Valorisation through Lactic Fermentation of Industrial Wastewaters from a Bean Blanching Treatment

In recent years, scientific research and industries have been focusing on the application of biological treatments aimed at imparting functional properties to waste products from food industries according to the principles on which the circular economy model is based, namely, the recovery, valorisation, and reuse of wastes. This work aimed at exploring the possibility of valorising waters from the blanching process of dried navy beans through lactic acid fermentation using Lacticaseibacillus paracasei CBA L74 as a starter. Two samples at different solid concentrations (0.75 degrees Bx and 1.25 degrees Bx) were fermented, and, in both cases, a bacterial load of 8 Logs and a lactic acid concentration of approximately 1.3 g/L were reached, despite the lack of nutrients. An unusual pH trend, characterised by an initial decrease and unexpected final rise, was observed during the fermentation of both samples: simultaneously, an increase in protein content was observed, suggesting that the proteolytic action of the microorganism could be responsible for the release of pH-increasing substances. In both cases, a slight increase in total polyphenols (approximately 23.3-33.72%) and flavonoids (approximately 42.3-52%) due to fermentation was observed, with a corresponding improvement in antioxidant capacity (approximately 25.32-37.72%). A significant increase in saponin concentration was determined for the most concentrated blanching water (from 2.87 +/- 0.28 to 6.68 +/- 0.69 mgOAE/mL), leading to an improvement in foaming properties and an enhanced capacity to produce stable emulsions. The obtained results confirmed the possibility of reducing water consumption from blanching operations, as well as finding valorisation opportunities for this side stream through a safe and inexpensive fermentation treatment.

Automated summary

In this study, the possibility of valorizing blanching water from dried navy beans through lactic acid fermentation was explored. The results showed that Lacticaseibacillus paracasei CBA L74 was able to ferment the water samples at different solid concentrations, reaching a high bacterial load and lactic acid concentration. Unusual pH trends and an increase in protein content were also observed during the fermentation process. Additionally, there was a slight increase in total polyphenols, flavonoids, and antioxidant capacity, as well as a significant increase in saponin concentration, which improved the foaming properties and emulsifying capacity of the blanching water.