El-Baz, A., Naeim, M. (2011). A TRIAL FOR IMPROVING QUALITY OF BIO-YOGHURT USING TRANSGLUTAMINASE. Journal of Food and Dairy Sciences, 2(7), 345-356. doi: 10.21608/jfds.2011.81958
Azza M. El-Baz; Manal A. Naeim. "A TRIAL FOR IMPROVING QUALITY OF BIO-YOGHURT USING TRANSGLUTAMINASE". Journal of Food and Dairy Sciences, 2, 7, 2011, 345-356. doi: 10.21608/jfds.2011.81958
El-Baz, A., Naeim, M. (2011). 'A TRIAL FOR IMPROVING QUALITY OF BIO-YOGHURT USING TRANSGLUTAMINASE', Journal of Food and Dairy Sciences, 2(7), pp. 345-356. doi: 10.21608/jfds.2011.81958
El-Baz, A., Naeim, M. A TRIAL FOR IMPROVING QUALITY OF BIO-YOGHURT USING TRANSGLUTAMINASE. Journal of Food and Dairy Sciences, 2011; 2(7): 345-356. doi: 10.21608/jfds.2011.81958
A TRIAL FOR IMPROVING QUALITY OF BIO-YOGHURT USING TRANSGLUTAMINASE
Dairy Microbiology and Dairy Chemistry Dept., Animal Production Res. Inst., Agric. Res. Center, Egypt.
Abstract
The aim of the present study was to investigate impact of adding transglutaminase (TGase) under different conditions on making bio-yoghurt. The TGase was added before (B) and after (A) heat treatment of milk (92oC/10min), followed by pre-incubation at 40oC (B1, A1) or 50oC (B2, A2) for 1h and inactivation at 80oC/2min. Bio-yoghurt was prepared by inoculation the milk with yoghurt starter and B. infantis (1:1). Chemical properties of the bio-yoghurt were affected by both heat treatment of milk and pre-incubation temperatures of the enzyme. TGase mostly increased values of pH, NPN/TN and TVFA and decreased the acidity values. Viscosity and water holding capacity (WHC) were significantly increased when TGase was added, especially, after heat treatment of milk, followed by pre-incubation at 50oC/1h (A2). The highest WHC values were correlated with minimum susceptibility to syneresis (STS). The control bio-yoghurt had the lowest WHC and the highest STS.
The maximum L. delbrueckii subsp. bulgaricus and B. infantis counts were found in fresh and stored bio-yoghurt made with TGase when added after heat treatment of milk with pre-incubation at 50oC/1h (A2). This increased counts of B. infantis throughout storage period and their populations remained above 107cfu/g.
The higher scores for all sensorial properties were recorded for bio-yoghurt made with TGase added after heat treatment of milk (A1, A2), while the lowest scores were given for the control. Generally, bio-yoghurt of acceptable quality can be made from heated milk (92oC/10min) followed by treatment with TGase (0.07%) with activation of the enzyme at 50oC/1h before fermentation.
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