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Abstract: Pasteurized shell eggs are eggs that have been thermally treated to eliminate harmful bacteria, however the treatment may also denature some of the egg white proteins. In this study the degree of denaturation and functional properties (emulsifying, foaming, and gelling properties) of egg white obtained from pasteurized eggs (EWP) were compared with those of unpasteurized eggs (EWUP). Data from differential scanning calorimeter showed that the EWP (ovotransferin, lysozyme, and ovalbumin) denatured at lower temperatures and required lower denaturation enthalpies than EWUP, indicating a partial loss of protein structure during the pasteurization process in the pasteurized eggs. The emulsion and foam stability formed from EWP were significantly (P < 0.05) lower than those of EWUP, however the EWP formed stronger gels than EWUP. To assess suitability of EWP as a cake ingredient, angel food cake was prepared using both egg whites. As compared to EWUP-cake, EWP-cake was significantly (P < 0.05) lower in volume, cohesiveness and springiness values, but significantly (P < 0.05) higher in hardness, gumminess and chewiness. Overall, the sensory panelists gave significantly (P < 0.05) higher scores for angel food cake prepared with EWUP. The differences in functional properties of egg white proteins and the quality of cake were due mainly to the higher levels of denaturation attained by EWP as a result of the pasteurization process.
Keywords: Pasteurized shell egg, protein functionality, denaturation, angel food cake
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Introduction
Egg is a highly nutritious food as it contains high quality proteins and a large variety of vitamins and minerals. The egg proteins have just the right mixture of essential amino acids needed by humans to build a strong body. The egg white, also known as the albumen, comprises approximately 58 % of the weight of an egg. The egg white consists of concentric layers; two thick whites separated by inner and outer thin whites. The chalazae are located within these layers of the albumen and are continuous with the vitelline membrane that surrounds the yolk. Over half of the protein in whites is ovalbumin, although conalbumin, ovomucid, and globulins (including lysozyme, which is able to lyse some bacteria) contribute lesser percentages of protein in the egg whites (Goetz and Koehler, 2005). Whites provide more protein than the...