A possible explanation for the stimulatory effect was that
L. acidophilus possessed the ability to utilize compounds supplied
by onion juice during growth, such as phytochemicals, polysaccharides,
vitamins, and/or minerals. Hervert-Hernandez et al.
(2009) found that grape polyphenols induced a significant
biomass increase of L. acidophilus during growth in liquid culture
media. However, not all plant extracts that were able to inhibit
pathogenic bacteria could stimulate fermentation by LAB. Yang
et al. (2012) found that ginger juice would inhibit the growth of
Streptococcus thermophilus and Lactobacillus bulgaricus and could
reduce the production of lactic acid.