Sustainable process for a production of food-grade vinegar by recycling pineapple waste

The alarming scenarios of food crisis for growing population, shortage of raw materials, food and natural resources, jointly with the problem of pollution, have direct attention to find alternative resources. The waste utilization from the agro-food industry is a major challenge to reduce food losses, to increase the sustainability of food production and, therefore, increase food security, especially in developing countries. The objective of this research is to get vinegar from pineapple waste by means of: A1) Enzymatic hydrolysis: the saccharification of pineapple peels and core is examined during laboratory- scale experiments in order to determine the optimal time-temperature conditions for cellulolytic, pectinolitic, and invertase enzymes. A2) Physical pre-treatments: microwave (MW), boiling (B), high pressure with pressure cooker (HPC) and with autoclave (HPA), aimed at altering the structure of the fibrous matrix, are tested in order to enhance the sugar yield of enzymatic hydrolysis. A3) Alcoholic fermentation: three strain of Saccharomyces cerevisiae, mixed either with Lactobacillus delbruekii or with Lactobacillus plantarum at 15-20-25 °C are evaluated in order to obtain different pineapple wines. A4) Acetic fermentation: Acetobacter aceti is added to each pineapple wine at 30 °C with air flow (volume/h): pineapple wine ratio from 2: 1 to 10: 1 on a pilot scale fermenter. Samples obtained from saccharification, alcoholic and acetic fermentation were analyzed for pH, total acidity, total soluble solid (TSS), sugars, acids, ethanol, and volatile compounds. A detailed characterization of vinegar was carried out through UHPLC-QTOF-MS.