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Performance of Starter in Yogurt Supplemented with Soy Protein Isolate and Biotransformation of Isoflavones during Storage Period
Author(s) -
Pham Thuy T.,
Shah Nagendra P.
Publication year - 2009
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1750-3841.2009.01141.x
Subject(s) - starter , streptococcus thermophilus , food science , chemistry , lactic acid , fermentation , lactobacillus , lactose , acetic acid , isoflavones , soy protein , bacteria , biochemistry , biology , genetics
In this study, soy protein isolate (SPI) (4%, v/w) was supplemented to the yogurt mix to increase the amount of biologically active isoflavone in yogurt (SY). The control yogurt was without any SPI supplementation (USY). The supplementation significantly ( P < 0.05) increased the lactose metabolism by the yogurt starter including Lactobacillus delbrueckii ssp. bulgaricus ATCC 11842 (Lb 11842) and Streptococcus thermophilus ST 1342 (ST 1342) during the fermentation process by 4.7%. The starter produced more acetic acid and less lactic acid in SY than that in USY and altered the ratio of lactic and acetic acid during the entire storage period. The viability of both Lb 11842 and ST 1342 in SY was significantly ( P < 0.05) lower than that in USY from 14 d of the storage period, however, their concentration still remained high (8.11 to 8.84 log CFU/g). The starter transformed 72.8% of total inactive isoflavone glycosides (IG) to active isoflavone aglycones (IA), increasing the IA content from 1.35 to 15.01 mg/100 g sample. During the storage period, IA concentration slowly rose from 15.02 to 15.51 mg/100 g sample.