Apple fermentation: Valorization of surpluses from the fruit industry

Fermentation is an anaerobic process in which sugars are converted into alcohol by bacterial enzymes or into lactic acid by yeasts. Apple is rich in vitamins and phytochemicals, mainly flavonoids, and it is responsible for antioxidant action. Apples that are unsuitable for fresh use or of inappropriate commercial size are not valued in the market, as they often do not have the physical characteristics the consumer appreciates and are therefore rejected. Furthermore, in industries and fruit processing, high amounts of waste are generated. Study possibilities for valorizing apple waste through fermentation, combining the circular and sustainable economy concepts. Local producers, processing industries, and commercial areas were contacted to establish collaborations and test different apple fermentation conditions, varying the part of the fruit used. Flasks with apple and water were placed in the oven at 30 ◦C, samples were collected every 24 h, and the pH was measured. The fermented products were analyzed to evaluate their antimicrobial activity, measuring the inhibition halo for Escherichia coli, Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Candida albicans. The most promising was the test with only apple pulp, since it was under these conditions that a greater inhibition halo was recorded compared to tests with combinations of pulp, peel, seed, and stem. Fermented apple pulp demonstrated greater activity in the sensitivity test for Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, and Staphylococcus epidermidis. Fermented apple appears to have antimicrobial activity against several species. It is necessary to repeat the tests and analyze the intermediate fermentation times. It would be interesting to vary the state of division of the fruit as well as to carry out biostimulation tests and bioinoculation. As a future project, in addition to analyzing antimicrobial activity, it is intended to identify fermented products, using UV/VIS spectrophotometry and HPLC.