Effects of Yolk Contamination, Shearing, and Heating on Foaming Properties of Fresh Egg White

Abstract

A series of experiments were conducted to evaluate effects of yolk contamination, shearing, and thermal treatment on foaming properties of liquid egg white. Samples obtained from industrial processing were also evaluated. Whipping and purging methods were both used to assess their effectiveness and sensitivity in evaluating foaming. A concentration as low as 0.022% (as-is basis) of yolk contamination caused significant reductions in foaming capacity and foaming speed. The neutral lipid fraction of egg yolk caused the major detrimental effect on foaming, and phospholipids fraction did not give significant foaming reduction at a concentration as high as 0.1%. High-speed and short-time shearing caused no apparent damage but longer shearing time significantly impaired foaming. Heat-induced foaming change is a function of temperature and holding time. Foaming was significantly reduced at a temperature of 55 degrees C for 10 min, whereas it did not change up to 3 min at a heating temperature of 62 to 64 degrees C. Industrial processing steps (pumping, pipe transfer, and storage) did not produce negative effects on foaming of the final products and the controlled pasteurization was actually beneficial for good foaming performance. Therefore, yolk contamination of the egg white was the major factor in reducing foaming properties of the white protein.

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“…In addition, there is practically no tolerance level for yolk contamination, i.e. even at the lowest testing concentration (0.01% yolk in white protein, as‐is basis) foaming was significantly reduced 1. This research also showed that neutral oil, rather than the polar phospholipids in the yolk, is the main contributor for reduced foaming.…”

“…The 0.4% yolk addition was used to simulate yolk contamination of the egg white for this study. The use of this level was determined based on the findings from our previous work,1 which showed that 0.4% yolk (as‐is basis) led to the lowest foaming performance (reached steady state) as measured by the purging method, but this level was still on the decline in performance as measured by the whipping method. The 0.4% yolk addition may represent a severe case of contamination in the industry.…”

“…One of the major applications of egg white protein is to make foams in various food systems. However, yolk contamination of egg white reduces protein's foaming properties, as quantified by Wang and Wang1 and described by many others in the past. Such contamination may not be completely avoidable, as indicated by sampling of the commercial products in comparison to the laboratory hand‐separated egg white for foaming performance testing.…”

“…A whipping method described by Wang and Wang1 was used. Briefly, whipping was performed at a speed setting of 10 (400 rpm) for 90 s with a KitchenAid mixer with a wire whip attachment.…”

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“…Wang and Wang (2009a) reported that the neutral lipid fraction (triacylglycerols) reduced foaming capacity at levels as low as 0.022% (w/w), but polar lipids had no effect at levels as high as 0.1%. Of the factors examined (pumping, pasteurization, storage), yolk contamination had the greatest effect on foaming performance.…”