Physicochemical changes and bitterness of whey protein hydrolysates after transglutaminase cross-linking.

Abstract

Whey protein hydrolysates are widely used in hypoallergenic formulas. The extensive hydrolysis required to reduce the protein antigenic potential frequently generates bitter-tasting peptides. This study investigates the effect of transglutaminase (TG) catalyzed cross-linking on physicochemical characteristics and bitter taste of whey protein hydrolysates. The chromatographic analysis showed a slight increase in the relative concentration of peptides (p < 0.05) with molecular mass of 1.4–3.5 kDa (SEC-HPLC) and changes in peak intensity and peptide hydrophilicity after TG-treatment (RP-HPLC). The MALDI-MS peptide fingerprinting presented changes in relative intensities and suppression of signals after TG-treatment, suggesting that cross-linking occurred, mainly in the m/z 1600–3000 range peptides. Changes in the spatial conformation of peptides after TG-treatment were evidenced by the intrinsic fluorescence of the samples. Despite the changes in the physicochemical characteristics of peptides, no differences (p > 0.05) in the intensity (6–7, on a scale up to 9) and duration (38 s) of the bitterness sensation were observed. Possibly, the presence of free glutamine and the significant amount of short peptides with no glutamine or lysine residue may have decreased the opportunities for cross-linking formation; therefore, the presence of bitter-tasting peptides was unchanged as a consequence of TG-treatment.