Nutritional characterization and the antioxidant properties of sweet orange and red grapefruit peels

Abstract

Sweet oranges (Citrus sinensis) and red grapefruit (Citrus paradisi) are fruits consumed frequently in the world, being part of the human diet for decades due to high nutritional and medicinal values. These are excellent sources of vitamin C, a powerful natural antioxidant that builds the body's immune system. Their consumption (natural or processed) generates more quantities of shells and wastes that cause pollution of the environment under incorrect handling conditions. The study was conducted to analyze the potential of orange and grapefruit peels, from a chemical point of view, to determine the nutritional value for inclusion in broiler feed. The orange peels were characterized by a 5.42% crude protein and 1.04% crude fat vs. 5.78% and 0.80% grapefruit. The total content of polyphenols (mg acid galic /g) determined was higher with 36.01% in grapefruit peels compared to those of oranges. Antioxidant capacity was determined by two in vitro methods. The grapefruit peels were characterized by a high antioxidant capacity (288.49 mmol /kg equivalent ascorbic acid) with 51.39% higher than the values of the orange peels, in the first method. For the second method, the determined antioxidant capacity was with 61.20% higher than the orange peels (95.46 mmol/ kg equivalent vitamin E). Based on these results, the analyzed byproducts fulfill the necessary conditions to be integrated into the animal feed, and they will be tested in an experiment on broiler chickens in order to improve the nutritional quality of the meat.