42-4 |
Acid and alkali unfolding and refolding strategies improve the foaming properties of egg albumen |
B. INGADOTTIR and H. G. Kristinsson. Dept. of Food Science & Human Nutrition, Univ. of Florida, 359 FSHN Bldg., Newell Dr., PO Box 110370, Gainesville, FL 32611-0370 Variable foaming qualities of egg albumen is a problem facing the egg processing industry. Modifications of the structure of egg albumen proteins may yield improvements in their foaming properties. The objective was to investigate if different low and high pH unfolding and refolding strategies would improve the foaming properties of egg albumen proteins and how these would affect the proteins conformation. Egg albumin proteins were subjected to a high (11.5) and low (2.5) unfolding pH for variable time followed by pH-readjustment (refolding) to either pH 4.5 or 8.5. Foams were produced from the pH-treated and untreated proteins at 5% protein concentration. The quality and stability of the foam was evaluated with foam overrun and liquid drainage, respectively. Conformational changes of the proteins were measured by changes in intrinsic tryptophan fluorescence at low and high pH and after pH readjustment and percent protein unfolding calculated. Acid and alkali-treatment of egg albumin improved foam overrun for both refolding conditions when compared to control. However, refolding the proteins to pH 4.5 gave better results when compared to refolding to pH 8.5. Acid and alkali-treated proteins refolded to pH 4.5 gave the best foam stability when compared to other samples. Alkali-treatment gave in general the best foaming properties. The proteins were less denatured at low compared to high pH. Refolding the proteins to pH 4.5 gave more recovery in the proteins native structure compared to refolding to pH 8.5 indicating that different structural forms of egg albumins yield different foaming properties. The results show that the foaming ability of egg albumin can be improved by using proper pH manipulation techniques. This provides valuable information on how directed structural changes in egg proteins could positively affect their function as foaming agents which egg ingredient processors could use for their benefit.
Session 42, Food Chemistry: Proteins II
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