Abstract
Microbial transglutaminase (MTGase) was isolated from the bacteria Streptoverticillium mobaraense and used to improve the yield and properties of soft cheese manufactured from cow milk by enhancing the cross-linking reaction among milk proteins. The enzyme was applied at different concentrations and at various addition times. Results indicated that the addition of the enzyme before rennet prevented milk coagulation while the simultaneous addition of MTGase and the rennet significantly decreased curd strength and cheese hardness and increased the loss of proteins and fat in the whey. It was found that the most suitable way of adding the enzyme was after coagulation and curd cutting. This treatment enhanced the cross-linking of whey proteins with the curd proteins which was proportional to the concentration of the added enzyme up to 60 enzyme units/liter. The cross-linking reaction was verified by SDS-PAG electrophoresis experiment which showed a high molecular weight band accompanied by a decrease in the density of αs-casein, β-casein and whey proteins bands. Transglutaminase affected the produced cheese composition noticeably by increasing protein content, total solids and decreasing the protein content of the whey. Sensory evaluation of the obtained product showed that the enzyme treated cheese was superior to the untreated cheese throughout all storage period (8 days).
