Egg white drying: Influence of industrial processing steps on protein structure and functionalities

Spray-dried egg white is commonly used as a food ingredient for its foaming and gelling properties. However, these properties are obtained thanks to dry-heating of egg white powder, which is necessary to offset the harmful effects of spray-drying process on egg white functionality. The purpose of the present work is to identify the processing steps responsible for the damages to egg white functional properties, and to understand the mechanisms that occur in order to limit these effects and to reduce dry-heating time. Two trials were performed and the measurements of egg white protein conformation and gel firmness were significantly different from one trial to another, thus emphasizing great variations in raw material characteristics. In spite of this trial effect, processing steps significantly modified egg white foaming properties. The most critical step was the spray-drying one that strongly damaged foaming properties. During this step, heat transfers and air–product interface area rather than shear rates were responsible for these changes. Then, it was the pumping and filtering steps that had also a considerable effect, due to the generation of shear rates and stainless steel–product interfaces, responsible for foaming property damages. On the other hand, concentration and desugarization steps had an interesting improving effect on egg white foaming properties.