process plants supported by world-leading applications and development expertise. We continue to help our customers optimise the performance and profitability of their plant throughout its service life with support services tailored to their individual needs through a coordinated customer service and spare parts network. CUSTOMER FOCUS Founded in 1910, APV, an SPX FLOW Brand, has pioneered groundbreaking technologies over more than a century, setting the standards of the modern processing industry. Continuous research and development based on customer needs and an ability to visualise future process requirements drives continued mutual growth. SPX FLOW Innovation Centre, Silkeborg, Denmark 3

4 Introduction to long life dairy, food and beverage products As one of the most complete food products of all, dairy products are very important in human nutrition. However, dairy products are also highly perishable and would easily lose their nutritional value, flavour and appearance if protective measures were not taken. Consequently, the dairy industry is one of the most advanced industries in the food processing area, taking care of the milk from when it leaves the udder of the cow through transportation to the dairy, processing, packaging, and distribution until it reaches the consumer. The technology of producing long-life products is today applied throughout the food and beverage industries and in many cases the processing plants are designed for multipurpose operation. When aseptic technology was introduced more than 50 years ago, it revolutionised the food industry by making it possible to distribute high quality food products over long distances in a cost-effective way. The heart of aseptic technology for production of long-life dairy products is aseptic processing, and since its introduction this concept has been developed and refined to a point where any need in respect of capacity, product viscosity, particulate content, acidity or sensitivity to heat treatment can be met while securing high quality, long-life products. SPX FLOW was one of the pioneers in aseptic processing and over the years we have developed a wide range of processing concepts to satisfy all the needs of the industry. In this publication, we will first discuss some of the micro-biological factors, which must be considered in all aseptic processing, together with the heating processes most commonly used for reducing micro-organisms in dairy products: pasteurisation, sterilisation and ultra high temperature (UHT) treatment. So-called commercial sterility is the aim of all UHT processes, and the extent to which this is achieved in a particular process can be measured, notably by reference to the bacteriological effect (B*) and the chemical effect (C*) of such processes. These factors are explained in the section Process Evaluation. The main part of the publication is devoted to an analysis of the processing systems of most interest to the dairy, food and beverage industry: Indirect Plate Steriliser, Indirect Tubular Steriliser, Steam Infusion Steriliser, High Heat Infusion Steriliser, Instant Infusion Pasteuriser, Steam Injection Steriliser and Indirect Scraped Surface Heat Exchanger (SSHE) Steriliser. In each case we describe the system, discuss its advantages and limitations, and list a number of products for which the system in question is particularly suitable (See Table 1 on page 5 and table 4 on page 28). The Pilot UHT Plant is able to combine most of the aseptic processes in one unit, which provides an efficient tool for pilot trials and product development. In aseptic processing, special consideration must be given to some of the auxiliary equipment required. Aseptic tanks are not a necessary requirement but often serve as a useful buffer for sterilised products. The area of extended shelf life products is becoming increasingly important, and the development of the Pure-Lac TM concept is offering the industry and the consumers new solutions and exciting opportunities. With the large number of options available it becomes important to be able to choose the solution, which provides the best quality product at a reasonable cost, giving safe and trouble-free operation. A separate section has been made to cover this subject. The process control system is not only necessary, it must incorporate up-to-date technology not least on the software side. Special attention must be given to the subsequent filling and packaging of aseptically processed products. Finally, we address the area of product development. SPX FLOWs world wide capabilities in respect of product testing makes it possible to work closely with customers in their efforts to upgrade production and launch new products. This publication is purely dealing with the indirect and direct heat transfer processes. SPX FLOW is also manufacturing various types of electrical or electroheat thermal processing equipment. This is dealt with in a separate publication. 4

5 Microbiology The key to production of long-life products with aseptic technology is a detailed understanding of the microbiology of food. Using the example of the dairy industry, the milk in the udder of a healthy cow is free from bacteria, but as soon as the milk comes into contact with the air it becomes contaminated with micro-organisms. If the temperature is favourable, the micro-organisms multiply and very soon the milk will turn sour (or putrefy), developing an unpleasant flavour. To prevent this from happening, the raw milk is sub jected to heat treatment. The term aseptic is usually defined as free from or keeping away disease producing or putrefying microorganisms. In the food industry the terms aseptic, sterile and commercially sterile are often used interchangeably. This is not strictly correct. Sterilisation means 100% destruction of all living organisms, including their spores, and this is very difficult to achieve. Commercial sterility means that the product is free from microorganisms, which grow and consequently contribute to the deterioration of the product. Microorganisms are extremely small and can only be seen under a microscope. However, hundreds or thousands of individual cells or groups of cells can form colonies, which are visible to the naked eye, and some colonies have colours, shapes, textures or odours, which make the organism identifiable. BACTERIA The term bacteria strictly means rod-shaped microorganisms only, but is also used in a loose sense to include all micro-organisms except yeast and moulds. The individual bacterium varies in size from 0.5 to 3 micron. The groups of bacteria, which are most important in the dairy industry are the lactic acid, coliform, butyric acid, and putrefaction bacteria. The bacterial count in milk coming from the farm varies from a few thousands bacteria/ml for high quality milk to several millions if the standard of cleaning, disinfection and chilling is poor. For milk to be classified as top quality, the CFU (Colony Forming Units) should be less than 100,000/ml. Bacteria are single-celled organisms, which normally multiply by binary fission, i.e. splitting in two. The simplest and most common way to classify bacteria is according to their appearance and shape. However, in order to be able to see bacteria, they must first be stained and then studied under a microscope at a magnification of approximately 1,000 X. DAIRY, FOOD & BEVERAGE PRODUCTS PLATE STERILISER Table 1: A variety of dairy, food and beverage products and their suitability for treatment in thermal heat processing systems. TUBULAR STERILISER STEAM INFUSION STERILISER HIGH HEAT INFUSION STERILISER INSTANT INFUSION PASTEURISER MILK X X X X X MILK (FLAVOURED) X X X X X MILK (EVAPORATED) X X X X STEAM INJECTION STERILISER MILK (CONCENTRATED) X X X X X MILK (SHAKE MIX) X X X X X CREAM X X X X X CREAM (WHIPPING) X X X X CREAM (SYNTHETIC) X X X X X SCRAPED SURFACE HEAT EXCHANGER SYSTEMS YOGHURT X X X X YOGHURT (DRINKING) X X YOGHURT (FRUIT) X X QUARK PRODUCTS SOYA MILK X X X X X BABY FOOD X X X X ICE CREAM MIX X X X X X CHEESE DIPS X X X X PROCESSED CHEESE X X X DESERTS / PUDDINGS X X X X WHEY PROTEIN CONC. X X COFFEE WHITENER X X X X X X X EGG-BASED PRODUCTS SAUCE X X X SOUPS X X COFFEE/ICE TEA X X FRUIT JUICE X X X X 5

6 Based on a method of staining, developed by the Danish bacteriologist Gram, bacteria are divided into Gram negative (red) and Gram positive (blue). The three characteristic shapes of bacteria are spherical, rod-shaped and spiral. Diplococci arrange themselves in pairs, staphylococci form clusters, while streptococci form chains. Another way of classification is according to temperature preference: Psychrotrophic bacteria (cold-tolerant) reproduce at temperatures of 7 C or below. Psychrophilic bacteria (cold-loving) have an optimum growth temperature below 20 C. Mesophilic bacteria ( loving the middle range) have optimum growth temperatures between 20 C and 44 C. Thermophilic bacteria (heat-loving) have their optimum growth temperatures between 45 C and 60 C. Thermoduric bacteria (heat-enduring) can tolerate high temperatures above 70 C. They do not grow and reproduce at high temperatures, but can resist them without being killed. Bacteria can only develop within certain temperature limits, which vary from one species to another. Temperatures below the minimum cause growth to stop, but do not kill the bacteria. They are, however, damaged by repeated freezing and thawing. If the temperature is raised above the maximum, the bacteria are soon killed by heat. Most cells die within a few seconds of being exposed to 70 C, but some bacteria can survive heating to 85 C for 15 minutes, even though they do not form spores. A third way of classifying micro-organisms is by their oxygen requirement. The availability of oxygen is vital to the metabolism of all organisms. Some bacteria consume oxygen from the atmosphere; they are called aerobic bacteria. However, to some bacteria free oxygen is a poison; they are called anaerobic bacteria and obtain the oxygen they need from chemical compounds in their food supply. Some bacteria consume free oxygen if it is present, but they can also grow in the absence of oxygen; they are called facultatively anaerobic. The acidity of the nutrient substrate for bacteria is also important. Sensitivity to ph changes varies from one species to another, but most bacteria prefer a growth environment with a ph around 7. Furthermore the salt and/or sugar concentration of a substrate has an important influence on the growth of bacteria. The higher the concentration, the more growth is inhibited. This is caused by the high osmotic pressure, which will draw water out from the cell, thereby dehydrating it. Osmotic pressure is used as a means of food preservation in sweetened condensed milk, salted fish and fruit preserves like jam and marmalade. SPORES The spore is a form of protection against adverse conditions, e.g. heat and cold, lack of moisture, lack of nutrients, or presence of disinfectants. Only a few bacteria are spore forming e.g. Bacillus and Clostridium. The spores germinate back into a vegetative cell and start reproduction when conditions become favourable again. The spores have no metabolism and can survive for years in dry air and are much more resistant to adverse conditions than bacteria. This includes heat treatment and it takes typically 20 minutes at 120 C to kill them with 100 percent certainty. The UHT time/temperature combination reduces the number of bacteria spores by a minimum of log 9, leaving very few bacteria spores in UHT treated products. ENZYMES When the milk leaves the udder it contains enzymes, the socalled original enzymes. Enzymes are also produced by the bacteria in the milk, the so-called bacterial enzymes. Enzymes are not micro-organisms but are formed as a result of the metabolism of microorganisms. The ability of enzymes to trigger chemical reactions can be important when UHT products are produced. 6

7 Some of the bacterial enzymes are able to cause sweet coagulation of milk products, which destroys the product. The majority of these enzymes are produced by Gram negative Pseudomonas bacteria developing mainly in cold raw milk stored for excessive time in milk cooling tanks, road tankers or milk silos. This problem will be aggravated if the milk has been contaminated because of unhygienic conditions or lack of cleaning-in-place (CIP). The vast majority of enzymes will be destroyed by UHT treatment, but a few may still be active in the final product. MOULDS Moulds belong to the fungi group of micro-organisms, which are very widely distributed in nature among plants, animals and human beings. Moulds normally grow anaerobically, and their optimum growth temperature is between 20 and 30 C. Moulds can grow in substrates with ph 2 to 8.5, but many species prefer an acid environment. The most common species in milk do not survive pasteurisation conditions, and the presence of mould in pasteurised products is therefore a sign of reinfection. The penicillium family is one of the most common types of moulds. Their powerful protein splitting properties make them the chief agent in ripening of, for instance, Blue Cheese. YEAST Yeast also belong to the fungi group of micro-organisms. They vary greatly in size. Saccharomyces cerevisiae, used for brewing of beer, has a diameter of 2 to 8 micron, but other species may be as large as 100 micron. Yeast has the ability to grow both in the presence and absence of oxygen. The optimum temperature is between 20 and 30 C. Optimum ph values are 4.5 to 5.0, but yeast will grow in the ph range of 3 to 7.5. From a dairy point of view, yeast are generally undesirable organisms. They ferment milk and cream and cause defects in cheese and butter. In the brewing, baking and distillation industries, on the other hand, they are very valuable organisms. BACTERIOPHAGES Bacteriophages belong to the group of micro-organisms called viruses. Viruses have no metabolism of their own and therefore cannot grow on a nutrient substrate. Viruses infect living cells in plants and animals. Bacteriophages (also known as phages) infect bacteria and are consequently a problem in all dairy processes where bacteria cultures are used. They are very small in size in the order of 0.02 to 0.06 micron and can only be seen in an electron microscope. Bacteriophages grow at temperatures between 10 and 45 C. They are killed by exposure to 63 to 88 C for 30 minutes and tolerate ph values in the range of 3 to 11. TOXICITY Micro-organisms, which are harmful to man or animals are called pathogens. They can cause death or severe illness by the secretion of toxins either directly into contaminated foodstuffs, which are subsequently eaten, or by transfer to an animal host offering ideal conditions for reproduction and further generation of toxins. Some toxins are inactivated by heat treatment at 60 C for one hour. Process classification A number of different expressions are commonly used in the food industry in relation to food preservation. This section will briefly describe the most common terms used. PASTEURISATION Most commercial liquid food products undergo some form of heat treatment, and pasteurisation is the most common. As it is usually bacterial growth that causes food to deteriorate, pasteurisation preserves the freshness of the food product. There are basically two ranges of pasteurisation: Low-temperature pasteurisation. For milk, this is based on heating the product to 72 to 76 C and holding at that temperature for at least 15 to 20 seconds (or equivalent) (Fig. 1). The pasteurisation may vary from country to country according to national legislation. A common requirement in all countries, however, is that the heat treatment must guarantee the destruction of unwanted micro-organisms and all pathogenic bacteria. 7

8 Temperature 135ºC Pure-Lac TM 85ºC High pasteurisation 72ºC Low pasteurisation life without causing any significant degradation in product quality. A typical temperature/time combination for high-temperature pasteurisation of ESL milk is 125 to 130 C for 2 to 4 seconds. This is also known in the USA as ultra-pasteurisation. SPX FLOW has in recent years developed a patented process where the temperature may be raised to as high as 135 C but only for fractions of a second. This is the basis for the Pure- Lac TM process described in a separate chapter, see table of contents. Time Fig. 1: Low-temperature pasteurisation. The shelf life of pasteurised milk is limited (typically 5 to 7 days) and primarily depends on raw milk quality and storage temperature. During the low-temperature pasteurisation the phosphatase enzyme is destroyed, while the peroxidase enzyme is preserved. This serves as a measure to control the process and distinguish it from high-temperature pasteurisation. High-temperature pasteurisation. This is based on heating the product to 85 C or higher for a few seconds (or equivalent) (Fig. 1 above). The aim is to kill the entire population of bacteria, which are pathogenic for both man and animals and almost all other bacteria as well. By careful monitoring of the process parameters a product with excellent quality can be obtained with minimum heat damage. The shelf life can be extended to several weeks in the cooling chain. The so-called Pure-Lac TM process is based on high-temperature pasteurisation. During the high-temperature pasteurisation both the phosphatase and the peroxidase enzymes are destroyed, and this serves as a measure to control that the process has actually taken place as specified. UHT TREATMENT UHT or Ultra High Temperature treatment is based on the fact that higher temperatures permit a much shorter processing time. By proper time and temperature combination it is possible to achieve commercial sterility with only limited undesirable chemical changes in the product. In terms of nutritive value, flavour and appearance, the quality of the product is more vulnerable to the duration of the treatment than to the temperature applied. ºC Direct Infusion High Heat Infusion Indirect UHT Fig. 2: Temperature profiles for direct infusion, high heat infusion and indirect UHT processes. ºC 150 Time EXTENDED SHELF LIFE The term extended shelf life or ESL is being applied more and more frequently. There is no single general definition of ESL. Basically what it means is the capability to extend the shelf life of a product beyond its traditional well-known and generally accepted shelf Minutes Fig. 3: Temperature profiles for conventional in-container sterilisation. 8

9 In the UHT process, the milk is typically heated to 137 to 150 C and held at that temperature for just a few seconds before it is cooled rapidly down to room temperature (Fig. 2 ). After the product has been cooled it is led to an aseptic filling machine in a closed piping system either directly or by way of an aseptic storage tank. The product obtained in this way has a shelf life at room temperature of several months. The quality of the final product depends on the raw material quality but also to a large extent on the type of heat treatment system applied. This is the case for UHT milk and for a wide range of long life food products like sauces, salad dressings, mayonnaise and soups, as well as for juices and soft drinks. In order to combat the Heat Resistant Spores (HRS) SPX FLOW developed the patented so-called High Heat Infusion system enabling heat treatment temperatures as high as 150ºC without adversely affecting the product quality and still maintaining acceptable running times in the order of 24 hours between cleaning. Products with very high viscosity are more difficult to handle in a UHT system, and SPX FLOW developed a special patented version of the infusion system to handle high viscosity products. This so-called Instant Infusion system is based on very short but controllable and well defined retention time in the infusion chamber. STERILISATION Sterilisation is another type of heating process used for products to increase keeping quality without refrigeration. The heat treatment takes place after the product is packed. The package with its content is heated to approx. 120 C and held at that temperature for 10 to 20 minutes after which it is cooled to room temperature (Fig 3 on page 8). Because of the lengthy heat treatment at a relatively high temperature this process reduces the nutritive value of the product, and it is also liable to change its colour and flavour considerably. EU CLASSIFICATION In the EU Milk Hygiene Directive (92/46) it is suggested that limits and methods to enable a distinction to be made between different types of heat treated milk may be established (Article 20). The proposed parameters, limits and methods may be summarised as shown in Table 2. By this method the hygienic requirements concerning food safety can be satisfied taking into consideration the keeping qualities over varying length of time. This method also makes it possible to establish a new definition of different types of fluid milk products in a way that is independent of the technology of the heat treatment and the filling such as for instance, Pure- Lac TM. It should be noted that the chemical criteria in Table 2 are the recommendation given by IDF and EU to the legislators, but the general perception is that this proposal will be followed. MILK HYGIENE DIRECTIVE 92/46/EU THERMISED PASTEURISED HIGH TEMPERATURE PASTEURISED HTP UHT STERILISED 63-65ºC/15 SEC. 71.7ºC/15 SEC. OR EQUIVALENT >135ºC AND >1 SEC. >135ºC AND > 1 SEC. PHOSPHATASE+ PHOSPHATASE- PEROXIDASE+ PHOSPHATASE- PEROXIDASE- 15 DAYS AT 30ºC OR 7 DAYS AT 55ºC 0 <10 CFU/0.1 ML 15 DAYS AT 30ºC OR 7 DAYS AT 55ºC 0 <10 CFU/0.1 ML ** ** ** ** BETA-LACTOGLOBULIN > 2600 MG/L & BETA-LACTOGLOBULIN > 2000 MG/L & > 50 MG/L & BETA-LACTOGLOBULIN < 50 MG/L OR LACTULOSE NOT DETECTABLE LACTULOSE < 40 MG/KG LACTULOSE < 600 MG/KG LACTULOSE > 600 MG/KG Table 2: Present legislation according to EU directive 92/46 ** IDF & EU suggestions for Dual Chemical Criteria 9

10 Process evaluation All UHT processes are designed to achieve commercial sterility. This calls for application of heat to the product and a chemical sterilant or other treatment that render the equipment, final packaging containers and product free of viable microorganisms able to reproduce in food under normal conditions of storage and distribution. In addition it is necessary to inactivate toxins and enzymes present and to limit chemical and physical changes in the product. In very general terms it is useful to have in mind that an increase in temperature of 10 C increases the sterilising effect 10-fold whereas the chemical effect only increases approximately 3-fold. In this section we will define some of the more commonly used terms and how they can be used for process evaluation. THE LOGARITHMIC REDUCTION OF SPORES AND STERILISING EFFICIENCY When micro-organisms and/or spores are exposed to heat treatment not all of them are killed at once. However, in a given period of time a certain number is killed while the remainder survives. If the surviving micro-organisms are once more exposed to the temperature treatment for the same period of time an equal proportion of them will be killed. On this basis the lethal effect of sterilisation can be expressed mathematically as a logarithmic function: K t = log N/Nt, where N = number of micro-organisms/spores originally present Nt = number of micro-organisms/spores present after a given time of treatment (t) K = constant t = time of treatment A logarithmic function can never reach zero, which means that sterility defined as the absence of living bacterial spores in an unlimited volume of product is impossible to achieve. Therefore the more workable concept of sterilising effect or sterilising efficiency is commonly used. The sterilising effect is expressed as the number of decimal reductions achieved in a process. A sterilising effect of 9 indicates that out of 109 bacterial spores fed into the process only 1 (100) will survive. Spores of Bacillus subtilis or Bacillus stearothermophilus are normally used as test organisms to determine the efficiency of UHT systems because they form fairly heat resistant spores. TERMS AND EXPRESSIONS TO CHARACTERISE HEAT TREATMENT PROCESSES Q 10 value. The sterilising effect of heat sterilisation increases rapidly with the increase in temperature as described above. This also applies to chemical reactions, which take place as a consequence of an increase in temperature. The Q 10 value has been introduced as an expression of this increase in speed of reactions and specifies how many times the speed of a reaction increases when the temperature is raised by 10 C. Q 10 for flavour changes is in the order of 2 to 3, which means that a temperature increase of 10 C doubles or triples the speed of the chemical reactions. A Q 10 value calculated for killing bacterial spores would range from 8 to 30 depending on the sensitivity of a particular strain to the heat treatment. D-Value. This is also called the decimal reduction time and is defined as the time required to reduce the number of microorganisms to one-tenth of the original value corresponding to a reduction of 90%. Z-Value. This is defined as the temperature change which gives a 10-fold change in the D-value. F 0 value. This is defined as the total integrated lethal effect and is expressed in terms of minutes at a selected reference temperature of C. F 0 can be calculated as follows: F 0 = 10 (T ) /z t / 60, where T = processing temperature ( C) z = Z-value ( C) t = processing time (seconds) 10

11 F 0 = 1 after the product has been heated to C for one minute. To obtain commercially sterile milk from good quality raw milk, for example, an F 0 value of minimum 5 to 6 is required. B* and C* Values. In the case of milk treatment some countries are using the following terms: Bacteriological effect: B* (known as B star) Chemical effect C* (known as C star) B* is based on the assumption that commercial sterility is achieved at 135 C for 10.1 seconds with a corresponding Z- value of 10.5 C; this reference process is giving a B* value of 1.0, representing a reduction of thermophilic spore count of 109 per unit (log 9 reduction). below 1 is generally accepted for an average design UHT plant. Improved designs will have C* values significantly lower than 1. The APV Steam Infusion Steriliser has a C* value of RESIDENCE TIME Particular attention must be paid to the residence time in a holding cell or tube and the actual dimensioning will depend on several factors such as turbulent versus laminar flow, foaming, air content and steam bubbles. Since there is a tendency to operate at reduced residence time in order to minimise the chemical degradation (C* value < 1) it becomes increasingly important to know the exact residence time region of sterilisation The B* value for a process is calculated similarly to the F0 value: B* = 10 ( T ) / 10.5 t / 10.1, where T = processing temperature ( C) t = processing time (seconds) HMF 10 µmol/l HMF 100 µmol/l threshold range of discolouration loss of thiamine = 80% 60% The C* value is based on the conditions for a 3 percent destruction of thiamine (vitamin B1); this is equivalent to 135 C for 30.5 seconds with a Z-value of 31.4 C. Consequently the C* value can be calculated as follows: C* = 10 ( T ) /31.4 t / 30.5 Fig. 4 on the right shows that a UHT process is deemed to be satisfactory with regard to keeping quality and organoleptic quality of the product when B* is > 1 and C* is < 1. The B* and C* calculations may be used for designing UHT plants for milk and other heat sensitive products. The B* and C* values also include the bacteriological and chemical effects of the heating up and cooling down times and are therefore important in designing a plant with minimum chemical change and maximum sterilising effect. The more severe the heat treatment is, the higher the C* value will be. For different UHT plants the C* value corresponding to a sterilising effect of B* = 1 will vary greatly. A C* value of Heating time or equivalent heating time in seconds HMF 1 µmol/l loss of thiamine = 3% / C*=1 lactulose 400 mg/l thermal death value = 9 thermophilic spor es / B*=1 UHTregion lactulose 600 mg/l ºC in K T Fig. 4: Bacteriological and chemical changes of heated milk (H.G. Kessler). 40% loss of lysine = 1% 20% 10% 11

12 In SPX FLOW the infusion system has been designed with a special pump mounted directly below the infusion chamber, which ensures a sufficient over-pressure in the holding tube in order to have a single phase flow free from air and steam bubbles. This principle enables SPX FLOW to define and monitor the holding time and temperature precisely and makes it the only direct steam heating system, which allows true validation of flow and temperature at the point of heat transfer. The concept is illustrated in Fig. 5. Even though the time/temperature combination is decisive for the final quality of the product attention also has to be paid to the actual heating profile since various reactions take place at different temperatures. This is illustrated in Fig. 6 in which type A deposit is a voluminous protein-rich deposit, whereas type B deposit is a mineral rich deposit developing primarily at high temperatures. In particular type A deposit, which originates from protein denaturation, must be minimised since it is harmful to the product quality. COMMERCIAL STERILITY Deposit build-up The expression of commercial sterility has been mentioned previously and it has been pointed out that complete sterility in its strictest sense is not possible. In working with UHT products commercial sterility is used as a more practical term, and a commercially sterile product is defined as one which is free from Type A deposit Type B deposit micro-organisms which grow under the prevailing conditions. Inlet to Heater Milk Flow Outlet to Holding Tube Multi-phase system: From other Direct UHT Systems Holding Tube without Centrifugal Pump V1 V2 V3 To Vacuum Chamber Fig. 6: Deposits in UHT plants. Temperature, ºC SIGHT GLASS V > V > V HOLDING TIME NOT DEFINED Holding Tube with Centrifugal Pump Single-phase system: From APV Infusion Chamber Fig. 5: Holding Tube. SIGHT GLASS To Vacuum Chamber TURBULENT FLOW OF LIQUID IS WELL DEFINED CHEMICAL AND BACTERIOLOGICAL CHANGES AT HIGH TEMPERATURES Heating milk and other food products to high temperatures results in a range of complex chemical reactions causing changes in colour (browning), development of off-flavours and formation of sediments. These unwanted reactions are largely avoided through heat treatment at a higher temperature for a very short time, and it is important to seek the optimum time/temperature combination, which provides sufficient kill effect on spores but, at the same time, limits the heat damage, in order to comply with market requirements for the final product. V RAW MATERIAL QUALITY It is important that all raw materials are of very high quality as the quality of the final product will be directly affected. Raw materials must be free from dirt and have a very low bacteria spore count, and any powders must be easy to dissolve. All powder products must be dissolved prior to UHT treatment because bacteria spores can survive in dry powder particles even at UHT temperatures. Undissolved powder particles will also damage homogenising valves causing sterility problems. Heat stability. The question of heat stability is an important parameter in UHT processing. Different products have different heat stabilities and although the UHT plant will be chosen on this basis it is desirable to be able to measure the heat stability of the products to be UHT treated. For most products this is possible by applying the alcohol test. 12

13 Choosing the right process When samples of milk are mixed with equal volumes of an ethyl alcohol solution the proteins become unstable and the milk flocculates. The higher the concentration of ethyl alcohol is without flocculation the better the heat stability of the milk. Production and shelf life problems are usually avoided provided the milk remains stable at an alcohol concentration of 75%. High heat stability is important because of the need to produce stable homogeneous products, but also to prevent operational problems like fouling in the UHT plant. This will decrease running hours between CIP cleanings and thereby increase product waste, water, chemical and energy consumption. Generally it will also disrupt smooth operation and increase the risk of insterility. In order to be able to produce a product with specific product qualities in the most cost-effective way it is essential to make the correct choice with respect to processing system and technology. In many cases the choice is straightforward, but in other cases there may be more options to choose between. Some of the more important questions to ask when choosing a system are: What is the specification of the product to be processed? Which are the quality requirements to the final product? Viscosity specifications of products and raw materials? Specification of particulate and fibre content/size and shape and variation in content? Acidity of product/high or low acid? Sensitivity to high temperatures/heat stability? Requirement for flexibility/multi-purpose systems? Requirement for variable capacity? PRODUCT SHELF LIFE STORAGE PASTEURISED MILK 5 TO 10 DAYS REFRIGERATED ESL/PURE-LAC TM 20 TO 45 DAYS REFRIGERATED UHT MILK 3 TO 6 MONTHS AMBIENT TEMP. SHELF LIFE The shelf life of a product is generally defined as the time for which the product can be stored without the quality falling below a certain minimum acceptable level. This is not a very sharp and exact definition and it depends to a large extent on the perception of minimum acceptable quality. Having defined this it will be raw material quality, processing and packaging conditions and conditions during distribution and storage, which will determine the shelf life of the product. Milk is a good example of how wide a span the concept of shelf life covers: The usual organoleptic factors limiting shelf life are deteriorated taste, smell and colour, while the physical and chemical limiting factors are incipient gelling, increase in viscosity, sedimentation and cream lining. Requirement for direct or indirect systems? Skills of technical personnel/operators? Fig. 7 on page 14 illustrates three of the selection criteria viscosity, capacity and content of particulates for the most common processing systems. The systems are often flexibly designed to allow for processing a range of products in the same plant. It is quite common to process both low-acid (ph>4.5) and highacid (ph<4.5) products in the same UHT plant. However, only low-acid products require UHT treatment to make them commercially sterile. Spores cannot develop in high-acid products such as juice, and the heat treatment is therefore only intended to kill yeast and moulds. Consequently high temperature pasteurisation at C for 15 to 30 seconds is sufficient to make most high-acid products commercially sterile. In some cases where new products have to be processed it may be necessary to carry out trials in small scale to observe the performance of specific products in different types of systems. SPX FLOW has designed a pilot unit for this purpose. 13

14 Viscosity cp l/h Capacity l/h 50,000 cp 500 cp 200 cp 100 cp 50 cp Plate Steriliser Steam Injection Steriliser Steam Infusion Steriliser Tubular Steriliser SSHE Steriliser Increasing particle size Fig. 7: Aseptic processing systems. The trend for processors to focus increasingly on flexibility to process a range of products and the importance of being able to produce high quality products has driven the choice of systems towards indirect tubular systems and direct steam infusion systems. The following sections will deal with the various heating principles and UHT systems followed by a more detailed comparison of the individual systems. THE HEAT TREATMENT PROCESSES SPX FLOW invented the plate heat exchanger in 1923 and has ever since pioneered new heat treatment principles. Scraped surface heat exchangers were developed in the USA while the direct steam infusion system was developed in Denmark. The tubular systems were developed partly in Denmark and partly in Germany and later supplemented by the corrugated tubular heat exchangers in Spain. In addition SPX FLOW is known for electroheat thermal processing equipment, which is dealt with in a separate publication. PLATE HEAT EXCHANGERS The plate heat exchanger is the most cost-effective and versatile method for indirect heating or cooling of liquid food pro ducts. Today SPX FLOW s comprehensive Paraflow range of plates is the basis for a wide range of plate heat exchanger applications in many industries, and in the food and dairy industry the plate heat exchanger is one of the most indispensable pieces of equipment. As illustrated in Fig. 8.1 on page 15 the plate heat exchanger incorporates a number of parallel, closely spaced stainless steel, gasketed and corrugated plates, which are compressed and locked together in a rugged frame. As product is pumped through the plate heat exchanger, the flow is distributed through narrow, corrugated flow passages, which produce a high level of turbulence resulting in high rates of heating or cooling with low hold-up volume. Product contact time is thereby reduced to a matter of seconds minimising thermal damage. A very important advantage of the plate heat exchanger is its extremely high regenerative capability, reducing energy require- 14

15 ments for heating or cooling by more than 90%. Plate heat exchangers provide a maximum amount of heat exchange surface in a minimum amount of floor space. of adjusting the annular space adds one further parameter for optimising the design. TUBULAR HEAT EXCHANGERS SPX FLOW has developed a range of sanitary tubular heat exchangers for the food industry, and an increasing number of customers choose this system. Various tubular systems are available, but the most commonly used system is the multi-tubein-tube (MTNT) system as illustrated in Fig The heat transfer modules are multiple small diameter sanitary tubes aligned within a large diameter shell. Product in Product out Media out Media in Fig. 8.1: APV Plate Heat Exchanger. The diameter of the inner tubes may vary, but is usually in the range of 10 to 12 mm for low viscous products like milk and juice. Media out The SPX FLOW tubular system is designed with a loose jacket around the tube bundles giving a floating head design. Product in Product out This allows thermal expansion without any risk of tube cracking, prevents stress corrosion and allows easy inspection of all heat exchange surfaces. Media in Fig. 8.2: APV Tubular Heat Exchanger. In some countries, e.g. Germany, the tubular system has become very popular because of its rugged construction and easy operation and maintenance. CORRUGATED TUBULAR HEAT EXCHANGERS SPX FLOW has extended its range of heat exchangers with corrugated tubular heat exchangers. By corrugating the tube wall it is possible to improve the heat transfer coefficient and consequently reduce the requirement for heating surface area. The corrugation causes increased turbulence and breaks the laminar flow in high viscosity products. Double-tube, triple-tube, quadruple-tube and multi-tube are the basis for the range as illustrated in Fig , 8.3.2, and The design of the double-, triple- and quadruple-tube makes it possible to arrange direct regeneration because both sides of the tube wall are a sanitary design. Through a variety in corrugation depth, pitch and angle it is possible to optimise heat transfer and pressure drop depending on shear characteristics of the product. Furthermore, the possibility Fig : APV Double Tube. Fig : APV Triple Tube. Fig : APV Quadruple Tube. Fig : APV Multi-Tube-in-Tube. 15

16 STEAM INJECTION NOZZLES SPX FLOW was one of the pioneers in applying steam in direct contact with a product to heat it to aseptic temperatures. The first generation systems were based on the steam injection principle and were launched under the Uperiser brand name. Product vessel. This creates a condensate film on the inner cone wall, which effectively prevents any burn-on of product. During the heating air, unwanted gases and odours are stripped off through the CIP inlet at the top of the cone. The product leaves the infusion chamber through the bottom of the cone through a pump and an expansion valve before it passes through the holding tube into the expansion vessel where the product is cooled down in a similar way as described for the injection heating system. Steam Fig. 8.4: APV Steam Injection Nozzle. The system operates by direct injection of steam through a specially designed nozzle as illustrated in Fig The injection of steam raises the product temperature instantly. In order to prevent the product from boiling it is necessary to pressurise the product during the steam injection to a pressure of 3 to 4 bar depending on the sterilisation temperature. As previously mentioned (Fig. 5 on page 12) this system ensures a single phase flow and a very accurate flow profile. The pump and the valve in the holding tube also serve as level control, which means that there is no product level prior to the pump and consequently no influence on the holding time due to varying liquid level at the bottom of the cone, since it will always be empty. Air out CIP in Steam in Product in Flash cooling takes place in a vacuum expansion vessel where the vacuum is maintained by means of a vacuum pump. The vacuum is controlled in order to ensure that the same amount of water is flashed off as was injected into the product as steam thereby preventing dilution/concentration of the product. STEAM INFUSION In the 1960s APV, An SPXFLOW Brand, launched the first steam infusion system under the Palarisator brand name. Since then significant developments and progress have taken place, which have led to one of the most sophisticated systems in the world. Cooling water in/out After pre-heating the product is pumped into the infuser, which is a pressure vessel fitted with cones at both top and bottom as illustrated in Fig 8.5. At the top cone the product is distributed through a number of nozzles (patented) and passes down through a steam atmosphere in a number of jets without hitting the walls of the vessel until it reaches the bottom cone. This is equipped with a cooling jacket keeping the temperature of the inner cone wall below the product temperature inside the Holding tube Fig. 8.5: APV Steam Infusion Chamber. The heating in the infuser is extremely rapid, and the final sterilisation temperature is reached in less than 0.2 seconds, which corresponds to a heating rate of 500 to 600ºC/second. The system is very flexible and can be used for a wide range of products covering a broad viscosity range. It provides an excellent product quality due to the gentle and rapid heating and subsequent cooling. 16

17 SCRAPED SURFACE HEAT EXCHANGERS SPX FLOW s product range includes a number of scraped surface heat exchangers specially designed to heat or cool viscous or sticky products or products containing particulates. The scraped surface heat exchanger consists of a smooth cylinder through which the product is pumped, counter current to the service medium in the surrounding jacket. The maximum operating pressure for the VT range is 6 bar while the HD range is able to operate at 12 bar maximum pressure. In terms of viscosity the VT model is able to process products with viscosity up to 100,000 cp. The HD range is a Heavy Duty model able to handle viscosity as high as 500,000 cp. Product out Product in Various aseptic UHT systems Media in Media out Fig. 8.6: APV Scraped Surface Heat Exchanger. Rotating scraper blades keep the heating surface free from deposits. The scraper blades are fixed to a rotating shaft called a dasher (Fig. 8.6). Selection of different blades and dasher types depends on the product being processed. The cylinders are usually characterised by their diameter and SPX FLOW supplies units of 4, 6 and 8 inches. Furthermore, both vertical (Fig. 9) and horizontal models (Fig. 10) are available. The most recent addition to the range is a VT+660 model with 0,65 m 2 surface area, which is 41 percent higher than for the 4 range. The best way to characterise UHT systems is to rank them according to the primary type of heating principle used for bringing the product into the aseptic area. The type of system preferred has developed differently in different countries at different times. In the following section we will give a brief description of each type of system available on the market today. For each system the advantages and limitations will be emphasised and finally the products most commonly processed in the system will be listed. All SPX FLOW UHT systems are pre-assembled and tested in the factory with steam. This minimises installation and start-up costs and ensures a safe and trouble-free plant commissioning. INDIRECT PLATE STERILISER UHT systems based on plate heat exchangers are used where the manufacturer s primary requirement is a dependable system for heating liquid products at minimum operating costs. In Fig a flow diagram illustrates the principle design including some of the processing parameters. 7 PRODUCT 90ºC 138ºC 4 4 FILLING ºC 75ºC STEAM 25ºC <25ºC CHILLED WATER COOLING WATER Fig. 9: APV VT+660 Scraped Surface Heat Exchanger. Fig.10: APV HD Scraped Surface Heat Exchanger. 1. Product to product regenerative 2. Homogeniser 3. Indirect heating 4. Holding tubes 5. Indirect cooling Fig. 11.1: Flowdiagram for Plate Steriliser. 6. Sterile tank 7. Cip unit 8. Sterilising loop 17

18 Energy recovery LOW MEDIUM HIGH Plant volume at 90% regenerative LOW MEDIUM HIGH PLATE PLATE TUBULAR TUBULAR Product shear at equivalent heat transfer LOW MEDIUM HIGH Heat transfer at equivalent surface LOW MEDIUM HIGH PLATE PLATE TUBULAR TUBULAR Fig. 11.2: Comparison of data for Plate and Tubular Steriliser. Careful design of the heating and regenerative systems optimises the performance of the system and minimises product damage. Fig above compares some key data for plate and tubular systems. The SPX FLOW system has a high degree of flexibility and can be supplied with variable capacity and with two-speed or variable speed homogenisers. The system can be built up to a maximum capacity of 25 to 30,000 l/h. Fig shows a typical design for an APV Plate Steriliser. Advantages Excellent for low viscosity products High regenerative effect and low energy consumption High heat transfer area in minimal space Easy inspection Low hold-up volume High degree of flexibility Variable capacity Large capacity plants Relatively low investment Low CIP costs Fig. 11.3: APV Plate Steriliser. Products Milk, flavoured milk Fermented milk products, drinking yogurt Cream, coffee whiteners Soy milk Baby food Juice Coffee, tea Combination plants for milk, juice, coffee, tea, etc. Limitations Limited capability for particulates or fibres Exchange of gaskets required periodically Unsuitable for high pressure drops Some product degradation may occur 18

19 Running time (hours) PRODUCT ºC 140ºC FILLING 9 7 5ºC ºC 25ºC Plate UHT Tubular UHT STEAM 10 COOLING WATER Tolerated pressure drop (bar) Tubular regenerative preheaters 2. Homogeniser 3. Holding tubes 4. Tubular final heater 5. Tubular regenerative cooler 6. Final cooler 7. Sterile tank 8. CIP unit 9. Sterilising loop 10. Water Heater Plate UHT Tubular UHT Fig. 12.1: Flow diagram for Tubular Steriliser. Particle sizes/fibre lengths (mm) Exact times will depend on particular products and microbiological considerations. Advantages Less vulnerable to fouling giving long production runs Plate UHT Tubular UHT Fig. 12.2: Comparison of data for Tubular and Plate Steriliser. High operating pressures are acceptable Processes products with fibres and particulates Processes high viscosity products INDIRECT TUBULAR STERILISER UHT systems based on tubular heat exchangers have become popular in many countries and are typically chosen where large volumes of commodity products has to be processed at the lowest possible costs. In Fig a flow diagram illustrates the principle design including some of the processing parameters. In Fig it is shown how the pressure drop affects the maximum running hours. In a plate based steriliser the increase in pressure drop is limited to 30 to 40 percent. This is not a limiting factor in tubular systems and 16 to 20 hours operating time between CIP is possible. It is also possible to operate with an intermediate cleaning each 20 hours and reduce the full CIP cycles to once a week, which may increase the capacity with as much as 7 to 9 percent. Low shear characteristics for cream Low requirement for gasket material and easy gasket exchange Very robust design Low maintenance costs Can be designed as a multi-purpose plant Easy to operate Limitations Lower regenerative effect than for plate sterilisers Slightly higher investment costs compared with plate sterilisers Higher degree of product degradation Products Milk, flavoured milk Fermented milk products, drinking yogurt Cream, coffee whiteners Whipping cream, ice cream mix Evaporated milk, desserts, puddings Soy milk Coffee, tea Juices, juices with pulp Salad dressings Gravy, sauces, soups Combination plants for milk, juice, coffee, tea, etc. Fig. 12.3: APV Tubular Steriliser. 19

20 STEAM INFUSION STERILISER Baby food, condensed milk UHT systems based on the infusion heating are used where the Processed cheese manufacturer wants to produce a high quality product with as Sauces little heat degradation as possible. Also flexibility in throughput and variety in product range speak for an infusion based system. In Fig a flow diagram illustrates the principle design including some of the processing parameters. The system can basically be supplied from 150 l/h (pilot plant) to PRODUCT 75ºC STEAM 2 COOLING WATER 4 COOLING 9 WATER 7 FILLING 44,000 l/hour with a temperature profile as shown in Fig VACUUM The plate heat exchangers for pre-heating and cooling can be replaced with tubular heat exchangers as an option. The SPX FLOW infusion UHT concept can also be supplied as an add-on solution to all common UHT plants from other manufacturers. 8 COOLING WATER 1 5ºC 1. Plate preheaters 2. Steam infusion chamber 3. Holding tube STEAM 143ºC 75ºC 25ºC <25ºC 4. Flash vessel 5. Aseptic homogeniser 6. Plate coolers 6 6 COOLING WATER 7. Aseptic tank 8. Non aseptic cooler 9. Condenser Fig shows a comparison of various temperature profiles for infusion based processes, which are all characterised by a very rapid and controlled heating and cooling profile and a short and carefully monitored holding time. Fig 13.3 shows an APV Steam Infusion Steriliser. Advantages Gentle and accurate heating in the infusion chamber Accurate holding time Superior product quality Closed loop during pre-sterilising High product flexibility Low fouling rate Long operating time Operator friendly Limitations Relatively higher capital costs compared to indirect systems Relatively higher operating costs due to lower heat regeneration Requirement for culinary steam Fig. 13.1: Flow diagram for Steam Infusion Steriliser. ºC Various Temperature Profiles for Direct Infusion Instant ESL UHT Hot FillIing / Spray Drying Filling Cold Filling Fig. 13.2: Time/temperature profiles for various infusion based processes. Time Products Milk, flavoured milk, creams Soy milk products Vla, custard, pudding Soft ice mix, ice cream mix Fig. 13.3: APV Steam Infusion Steriliser. 20

21 HIGH HEAT INFUSION STERILISER The growing incidents of heat resistant spores (HRS) are challenging traditional UHT technologies and setting new targets. The HRS are extremely heat resistant and require a minimum of 145 to 150 C for 3 to 10 seconds to achieve commercial sterility. If the temperature is increased to this level in a traditional indirect UHT plant it would have an adverse effect on the product quality and the overall running time of the plant. Furthermore it would result in higher product losses during start and stop and more frequent CIP cycles would have to be applied. Using the traditional direct steam infusion system would result in higher energy consumption and increased capital cost. On this basis SPX FLOW developed the new High Heat Infusion system. Desserts Other products with conventional infusion systems PRODUCT 2 5ºC 60ºC VACUUM 90ºC 125ºC COOLING WATER COOLING 8 8 WATER STEAM STEAM 1. Tubular preheaters 2. Holding tube 3. Flash vessel (non aseptic) 3 4. Non aseptic flavour dosing (option) 5. Steam infusion chamber 6. Homogeniser (aseptic) 5 STEAM 150ºC 75ºC 25ºC Fig. 14.1: Flow diagram for High Heat Infusion Steriliser. 7. Tubular coolers 8. Tubular Heaters 9. Aseptic tank 10. Non aseptic cooler 9 FILLING In Fig a flow diagram illustrates the principle design including the most important processing parameters while Fig shows the temperature/time profile in comparison to conventional infusion and indirect systems. UHT of products with HRS (comparative temperature profiles with Fo= 40) ºC 150 Note that the vacuum chamber has been installed prior to the infusion chamber. This design facilitates improvement in energy recovery and it is possible to achieve 75% regeneration compared to 40% with conventional infusion systems and 80 to 85% with indirect tubular systems Fig shows a design of a High Heat Infusion system delivered as a combi-plant consisting of an APV Tubular Steriliser with the infuser module added on. Advantages Micro-biological product safety by elimination of HRS spores Very long operating time between CIP Reduced contamination risk having vacuum chamber on non-aseptic side No flavour losses Add-on solutions and combi-systems 0 Direct UHT 150ºC High Heat Infusion 150ºC Indirect UHT 147ºC Reference Indirect UHT 140ºC Fig. 14.2: Time/temperature profiles illustrating High Heat Infusion processing parameters. Time Limitations Capital investment costs Requirement for culinary steam Products Milk and milk products Fig.14.3: APV High Heat Infusion Steriliser. 21

22 INSTANT INFUSION PASTEURISER The infusion heating principle has increasingly been used for high viscous and sticky products. However, some products have Steam in Air out CIP in Product in been found to be very difficult or nearly impossible to handle unless very short run-times were accepted. This challenge led SPX FLOW to develop the patented Instant Infusion system. The objective was to design a system where a high kill rate can be achieved using high pasteurisation temperatures and very low holding time (<0.5 second) for products like egg white and whey protein concentrate. The patented design principle for the Instant Infusion Pasteuriser is based on the conventional infusion system. In order to have an efficient removal of the viscous and sticky product from the infusion chamber, a positive displacement Cooling water in/out pump has been placed in the outlet tube from the bottom cone very close to the actual cone. This effectively prevents any type of build-up of product at the bottom of the infusion chamber and it has been possible to increase the number of operating hours between CIP cleanings from a few to more than 20 hours for some products. In Fig 15.1 is shown the design of the infusion chamber with the pump arrangement. Fig shows an industrial installation of an Instant Infusion plant. Fig. 15.1: Instant Infusion Chamber. Advantages Can handle high fouling products with long running time (>20 hrs.) High degree of flexibility Reduced chemical changes in comparison to conventional infusion Very high product quality Products Whey protein concentrate Egg-based products Baby food Processed cheese Fig. 15.2: APV Instant Infusion Pasteuriser. 22

23 PRODUCT STEAM INJECTION STERILISER 75ºC This system operates by direct injection of steam into the product through a specially designed nozzle as previously described STEAM 2 COOLING 9 WATER FILLING (Fig. 8.4 on page 16). 4 7 The heating is followed by flash cooling and final cooling, which take place in either plate heat exchangers or tubular heat exchangers. The system is in its basic design quite similar to an infusion system where the infuser has been replaced with an injection nozzle. (Fig. 16.1) 8 COOLING WATER 1 5ºC 1. Plate preheaters 2. Steam injection nozzle 3. Holding tube STEAM 3 5 VACUUM 143ºC 75ºC 25ºC <25ºC 4. Flash vessel 5. Aseptic homogeniser 6. Plate coolers 6 6 COOLING WATER 7. Aseptic tank 8. Non aseptic cooler 9. Condenser Long operating times are possible because only a very small area in the nozzle is subject to fouling. Product The operating economy has been optimised through optimisation of plant design, processing parameters and careful process control. Steam Fig. 16.1: Flow diagram for Steam Injection Steriliser. The injection system handles low to medium viscosity products, in the capacity range from 2,000 to 25,000 l/hour. Fig shows an APV Steam Injection Steriliser. Advantages Good product quality Long production runs Handles heat-sensitive products Limitations Higher capital costs than for indirect systems Higher operating costs due to lower heat regeneration Mostly used for low viscosity products Requirement for culinary steam Fig. 16.2: APV Steam Injection Steriliser. Products Milk, flavoured milk, cream Soy milk Ice cream mix 23

24 SCRAPED SURFACE HEAT EXCHANGER STERILISER Scraped surface heat exchangers (SSHE) are the most suitable equipment for treatment of high viscosity food products and food products containing larger particles. Products Milk concentrate Yogurt Processed cheese Whey protein concentrate Quark products Baby food Compotes Puddings, dips Sauces, soups Fig. 17: APV SSHE Steriliser. In a typical aseptic plant the product is pumped by a rotary lobe pump or similar to feed one or more heating cylinders followed by a holding tube and one or more cooling cylinders. Capacities up to approximately 10,000 l/hour are available but this depends to a large extent on the physical characteristics of individual products. Since the nature of the products can vary considerably in terms of viscosity, stickiness or size and fragility of the particles, each system is individually engineered to suit a particular product. Even though systems based on SSHE are relatively expensive, both in terms of investment and energy consumption, they are still very competitive compared with batch sterilising systems. PILOT UHT PLANT The constant pressure on manufacturers to produce quality products at the lowest possible cost creates a need for evaluating the most suitable process system and optimising processing parameters. Using production plants for tests on new products and processes is both uneconomical and difficult. Therefore SPX FLOW developed a new generation of pilot plants, which gives manufacturers the possibility of performing tests on a small scale with easy operation, flexibility and scaling up accuracy. The continuous UHT pilot plant Fig. 18 has a capacity of 60 to 200 l/h and is designed for indirect tubular and direct steam infusion heating. Fig. 17 shows an SSHE based steriliser equipped with VT 4 cylinders. Advantages Handles high-viscosity products Handles sticky products Handles particulates up to approximately 13 mm Handles heavy-fouling products Limitations Relatively high capital cost Relatively high energy requirements Higher maintenance costs owing to scraper blades, bearings and seals High spare parts requirement Limitation in respect of size of particulates Fig. 18: APV UHT Pilot Plant. 24

25 However, the following options can be included in the standard system: High Heat Infusion Indirect Plate Direct Steam Injection Pasteurisation Deaeration/Deodorisation Scraped Surface Heat Exchanger and/or any combinations. It is also possible to provide variable temperature and holding time profiles. This makes the pilot plant extremely versatile. The plant can be supplied with a 500 litre sterile tank, which will form a link between the pilot plant and a filling machine. Many manufacturers choose to invest in their own pilot plant for in-house testing and product evaluation, but in other cases they may choose to use one of SPX FLOW s test and development centres. Reduced investment. As the filling machines are the most expensive part of an aseptic processing line, it is important that they are utilised to their full capacity. To this end the aseptic tank is installed. By increasing the operating time of the fillers, a small increase in the capacity of the UHT plant creates the possibility of lengthening the production run significantly. The aseptic tank is equipped with steam-shielded aseptic valve clusters and supplied with sterile air at constant pressure. This provides for a perfect balance between supply and demand from the aseptic tank. The aseptic tank is also fully automated, using programmable logic controllers (PLC), and the control system can be connected either to the UHT control system or to one of the filling machines. Fig. 19 shows the APV Sterile Tank. STERILE TANK It is not always practically possible to feed a sterile product directly from the processing plant to the filling machine. This is where the aseptic tank comes in as a buffer between processing and filling units. Besides serving as a buffer and storage tank for the sterilised product the aseptic tank also adds an important degree of flexibility to the production process as it provides for: Continuation of production regardless of interruption in filling rate. Usually one UHT line is connected to several filling machines with variable capacity. If the filling rate is not at a maximum, the UHT plants need to have a variable capacity or the product must be recirculated if allowed by local regulations. Continuation of filling during intermediate CIP or interruption in UHT operations. Many UHT plants need intermediate CIP after 8 to12 hours of operation, depending on the UHT system, product quality and type of product to be processed. The aseptic tank ensures that this process can be performed without interrupting the operation of the filling lines. Fig. 19: APV Sterile Tank. 25

26 THE PURE LAC TM PROCESS Based on investigations of consumer requirements and the present market conditions in a large number of countries the objective of Pure-Lac TM was defined as follows: Fig. 20: APV Parasol Deaerator. DEAERATOR Deaeration is essential for production of high quality products. While the products in the infusion systems are deaerated in the infusion chamber this is not the case when indirect heating systems are used. In these cases the dearation can be solved through the installation of the APV Parasol Deaerator, designed to remove dissolved or entrained air under vacuum. The product is sprayed into a vessel as a thin film in a parasol form, maximising product surface area and deaeration efficiency. The APV WI+ centrifugal pump is used to ensure pumping of high viscous products under vacuum. The APV WI+ pump is equipped with an APV Universal inducer acting as a helical screw pump mounted to the pump shaft in front of the impeller, which reduces the risk of cavitation especially when pumping high viscous products. The air content can be reduced to as low as 0.5 ppm oxygen. The APV Parasol Deaerator is shown in Fig. 20. Extended shelf life/esl In many parts of the world the production of fresh milk presents a problem in regard to keeping quality. This is due to inadequate cold chains, poor raw material and/or insufficient process and filling technology. Until recently, the only solution has been to produce UHT milk with a shelf life of 3 to 6 months at ambient temperature. In order to try to improve the shelf life of ordinary pasteurised milk, various attempts have been made to increase pasteurisation temperature and this led to the extended shelf life concept as referred to earlier in this publication. SPX FLOW has in cooperation with Elopak developed the Pure- Lac TM concept, which in a systematic way attacks the challenge of improving milk quality for the consumer. A sensory quality equal to or better than pasteurised products A real life distribution temperature of neither 5 C, nor 7 C but 10 C A prolonged shelf life corresponding to 14 to 45 days at 10 C depending on filling methods and raw milk quality A method to accommodate changes in purchasing patterns of the consumer An improved method for distribution of niche products To cover the complete milk product range, i.e. milk, creams, desserts, ice cream mix, etc. To provide tailored packaging concepts designed to give maximum protection using minimum but adequate packaging solutions Having reviewed the range of cold technologies available it became obvious that most of them were only suited for white milk. Furthermore the actual microbiological reduction rate for some of the processes were inadequate to provide sufficient safety for shelf life of more than 14 days at 10 C. Table 3 is a comparison between various processes and their ability to reduce bacteria and various types of spores. Using the data in Table 3 on a milk containing 10 to 100 spores/ml in the raw milk out of which 10 percent are psychrotrophic spores, the following result is achieved: Microfiltration, log 3 reduction 1 to 10 psychrotrophic spores per litre in the final product Every carton is a potential risk DECIMAL REDUCTION OF VARIOUS BACTERIA AND SPORES TYPE CENTRI FUGATION MICRO FILTRATION PURE LAC TM TOTAL BACTERIA AEROBIC SPORES AEROBIC PSYCHRO- TROPHIC SPORES < AEROBIC SPORES Table 3: Comparison of various methods for reducing the number of bacteria and spores in liquid milk. 26

27 Pure-Lac TM, log 8 reduction < 1 psychrotrophic spore per litre in the final product Large safety margin and excellent quality buffer Bacteria-removing centrifuges are also used to improve the quality of drinking milk. As shown in Table 3 on page 26 the decimal reduction of bacteria and spores is less efficient than for microfiltration. By reducing the throughput to half of the nominal capacity or by double centrifugation the reduction is improved by at least one decimal, which brings it closer to microfiltration. However, double centrifugation increases the investment and operating costs considerably, and this combined with the loss of milk in the bacterial concentrate in the order of 1 to 6% reduces the attractiveness of using bacteria removing centrifuges to extend the shelf life of milk. The basis for the process is the infusion technology as described. Several years of research and development have resulted in a technology, which provides an extremely gentle heating to a temperature of 130 to145 C in less than 1 second. The rate of heating is very fast in the order of 500 to 600 C/s providing all the benefits previously described. With a combination of this process technology, the appropriate filling technology and a suitable carton it is possible to produce and guarantee products with as good a taste and flavour as pasteurised milk, having a shelf life up to 45 days at a storage temperature of 10 C. For comparison the same milk pasteurised at 72 C would have a shelf life of 1 to 2 days under the same storage conditions, while it would keep fresh for 10 days at a storage temperature of 4 C. Comparison between different systems As illustrated in the presentation of the various technologies there is a wide choice and there are several considerations to be made before the final decision is taken. SPX FLOW s team of experts is available to advise on selecting the most appropriate technology for each specific requirement. Table 4 on page 28 provides a rough guideline of the advantages and disadvantages of different technologies in relation to a variety of products. This is meant as a guideline to make the right choice, which in many cases may be obvious while in other cases more difficult. As mentioned in the section on the APV Pilot Plant this provides a tool for testing different products using different heating technologies, and this may sometimes become necessary to ensure the correct choice. Process controls One of the most important aspects of an aseptic plant is the process control system. It must continuously monitor all process parameters and take reliable corrective action in case of a failure. Today all of SPX FLOW s UHT systems operate under a PLC (Programmable Logic Controller) or a DCS (Distributed Control System) based on the world leading brands, providing the best possible repeatability and reliability in the operation. This means consistent product quality, package after package, day after day. Human error is minimised and greater production efficiency is achieved. There are many systems, which are capable of successfully operating an aseptic plant. However, when it comes to choosing the right concept for the process control system there are additional factors to take into consideration. Such factors include hardware durability and availability, service from the supplier and communication ability with surrounding control systems in the plant. The operating personnel s familiarity with a particular control system is also important, and there may be special regulatory codes, which require adaptation of control systems. The world leading process technology a result of many years development and experience is built into our software packages. The control system has already been tested in many similar applications and they are always pretested prior to delivery. Fig. 21 shows an SPX FLOW production management system: The APV Factorty Expert Concept. Fig. 21: APV Factory Expert 27

28 PLATE STERILISER TUBULAR STERILISER STEAM INFUSION STERILISER STEAM INJECTION STERILISER HIGH HEAT INFUSION STERILISER INSTANT INFUSION PASTEUR ISER SSHE STERILISER MILK LOW COST HIGH QUALITY POOR QUALITY HEAT RESISTANT SPORES FLAVOURED MILK FOULING PRODUCT (CHOCOLATE) VOLATILE AROMA DIFFICULT TO STERILISE (COCOA) SENSITIVE COLOUR CREAM WHIPPING CREAM STABILISED DESSERTS COOKED CREAM COFFEE WHITENERS MILK-BASED VEGETABLE OIL-BASED (EMULSIFIED) FOULING/HIGH PROTEIN CONTENT AND STABILISER JUICE WITH PULP, FIBRES >1 MM WITH PULP, FIBRES <1 MM WITHOUT PULP AND FIBRES YOGHURT QUARK BABY FOOD MILK CONCENTRATE PUDDINGS STABILISED, HIGH SOLIDS, STARCH STABILISED WITH CARRAGEENAN SOY MILK LOW COST HIGH QUALITY POOR QUALITY RAW MATERIAL COFFEE AND TEA SOUPS AND SAUCES OTHER CONSIDERATIONS HEAT STABILITY ASEPTIC PRODUCT FLEXIBILITY MAINTENANCE = EXCELLENT 2 = GOOD 3 = ACCEPTABLE 4 = POSSIBLE 5 = NOT RECOMMENDED Table 4: Comparison between the most commonly used processing systems rated on a scale from 1 to 5: 28

29 Filling and packaging Product development In order to preserve their high micro-biological quality, aseptically processed products must be packed aseptically. Even at room temperature, the packaged product then has a shelf life of several months. In aseptic filling and packaging, the aseptically processed product is filled under aseptic conditions into commercially sterile containers, which are either preformed or formed in conjunction with the filling operation. After the filling has been completed, the containers are hermetically sealed. The resultant packages are liquid-proof and exclude air, light and bacteria. This method of processing and packaging allows for the use of paperboard, plastic containers or pouches as packaging materials, and eliminates the need for cans and energy inefficient retort heating systems. The choice of packaging concept depends on product type, unit cost and customer preference. Environmental concerns, volume of waste and the possibility of recycling of packaging material become increasingly important depending however, on the stage of development of the community. New products are developed more rapidly than ever before in order to satisfy demands in the consumer market. Simultaneously the life-cycle of the individual products tends to shorten. These conditions force the producers to intensify and accelerate product development. Capabilities in aseptic processing and related disciplines enable SPX FLOW to support customers to develop new value added products at the highest possible speed. This can be achieved through product testing in the test and development centres around the world or by means of an APV Pilot Plant installed at the customers site. SPX FLOW is keen to work in partnership with customers in order to accelerate the product development process. It is the objective of SPX FLOW to deliver innovation, quality and reliability to the dairy, food and beverage industry and in this way contribute to safe and high quality products for the consumer. SPX FLOW is not a manufacturer of packaging systems but cooperates with all companies in the packaging sector and is able to supply the appropriate solution for complete and turnkey systems. With an SPX FLOW system, customers are assured of a complete aseptic processing line producing high quality products packed for the specific market in the most cost-effective way. 29

30 About SPX FLOW ABOUT SPX FLOW SPX FLOW, based in Charlotte, North Carolina, USA, has an annual turnover of approximately 5 billion USD 16,000 employees, an extensive product portfolio and a strong financial base, well-geared for growth. SPX FLOW is serving many industries including the dairy, food, beverage, brewery and personal care industries. SPX FLOW has brought together a number of highly recognised global brands, including APV, Anhydro, Gerstenberg Schröder, which form the back bone of our food & beverage offerings and activities. CUSTOMER CENTERED SOLUTIONS With a strong synergy between the SPX FLOW brands as well as a solid knowledge and innovation platform, SPX FLOW can offer our customers a broad range of products, systems and innovative solutions as well as services reflecting the industry and consumer trends such as: ABOUT THE APV BRAND Part of SPX FLOW Corporation and operating worldwide with employees in over 35 countries, the APV brand provides manufacturing solutions and process equipment to customers in the food, dairy, beverage, brewing, healthcare, power, chemical, marine, biotechnical and petrochemical industries. The APV brand provides a unique range of highly functional solutions and products that address key business drivers. APV bases its solutions on advanced technology products including pumps, valves, homogenisers and heat exchangers, as well as production efficiency experience, development expertise, maintenance management and regulatory compliance. New innovative products for specific consumer groups Better utilisation of best from nature for healthy and natural products and enhanced functional properties. Increased food safety, productivity and sustainably processes whilst return best to nature. 3 0

31 Contact Us WE ARE EASY TO GET IN TOUCH WITH IF YOU WOULD LIKE TO KNOW MORE ABOUT HOW WE CAN HELP YOU. WE CAN ASSIST YOU IN THE FOLLOWING WAYS: General advice and guidance in connection with your test planning Suggestions of plant and equipment most suited to your purpose Booking of test facilities and, if required, our experts and technicians CONTACT US TODAY AT SPX FLOW Phone: We look forward to hearing from you. 31