# Banana Puree Lactic Fermentation: The Role of Ripeness, Heat Treatment, and Ascorbic Acid
## 4 Discussion  
Industries are increasingly interested in functional foods such as probiotics (i.e., live microorganisms that, when administered in adequate amounts, confer a health benefit on the host [18]) and postbiotics (i.e., preparation of inanimate microorganisms and/or their components that confers a health benefit on the host [19]). Most of these types of functional foods are dairy-based products [20; 21; 22], but products of a different nature are also on the rise. The ability of the bacterial strain that was used in the present study to ferment food matrices, such as cereals and legumes, has previously been demonstrated [17; 23; 24; 25; 26; 27; 28; 29], and its probiotic activity has also been confirmed in previous studies [30; 31; 32; 33]; in the present work, its ability to ferment an industrial product, such as banana puree, was investigated. Banana, both as a fresh or processed fruit, is one of the most consumed fruit crops worldwide, starting from infancy. Because of its nutritional composition, it seems to be a good substrate for fermentation, as previously studied [34; 35]. Fermentation is a processing technology useful for increasing shelf life and improving organoleptic properties, and it is also a method to obtain functional foods. The present work was aimed at understanding the feasibility of fermenting an industrial product, i.e., banana puree, to obtain a potential functional  
Figure 4: Protocol 3 (ascorbic acid addition of 0, 500, or 1000 ppm) fermentation results at different sampling times (t0, t4, t16, t20, t24, t40, t44, and t48): (**A**) pH values, (**B**) bacterial growth (CFU mL\({}^{-1}\)), and (**C**) lactic acid production in g L\({}^{-1}\). Bars represent standard deviation of three independent experiments. Student’s \(t\)-test. * \(p<0.05\), ** \(p<0.01\), *** \(p<0.001\). food, paying attention to how the raw material (unripe or ripe banana) and the production process itself can impact fermentation. For this purpose, a banana-puree industrial process was reproduced at the lab-scale, with fermentation as the final step. The measurements of pH reduction, growth of \(L\). _paracasei_, and production of lactic acid were used as indicators for the analysis of fermentation performance. Three different experimental protocols were tested. The first protocol was designed to determine whether unripe or ripe banana was a better raw material to be fermented. Significant differences were noted in fermentation performance, i.e., sixth-grade or ripe bananas gave better results in terms of \(L\). _paracasei_ growth, lactic acid production, and pH reduction as compared with second-grade bananas, for which an early bacterial death phase was observed. A similar result was observed by [PERSON] and [PERSON] [34], who studied the fermenting ability of five different strains on ripe and unripe banana puree. They showed a pH reduction (as a fermentation indicator) also for unripe banana puree, but only after several days. This is probably due to the difference in nutritional composition of second- and sixth-grade bananas. The ripening of bananas, in fact, leads to an increase in the content of soluble sugars, more accessibility to bacteria and, at the same time, a decrease in starch [4, 36, 37] and depolymerization of pectin [38]. Another factor that promotes fermentation in sixth-grade bananas could be the fact that fructan concentrations are higher in ripe bananas than those in unripe bananas [39], keeping in mind that fructans are considered to be prebiotic compounds for some bacterial strains [40]. After we determined the better raw material for fermentation (ripe bananas), we focused on the banana-puree production steps considered to be \"more risky\" for good fermentation, i.e., heat treatment and ascorbic acid addition, commonly used as an anti-browning agent. The heat treatment is considered risky for fermentation due to the possibility of reducing proteins, vitamins [13], or other elements useful for microbial metabolism.