Changes in nutrients, energy, antioxidant and carotenoid levels of dried tomato (lycopersicon esculentum) pomage treated with aspergillus niger solid-state fermentation

Abstract

Tomato pomace (TP), utilized improperly is not namely causes a waste of valuable resources but also increases environmental pollution. In this study, possibilities improving nutrient composition by fermenting dry TP with Aspergillus niger was investigated for the value-added utilization of this pomace in animal feed. The TP, dried at 65°C for 8 hours with a simple layer and under a laminar airflow drying oven, was subjected to solid-state fermentation. After unfermented and fermented dry pomaces were milled in 2 mm sieve, proximate analysis and the analysis of cellulosic fractions were performed. Roughage quality indices were calculated using cellulosic fractions. Fermentation of TP with Aspergillus niger inoculant increased the amount of dry matter (82.98 vs 91.47%), crude fiber (21.71 vs 23.00%), neutral detergent fiber (29.70 vs 35.92%), acid detergent fiber (25.22 vs 26.84%), acid detergent lignin (7.91 vs 10.77%), hemicellulose (44.71 vs 90.78), crude protein (13.70 vs 21.37%), ether extract (2.82 vs 3.52%) and ash (10.57 vs 13.24%) compare to unfermented TP. Fermentation process decreased nitrogen-free extract (51.19 vs 38.86%), non-fiber carbohydrates (46.03 vs 29.47%) and quality index as relative feed value (216.9 vs 176.1) and relative forage quality (242.5 vs 195.5) and metabolizable energy (2.66 vs 2.60). Ferric reducing antioxidant power (FRAP), DPPH free radical (2,2-diphenyl-1-picrilhydrazil) and total phenolic content of TP did not increase by fermentation. Concentration of β-carotene and lycopene of TP decreased after fermentation with A niger. The results indicate that the selected strains of A. niger can be used to enrich the chemical composition of TP, except for cellulosic fractions and also carotenoids and antioxidant activity.