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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