The Effect Of Storage Methods On Egg Quality And Organoleptic Properties Of Brown Egg Type Of Domestic Fowl
Abstract
Three experiments were conducted to evaluate the effect of storage method on internal and external egg quality, microbial load and sensory attributes of eggs stored under four different storage conditions. A total of 250 eggs were used for the analysis. The internal and external egg quality traits studied were: egg weight, egg height, egg width, shell thickness, shell weight, shape index, albumen width, albumen height, albumen weight, yolk height, yolk width, yolk weight, yolk and albumen pH, Haugh unit, albumen and yolk index. The storage periods were 1, 2, 3, 4, 5 and 6 weeks while the methods were room temperature, oiling, refrigeration and sawdust. The conditions mimicked the everyday methods of handling eggs domestically. Microbial analysis was done at the end of each storage period. The Organoleptic parameters studied under sensory evaluation were appearance, odour, taste, mouth-feel and overall acceptability. Data were subjected to ANOVA using the general linear model of SPSS 20.0 software and where statistical variation (P>0.05) was observed the means were compared using Duncan Multiple Range Test (DMRT). Effect of storage methods on external and internal egg quality traits was significant for egg height, egg width, shell thickness, shape index, yolk weight, and albumen and yolk pH. Refrigeration has the closest values to fresh eggs and oiling had the closest values to refrigeration. Values for fresh eggs and refrigerated eggs respectively Haugh unit (80.21 vs.67.39), albumen height (0.70 vs. 0.53), and yolk height (1.64 vs. 1.33) indicates a minimal loss in egg quality compared to other treatment groups. Egg weight, egg height and shell weight were statistically significant but the values for egg height and shell weights for the different storage periods were not significantly different from each other. All internal traits were statistically significant for storage period. Egg weight (54.60 vs. 64.79), albumen (0.70 vs. 0.26) and yolk height (1.64 vs. 0.59), Haugh unit (80.21 vs. 38.52), albumen (9.06 vs. 0) and yolk indices (40.13 vs. 12.06) decreased with storage time while albumen width (7.55 vs. -) and yolk width (4.13 vs. 12.06); yolk pH (6.10 vs. 6.81) and albumen pH (7.75 vs. 8.44) increased. Thus, lower quality was recorded with increased storage time. Sensory evaluation was done in a completely randomized design to evaluate the organoleptic parameters of eggs stored under the four different storage conditions for the six week duration of the study. Boiled egg samples were rated by a 10-man panelist using the 9-point hedonic scale. All organoleptic parameters tested were statistically significant (P>0.05). Results obtained showed that oiling best preserved sensory qualities of egg. Mean score value for the overall acceptability of eggs stored under oiling, room temperature, refrigeration and sawdust were 6.9, 4.1, 2.7 and 2.7 respectively.Freshly laid and stored domestic fowl eggs of 1, 2, 3, 4, 5 and 6 weeks old respectively were microbiologically analyzed for organisms on their shells. Specific organisms cultured were Salmonella/Shigella, Escherichia coli and vibro cholera. Analysis was carried out by plating on nutrient agar, salmonella shigella agar, thiosulphate bisalt sucrose agar, potato dextrose agar and eosin methylene blue using spread media plate. Results from the study indicate the presence of bacteria and fungi load on fresh egg and its increase with storage time. A decrease in Salmonella/Shigella load (fresh eggs to week 2), E. coli load (fresh eggs to week 2) and vibro cholera load (fresh eggs) was also observed. It was concluded that refrigeration best maintained internal and external qualities of egg and oiling best maintained the sensory qualities of stored eggs. It was suggested that eggs be disinfected with approved non-toxic disinfectants to reduce egg shell microbial load and the incidence of pathogenic microorganisms
Chapter One
Introduction
1.1 Background Of The Study
Eggs (like other agricultural products) are perishable and consequently require proper and effective storage to reduce post harvest losses. Eggs are delicacies relished in both rural and urban areas with chicken eggs being the most popularly produced and consumed (Fasina et al., 2012). Eggs are highly palatable and can be prepared or utilized in a number of ways. Eggs are perfectly balanced foods containing proteins, vitamins (except vitamin C ) and minerals required for good health by both the young and old (NECC, 2014). According to FAO (2003), eggs are consumed primarily as protein sources and are considered as complete proteins because they contain all nine essential amino acids making them an excellent source of high quality protein (93.7%).
Eggs come in a variety of colours (white, brown, tinted, white to tinted, blue) depending on the breed and variety of the bird (Doug et al., 2002). In Akwaibom state Nigeria, brown eggs are mostly produced and consumed. Consumers of egg pay more attention to egg shell colour though there is little or no direct relationship between shell color and nutritional characteristics/content of the egg (Scotts and Silversides, 2000).
Eggs are collected and stored prior to period of consumption which could range from days to months depending on the method of storage. Common storage methods include Wet sand storage, storage in plastic trays or open bowls under room temperature, storage in sawdust, storage in polyethene bags, oiling and cold refrigeration. The latter is least practiced in Nigeria for a number of reasons but mainly due to the poor state of power supply in Nigeria and also due to ignorance as most people who own refrigerators do not think it right to store eggs in the refrigerators. Egg storage influences the rate at which eggs undergo physical and biochemical changes that lead to the reduction in egg quality thus influencing its nutritional composition and acceptability for consumption and other uses(Fasina, 2012; Mohammed, 2011; Okeudo et al, 2005; Raji, 2009; Scotts and Silversides, 2000).
According to Stadelman (1986), egg quality refers to the characteristics of an egg that will affect its acceptability to the consumer. It then becomes necessary to properly store eggs in order to maintain its quality and also to derive maximum utility from consumption of eggs.
1.2 Statement Of The Problem
Currently, poultry production is fast becoming intensive in Nigeria and has become a dependable source of income for many farmers. With increase in poultry production and harvest of poultry products, we are faced with the pressing need to preserve poultry products- in this case- eggs to prevent or reduce post harvest losses due to spoilage and wastage.
1.3 Objectives Of The Study
The objectives of the study are:
To examine the effect of storage methods on egg quality and organoleptic properties of brown egg type of domestic fowl in Akwa ibom state.
To examine the microbial load of eggs stored under different conditions.
1.4 Justification For The Study
There is marked increase in poultry production in Nigeria as a result of the steady and substantial income actualized from its production particularly in layer production as eggs are gotten almost every day under proper management. This increase in productivity heralds the pressing need to effectively store and preserve poultry produce (particularly eggs as related to the study) in the hands of the producers as well as the consumers.
Eggs spoil in homes due to improper storage leading to deterioration in egg quality both physically and chemically (Obi and Igbokwe, 2011). Observed changes include watery albumen, enlargement and flattening of egg yolk and air cells and absorption of off-flavours and odours (FAO, 2003; Mohammed, 2011; Scotts and Silversides, 2000).This study aims at identifying a suitable storage method that will significantly reduce the rate at which biological and physico-chemical changes occur within the egg.
Chapter Five
Summary, Conclusion And Recommendation
5.1 Summary And Conclusion
Results from the study show that the effect of storage method on the external quality traits of egg was statistically significant for only egg weight and shell weight. Shell weight and yolk weight did not differ significantly (P>0.05) with storage time and the values for shell weight for fresh eggs did not significantly differ from that of the four storage treatments used in the study. This shows that effect of storage method on rate of occurrence of gaseous losses in stored eggs. Oiling had the least weight loss while room temperature had the highest loss. Oiling provides barrier to evaporation and other gaseous losses but does not replace the need for cool refrigeration. All internal egg quality traits tested except albumen and yolk pH and yolk weight were significantly affected by storage. Of the storage methods used in the study, refrigerated eggs had values closer to fresh eggs and eggs stored under room temperature and in sawdust had the lowest values. This shows the practical advantage of refrigeration over the other storage methods used in the study.Okeudo et al., (2005), observed that it is necessary to package eggs in gas proof materials before refrigeration as refrigeration cannot completely preserve the quality of eggs during storage period. However, in situations where power supply is unstable, oiling is the next best alternative.
From the study, it was observed that egg weight, albumen and yolk height, Haugh unit, albumen and yolk indices decreased with increased in while albumen and yolk pH, and yolk width increased albumen and yolk width decreased with storage time. Egg width, shell thickness and shape index were not affected by storage time. This shows the depreciation in egg quality with storage time.
Results from the sensory evaluation carried out in the study showed that oiled eggs were most preferred to eggs stored under the other storage methods used in the study having a value of 6.9 (like moderately) for the overall acceptability while the rest had values below the mean score on the 9-point hedonic scale. For reasons unknown, oiling best preserved the sensory quality of eggs.
Results from the microbial analysis of egg samples of the different storage methods used in the study indicate the presence of both spoilage and pathogenic organisms. From the study, the presence of bacteria and fungi isolates on shell of fresh and stored eggs were observed. Presence of bacteria and fungi on fresh eggs indicates trans-ovarian and oviductal (mother to foetus) transmission (Kristy, 2011). There was a general increase in total bacteria and fungi loads on egg shell analyzed with time but Escherichia coli, Salmonella/Shigella and vibro cholera load of eggs used in the study decreased with increased storage time. Presence of Salmonella and E. coli in eggs indicates faecal contamination probably from fecal contaminated feeds or drinking water. In conclusion, refrigeration is the best storage method and should be used where facilities are available and power supply is dependable. Oiling best preserved sensory quality of egg but should not replace the need for cool refrigeration and finally, this study shows the need for disinfection of eggs in egg production facilities in Akwa Ibom state, Nigeria.
5.2 Recommendation
Having tested the effect of storage methods (room temperature, sawdust, oiling and refrigeration) and period (weeks 1, 2, 3, 4, 5 and 6) on external and internal egg quality traits, microbial load and sensory quality, the following have been recommended:
Disinfection of fresh eggs at egg production facilities.
Cool storage of oiled eggs.
Packaging of eggs before cool storage, and
Maximum storage period of eggs for home use should be five weeks.
