Effects Of MTG On Yoghourt Quality

Transglutarainase(systemticname:protein-glutamine :amine-glutamy transferase, EC2. 3. 2. 13, TGase) catalyses an acyl group transfer between r -carboxyamide group of peptide-bound glutaminyl residues (acyl donor) and the primary amino groups in a variety of amine compounds (acyl acceptor), including peptide-bound ε-amino groups of lysyl residues. As a kind of stabilizer TGase has been proved to be safe to human and widely applied in food industry.The effects of transglutaminase (TGase) on yoghourt quality were studied. The results are as follows:With the addition of TGase, the texture of yoghourts was improved. Yoghourts treated with TGase had a higher hardness, breaking force and chewiness than untreated samples through TPA analysis.TGase treatment of milk prior to fermentation led to prolonged fermentation , while the concomitant use of TGase and starter culture had no influence on fermentation.Post acidification of yoghourt (i. e titratable acidity) during cool storage was lower for products from enzyme-treated milk. This applies both for products cross-linked prior to fermentation with enzyme inactivation and for simultaneous use of culture and TGase without inactivation of the enzyme.Sensory studies revealed that odour and taste properties of products from TG-treated milk were not distinctive from untreated products but showed a slight whey seperation, a shiner surface and a significantly firmer consistency than the control sample. On the other hand, products from TG-treated milk were described as viscosity increased while less skim milk powder was used.During 4 weeks storage at 4-6°C, investigations of assessing microbiological characteristics and on shelf life of stirred yoghourt products after addition of TGase have been analyzed.The result shows that addition of a non-inactivated TGase product has astabilizing effect on the living cell counts of the lactobacilli in the yoghourt product during storage at4-6°C.Because of the formation of casein macropolymer after TGase treatment, the macropolymer molecules were so large that they were unable to penetrate the stacking or the separation gels in SDS-PAGE.Using scanning electron microscopy (SEM), it was found that the casein modified appeared more tight and uniform than the untreated.The TGase treatment resulted in a substantial increase in storage modulus values of casein.