Effect of initial product temperature and initial pH on foaming time during vacuum evaporation of liquid whole eggs.

During earlier studies on vacuum concentration of liquid egg white, the phenomena of foaming during the initial stages of the process were reported. In these studies, it was also shown that no concentration took place during the foaming period that varied from test to test. To minimize the total process time, this present study was undertaken to investigate what variables contributed to foaming, how they could be controlled, and what effect they had on product quality and functional properties. This study investigated the relationships among initial product temperature, initial pH, and foaming of liquid whole eggs. Two temperatures (9 and 20 C) and three pH levels (6.5, 7.3, and 8.5) were studied using a vacuum evaporation system with a maximum vacuum of 5 kPa. Tests showed that higher initial pH levels had decreased foaming times. At the end of foaming experiments, the liquid whole egg was evaluated to determine the extent of functional property change during foaming. A decrease in foaming time resulted in a decrease in whip time. The cakes made from the processed liquid whole egg had larger volumes than those from the unprocessed control. Furthermore, the liquid whole egg, which foamed the longest, had higher (P < 0.05) cake volumes. Our current experiments also verified our earlier findings that no product concentration takes place during the foaming process.

Relationship of eggshell ultrastructure and shell strength to the soundness of shell eggs.

Factors affecting the soundness of shell eggs are of primary concern to egg processors due to substantial financial losses from cracked and leaker eggs. Ultrastructural analyses were used to examine the palisade layer width and mammillary knob layer thickness of sound, cracked, and leaker eggshells. Subjective observations were also made. There was no significant difference (P > 0.05) in the width of the palisade layer or the mammillary knob layer among sound, cracked, and leaker eggshells. The eggshell strengths of sound, cracked, and leaker eggs were evaluated using puncture force and shell thickness measurements. Sound eggshells were found to have a significantly (P < 0.05) higher mean puncture force (35.3 N) than cracked (30.4 N) and leaker (28.4 N) eggshells. The mean puncture force values for cracked and leaker eggshells were not significantly different from each other (P > 0.05). Regression and correlation analyses indicated a significant correlation (P < 0.01; r = 0.61) between palisade layer width and puncture force. The mean shell thickness values for cracked (0.36 mm) and leaker (0.35 mm) eggs were significantly lower (P < 0.05) than those of sound eggs (0.38 mm), although cracked and leaker eggshell thickness did not differ significantly (P > 0.05). The correlation coefficient between puncture force and shell thickness was significant (P < 0.01; r = 0.56), indicating a possible relationship.