EGG QUALITY AS AFFECTED BY STORAGE AND HANDLING METHODS

Transcription

1 EGG QUALITY AS AFFECTED BY STORAGE AND HANDLING METHODS BASIL KAMEL', C. BOND and M. DIAB Kuwait Institute for Scientific Research P. 0. Box Kuwait Received for Publication August 10, 1979 ABSTRACT The quality and shelflife of fresh eggs were studied under simulated climatic conditions as found in Kuwait. Three groups of eggs (unwashed, washed, and washed and oil treated) were used. The treated eggs were stored at 5", 25", 37" and 42 C. Internal and external quality and sensory evaluation of the eggs stored up to 75 days were determined. The quality of the unwashed and washed eggs stored at 37 C and 42 C deteriorated rapidly while the wash and oil treatment extended shelflife but decreased in quality to C over a period of time. The percent weight loss in the oil treated eggs at all temperatures was about 0.6% while the washed and unwashed lost more depending upon the temperature and storage time. All parameters studied for interior quality showed that oil treated eggs were significantly better than untreated eggs even at 42 C. Sensory evaluation on boiled eggs indicated that changes in flavor and overall quality for untreated eggs stored at high temperatures were obvious while little change in texture was observed. It was concluded that under Kuwaiti conditions eggs should be oil treated directly after collection and stored at or below 25 C so that the quality and shelflife can be extended significantly. INTRODUCTION The egg is a highly perishable food product and may lose quality rapidly if not given proper care during the period of time between collection and consumption. The interior of an egg is not perfectly protected by its shell and is affected by external environmental conditions. Various quality Present address: Department of Food Science, University of Guelph, Guelph, Ontario NlG 2W1. Canada Journal of Food Quality 3 (1980) All Rights 1980 by Food & Nutrition Press, Inc., Westport, Connecticut 261

2 262 BASIL KAMEL, C. BOND AND M. DIAB attributes of eggs are lost as an egg ages. The factors associated with extent of quality loss are time, temperature, humidity and handling. The rate of change in the albumen and yolk is a function of temperature and movement of carbon dioxide through the shell. The temperature in Kuwait averages about 45"+ 3 C in a long summer of eight months and about 20" k 5 C in winter with high relative humidity sometimes reaching 9095s. At present Kuwait has a population of about 1.1 million with an egg consumption of 450 millionlyear (BP report to KISR) half of which is produced locally and half imported from different countries such as Romania, Bulgaria and Lebanon. Predicted population growth in Kuwait is expected to be between million by the year 2000 and demand for eggs may be expected to increase proportionately. By that time local production is expected to rise to a level satisfying the demand. At present, quality control, good processing, handling and storage facilities in Kuwait are lacking. Therefore, a high percentage of eggs deteriorate in quality and eventually go to waste. In the future, appropriate measures will need to be taken by producers, distributors and consumers in Kuwait so that all will benefit from maximum production of quality eggs satisfactory to the consumer. This could be achieved by having the producers charge on the basis of candled quality which eventually would result in a high percentage of eggs candled as A or AA quality. Distributors are interested in a high yield of eggs with good quality whereas the consumer desires eggs with good brokenout appearance and acceptable flavor. Since producers and distributors depend on consumers' acceptance and purchases, the production and preservation of eggs with superior broken out quality should be of primary importance in their operations. This study was undertaken to establish the best handling and storage conditions for eggs so that both shelflife and high quality could be extended to the maximum under Kuwait conditions. REVIEW OF LITERATURE Various quality attributes of the albumen and yolk are lost as an egg ages. Factors associated with extent of quality loss are time, temperature, humidity and handling. Van Wagenen (1949) reported that quality changes occurred in eggs held at 35", 45", 55", 65" and 80 F and concluded that 45 F was the most desirable temperature for holding eggs on the farm. Funk (1944) reported that thick albumen was converted to thin albumen very slowly at temperatures of 30" to 50 F but quite rapidly at 80" to 100 F.

3 EGG QUALITY 263 The rate of exchange in the albumen and yolk is a function of temperature and movement of carbon dioxide through the shell. The lower the temperature down to the freezing point, the slower the rate of quality decline. Stadelman et af. (1954) reported that nonrefrigerated eggs at 60 F lost on the average 1.51 Haugh units per day but refrigerated eggs stored at 50 F lost only 0.56 units per day. The Haugh unit values dropped from 80 to 53 in nonrefrigerated and to 68 in the refrigerated eggs. Goodwin et al. (1962) compared the effectiveness of sprayoiling with no oiling with respect to albumen, ph and Haugh units after7,14, and 21 days storage at 50 F. They found in all instances that eggs oiled within an hour of laying had higher Haugh units than eggs oiled at other times. Homler and Stadelman (1963) compared the effect of no oiling, oiling before washing, oiling after washing and oil both before and after washing on Haugh units and weight loss of eggs held for 3 weeks at 72 F or 6 weeks at 55 F. Nonoiled eggs had lower average Haugh units and a higher weight loss than any of the oiling treatments in both storage conditions. Oiling before compared favorably with oiling after washing with respect to Haugh units. On percent weight loss, oiling after washing was preferable. Oiling both before and after washing resulted in the highest Haugh units and lowest weight loss of any of the treatment groups. The importance of careful and prompt washing and oiling of eggs in lieu of storage temperatures was stressed by Heath and Owens (1978). Sample Preparation MATERIALS AND METHODS Eggs used in this study were collected from KISR Poultry Hatcheries Laying Flock during a period of five days. Eggs collected were stored in a refrigerator at 4" f 1 C until used. The 4500 eggs were then pooled out and divided randomly into three groups, each group having 1500 eggs. Each group was then processed according to one or the three following treatments : (1) Unwashed. The unwashed eggs were placed in trays and the individual weight of each egg was determined. (2) Washed. The eggs were washed with distilled water at a temperature of 65" f 2 C then dipped in 50 ppm chlorine solution for 5 s, placed on filter paper and dried in hot air. Each individual egg was then weighed and placed in a flat of 30 eggs capacity. (3) Washed and Oil treated. Eggs were washed and dried as above then dipped in food grade mineral oil (Fisher) at 22" f 1 C for 5 s, then air dried, weighed individually, and placed in flats.

4 264 BASIL KAMEL, C. BOND AND M. DIAB A set of each treatment was then stored at temperatures of 5, 25, 37 and 42? 1 C for various periods of time. The relative humidity in the storage area was between 7580%. Quality Measurements Quality determinations (external and internal) of the fresh and stored eggs as well as organoleptic properties of boiled eggs were obtained. Egg quality which included ph, yolk to albumin ratio (measured by Vernier), egg shell thickness (Ames Thickness, micrometers), yolk color (Yolk color, Fan Roche), yolk index and Haugh units (using Micrometers or height gauge). Standard candling procedure for internal quality and Air Cell Depth were determined using official egg cell gauge. For sensory determination 10 eggs of each treatment at each storage temperature were boiled for 15 min, cooled, peeled and cut into slices and presented to 10 panelists. All panelists were staff members from different departments in K.I.S.R. All sensory evaluations were performed in duplicate by the same panelists who evaluated the boiled egg as equal to or inferior to the fresh control, and if inferior, to what degree on a 5 point scale, with 1 = no difference, 2 = slightly, 3 = moderate, 4 = much, and 5 = extremely inferior. The panelists first scored each sample for flavor, texture and finally overall sensory quality. Handling and Shell Quality RESULTS AND DISCUSSIONS This study was conducted in a way to establish the best conditions for extending the shelflife of fresh eggs under harsh Kuwait weather conditions. Data in Table 1 show percent weight loss in eggs after storage up to 75 days at different temperatures. It is very clear that the oil treated eggs at all temperatures showed little loss compared to the washed and unwashed eggs. On the average, oil treated egg loss was 0.65% compared to 5.9% and 5.1% for unwashed and washed eggs. Also the data showed that lowering storage temperatures resulted in less weight loss. Although temperatures just above the freezing point are the most effective in maintaining quality, eggs are generally held between 50" and 60 F where storage times are limited to a few days. Quality decline at this higher level is slightly greater, but the costs of refrigeration are considerably less. A relatively high moisture level in the air of the holding room is desirable to minimize loss of water from the egg. Above 80% relative humidity, however, mustiness and off odor may develop.

5 Table 1. Effect of washing and oiling treatments on percent weight loss of raw eggs stored at 5" to 42 C for up to 75 days Treatment Temp. "C Holding Time (days) No Wash Wash Wash + Oil

6 266 BASIL KAMEL, C. BOND AND M. DIAB Shell quality characteristics considered were cleanliness and soundness. It is essential that eggs reach the consumer with sound, clean shells, if satisfaction is to be achieved. From the viewpoint of appearance, washing is the most effective and simplest method for removing dirt and stains from the shell surface. But with washing, there are possibilities of bacterial penetration through the shell which may result in a rotten egg. Therefore, care must be taken when the egg is washed. Careful attention must be paid to the temperature difference between eggs and wash water. Clean water must always be used employing a sanitizer and drying the egg after washing. Also, shell thickness of at least 0.33 mm is needed if the egg is to have a better than 50% chance of moving through normal market handling without breaking. In our study, the average shell thickness was 0.35 mm and the average shell weight was 7.63 g. Interior Quality For the interior quality, several parameters were determined to follow up the deterioration in the egg. Air Cell depth was determined on 15 eggs. Results in Table 2 showed that storing eggs at high temperatures increased air cell beyond 318 in. which caused egg quality to drop below grade C. The higher the temperature the faster the deterioration. No differences were noticed between washed and unwashed eggs but eggs washed and oil treated retained better quality. Albumen ph was measured immediately for all broken eggs. Again, oil treated eggs showed lower values and maintained their quality much better than the unwashed and washed eggs stored at the same tempeatures. ph changes were higher at high storage temperatures as shown in Table 3. In addition to holding eggs at lower temperatures to preserve quality, they may be oil processed to seal the pores of the shell. This treatment not only retards the loss of moisture but also reduces loss of carbon dioxide from the egg. As a result, the ph of the albumen rises less rapidly. Since thinning of the thick white and deterioration of the yolk membrane are accelerated by a rise in ph, oiling slows down these undesirable changes and improves broken out quality. If the oiling process is delayed several days, it is less effective in preserving quality since a high proportion of carbon dioxide has escaped. Therefore, eggs are often oiled as they are gathered in the laying house or shortly thereafter. The most widely used measure of Albumen condition is the Haugh unit. This method consists of measuring the height of thick albumen which is related to egg weight. The higher the Haugh value, the better the albumen quality of the egg. Tables 4, 5 and 6 present different measures of interior quality including Haugh units, yolk index and yolk to albumen ratio. All these parameters could be used to indicate any deterioration in interior

7 Table 2. Effect of washing and oiling treatments on air cell depth (in.) of raw eggs stored at 5' to 42OC for up to 75 days Treatment No Wash Wash Wash + Oil Temp. OC Holding Time (days) /16 3/16 3/163/8 1/8 1/8 3/16 1/H 3/16 3/16 1/8 1/8 3/16 1/83/ /16 6 1/8 3/16 3/16 3/163/8 3/163/8 1/X 1/8 3/16 3/8 3/163/8 1/8 1/8 3/16 1/83/16 1/8 3/16 9 1/8 3/ /16 3/163/8 3/ /8 3/16 3/8 3/163/8 1/8 1/8 3/16 1/83/16 3/ / / / /16 1/8 3/16 3/163/8 3/163/8 1/8 1/8 3/16 3/8 3/ /8 3/16 3/163/8 3/8 1/ /11 3/8 1/8 3/16 1/8 3/16 3/8 3/163/8 26 1/8 3/16 3/163/8 1/8 3/16 3/163/8 1/8 3/16 1/8 3/ /16 3/163/8 1/8 3/16 3/163/8 1/8 3/16 3/163/8 40 3/163/8 3/8 3/ /8 1/8 3/16 3/163/8 47 3/16 3/8 1/8 3/16 3/163/8 61 3/ /16 1/8 3/16 3/8 75 3/163/8 3/16 1/8 3/16 3/8 3/163/8 3/163/8 1/8 in. = Ah PuJit~, 3/16 in = A Quality. 3/8 rn. = B Quality

8 268 BASIL KAMEL, C. BOND AND M. DIAB Table 3. Variation in ph of albumen unwashed, washed, and washed and oiltreated eggs stored at 5" to 42'C up to 75 days Treatment No Wash Wash Wash + Oil Temp. O C Holding Time (Days) Fresh average of 6 readings = 8.64 Table 4. Average Haugh units of unwashed, washed and oil treated eggs held up to 75 days at 5O42OC Treatment No Wash Wash Wash + Oil Temp. OC Holding Time (Days) Average Haugh unit of fresh onedav old egg was = Average weight of egg eas = g.

9 EGG QUALITY 269 Table 5. Average yolk index of unwashed, washed and oiltreated raw eggs held up to 75 days at 5"42"C Treatment No Wash Wash Wash + Oil Temp. "C Holding Time (Days) lo , Fresh average of 6 readings = 0.43 Table 6. Average yolk to albumen ratio of unwashed, washed and oiltreated raw eggs held up to 75 days at 5"42"C Treatment No Wash Wash Wash + Oil Temp. "C Holding Time (Days) ~ Fresh average of 6 readings = 3.20 qualities. The results confirmed each other and indicated that oil treated eggs kept yolk and albumen quality better than the untreated eggs. Also at longer holding times and higher temperatures, the quality was consistently reduced compared to fresh and to oil treated eggs held at. lower temperatures.

10 270 BASIL KAMEL, C. BOND AND M. DIAB As the egg ages, water migrates from the albumen to the yolk, thus increasing the weight of the yolk. The rate of water transfer is a function of holding temperatures ; faster migration occumng at higher temperatures. The migration of water to the yolk results in a stretching and weakening of the vitelline membrane. Yolk color is generally determined by using color comparators and assigning numerical values. In our study, the average yolk color value for all eggs determined was 8 to 9. The comparison of overall quality of eggs for all treatments studied indicated that oil treatment extended shelflife and retained B quality even after 19 days storage at 42 C while the untreated egg dropped to C and below after only 9 days storage. Eggs stored at 5 C for all the treatments kept their high quality even after 75 days of storage (Table 4). Table 7. Sensory scores of boiled eggs stored at tempeatures of 5"42 C from 742 days Treatment No Wash Wash Wash + Oil Temp. "C Holding Time (Days) B Texture C Overall Quality Taste panel average scores are: 1 = no difference; 2 = slight; 3 = moderate; 4 = much and 5 = extremely inferior

11 Average Yolk to Shell Shell Date of Haugh Weight Albumen Yolk Weight Thickness Air Cell Qua Collection Origin Unit g Ratio Index ph g (mm) (in.) lity April 3 Kuwait /8 B April 23 Kuwait / B April 23 Bulgaria /8 318 B April 23 Lebanon C May 7 Lebanon B May 7 Bulgaria B May 21 Kuwait B May 21 Romania /16 A May 21 Lebanon B June 5 Bulgaria C June 5 Kuwait /8 A June 5 Lebanon /163/8 C Average B M Q 0 Table 8. Quality of local market eggs

12 272 BASIL KAMEL, C. BOND AND M. DIAB Sensory Quality Sensory quality and consumer acceptance is the most important parameter for determination of any food quality. In this investigation, boiled eggs from all treatments and different holding times and temperatures were presented to taste panels, who were asked to compare their flavor, texture and overall quality with a fresh boiled egg as reference. Table 7 shows the average scores obtained by the panels, indicating that they were able to detect differences in flavor and overall quality. Little differences in texture could be detected. However, a drastic drop in flavor scores was obvious at storage temperatures of 37" and 42 C especially for the washed and unwashed eggs. Oiltreated eggs retained good flavor compared to the other treatments. Comments from all panelists indicated that visual changes were obvious in air cell and yolk movement from the center toward the wide end of the egg especially for untreated eggs stored at high temperatures. Other changes which affected flavor are obvious from Table 7. Table 8 presents quality parameters of imported eggs sold in Kuwait. From the data presented, ther overall quality is low. These eggs were purchased from the central fruit and vegetable market where storage conditions and handling are poor. The quality of such eggs will drop to lower values when sold to small outlets and stored under their conditions. By the time the product reaches the consumer, it is of poor quality due to lack of favorable storage conditions. Therefore, more attention in handling and processing of eggs is recommended for Kuwait if better quality and longer shelflife is desired. From our study, we could recommend that treating eggs after gathering, with mineral oil, then storing at low temperatures such as 25 C or lower with a relative humidity of 7540% will definitely extend shelflife and minimize egg spoilage and deterioration. REFERENCES FUNK, E. M The Cooling of Eggs. Missouri Agri. Exp. Sta Bulletin 350. GOODWIN, J. L., WILSON, M. L and STADELMAN, W. J Effects of oiling time, storage position and storage time on the condition of shell eggs. Poultry Sci. 42, 840. HEATH, J. L. and OWENS, S. L Effect of oiling variables on storage of shell eggs at elevated temperatures. Poultry Sci. 57, HOMLER, B. E. and STADELMAN, W. J The Effect of oiling before and after cleaning in maintaining the albumen condition of shell eggs. Poultry Sci. 42, 190. STADELMAN, W. J., BAUM, E. L., DARROCH, J. F. and WALKUP, H. G A comparison of quality in eggs marketed with and without refrigeration. Food Technol. 8, 488.

13 EGG QUALITY 273 STADELMAN, W. J. and COTTERILL, 0. J. (eds.) Egg Science and Technology, AVI Publishing Co., Westport, Conn. VAN WAGENEN, A., HALL, G. 0. and ALFMANN, M Temperature and humidity in the short time holding of eggs. Proc. Seventh World Poultry Congress 6, 516.