ABSTRACT
gg is a nutrient dense food. The cylical egg glut characterized by egg spoilage, quality deterioration and wastage imparts negatively on poultry farmers. Powdered dried egg provides a convient alternative to this problem. The focus of this study was to compare and evaluate differently processed whole eggs into powder farm. Two experiments were conducted to evaluate the potential of whole egg powders made from different processing methods. The first compared the yield, proximate composition, microbiological load, functional properties and organoleptic attributes of fried egg and cake from differently processed (Spray dried- commercial, Freeze dried and Dehydrated) whole egg powders. The second assessed the effect of egg age on the proximate composition, microbiological load, functional properties and organoleptic attributes of cookies and cake made from dehydrated whole egg powder. The treatments in experiment one were the Spray Dried, Freeze Dried and Dehydrator Dried Whole Egg Powders represented as SDWEP, FDWEP and DDWEP respectively. Thirty five eggs each were used to produce the FDWEP and DDWEP while the SDWEP was obtained from United State of America. The Experimental design was a completely randomized design. Powder percentage yield of 1000g raw eggs (26.7%) and crude protein (52.78%) was highest (P<0.05) from SDWEP. Salmonella spp observed in raw eggs was destroyed by heat from the processing methods in the whole egg powders. The microbial load was within the 2cfu/g acceptable limits. Functional properties were generally significantly (P<0.05) higher for raw eggs than the whole egg powders, however with no significant (P< 0.05) differences for foaming capacity, foaming stability, emulsifying activity, swelling capacity and bulk density. Fried eggs from raw eggs generally had the highest (P<0.05) organoleptic rating but did not differ from SDWEP, FDWEP for texture and taste, SDWEP and DDWEP for flavour, SDWEP and DDWEP for general
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acceptability. All whole egg powders compared equally for all indices. Cake colour differed significantly (P<0.05) with Raw, SDWEP and DDWEP rating equally (5.50, 4.40, 4.30 respectively). In experiment two, treatment (weeks 1, 2, 3, 4) had a significant (P<0.05) effect on the crude protein indices of raw eggs with a decline from 50.96 to 42.91% as the eggs aged. Microbial load were within permissible limits. Salmonella spp and E. coli were absent. Foaming capacity declined (37.66-28.22%) with age but was only significant at the 4th week. Emulsifying capacity, water absorption, water and oil retention capacity with values of 29.85%, 0.86g, 0.52g and 0.52g respectively were best (P<0.05) at the second week. The crude protein and ether extract of the whole egg powder declined from 50.96-42.91% and 5.01-3.87% respectively as eggs aged from one to four weeks. The Microbial load was within permissible limits. Foaming capacity (30.41%), emulsifying capacity (29.41%), swelling capacity (118.74%), water and oil absorption (0.29, 0.29%) were best (P<0.05) at weeks 2, 1 and 3 respectively. Cookies and cakes produced from whole egg powders of one to four weeks of age were generally accepted without specific preference. This study concludes that whole egg powders produced by spray, freeze or dehydrator methods are generally accepted and serve as good alternatives to fresh eggs in addition to their use in the confectionary industry not compromising the final product quality. Dehydrator dried whole egg powder from 3 week old eggs may also be safely used in the confectionary industry without health or product quality disadvantages.
TABLE OF CONTENTS
Cover Page ………………………………………………………………………….Error! Bookmark not defined.
Fly Page………………………………………………………………………………Error! Bookmark not defined.
Title Page ……………………………………………………………………………………………………………………….. i
DECLARATION …………………………………………………………………………………………………………… iii
CERTIFICATION …………………………………………………………………………………………………………. iv
ACKNOWLEGDEMENT ………………………………………………………………………………………………. vi
ABSTRACT…………………………………………………………………………………………………………………. vii
CHAPTER ONE …………………………………………………………………………………………………………….. 1
1.0 INTRODUCTION ………………………………………………………………………………………………… 1
1.1 Problem Statement …………………………………………………………………………………………………… 3
1.2 Justification ……………………………………………………………………………………………………………. 3
1.3 Objectives……………………………………………………………………………………………………………….. 4
CHAPTER TWO ……………………………………………………………………………………………………………. 5
2.0 LITERATURE REVIEW ………………………………………………………………………………………. 5
2.1 Eggs…………………………………………………………………………………………………………………….. 5
2.2 Egg Production Worldwide in Nigeria ……………………………………………………………………….. 5
2.3 Composition of Eggs……………………………………………………………………………………………….. 6
2.3.1 Eggshell…………………………………………………………………………………………………………………. 8
2.3.2 Egg Membrane ……………………………………………………………………………………………………… 8
2.3.3 Egg White ……………………………………………………………………………………………………………. 8
2.3.4 Egg Yolk ………………………………………………………………………………………………………….. 9
2.4 Nutritional Value of Eggs ……………………………………………………………………………………….. 10
2.4.1 Factors Influencing Egg Nutritional Quality …………………………………………………………….. 12
2.5 Egg Powder ……………………………………………………………………………………………………….. 13
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2.5.1 Advantages of Egg Powder ……………………………………………………………………………….. 14
2.6 Uses and Nutritional Benefits of Eggs Both in Raw and Powdered Forms………………….. 15
2.6.1 Confectionary Industry……………………………………………………………………………………… 15
2.6.2 Medicine and Production of Vaccines ………………………………………………………………… 16
2.6.3 Cosmetic Industry ……………………………………………………………………………………………. 17
2.6.4. Industrial Uses …………………………………………………………………………………………………… 18
2.7 Effect of Heat on Eggs ……………………………………………………………………………………………. 18
2.8 Safety Concerns of Egg Use …………………………………………………………………………………. 19
2.8.1 Salmonella…………………………………………………………………………………………………………. 19
2.8.2 Escherichia coli ………………………………………………………………………………………………….. 21
2.8.3 Regulations Concerning Microbiological Safety of Foods………………………………………….. 21
2.9 Processing Methods of Egg Powder ………………………………………………………………………… 22
2.9.1 Dehydration…………………………………………………………………………………………………………. 22
2.9.1.1 Merits and Demerits of Dehydrated Food …………………………………………………………….. 24
2.9.2 Freeze drying method………………………………………………………………………………………….. 24
2.9.2.1 Merits and Demerits of Freeze Dried Food ………………………………………………………….. 25
2.9.3 Spray drying method …………………………………………………………………………………………… 25
2.9.3.1 Merits and Demerits of Spray dried eggs ………………………………………………………………. 26
2.10 Functional properties of Eggs and Egg powder ……………………………………………………….. 26
2.11 Organoleptic Properties of Cakes ………………………………………………………………………….. 30
3.0 MATERIALS AND METHODS……………………………………………………………………………. 31
3.1 Experimental sites ………………………………………………………………………………………………… 31
3.2. Experiment One: Production and Evaluation of Differently Processed Whole Egg Powders………………………………………………………………………………………….31
3.2.1 Egg Powder Production…………………………………………………………………………………….. 31
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3.2.2 Proximate Composition Analysis: …………………………………………………………………………. 32
3.2.2.1 Dry matter (DM) ………………………………………………………………………………………………… 32
3.2.2.2 Crude Protein (CP)……………………………………………………………………………………………… 33
3.2.2.3 Ash Value………………………………………………………………………………………………………….. 34
3.2.2.4. Ether Extract (crude fat)……………………………………………………………………………………… 34
3.2.2.5 Nitrogen Free Extract (NFE)………………………………………………………………………………… 34
3.3 Microbial-count Analyses ………………………………………………………………………………………. 35
3.3.1 Total bacteria, Coliform and Non-coliform: ……………………………………………………………… 35
3.3.2 Culture of fungi:………………………………………………………………………………………………….. 35
3.3.3 Selective isolation of Salmonella spp: ………………………………………………………………….. 35
3.4 Functional Properties ……………………………………………………………………………………………. 36
3.4.1 Emulsifying Activity……………………………………………………………………………………………. 36
3.4.2 Swelling Capacity ……………………………………………………………………………………………….. 36
3.4.3 Foaming Stability/ Foaming Capacity ……………………………………………………………………. 37
3.4.4 Bulk Density ………………………………………………………………………………………………………… 37
3.4.5 Water and Oil Absorption Capacity (WAC/OAC) ………………………………………………….. 37
3.4.6 Water and Oil Retention Capacity (WRC/ORC) …………………………………………………….. 38
3.5 Sensory Analysis…………………………………………………………………………………………………… 38
3.5.1 Preparation of Un-Spiced scrambled egg …………………………………………………………………. 39
3.5.2 Production of Cake ……………………………………………………………………………………………….. 39
3.6 Experiment Two: Effect of Egg Storage Period on Whole Egg Powder Quality ……………. 39
3.7 Statistical Analysis ………………………………………………………………………………………………… 40
3.7.1 Model ………………………………………………………………………………………………………………… 40
4.0 RESULTS AND DISCUSSIONS ……………………………………………………………………………. 41
4.1 Product Yield ……………………………………………………………………………………………………….. 41
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4.2 Proximate Composition of Egg Powders …………………………………………………………………… 41
4.3. Microbial load of Egg Powders ………………………………………………………………………………. 44
4.4 Functional Properties of Egg Powders………………………………………………………………………. 44
4. 5 Organoleptic Evaluation of Fried Egg Powders ………………………………………………………… 47
4.6 Organoleptic Evaluation of Cakes Made from Egg powders ……………………………………….. 50
4.7 Effect of Egg Storage period on Whole Raw Egg Proximate Composition ……………………… 50
4.8 Effect of Egg Storage period on Whole Raw Egg Microbial load ……………………………….. 52
4.9 Effect of Egg Storage period on Whole Raw Egg Functional Properties ……………………….. 52
4.10 Effect of Egg Storage period on Whole Egg Proximate Composition …………………………. 55
4.11 Effect of Egg Storage period on Functional Properties of Whole Egg Powder……………… 55
4.12 Effect of Egg Storage period on Functional Properties of Whole Egg Powder……………… 58
4.13 Effect of Egg Storage period on Organoleptic Evaluation of Cakes ……………………………. 58
4.14 Effect of Egg Storage period on Organoleptic Evaluation of Cookies …………………….. 61
5.0 CONCLUSIONS AND RECOMMENDATIONS ……………………………………………………. 63
5.1 Conclusions …………………………………………………………………………………………………………. 63
5.2 Recommendations ……………………………………………………………………………………………….. 63
REFERENCES …………………………………………………………………………………………………………….. 64
APPENDICES ……………………………………………………………………………………………………………… 73
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CHAPTER ONE
1.0 INTRODUCTION
Agriculture in Nigeria has over the last few years received increasing attention with both Federal and State Governments encouraging the Nigerian populace especially the youth to embrace agriculture as a profession and a means out of the current recession (African Economic Outlook, 2012).
USDA (2013) as cited by Heise et al. (2015) reported that of the various components of animal husbandry, poultry farming is the most popular and probably lucrative. Nigerian Federal and State governments are investing in poultry production. Egg production plays a vital role in poultry farming and has been on the increase with various government programmes such as “Feed the School Children” encouraging more people to embark on poultry production. Eggs are laid by female animals of many different species, including birds, reptiles, amphibians, mammals, and fish, however among other avian the most popular choice for egg consumption are chicken eggs. They are a cost effective animal protein with a potential to contribute to food and nutrition security and generate rural household livelihoods (Lannotti et al., 2014) and are considered to be nature‟s most nearly perfect food for mankind and are therefore used as the reference protein for assessing protein quality of other proteins. Eggs are also sources of vitamins A, D, B1 (Olomu, 2011).
Eggs in general are one of the cornerstones of baked goods and cooking with breads, cakes, bakery mixes, and an assortment of desserts owing much of their unique texture, taste and moisture to the egg. Eggs are low in saturated fats and are good sources of high quality protein and varying amounts of 13 essential vitamins and minerals, including Vitamin A, B12 and folate hence them being termed as a “nutritional powerhouse”. Eggs are extremely perishable and must
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be kept refrigerated as they have a relatively short shelf life. They are also delicate and bulky thereby having increased risk of breakage during transportation. (Lauber, 2007; 2017)
The cyclical egg glut in Nigeria characterized by egg spoilage, egg quality deterioration, and wastage in the process of transporting excess eggs which eventually results in loss of inputs to poultry farmers which spans for about 3 months /year is on the increase as more individuals embark on poultry production in order to alleviate poverty and unemployment. Poultry farmers across the nation have cried out that the glut being experienced was likely to discourage farmers from further production and cause a collapse in the poultry sector (African Economic Outlook, 2012). The situation has not changed even as at today (Okojie, 2017).
Powdered, dried eggs provide a convenient alternative to fresh eggs and add quality and consistent performance to the list of attributes. In addition, dry egg products can be stored up to a year or longer under proper storage conditions, the risk of bacterial contamination due to improper handling is significantly reduced as well as the cleanup time. Powdered, dried eggs are a solution to bulkiness and fragility of fresh eggs as well as storage challenges as they can be stored up to a year or longer under proper storage conditions, (Jay, 2000). For bakers, powdered egg products provide consistency from batch to batch and are always ready. Egg solids blend well with other dry ingredients and can be used immediately without cracking or thawing (Anonymous 2010) and when it comes to using eggs as a source of protein for dietary supplement or muscle gain, eggs rate as the cheapest source of high quality protein and egg powder further reduce this cost (Heymann, 2015). It an ideal alternative for individuals who cannot consume dairy products due to lactose intolerance as it is lactose free (Greenfield, 2013).
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Several processing and preservation methods like spray drying, tray drying and freeze drying techniques have been adopted with advantages and disadvantages on the qualities of the products (Potter and Hotchkiss, 2006). The use of dehydrator is another method for making egg powder with both dehydrated and freeze dried food having similar benefits, including a potentially far longer shelf life than home canned food as they are both stable products when stored in a cool, dry place (Dodrill, 2014). Powdered eggs are popular in several developed countries with little or no differences reported between fresh eggs and egg powder however, Nigeria despite her achievement in agriculture most especially in poultry-egg production, has a limited or practically no provision for handling processing of eggs. This study explored some adaptable processes of transforming fresh eggs into whole egg powder thereby extending its shelf-life while still maintaining its richness.
1.1 Problem Statement
For about a decade now, a huge attention has been shifted to poultry farming most especially for egg production especially in the light of the current recession. However, farmers have been bedeviled with a major setback in the management of eggs after production resulting from higher supply and lower demand thereby leading to egg-glut. Egg glut over a period of time results in a compromise of egg quality (deterioration and spoilage). The attempt to transport excess eggs from one location to another in times of glut has its attendant problem of egg breakage and deterioration of the internal quality thereby enhancing micro-organism penetration.
1.2 Justification
Several challenges posed by egg-glut so far have brought losses in place of gain to both small and large-scale producers. Therefore, this research focused on how to manage glut conditions by exploring methods of processing raw eggs to egg powder in order to extend its shelf-life as well
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as make transportation convenient without fear or risk of wastage. The egg powder would also be a useful resource both in homes and in the confectionary industry.
1.3 Objectives
The broad objective of this research was to conduct a comparative evaluation of whole egg-powder produced from different processing methods.
Specific objectives were to:
i. Produce whole egg powder through freeze drying and dehydrator processing methods.
ii. Compare the yield, proximate, microbial and functional properties of a commercial whole egg-powder with freeze dried and dehydrator processed whole egg powders.
iii. Compare the organoleptic properties of fried egg and cake prepared from freeze dried, dehydrator processed, commercially whole egg powders and raw egg.
iv. Determine the effect of egg age on the proximate, microbial and functional properties of whole egg powder processed by dehydrator method.
v. Determine the effect of egg age on the organoleptic properties of cookies and cake prepared from whole egg powder processed by dehydrator method.
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