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