Fermentation of honey-sweetened soymilk with Bifidobacterium lactis Bb-12 and Bifidobacterium longum Bb-46: fermentation activity of bifidobacteria and in vitro antagonistic effect against Listeria monocytogenes FSL N1-017

The influence of the honey addition on the fermentative activity of Bifidobacterium lactis Bb-12 and Bifidobacterium longum Bb-46 in soymilk was determined. Additionally, the inhibitory potential of honey-sweetened fermented soymilk against Listeria monocytogenes strain was examined. Two monofloral honey types were added to soymilk before the fermentation: dark-coloured chestnut honey and light-coloured acacia honey. On the basis of our previous studies on cow and goat milks, the basic hypothesis of this study was that the addition of honey could influence the growth of Bifidobacterium lactis and Bifidobacterium longum during the fermentation of soymilk. The addition of honey also influenced the decrease of raffinose and stachyose contents during fermentation. Furthermore, a higher inhibitory potential was assumed against Listeria monocytogenes caused by the honey addition. The obtained results show that both types of honey influenced the fermentative activity and numbers of Bifidobacterium lactis Bb-12 and Bifidobacterium longum Bb-46 viable cells in soymilk. Chestnut honey strongly influenced the acidity increase during the soymilk fermentation. A disc assay showed that the development of the inhibition zones of the growth depended on the type and concentration of honey, as well as on the type of milk. The chestnut honey had generally a higher inhibitory effect than acacia honey.