Restoring the rennetability of transglutaminase-treated casein micelles

Treatment of milk with the cross-linking enzyme transglutaminase (TGase) has many beneficial effects on the functionality of milk proteins. However, applications for TGase thus far lie outside cheesemaking, as treatment with TGase impairs rennet coagulation of milk. Therefore, strategies to restore the rennet-induced coagulation of TGase-treated milk were studied. Renneting was monitored by diffusing wave spectroscopy. Adding CaCl₂ (5 or 10 mmol L-1 ) or ethanol (5 or 10%, v/v) improved the rennetability of TGase treated milk, with the former far more efficient than the latter. The CaCl2- and ethanol-induced improvement of renneting of TGase-treated milk further supports the hypothesis that TGase-induced impaired rennet coagulation of milk is primarily due to effects of TGase treatment on the aggregation of para-casein micelles.