Production of highly soluble and functional hydrolysates from sunflower proteins

Abstract: Exploitation of plant proteins as an alternative to animal proteins currently presents an important challenge for food industries. Many processes to produce sunflower protein isolates were reported, but the resulting isolate solubility was usually poor (40%). This is particularly marked at neutral pH, corresponding to the sunflower protein isoelectric point and being also the pH range of many food formulations (sausage, pasta). Limited enzymatic hydrolysis is often implemented to improve the protein solubility. Furthermore, proteolysis reaction can release large peptides promoting the improvement of the protein functional properties. However, according to the reaction advancement and the enzymatic mechanism, the hydrolysates can be composed of small peptides, less effective in reducing interfacial tension and stabilizing the emulsions or foams formed. An appropriate trade-off (solubility/techno-functional properties) may thus be difficult to identify and most of the classical approaches applied in studies to do this are largely empirical. The goal of the present work was to find the appropriate hydrolysis conditions for improving the sunflower protein solubility at neutral pH while maintaining the good techno-functional properties of initial proteins. For this purpose, first we selected the suitable enzymes by analyzing the solubility profile. The individual Alcalase and Prolyve enzymes were chosen. Then, the influence of operating conditions on hydrolysis kinetics and enzymatic mechanism was studied to identify the target hydrolysis conditions and control the hydrolysate compostitions. The chosen conditions were implemented and solubility and techno-functional properties were evaluated. As a result, controlled enzymatic hydrolysis significantly improved the sunflower protein solubility at neutral pH (twofold increase) and generated highly soluble hydrolysates ( >80%). The limited proteolysis also maintained the good foam capacities and even allowed improving the initial foam stabilities and emulsifying capacities and stabilities of sunflower proteins. Our results can greatly the development of sunflower protein products in the future.