Transglutaminase-induced chemical and rheological properties of cheese

Ca2+-independent transglutaminase isolated from Streptoverticillium mobaraense was used to obtain a novel cheese we called “crosslinked cheese.” We characterized both the cheese obtained by adding transglutaminase and milk clotting enzyme at the same time, and the one produced by adding transglutaminase, following cutting of the coagulum. In both cases, water content and cheese yields were higher, whereas protein content significantly increased from 33.8% to 39.5% only in the second type of crosslinked cheese. Isoelectric focusing of the protein extracted from the prepared cheese samples on a thin layer of polyacrylamide gel indicated that mainly β-caseins were involved in the transglutaminase-catalyzed crosslinks occurring in the curd. Few αs1-casein isoforms were entrapped in the curd matrix only when transglutaminase was added at the same time as the coagulant enzyme. Soluble nitrogen determination and HPLC peptide analysis indicated a markedly reduced proteolysis of crosslinked cheese during ripening, probably responsible for the observed enhancement of their hardness in comparison with the control cheese, obtained in the absence of transglutaminase.