Study on Exopolysaccharide and Probiotic-Rich Yogurt Production
Date Issued
2008
Date
2008
Author(s)
Lin, Chia-Chun
Abstract
Exopolysaccharides (EPS) of lactic acid bacteria are polysaccharides secreted extracellularly by lactic acid bacteria. Several advantages of producing exopolysaccharide by lactic acid bacteria include GRAS nature of the organisms and the enhanced consistency and texture of the products by EPS. However, low EPS yield limited the commercial use of lactic acid bacteria on EPS production. The objective of this study, therefore, was to investigate the effects of lactic acid bacteria and incubation temperature on EPS production for producing EPS and probiotic-rich yogurt. Each of the 4 culture strains including (A) 5% yogurt bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus), (B) 5% yogurt bacteria and 5% ropy L. helveticus BCRC14030, (C) 5% yogurt bacteria and 5% probiotics (L. acidophilus , Bifidobacterium bifidum and L. casei), and (D) 5% yogurt bacteria, 5% ropy L. helveticus BCRC14030, and 5% probiotics was inoculated into a reconstituted milk containing 17% dried milk powder. After incubated at 30, 40, and 50oC until pH reaching 4.6±0.1, the fermented medium was homogenized to yield stirred yogurt. EPS yield, ropiness value, the composition of monosaccharide, viscosity of fermented medium, vible count, syneresis and sensory evaluation were analyzed. The highest EPS yield of （0.20-0.60 g/L） was observed at 30 and 40 ℃. However, no significant difference in EPS production was found among four different culture strains. The syneresis of yogurt was severe at 50℃. Highest ropiness value of EPS (96 cm) was found in the yogurt inoculated with yogurt bacteria and L. helveticus BCRC14030 at 30oC. Treatment D was fermented under 30,40 and 50℃, and the results showed that treatment D had higher EPS ropiness value than treatment A Under 30℃ of fermentation, the viscosity of treatment B were not significantly higher than treatment A (P > 0.05), but was significantly higher than the treatment E.nder 30℃,40 and 50℃ of fermentation, probiotic counts did not decrease in treatments C and D during 15 days of storage. However, the viable count of L. elveticus BCRC 14030 decreased in treatment B. In addition, the viable counts of neither probiotics nor L. helveticus BCRC 14030 changed in treatment D during storage. In sensory evaluation, mouth thickness of treatments B,C and D were better than commercial yoghurt. Treatments A, C, D and commercial yoghurt had acceptable. In conclusion, inoculation of yogurt bacteria, L. helveticus BCRC 14030 and probiotics with a reconstituted milk and incubated at 30℃ produced the highest EPS yield, ropiness value and probiotic counts, and lowest degree of syneresis, therefore, was suggested for EPS and probiotic-rich yogurt production.
Subjects
exopolysaccharide
probiotic
yogurt
lactic acid bacteria
syneresis
Type
thesis
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