Fermentation of Calcium-Fortified Soymilk with Lactobacillus: Effects on Calcium Solubility, Isoflavone Conversion, and Production of Organic Acids

Authors

  • A.L. Tang,

    1. Authors Tang and Stojanovska are with School of Biomedical Sciences, Victoria Univ., St. Albans Campus, P.O Box 14428, Melbourne, VIC 8001, Australia. Author Shah is with School of Molecular Sciences, Victoria Univ., Werribee Campus, P.O. Box 14428, Melbourne, VIC 8001, Australia. Author Wilcox is with Clinical Nutrition and Metabolism Unit, Monash Medical Centre, Clayton, VIC 3168, Australia. Author Walker is with Preventative Cardiology Unit, Baker Heart Research Inst. and Dept. of Dietetics, Monash Univ., Clayton, VIC 3168, Australia. Direct inquiries to author Shah (E-mail: nagendra.shah@vu.edu.au).
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  • N.P. Shah,

    1. Authors Tang and Stojanovska are with School of Biomedical Sciences, Victoria Univ., St. Albans Campus, P.O Box 14428, Melbourne, VIC 8001, Australia. Author Shah is with School of Molecular Sciences, Victoria Univ., Werribee Campus, P.O. Box 14428, Melbourne, VIC 8001, Australia. Author Wilcox is with Clinical Nutrition and Metabolism Unit, Monash Medical Centre, Clayton, VIC 3168, Australia. Author Walker is with Preventative Cardiology Unit, Baker Heart Research Inst. and Dept. of Dietetics, Monash Univ., Clayton, VIC 3168, Australia. Direct inquiries to author Shah (E-mail: nagendra.shah@vu.edu.au).
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  • G. Wilcox,

    1. Authors Tang and Stojanovska are with School of Biomedical Sciences, Victoria Univ., St. Albans Campus, P.O Box 14428, Melbourne, VIC 8001, Australia. Author Shah is with School of Molecular Sciences, Victoria Univ., Werribee Campus, P.O. Box 14428, Melbourne, VIC 8001, Australia. Author Wilcox is with Clinical Nutrition and Metabolism Unit, Monash Medical Centre, Clayton, VIC 3168, Australia. Author Walker is with Preventative Cardiology Unit, Baker Heart Research Inst. and Dept. of Dietetics, Monash Univ., Clayton, VIC 3168, Australia. Direct inquiries to author Shah (E-mail: nagendra.shah@vu.edu.au).
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  • K.Z. Walker,

    1. Authors Tang and Stojanovska are with School of Biomedical Sciences, Victoria Univ., St. Albans Campus, P.O Box 14428, Melbourne, VIC 8001, Australia. Author Shah is with School of Molecular Sciences, Victoria Univ., Werribee Campus, P.O. Box 14428, Melbourne, VIC 8001, Australia. Author Wilcox is with Clinical Nutrition and Metabolism Unit, Monash Medical Centre, Clayton, VIC 3168, Australia. Author Walker is with Preventative Cardiology Unit, Baker Heart Research Inst. and Dept. of Dietetics, Monash Univ., Clayton, VIC 3168, Australia. Direct inquiries to author Shah (E-mail: nagendra.shah@vu.edu.au).
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  • L. Stojanovska

    1. Authors Tang and Stojanovska are with School of Biomedical Sciences, Victoria Univ., St. Albans Campus, P.O Box 14428, Melbourne, VIC 8001, Australia. Author Shah is with School of Molecular Sciences, Victoria Univ., Werribee Campus, P.O. Box 14428, Melbourne, VIC 8001, Australia. Author Wilcox is with Clinical Nutrition and Metabolism Unit, Monash Medical Centre, Clayton, VIC 3168, Australia. Author Walker is with Preventative Cardiology Unit, Baker Heart Research Inst. and Dept. of Dietetics, Monash Univ., Clayton, VIC 3168, Australia. Direct inquiries to author Shah (E-mail: nagendra.shah@vu.edu.au).
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Abstract

ABSTRACT:  The objective of this study was to enhance calcium solubility and bioavailability from calcium-fortified soymilk by fermentation with 7 strains of Lactobacillus, namely, L. acidophilus ATCC 4962, ATCC33200, ATCC 4356, ATCC 4461, L. casei ASCC 290, L. plantarum ASCC 276, and L. fermentum VRI-003. The parameters that were used are viability, pH, calcium solubility, organic acid, and biologically active isoflavone aglycone content. Calcium-fortified soymilk made from soy protein isolate was inoculated with these probiotic strains, incubated for 24 h at 37 °C, then stored for 14 d at 4 °C. Soluble calcium was measured using atomic absorption spectrophotometry (AA). Organic acids and bioactive isoflavone aglycones, including diadzein, genistein, and glycetein, were measured using HPLC. Viability of the strains in the fermented calcium-fortified soymilk was > 8.5 log10 CFU/g after 24 h fermentation and this was maintained for 14-d storage at 4 °C. After 24 h, there was a significant increase (P < 0.05) in soluble calcium. L. acidophilus ATCC 4962 and L. casei ASCC 290 demonstrated the highest increase with 89.3% and 87.0% soluble calcium after 24 h, respectively. The increase in calcium solubility observed was related to lowered pH associated with production of lactic and acetic acids. Fermentation significantly increased (P < 0.05) the level of conversion of isoflavones into biologically active aglycones, including diadzein, genistein, and glycetein. Our results show that fermenting calcium-fortified soymilk with the selected probiotics can potentially enhance the calcium bioavailability of calcium-fortified soymilk due to increased calcium solubility and bioactive isoflavone aglycone enrichment.

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