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Emulsifying and foaming properties of transglutaminase-treated wheat gluten hydrolysate as influenced by pH, temperature and salt

Agyare, Kingsley K., Addo, Kwaku, Xiong, Youling L.
Food hydrocolloids 2009 v.23 no.1 pp. 72-81
wheat gluten, emulsifying properties, foaming properties, enzymatic treatment, protein-glutamine gamma-glutamyltransferase, protein hydrolysates, alkalinity, acidity, food processing quality, foaming capacity, solubility, electrostatic interactions
Hydrolyzed wheat gluten (GH, 77-85% protein) was prepared by limited hydrolysis with chymotrypsin at 37°C for 4h (degree of hydrolysis=6.4%) and 15h (degree of hydrolysis=10.3%). The effect of microbial transglutaminase (MTGase) treatment (55°C for 1h, or 5°C for 18h) on the emulsifying and foaming properties of GH was evaluated under selected food processing conditions (pH 4.0 and 6.5, 0 and 0.6M NaCl, and temperature 20 and 5°C). At pH 4.0 and 0M NaCl the MTGase treatment substantially increased foaming capacity (FC) of GH compared with their respective control GH samples, as a result of enhanced peptide adsorption to the air-water interface, but FC was similar for both control and MTGase-treated GH at pH 6.5. In contrast, foam drainage stability (FS) of MTGase-treated GH decreased at pH 4.0, but increased significantly (P<0.05) at pH 6.5 when compared with their respective control GH samples. The FC and FS were affected by 0.6M NaCl in a pH-dependent manner. The MTGase treatments increased emulsion activity index up to 15-fold at pH 6.5, while emulsion stability index was influenced by emulsion temperature and ionic strength conditions. The MTGase-induced changes in functional properties of GH were attributed to pH-dependent solubility changes, the amphiphilic nature of gluten peptides and increased electrostatic repulsion resulting from deamidation.