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.
CHAPTER ONE
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.
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.
