Effects of Spinach Leaf Extracts on Quality Characteristics and Phenolic Profile of Sunflower Oil

Abstract

Spinach extract is added to sunflower oil in different ratios to assess its suitability during thermal stress. The fortified sunflower oils are thermally oxidized along with their control. Fortified sunflower oils are characterized for peroxide (PV), p‐anisidine (AV), thiobarbituric acid (TBARS), total phenolic contents, and radical scavenging activity (RSA). Polyphenols in the oil samples are extracted and identified using reversed phase high‐performance liquid chromatography with a diode array detection system (HPLC‐DAD). Results reveal separation and identification of 14 and 22 polyphenolic compounds in control and fortified oil samples, respectively. The major phenolic compounds are p‐hydroxybenzoic acid (1.99–11.3 μg g−1), p‐coumaric acid (0.22–10.2 μg g−1), isorhamnetin‐3‐(hydroxyferuloyl‐glucoside)‐7‐glucoside (0.14–13.8 μg g−1), apigenin (0.15–13.2 μg g−1), kaempferol‐3‐(p‐coumaroyl‐diglucoside)‐7‐glucoside (3.88–19.8 μg g−1), apigenin‐2‐O‐pentoxide‐8‐hexoside (0.42–39.7 μg g−1), quercetin‐3‐(sinapoyl‐diglucoside)‐7‐glucoside (1.99–11.3 μg g−1), and kaempferol‐3‐(sinapoyl‐diglucoside)‐7‐glucoside (1.73–34.6 μg g−1). Significant variations are observed in the composition of these phenolic compounds during heating. Remarkable beneficial changes are also observed in the characteristics of the oils such as peroxide, anisidine, and TOTOX values during thermal treatment. In conclusion, spinach leaf extracts are protective and beneficial for thermal stability of sunflower oil.Practical Applications: Thermal stability of frying oil is an important topic in food science and technology. The low stability of frying oils can be enhanced with the addition of natural antioxidants. Food industries may use antioxidants from plant leaves extract, especially spinach leaf, extracts to be very beneficial. The phenolic profile, lipid oxidation, and antioxidant activity of sunflower oil fortified with spinach leave extracts are enhanced. These results suggest that spinach leaves extract is beneficial in terms of lipid oxidation parameters and serve as a good source of important phenolic compounds.Spinach extract added to sunflower oil is beneficial during thermal stress. Significant variations are observed in the composition of different phenolic compounds during heating. Spinach extract contributes beneficial changes to the quality characteristics of the oils such as peroxide, anisidine, and TOTOX values.