Consequences of superfine grinding treatment on structure, physicochemical and rheological properties of transglutaminase-crosslinked whey protein isolate

Impacts of superfine grinding treatment (0, 2, 4, 6, 8 or 10 h) on structure, physicochemical and rheological properties of transglutaminase (TGase)-crosslinked whey protein isolate (WPI) were investigated. Size exclusion chromatography showed that high molecular weight polymers were formed in TGase-treated sWPI (WPI treated with superfine grinding), whereas its consumption of free amino groups reached the maximum at grinding 8 h and 10 h. With the milling time extended from 0 to 10 h, particle size of the TGase-crosslinked sWPI gradually increased. Emission spectrum shifted from 338.6 nm to 340.6 nm after sWPI treated with TGase. Meanwhile, TGase-crosslinked sWPI had higher apparent viscosity, emulsifying properties than TGase-crosslinked WPI, but the solubility of TGase-crosslinked sWPI was lower than sWPI. Superfine grinding treatment remarkably increased beta-sheet and random compositions in TGase-crosslinked sWPI. These findings indicated that superfine grinding treatment could enhance the TGase cross-linking degree, and improve rheological properties in TGase-crosslinked WPI.