Studies of the ability of probiotics to ferment cereal flours are necessary to obtain products with enhanced nutritional value. In this study, Lactobacillus paracasei CBA-L74 was used to ferment cereal aqueous mixtures containing both oat (7.5% w/v) and rice flours (7.5% w/v), with and without glucose, to understand whether glucose addition could have any effect on growth and metabolism. Viability, pH, metabolites production during fermentation (24 h, 37 °C) and substrates reduction were analysed. The strain showed good growth in the cereal aqueous mixture both with and without glucose addition, but suspensions prepared with glucose showed the best results. A bacterial concentration of 7 log CFU mL −1 , a pH value of 4.70 and lactic acid production of 1250 mg L −1 were achieved when fermentation was performed without glucose addition, while in the presence of glucose, a t 24 bacterial growth of 8 log CFU mL −1 was reached, with a pH value of 3.11 and lactic acid production of 6050 mg L −1 .

Banana puree, due to its nutritional composition, is a good substrate for fermentation in the development of probiotic products. The production of banana puree mainly consists of three phases, i.e., raw material pretreatment, heat treatment, and the addition of anti-browning agents. In this study, we conducted three experimental protocols to evaluate the effect of ripeness grade, heat treatment, and ascorbic acid addition on fermentation performance. At the end of each protocol, the substrate was subjected to the fermentation process (37 °C, 48 h), and then measurements of pH reduction, microbial growth, and lactic acid production were used as markers in the analysis of fermentation performance. Ripe bananas produced better results than unripe bananas whose fermentation appeared to be inhibited. Therefore, ripe bananas were used to test the effect of two different heat treatments (sterilization (121 °C, 20 min) versus tyndallization (70 °C, 30 min; 37 °C, 30 min; 70 °C, 30 min)) on banana puree fermentation, and no significant differences were observed. Finally, 500 or 1000 ppm of ascorbic acid, normally used as an anti-browning agent, was added to ripe tyndallized bananas. No differences in fermentation results were observed between the two tested conditions, though values obtained for growth and lactic acid production were significantly lower than those from fermentation of banana puree without ascorbic acid.