Abstract:

Objective: The effect of single and combined inoculation with different strains on the contents of
deoxynojirimycin (DNJ), polysaccharides, flavonoids and polyphenolics in fermented mulberry leaf tea was studied.
Methods: DNJ was determined by HPLC, and flavonoids, polysaccharides and polyphenols were determined
spectrophotometrically. Results: Compared with naturally fermented mulberry leaf tea, DNJ content in 10 of 14 samples
obtained from inoculated fermentation was decreased or unchanged. It was decreased by a maximum of 6.42% in mulberry
leaf tea fermented by Trichoderma viride but increased in 4 samples from inoculated fermentation, by a maximum of 10.63%
in the one fermented by Rhizopus japonicus Vuillemin. The contents of flavonoids, polysaccharides and polyphenols in most
of the fermented mulberry leaf tea samples from inoculated fermentation were decreased compared to natural fermentation,
and the highest decreases in flavonoids, polysaccharides and polyphenols by 23.64%, 14.49% and 32.26% were observed for
the one fermented by Aspergillus niger. The content of flavonoids was increased by 5.82% by fermentation with Rhizopus
japonicus Vuillemin, and the content of polyphenols by up to 9.68% using Rhizopus japonicus Vuillemin in combination
with Penicillium. Conclusion: DNJ, flavonoids and tea polyphenols in fermented mulberry leaf tea can be considerably
increased by inoculation with Rhizopus japonicus Vuillemin.

Key words: fermentation, mulberry leaf tea, DNJ, flavonoids, polysaccharides, polyphenols