Abstract
In the present study soybean (Glycine max L.) was included in cow and camel milk during fermentation. The resulting soybean-yogurt was evaluated with respect to the changes of post-acidification, viable cell counts (VCC) of Lactobacillus spp. and Streptococcus thermophilus, total phenolic content (TPC) and antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) inhibition assay during 21 days of refrigerated storage. The presence of soybean in fresh cow- and camel-milk yogurts did not affect pH reduction compared to respective plain-yogurt. However, soybean–camel milk yogurt showed significant reduction in pH (4.05 ± 0.06) compared to plain-yogurt 4.35 ± 0.02 on day 7 of storage. Titratable acidity (TA) increased in soybean–cow milk yogurt (p < 0.05) but not in soybean–camel milk yogurt as compared with respective plain-yogurt during period of storage. The presence of soybean in fresh yogurt showed increased (p < 0.05) in Lactobacillus spp. VCC by 10% in cow milk-yogurt and 30% in camel milk-yogurt compared to respective plain-yogurts. On the other hand, VCC of S. thermophilus was higher (p < 0.05) in the presence of soybean in cow milk yogurt than in camel milk yogurt. Soybean–camel milk yogurt had 2-folds higher TPC on day 0 and 7 (149.59 ± 1.8 and 111.44 ± 2.8 μgGAE/ml respectively) than plain-camel milk yogurt (60.04 ± 0.01 and 55.22 ± 0.01 μgGAE/ml respectively). The highest value of TPC in soybean–cow milk-yogurt was showed on day 21 of storage (43.17 ± 1.2 μgGAE/ml). The antioxidant activity increased (p < 0.05) in the presence of soybean in both cow and camel milk yogurts compared to respective controls. The highest antioxidant activity was shown on day 0 for soybean–cow milk yogurt (61.76 ± 2.2%) and day 7 for soybean–camel milk yogurt (53.16 ± 0.1%). In conclusion, the addition of soybean in both cow- and camel-milk yogurts enhanced the viability of LAB and antioxidant activity during refrigerated storage.
บทคัดย่อIn the present study soybean (Glycine max L.) was included in cow and camel milk during fermentation. The resulting soybean-yogurt was evaluated with respect to the changes of post-acidification, viable cell counts (VCC) of Lactobacillus spp. and Streptococcus thermophilus, total phenolic content (TPC) and antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) inhibition assay during 21 days of refrigerated storage. The presence of soybean in fresh cow- and camel-milk yogurts did not affect pH reduction compared to respective plain-yogurt. However, soybean–camel milk yogurt showed significant reduction in pH (4.05 ± 0.06) compared to plain-yogurt 4.35 ± 0.02 on day 7 of storage. Titratable acidity (TA) increased in soybean–cow milk yogurt (p < 0.05) but not in soybean–camel milk yogurt as compared with respective plain-yogurt during period of storage. The presence of soybean in fresh yogurt showed increased (p < 0.05) in Lactobacillus spp. VCC by 10% in cow milk-yogurt and 30% in camel milk-yogurt compared to respective plain-yogurts. On the other hand, VCC of S. thermophilus was higher (p < 0.05) in the presence of soybean in cow milk yogurt than in camel milk yogurt. Soybean–camel milk yogurt had 2-folds higher TPC on day 0 and 7 (149.59 ± 1.8 and 111.44 ± 2.8 μgGAE/ml respectively) than plain-camel milk yogurt (60.04 ± 0.01 and 55.22 ± 0.01 μgGAE/ml respectively). The highest value of TPC in soybean–cow milk-yogurt was showed on day 21 of storage (43.17 ± 1.2 μgGAE/ml). The antioxidant activity increased (p < 0.05) in the presence of soybean in both cow and camel milk yogurts compared to respective controls. The highest antioxidant activity was shown on day 0 for soybean–cow milk yogurt (61.76 ± 2.2%) and day 7 for soybean–camel milk yogurt (53.16 ± 0.1%). In conclusion, the addition of soybean in both cow- and camel-milk yogurts enhanced the viability of LAB and antioxidant activity during refrigerated storage.
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