University of Limerick, Limerick, Ireland
High protein content dairy ingredients are routinely produced in the food industry. During production, these ingredients are evaporated prior to spray-drying. A limitation in drying efficiency is the viscosity associated with high total solids evaporates. Selective enzymatic protein hydrolysis can be used to reduce viscosity thereby increasing the total solids in the evaporate which may be presented to the dryer. The aim of this work was to study the change in viscosity of whey protein concentrate (WPC 80% protein) selectively hydrolysed using food-grade enzymes and to investigate the effect of spray-drying, if any, on enzyme inactivation and nutritional quality. WPC at 10% (w/v) total solids was hydrolysed with 3 different enzyme preparations at an enzyme:substrate of 0.5% at 50°C for 4h. The viscosity and gelation temperature of the hydrolysates (WPHs) were determined with a viscometer and a rheometer. The WPHs were spray-dried at an inlet temperature of 180 and 200°C. The degree of hydrolysis (DH%), protein quality and residual enzyme activity (RA%) were determined using the 2,4,6-trinitrobenzenesulfonic acid, Kjeldahl nitrogen estimation and azocasein methods, respectively. The DH of the WPHs ranged from 3 to 11%. Hydrolysis resulted in a maximal decrease of 17% in viscosity compared to WPC and had a minimal effect on gelation temperature. The protein nitrogen content did not change with spray-drying. The RA was unaffected for WPHs generated with two of the enzymes, whereas one WPH showed a decrease of 11 and 20%, respectively, for evaporates spray dried at inlet temperatures of 180 and 200°C. In conclusion, enzymatic hydrolysis of WPC with selected food-grade enzymes reduces the viscosity of high protein solutions and the spray-drying process led to a small decrease in hydrolysate RA depending on the hydrolytic enzyme preparation used.
Dr. Miryam Amigo-Benavent obtained her BSC degrees in Biology and Food Science and Technology in Madrid (Spain), where she also completed her PhD in Food Science and Technology in 2009. She worked as a postdoctoral researcher for the Institute of Food Science Research and the Institute of Food Science, Technology and Nutrition (CSIC). Since 2015, she is a postdoctoral researcher working at the University of Limerick (Ireland). Her research topics include the study of peptides, proteins and polyphenols with biological activity (antioxidant capacity, insulin and muscle protein synthesis regulation, among others) using cell models and human studies. In 2018, she joined the Dairy Processing Technology Centre at the University of Limerick where she is studying the effect of enzymatic hydrolysis to increase energy efficiency during drying of dairy protein ingredients.