Sour orange fruit (Citrus aurantium) seeds: Humble seeds bursting with goodness

Physicochemical properties of sour orange (Citrus aurantium) seeds including its length, weight, density (bulk, tapped, and true), porosity, 1000-grains weight, approximate analysis were assessed.  Color parameters (L*, a*, b*), total phenolic and ascorbic acid contents were evaluated. While soaking seeds in water, prior to oil extraction by n-hexane, an aqueous oily layer (AQO) was formed where its characteristics was determined. The oil content of seeds was extracted by conventional (Soxhlet) and two fairly novel methods (ohmic-assisted extraction (OAE) and ultrasound-assisted extraction (UAE)). To facilitate the oil extraction by OAE, a novel approach was established. In the latter, brine was added to n-hexane to ensure a suitable conductivity was established between the two platinum electrodes. The extraction yield and specific energy consumption for each method were evaluated and oil characteristics including color profile (in terms of ΔE), fatty acid composition, refractive index, total phenolic contents, antioxidant activity and anisidine value were assessed. The highest and lowest oil yield of about 50% and 3% was obtained using Soxhlet and maceration, respectively. The lowest specific energy consumption of 5 kWh/kg was achieved when oil extraction was performed by OAE. The extracted oil contains substantial amount of unsaturated and saturated fatty acids. Interestingly, the highest total phenolic content (about 0.9 mg GAE/ g oil) was associated with the aqueous oil. The extraction of valuable components from a waste in a fruit processing plant not only reduces the environmental impact of waste disposal but also present a new valorization method in the food industry.