Co-fermentation of onion and whey: a promising synbiotic combination

Juice from three different onion varieties was mixed with sweet whey and used as growth 18 substrate for four lactic acid bacteria strains, isolated from agri-food by-products, to 19 evaluate the possibility to exploit such substrates, known to be reach in bioactive 20 molecules, as fermented drinks for human consumption. Results show good growth 21 performance for Lactobacillus fabifermentans, L. plantarum and Streptococcus 22 macedonicus. On the contrary S. thermophilus did not grow in the mixture while S. 23 macedonicus did not develop in pure onion juice. After 48 h the overall sugar content 24 decreased significantly. In particular, glucose was not utilized while inulin was completely 25 preserved. Moreover, MS/MS analysis revealed the presence of the rare trisaccharide 26 lactosucrose. 27 In the light of these considerations, the formulation obtained may be considered a potential 28 synbiotic product with pleasant taste and beneficial effects for consumers and also an eco-29 friendly solution to convert an agro-food by-product into value added products.