TEMPERATURES IN EGG PRODUCT FOAMS DURING VAT PASTEURIZATION

SUMMARY– Most egg products are pasteurized in continuous‐flow equipment, but small quantities are more economically processed in a vat pasteurizer. By insulating itself, the surface foam in the vat process may be below pasteurization temperature for a significant part of the holding time and salmonellae in the foam may survive. Using a 100‐gal vat, we generated foams on 5 egg products and measured foam temperatures during pasteurization. Maximum jacket temperature was held to 160°F and no product burn‐on was observed in the vat. All products were held above their respective pasteurization temperatures for 30 min. The minimum temperature of a 6.5‐in. liquid whole egg foam was below pasteurization temperature for 11 min after start of pasteurization. The delayed heating effect of a 1‐in. foam on sugared yolk (10% sucrose by weight) was 13 min. Yolk and salted yolk (10% salt by weight) foams were below liquid temperature during heating; however, in both cases liquid and foam reached pasteurization temperature simultaneously. Minimum temperature of plain egg white foam (pH 9.0) did not reach pasteurization temperature during the holding period. In vat pasteurization, the holding time begins when the liquid reaches pasteurization temperature, and the holding time should be long enough for both foam heating and pasteurization of foam. Except for egg white, about 15 min was required to heat foam to pasteurization temperature. Adding 15 min for pasteurization of the foam yielded a total holding time of 30 min, with the temperature of pasteurization established on the basis of the 15‐min holding time for the foam as follows: liquid whole egg, 133°F; yolk and yolk blends, 135°F; sugared and salted yolk, 139°F. With egg white, foam heating times were in excess of 30 min, and vat pasteurization, with a holding time of 30 min, was not effective.