Use of food-grade proteases to recover umami protein-peptide mixtures from rice middlings

The effects of enzymatic hydrolysis induced by food-grade exo- plus endo-proteases (i.e. Umamizyme and Flavourzyme) on the sensory characteristics and functional properties of rice middlings were investigated. Enzymatic hydrolysis was confirmed by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE), by monitoring the rate of hydrolysis with the Coefficient of Protein Degradation (CPD). The presence of medium-low size polypeptides at the end point of 24 h was detected, resulting from 24.84 ± 1.28 % and 67.04 ± 0.55 % hydrolysis for Flavourzyme and Umamyzyme, respectively. Sensory and functional properties, including emulsifying and foaming properties, were evaluated on hydrolysates obtained after 24 h incubation. The sensory analysis described the umami taste as the most intense attribute for all the products and good emulsifying and foaming properties were observed, mainly in Umamizyme hydrolysates. Then the hydrolysis procedure here described could be convenient to provide ingredients characterized by a good taste profile and by functional properties useful for industrial food processing, storage and consumption.

► A new method to obtain peptides with umami taste from rice middlings is described. ► Proteins are extracted and hydrolyzed in a single step using food-grade proteases. ► Hydrolysates show a high umami taste and flavor enhancer properties. ► Good emulsifying and foaming properties promote industrial applications.