The Influence of Selected Prebiotics on the Growth of Lactic Acid Bacteria in the Bio-yogurt Production

Tan, Boon Kun (2019) The Influence of Selected Prebiotics on the Growth of Lactic Acid Bacteria in the Bio-yogurt Production. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

A study of types of prebiotics (inulin, FOS and basil seed gum) in the production of bio-yogurts was conducted with the use of two main ingredients: fresh milk and starter culture obtained from commercial yogurt product. Three different concentrations of selected prebiotics (Inulin and FOS: 1-3% w/v; Basil seed gum: 0.1-0.3% w/v) were used to conduct formulation trials and analysis tests in triplicates. Responses collected included pH, total soluble solids (oBrix), total titratable acidity (%), syneresis (%), viscosity (cP), total sugar content (g/100 mL), viable cell count, proximate analysis and sensory evaluation (Quantitative Descriptive Analysis (QDA), hedonic test and ranking test). The results showed that pH dropped after the addition of prebiotics whereas the total soluble solid and total sugar content increased with the increasing concentration of prebiotics except for basil seed gum. Total titratable acidity increased significantly with the addition of basil seed gum from 0.90±0.02% lactic acid equivalent to 1.02±0.10%. Prebiotics addition increased the syneresis and viscosity of the bio-yogurts yet these rheological measurement decreased as the concentration of prebiotics increased. Inulin was found to be less effect in promoting the growth and viability of Lactobacillus bulgaricus but significantly increased the viability of Streptococcus thermophilus. In contrast, FOS was found to be less effect in promoting the growth and viability of Streptococcus thermophilus but significantly increased the viability of Lactobacillus bulgaricus. Basil seed gum can be alternative choice for prebiotic as it improved the viability of both probiotic bacteria from 6.38±0.03 log CFU/ml to the range of 7.24±0.05 to 7.67±0.03 log CFU/ml for Lactobacillus bulgaricus and from 9.34±0.03 log CFU/ml to 11.25±0.03 log CFU/ml for Streptococcus thermophilus with the concentration of 0.1% (w/v). QDA was conducted based on the fermented samples’ appearance, aroma, taste and mouthfeel and significant changes (p<0.05) in sweetness (FOS 3% w/v, BSG 0.1-0.3% w/v) were detected by the trained panels. Hedonic test shown that commercial product acquired the highest overall acceptability with the score of 5.67±0.60 followed by FOS 3% (w/v) sample with the score of 5.15±1.22. In ranking test, there were 43% of panels ranked commercial product as most preferred followed by 40% of panels ranked samples with FOS 3% (w/v) as most preferred.