A TRIAL FOR IMPROVING QUALITY OF BIO-YOGHURT USING TRANSGLUTAMINASE | ||
| Journal of Food and Dairy Sciences | ||
| Article 3, Volume 2, Issue 7, July 2011, Pages 345-356 PDF (528.32 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jfds.2011.81958 | ||
| Authors | ||
| Azza M. El-Baz; Manal A. Naeim | ||
| 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. | ||
| Keywords | ||
| Transglutaminase; Bifidobacteria; Bio-yoghurt | ||
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