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Metabolite Profile of Lactic Acid-Fermented Soymilk

Traditional soy foods produced in Asia are known to have lipid metabolism-modulating effects. Soy protein and isoflavones are the major bioactive components in soy foods. Clinical analyses and meta-analyses have demonstrated the lipid metabolism-modulating effects of combined isoflavones and soy protein.

Soymilk is the simplest soy food, but some individuals find the flavor unpalatable. Thus, we used soymilk fermented by lactic acid bacteria of vegetable origin to make its flavor more palatable. Lactic acid fermentation converts the isoflavone glycosides in soymilk to isoflavone aglycones, enhancing their absorption in the intestine. Previous studies have shown that isoflavone aglycone-rich soymilk fermented by Lactobacillus delbrueckii subsp. delbrueckii, strain TUA-4408L (F4408) has stronger lipid metabolism-modulating effects than isoflavone aglycone-poor soymilk fermented by Lactobacillus delbrueckii subsp. delbrueckii, strain TUA-4404L (F4404). As such, fermentation products other than isoflavone aglycones may also exert lipid metabolism-modulating effects. Therefore, the present study aimed to compare the metabolites in soymilk (SM), F4404, and F4408 via a metabolomics approach.

In the study, two fermented soymilk products were prepared from soymilk via lactic acid fermentation for 15 h using Lactobacillus delbrueckii subsp. delbrueckii, strain TUA-4404L (F4404) or TUA-4408L (F4408). The soymilk metabolome analyses were carried out at Human Metabolome Technologies Inc. (HMT, Tsuruoka, Japan). Capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) was carried out using an Agilent CE Capillary Electrophoresis System. Liquid chromatography-time-of-flight mass spectrometry (LC-TOFMS) was carried out using an Agilent 1200 series RRLC System SL equipped with an Agilent LC/MSD TOF (Agilent Technologies). Mass spectrometry (MS) analysis was carried out in both positive and negative ion electrospray ionization (ESI) modes of detection.

The results indicated that various aglycones including isoflavones, flavones, flavonols, and flavanones increased in both F4404 and F4408 compared with SM. The increases in isoflavone and flavanone aglycones were greater in F4408 than in F4404. Some types of dipeptides and free amino acids, especially ornithine, increased in both fermented soymilks. The increase in free amino acids, especially ornithine, was higher in F4408 than in F4404. Thus, F4408 exhibited stronger glycosidase and protease activities than F4404. Functional components produced by lactic acid fermentation are known to improve lipid metabolism.

In conclusion, it is suggested that not only isoflavone aglycones but also other functional components exert lipid metabolism-modulating effects in fermented soymilks, especially soymilk fermented using TUA-4408L.


Article by Maki Kobayashi, et al, from Japan.

Full access: http://mrw.so/4qCr3o

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