Pretreatment with citric acid or a mixture of nitric acid and citric acid to suppress egg white protein deposit formation on stainless steel surfaces and to ease its removal during cleaning

Fouling, adhesion of protein onto a food contact surface, is an important difficulty hindering the pasteurization processing of egg products. To explore a strategy for efficient cleaning of a food contact surface fouled by adherent egg protein, this study investigated the effects of stainless steel surface pretreatment with citric acid or a mixture of nitric acid and citric acid on the adhesion and removability of egg white protein. The 1.05% citric acid pretreatment for 120 min was effective to suppress egg white protein adhesion to a stainless steel surface at 30-80 °C. Pretreatment with nitric acid (1.05% or 4.55%) containing 1.05% citric acid was also effective at 60 °C, which is relevant as a practical pasteurization temperature of egg products. Reducing the pretreatment time from 120 to 15 min was still effective to suppress egg white protein adhesion significantly. Pretreatment with 1.05% nitric acid containing 1.05% citric acid caused higher removability of adhered protein during the cleaning process, especially at higher temperatures. These results demonstrate that pretreatment with nitric acid containing citric acid might be an excellent choice for promoting the efficient cleaning of food manufacturing equipment that has been fouled with egg products.