Application of lactic fermentation of yam (Dioscorea spp.) and mango (Mangifera indica) from Montes de María

Acid lactic fermentation was evaluated as a transformation and value-generation process in different substrates obtained from yam ( Dioscorea spp.) and mango ( Mangifera indica ). The challenge of the research was using simple analytical techniques of a few physicochemical response variables, to implement the results in the rural Colombian setting. Three yam varieties ( Dioscorea rotundata, Dioscorea trifida, and Dioscorea alata ) were used to produce yam beverages with different water ratios (1:3, 1:5, 1:10 and 1:15). With pH, acidity titratable after fermentation (0, 4 and 8h at 42°C) and sensorial results, Dioscorea rotundata and a ratio 1:5 were selected to produce mixes with mango as fermentation substrates. Three commercial mixed lactic starters with different lactic bacteria compositions were evaluated in six substrates. In all cases, a pH decrease and acidity increase were observed due to lactic fermentation, but the results are influenced by culture and substrate composition. Acid production was associated with lactic bacteria growth in a traditional starter (starter A, with Streptococcus thermophilus, Lactobacillus delbrueckii ssp . lactis, Lactobacillus delbrueckii ssp . bulgaricus ), from 4 to 7 log CFU/mL after 8 hours of fermentation at 42°C. But, when starters (B and C) with additional probiotic microorganisms ( Lactobacillus acidophilus, Bifidobacterium lactis ) were used, higher acidification was observed without bacteria growth. In all fermented beverages, yam and mango mixes, high concentrations of acid lactic bacteria were around 7 log CFU/mL after 8 hours of fermentation at 42°C. The final pH of fermented yam beverage with starter A was higher (5.30) than with starters B or C; or the pH of mixes with mango (between 4.55 and 3.80).