Corn Oil Enrichment with Waste Orange Peel Polyphenols and Its Effect on Oxidative Resilience: Stirred-Tank Versus Ultrasonication Mode

The use of synthetic antioxidants as edible oil stabilizers against oxidative rancidity is the method of preference for the relevant industries, yet these additives have been a subject of intense debate regarding adverse effects of their long-term consumption. In the search of natural replacers, interest has been focused on residual plant materials that could be used as cost-effective sources of oil antioxidants. In this line, this investigation aimed at studying the effect of enrichment of corn oil using waste orange peels (WOP), targeting at fortifying the oil with natural polyphenolic antioxidants, to provide effective shielding against oxidation. Initial comparison of two modes, a stirred-tank and an ultrasound-assisted one, evidenced that the latter was more efficacious in enriching corn oil with total polyphenols. However, detailed examination of the polyphenolic composition revealed that the oil enriched with the stirred-tank mode may have almost two times higher polyphenolic content, which mounted up to 109 mg per kg of oil. The major polyphenolic constituents identified were polymethylated flavones, but also ferulic acid and naringenin. Oil stability trials including the monitoring of peroxide value and p-anisidin value, demonstrated that the oil enriched with WOP polyphenols using the stirred-tank mode exhibited significantly higher oxidative resilience compared to control (neat oil), but also compared to the oil enriched using ultrasonication. Furthermore, it was observed that when neat oil was ultrasonicated, it also displayed exceptional stability against oxidation. Based on the outcome of this study, it is recommended that WOP, owed to their richness in lipophilic flavonoids, might be an ideal candidate for edible oil fortification, which could provide the oil with natural powerful antioxidants. Such a process could lend oils high oxidative resilience, but also functional ingredients.