Comparative Evaluation of Some Bioactive Compounds in Raw and Boiled Egg Varieties: Eggs, Potential Nutraceuticals?

Abstract

Aims: To comparatively evaluate some bioactive compounds (egg white proteins) of chicken (exotic and local), turkey, quail and guinea fowl eggs in their raw and boiled forms. It also aimed at ascertaining claims on egg being a functional food. Study Design:  Experimental. Place and Duration of Study: Department of Biochemistry, University of Calabar, Calabar and Department of Pharmacology, University of Nigeria, Nsukka, February to July 2017. Methodology: Freshly-laid poultry-bred eggs were purchased, cleaned and divided into 2: one batch was broken and the egg white separated while the other was boiled by submerging the eggs in boiling water at 100°C for 10 min, before taking out the egg whites. The raw and boiled albumen were homogenized before analyses. A combination of methods involving separation of egg white proteins using ion-exchange chromatography, purification using tangential flow filtration and quantification using the colorimetric Bradford assay. Results of the quantitative estimation of avidin, lysozyme, ovalbumin, ovotransferrin and flavoprotein concentrations were statistically compared using analysis of variance (ANOVA). Results: It was observed that concentrations of the bioactive compounds (except ovalbumin) were significantly (P < 0.05) higher among the raw eggs than the boiled ones. Raw turkey egg had the highest avidin content (15.83 ± 0.15 µg/g) and this was significantly different (P < 0.05) from the others, while quail had the lowest avidin concentration (8.47 ± 0.20 µg/g) even among the boiled samples. Ovalbumin, a storage protein, was the most abundant of the egg white proteins (50-55%). Conclusion: Quail eggs are healthier due to their relatively safer content of avidin, higher contents of flavoprotein and ovotransferrin; turkey egg with exceptionally higher avidin concentrations, should be consumed in moderation in order to reduce the risk of biotin deficiency. The presence of these bioactive compounds in significant quantities also show that eggs may serve as functional foods.