Effect of microbial transglutaminase treatment of milk on the quality parameters of labneh during long-term storage

In this study, the effects of different concentrations (1, 2, and 3 U/g protein, namely 1U, 2U, and 3U) of microbial transglutaminase (MTGase) enzyme on the quality parameters of labneh during the storage was investigated. According to the results, enzyme treatment significantly decreased the syneresis from 18.967 (control) to 10.754 (3U group), and lower values were found in the enzyme-containing samples during storage. Moreover, MTGase treatment increased the protein and fat content of labneh samples from 8.99% to 13.47% to 10.53% and 14.27% in the 3U group, compared to control group, and thus, higher total solids were obtained. Although no dramatic changes were observed in the a* and b* values regardless of the MTGase treatment, the L* values have increased as the enzyme concentration increased (from 90.94 to 92.68), which is a positive outcome in terms of consumer acceptability. Moreover, the texture analysis revealed an increase in the hardness of 3U group (267.15 g) compared to the control (142.96 g), along with higher rheological module values. As a result, the acidity development was retarded due to the formation of stronger gel network. In conclusion, the formation of more covalently bonded three-dimensional protein gel structure induced by the MTGase, especially at 2U and 3U groups, was found to delay acidity development, improve the texture and rheology, as well as maintain the texture for at least 30 days compared to the control group, which would positively affect the consumer acceptability and shelf-life.