Microbial, Nutritional, and Antioxidant Stability of Fruit and Vegetables Discards Treated with Sodium Metabisulfite During Aerobic and Anaerobic Storage

Fruits and vegetables are a rich source of natural antioxidants; therefore their discards can be viewed as a functional feed ingredient in animal nutrition. The aim of present study was to examine the effects of sodium metabisulfite (SMB) on microbial, nutritional, and antioxidant stability of fruit and vegetable discards (FVD) under laboratory- and large-scale conditions. Initially, FVD were mixed without or with 6 g SMB/kg biomass, aerobically challenged for 7 days, and then stored anaerobically up to 28 days. Under both aerobic and anaerobic conditions, negligible loss of the nutrient constituents was evident in SMB-treated FVD. Conversely, the rapid rise in the microbial population of FVD (without SMB) resulted in biomass deterioration and substantial dry matter loss and sugar exhaustion. Although the prolonged storage of SMB-treated FVD resulted in the moderate loss of carotenoids, total phenolics and DPPH radical scavenging activity slightly changed. Overall, a series of laboratory- and large-scale experiments demonstrated the effectiveness of SMB in conserving the nutrient constituents and the antioxidant capacity of FVD under aerobic and anaerobic storage, which might enable a viable route to the effective utilization of these discards as a functional ingredient for animal feed applications.