Effect of basil seed gum and its hydrolyzed oligosaccharides on yogurt culture growth and yogurt quality : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Auckland, New Zealand
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Date
2025
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Massey University
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Abstract
Basil seeds are surrounded with a mucilage layer that has a remarkable swelling index in water and a high-water holding capacity. Basil seed gum (BSG) from this mucilage layer is a potential novel stabilizer for the food industry. The heterogeneous structure of BSG can affect digestibility in the body but it brings health benefits, such as balancing blood sugar levels, blood cholesterol and weight management, and is a good source of dietary fibre. The primary objective of this study was to examine the effects of basil seed gum (BSG) extracted from RO water in yogurt production. Secondly, it aimed to investigate the influence of enzyme-hydrolyzed BSG oligosaccharides on yogurt cultures and yogurt quality. Additionally, the study explored the use of erythritol as a sucrose replacement in yogurt production and its potential effects. Overall, this research examines the potential of BSG and its oligosaccharides as functional ingredients for enhancing yogurt production. The gum layer was successfully extracted in RO water instead of alkaline water, with a dry gum yield of 24.27 ± 0.64% at 50ºC, 1000 rpm for 2 h. BSG added at 0.06% to yogurt fermentation improved gel stability and water-holding capacity in yogurt samples but did not enhance the growth of YO-MIX® 726 yogurt cultures. BSG-oligosaccharides obtained through hydrolysis with xylanase in RO water under optimal conditions (E/S 2, 4 h, 65ºC) significantly improved the growth parameters of YO-MIX® 726 Lactobacillus acidophilus. The highest cell density (Max) of 1.02 OD₅₉₅ₙₘ was observed at 4% BSG-Oligosaccharides with maximum growth rate (µMax) at 0.10 h⁻¹ , compared to the control with 0.29 OD595nm and 0.06 h⁻¹, respectively. However, the highest prebiotic score (0.53) was observed at 3% of BSG-Oligosaccharides obtained from xylanase hydrolysis in RO water. BSG-Oligosaccharides enhanced the growth of YO-MIX® 726 probiotics at a concentration 1.5% and strongly protected cell survival after 21-Day shelf-life storage at 4ºC. Meanwhile, erythritol had no significant effect on yogurt quality or the yogurt cultures at ≤ 8%. A novel yogurt formulation containing 0.03% water-extracted BSG, 1.5% BSG Oligosaccharides from xylanase-hydrolyzed BSG in water, and 4% erythritol as a sugar substitute demonstrated reduced whey separation, improved bacterial growth, and enhanced probiotic survival. This product shows promise as a low-glycaemic, probiotic functional food with potential prebiotic benefits.
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Figures 2.1, 2.3 and 2.4 are reproduced with permission.