Machinery Needs for Processing of Locust Bean Seeds in Nigeria

返回 Return Machinery Needs for Processing of Locust Bean Seeds in Nigeria OLAOYE, J. O. (Agricultural Engineering and Biosystems Department, University of Ilorin, P. M. B. 1515, Ilorin 240003, Nigeria jolanoye@unilorin.edu.ng, +2348035812797) Abstract The most important use of African locust bean is found in its seed, which is a grain legume, although it has other food and non-food uses. The locust bean, when dehulled and cooked, is fermented to form a strongsmelling food condiment/flavouring agent in the entire Savannah region of West Africa. The condiment is called dawadawa in Niger and northern Nigeria and Ghana, iru in southern Nigeria and soumbala in Burkina Faso, Mali, Cote d Ivoire and Guinea. Apart from being a food condiment the fermented bean also contributes to the calorie and protein intake. The production of fermented locust bean has remained a traditional family art practiced in homes with rudimentary utensils. There were several constraints to the production and consumption of the condiment. These include, among others, low production due to the use of rudimentary equipment, high wood fuel consumption and poor manufacturing practices. The major processing conditions include Dehulling or Decorticating of the locust beans, Depulpping of the locust beans and fermentation of the seeds. These operations are time consuming, laborious and inefficient. Consequently, the derived products from these seeds are not generally acceptable to consumers due to primitive handling procedure and low capacity to meet the high demand from the growing urban population. The objectives of these studies are to identify some of the unit operation bottle neck during processing of locust bean seeds, suggest possible and necessary production techniques on how to modernize and upgrade the production technology and also to optimise processing conditions of the seeds. Keywords: Locust bean seeds, Processing, Condiment, Fermentation, Dehulling, Decorticating 1. Introducation African locust bean (Parkia biglobosa) is common around villages in the Savannah areas of West Africa where it is left standing when land is cleared or sometimes planted and trees are individually owned. The crop is commonly called carob because of a valuable product (carob) derived from it. Locust bean is popular for the production of soup condiment. Fermented legumes, oilseeds and nuts are commonly used as condiments. Some examples are iru from the locust bean, ogiri from the castor seed and soy sauce from the soy bean. Iru or dawadawa is a condiment used in many African dishes especially those of Nigeria. Its high protein content 1-53

makes it a valuable component in the diets of poor families. Locust bean is commonly found in Tropical Africa and the Mediterranean (Odunfa, 1982). A tree yields 13 kg of seed. A total of 200, 000 t of bean per year was estimated for Northern Nigeria. In addition, a large quantity is produced in the savannah region of Kwara, Niger, Oyo, Ondo, and Ekiti States of Nigeria. It is prominent in the entire savannah region of West Africa. More than 100 million people in West Africa use iru as food stuff (Odunfa, 1982). All the parts of the crop are useful. It is used as a food condiment and is a good substitute for meat because it is high in protein, fat, and vitamins Countries (Obizoba and Atu, 1993) and it is rich in tannin and mineral contents (Obizoba and Atu, 1993, Enujiugha and Ayodele-Oni, 2003). The pods are used for the production of locust bean gum. This gum is used around the world as a thickening agent and stabiliser in many food products such as mayonnaise and within the textile industry as a print thickener (Glasson Grain Ltd, 2006). The fermented bean pulp waste contained protein 11.75 %; ash, 15.86 %; crude fibre, 21.55 %; starch, 32.14 %; dry matter, 93.5% and moisture, 6.5 % while the unfermented pulp contained protein 10.13 %; ash content, 14.14%; crude fibre 22.63%; starch, 28.20%; dry matter, 92.5% and moisture, 7.5%. The unfermented locust pulp waste exhibited a stronger binding effect than corn starch after 12 weeks storage (Akegbejo-Samsons et al, 2004). 2. Methodology Production Challenges and Processing of Locust Bean The two major challenges involve in production and processing locust bean are identified as production bottleneck associated with the crop's seasonality and perenniality and primitive and traditional processing procedure with the attendant low quality and quantity of the derived products. The challenging issues confronting the production and utilization of this important crop can be better amplified by considering the processing conditions of the various product derivatives from locust bean seed (Fig.1). Beaumont (2002) identified several constraints to the production and consumption of the condiment. These include, among others, low production due to the use of rudimentary equipment, high wood fuel consumption and poor manufacturing practices. Consequently, the production of this food condiment has not increased substantially. Its declining popularity, especially among the growing urban population has led to rapid increase in the import of foreign soup flavours. In order to increase supply, it is necessary to modernise production techniques and optimise processing conditions. Oloso (1988) gave a four-point suggestion on how to upgrade the production technology of fermented locust bean. According to him, a steamer should be designed to hasten the softening of the bean coat, a machine should be designed to remove the bean coat, optimum temperature and relative humidity should be provided to reduce the time required for fermentation and a better post fermentation technique is necessary to protect and prolong shelf-life and to render the fermented bean in a more presentable form. Other researchers reported on the effects of soaking duration, soaking water temperature and steaming on dehulling. 1-54

Harvesting Threshing Locust Bean Seed and Pulp Chaff Depulping Locust Bean Pulp Size Reduction Soaking Locust Bean Seed Soaking in Water Mixing of Biomass & Binder Extraction by Heat Treatment Drying Boiling Compaction Dye Tanni Produced Potash Soaking Cooking & Sedimentation Briquette Formed Locust Bean Sheath Removed Decoating Decanting Process Fermentation Dawadawa / Iru Clear Sikomu Drink Sludge & Fibre Waste discharged Figure 1: Processing Procedure for Production of Major Products derivatives from Locust Bean Seed 1-55

Local Processing and Art of Production of Products from Locust Bean African locust beans can only be eaten after processing to remove toxins and anti-nutrients. Processing also produces foods that taste good. The major processing techniques involve harvesting, decorticating, depulpping and drying to obtain the locust bean seeds that represent the major raw material from this important crop. The local processing methods are illustrated in the figures 2 to 7. The local production is mostly rigorous, time consuming and unhygienic. Dehulling of the locust beans is time consuming, laborious and inefficient. The procedure had witnessed little or no substantial technological transformation and progress in the manufacturing techniques. The recent popularity of iru as a condiment has attracted research interest in development of machinery to handle some of its unit process operations. Figure 1 shows flow chart for processing of locust bean into its major derivatives. The Locust bean seed contains 39 49 % protein, 31 to 40% oil and 1.7 to 15.4% carbohydrate (Campel platt, 1980). The nutritional value of African locust beans has been found to be very important particularly in the developing countries where the demand for protein supplementation is audibly high in all ages. Traditional iru processing is still carried out at a domestic level. However, its popularity as a condiment has resulted in the current interest in the production of iru cube, a product, which is similar to a stock cube. Good-quality raw materials that have been efficiently graded and sorted, simple equipment, optimum conditions, and attractive packaging are the key requirements of a food fermentation industry. Primary Crop Processing and Secondary Food Processing for Production of Locust Bean Products The processes involved in the production of Iru condiment which represents one of the major locust bean products right from the raw substrate are highlighted and as shown in flow chart Fig. 8. Modern processing techniques are required to improve on the traditional methods of processing and fermentation of the seeds. Appropriate processing conditions need to be developed to subject the crop to a form that the produce can be stored with a relatively long storage life. These conditions can also help to eliminate pests and microorganisms that cause spoilage. The processing stages are identified as primary crop processing and secondary food processing. It has been observed that each stage need appropriate machine intervention for effective product development. The primary crop processing involves drying, decorticating and depulping of locust bean seeds from the pod. These processes are to enhance the seed quality conditions and to subject it to a condition that will improve further food processing conditions. The processes are to condition the seed into an intermediate state that will encourage long storage life of the finished crop product. The secondary food processing stage is to convert the seed from the intermediate finished product into the desired cube. This stage requires fermentation and cubing operations. Primary Crop Processing 1-56

The various machines required for the identified unit operations during the primary crop processing are Cabinet Dryer, Decorticating and Depulping Machines. The drying process is to prepare and subject the moisture content of crop to an optimum value prior decorticating process. Fig. 2: Harvested Locust Bean Pod under Storage Condition Prior Decorticating Fig. 3: Drying of Locust Bean Pod under the Sun Prior Decorticating Fig. 4: Manual Locust Bean Decorticating Fig. 5: Preparation of decorticated Locust Procedure Bean for depulpping at the River Side Fig. 6: A Traditional Tool for Depulpping Fig 7: Clean Locust Seeds Locust Bean Seed 1-57

Locust Bean Raw Material Collection Primary Crop Processing Operations Drying of Harvested Pod Decorticating Depulping Drying Secondary Food Processing Operations Fermentation Cubing Pasting of Fermented iru Drying of Fermented iru Paste Cubing / Pelletizing Pulverizing Drying Mixing with Binder Packaging Mixing / Pelletizing Packaging Figure 8: Flow Chart Showing the Unit Operations involved in the Production of Iru Cube 1-58

The decorticated locust bean must be depulped by removing the yellowish portion of the fruit and separate the seed for further food processing. The decorticated seed must be properly dried prior storage or it could be used directly through the food processing stage. The required decorticating machine is to decorticate the locust bean pod through threshing action similar to the effect created by a tooth peg threshing mechanism. The hydro cyclone (Fig. 9) developed for the separation of hulls from the cotyledons of locust bean was designed in accordance with Rietma s optimum design for classification. The cyclone has a diameter of 350mm. It has a volumetric capacity of 0.034m 3 and an inlet flow rate and power rating of 0.011m 3 /s and 0.60kw respectively. The radical velocity of particles in the cyclone was calculated to be 0.09rad/s. Separation efficiency of 66%, 37%, 65% and 68% was obtained for common bean, locust bean, soya bean and cowpea respectively (Adewumi, 1997). Olaoye (2005) reported on a locust bean depulpping machine. The depulpping machine (Fig. 10) has capacity to depulp the locust bean. The clean bean can be processed into the desired locust bean product derivatives through associated food processing procedure. The manually operated concave type locust bean dehuller (Fig. 11) has a power rating of 0.16 kw with a capacity of 20 kg/h. It recorded a maximum efficiency of 70.9% at a roller peripheral speed of 300 rpm, concave dehulling length of 240 rpm and concave clearance of 8 mm. Development of fermentation processes Fermentation is a process in which certain bacteria or fungi are allowed to grow in a food to improve its flavor and / or digestibility. As these microorganisms absorb and process nutrients and excrete waste products they affect the flavor, nutritional value, texture, and storage life of the food. The organisms break down proteins, convert starches to simple sugars, and can increase or make various vitamins and minerals more available. In other words, these organisms are feeding on and digesting the food. Because the process of breaking foods down into their constituent parts has already begun, fermented foods can be easier for people to digest than the same food before fermentation. For example, the seeds of the African locust bean are inedible before fermentation and processing to make iru, a flavorful condiment. Fermentation lengthens the storage life of foods because the presence of the fermenting organisms prevents other, spoiling organisms from becoming established. Often this is because fermentation changes the ph of the food, for example making it so acid that only Lactobacilli spp. bacteria will survive. Fermentation can also reduce or eliminate some anti-nutrients such as phytates and oligosaccharides. Traditional fermentation processes at the cottage level use simple operations and equipment. Fermentation may be carried out on a solid substrate or under submerged conditions. Traditionally, iru is made by boiling the dried locust beans for about 24 hours. With the addition of ash the seed coats are removed. The seeds are then boiled again for about two hours. While the seeds are still very hot they are drained, transferred to a basket and covered with leaves. This helps to retain heat and create a humid atmosphere. The beans are allowed to ferment 1-59

for two to three days, after which time the leaves are removed and the seeds are crushed to a paste. Fig. 13 presents illustration of packaging of iru by traditional (left) and modern industrial (right) methods. Fig 9: Hydrocyclone for Separating the Hulls from Locust Beans Fig.10: A motorized Locust Bean Depulpping Machine Source: Adewumi, 1997. Source: Olaoye, 2005 Fig. 11: Manually Operated Concave Type (charcoal fueled) Dehuller Fig. 12: Steamer Unit for Locust Bean for Locust Bean Source: Adewumi and Igbeka, 1993 Source: Adewumi and and Olalusi, 1998 1-60

Fig. 13: Packaging of iru by traditional (left) and modern industrial (right) methods Cubing and Packaging of Iru Condiment The temperature, ph, and aeration are to be optimized for efficient output. The Iru is one of the traditional fermented condiments used to flavour soups and stews in Nigeria. The traditional alkaline fermentation of locust beans using Bacillus subtilis will be modernized in the production of iru cubes. The main challenge is the scaling-up of the fermentation processes, it involves heavy capital investment in equipment design, defining regulatory conditions of moisture, ph, temperature, oxygen transfer, aeration, and agitation, and calculating microbial growth characteristics. Various shapes can be moulded from the paste and finally the paste is sun dried. The challenge is to package Iru condiment into a cube form. The presentation is to add values to the traditional presentation of iru, to condition the condiment and subject it to durable storage conditions with an extended self life. Laboratory investigation, process and machine design, and system analysis are required. Appropriate machines are to be utilized to achieve this process. Various identified processing factors and machine variable are to be evaluated to obtain the desired optimum operating conditions for producing iru cube. The Dadawa cubes are not common in the market as the Knorr cubes produced as another form of seasoning by the same company is given more prominence and preference. Therefore, it is highly necessary to meet the identified machinery needs for this important crop to ensure continuous availability of the locust bean products derivatives. 3. Conclusion The machinery requirements for production and processing of locust bean seed into its numerous products were presented. The current local art of processing of locust bean into iru was carefully discussed. The research activities on various processes and machines related to locust bean seeds were highlighted and the major production constraints were adduced. The specific area of need of the process conditions and machinery needs to meet production demand of the products from locust bean were discussed. 1-61

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