Changes in rheological behaviour and functional properties of hen’s egg yolk induced by processing and fermentation with phospholipases

Summary Functional changes of hen’s egg yolk rheological behaviour as a result of processing (pasteurisation, freeze‐drying) and modifying its phospholipids using phospholipase A 1 (PLA 1 ) and phospholipase A 2 (PLA 2 ) were studied. It could be shown how fermentation with phospholipases affects the different steps of heat‐induced gelation of egg yolk. As a consequence of fermentation of native yolk with 0.1% PLA 1 , the first viscosity maximum was shifted from 79 to 97 °C. In fermented pasteurised yolk, the homogenous gel‐like consistency from the first viscosity maximum was even stabilised up to 100 °C. The second viscosity ascent, which indicates solid gel structures (caused by aggregation of denatured proteins), was prevented entirely. In contrast to pancreatic PLA 2 , fermentation of egg yolk with microbial PLA 1 resulted in a hydrolysis of approximately 78% of phosphatidylethanolamine and a significant change in flow behaviour (of yolk solutions).