UVM Theses and Dissertations
Format:
Print
Author:
Wang, Wenbo
Dept./Program:
Nutritional and Food Sciences
Year:
2010
Degree:
MS
Abstract:
It is difficult to produce goat's milk yogurt with consistency comparable to cow's milk yogurt. In the present study, probiotic goat's milk yogurt was prepared using a commercial starter culture containing Lactobacillus bulgaricus (L. bulgarlcus) and Streptococcus thermophilus (s. thermophilus), probiotics, Lactobacillus acidophilus (L. acidophilus), Lactobacillus easel (L. easel) and b{fzdobacterlum, and gellation agents, polymerized whey protein (PWP, 0.4%) and pectin (0.3%). Cow's milk yogurt was also prepared as a control. Both yogurts were analyzed for chemical composition, mold and yeast counts, changes in pH, titratable acidity (TA), and viscosity, and probiotic survivability during storage.
The gross composition of both goat's and cow's milk yogurts were: total solids: 11.83 ± 0.23% and 12.40 ± 0.09%; fat: 2.81 ± 0.23% and 2.52 ± 0.33%; protein: 3.40 ±0.05% and 3.42 ±0.16%; carbohydrates: 4.77 ± 0.42% and 5.71 ± 0.41 %; ash: 0.84 ± 0.03% and 0.74 ± 0.01 %, respectively. Syneresis of goat's milk yogurt was significantly decreased by addition of PWP (0.4%). There was no significant difference (P =0.0876) in viscosity during the 12-week storage. TA and pH both showed significant difference (P <0.0001) over the 12 weeks. Both L. easel and bi/idobacterlum remained viable and their populations were above 106 colony-forming units (CFU)/g during storage.
However, there were no viable counts of L. acldophilus by the fourth week for goat's milk yogurt and by the seventh week for cow's milk yogurt. Both mold and yeast were not detected in the products. Scanning electron microscopy (SEM) analysis for the microstructure of goat's milk yogurt showed that PWP interacted with casein micelles to form a comprehensive network in the yogurt gel. The results indicated that PWP may be a novel protein-based thickening agent for improving the consistency of goat's milk yogurt and other products alike.
The gross composition of both goat's and cow's milk yogurts were: total solids: 11.83 ± 0.23% and 12.40 ± 0.09%; fat: 2.81 ± 0.23% and 2.52 ± 0.33%; protein: 3.40 ±0.05% and 3.42 ±0.16%; carbohydrates: 4.77 ± 0.42% and 5.71 ± 0.41 %; ash: 0.84 ± 0.03% and 0.74 ± 0.01 %, respectively. Syneresis of goat's milk yogurt was significantly decreased by addition of PWP (0.4%). There was no significant difference (P =0.0876) in viscosity during the 12-week storage. TA and pH both showed significant difference (P <0.0001) over the 12 weeks. Both L. easel and bi/idobacterlum remained viable and their populations were above 106 colony-forming units (CFU)/g during storage.
However, there were no viable counts of L. acldophilus by the fourth week for goat's milk yogurt and by the seventh week for cow's milk yogurt. Both mold and yeast were not detected in the products. Scanning electron microscopy (SEM) analysis for the microstructure of goat's milk yogurt showed that PWP interacted with casein micelles to form a comprehensive network in the yogurt gel. The results indicated that PWP may be a novel protein-based thickening agent for improving the consistency of goat's milk yogurt and other products alike.