Enhancement of bioactive compounds and oxidation stability of soybean oil by enrichment with tocols and γ‐oryzanol extracted from rice bran using ultrasound and ohmic heating

Abstract

Soybean oil is beneficial from a nutritional viewpoint; however, the high concentration of polyunsaturated fatty acid presents a high risk of oxidation. This study incorporated α‐ and γ‐tocopherols and γ‐oryzanol as natural antioxidants from rice bran into soybean oil to improve oxidation stability of the oil using ohmic heating‐assisted ultrasound extraction. Moisturized bran (30% wet basis) was pretreated using an ohmic heater at 100 and 200 V/cm before ultrasound extraction using soybean oil as a green solvent. Raw and steamed rice bran extracted by ultrasound without ohmic heating were used as controls. Enriched soybean oil obtained from ohmic heating pretreatment gave the highest concentration of α‐ and γ‐tocopherols, γ‐oryzanol, and antioxidant activities with low concentrations of free fatty acids, thiobarbituric acid, and peroxide values. Results suggested that ohmic heating‐assisted ultrasound extraction showed potential to enrich soybean oil with bioactive compounds. Practical applications Soybean oil can be enriched with tocols and γ‐oryzanol from rice bran to increase oil quality and oxidative stability. Ohmic heating was applied to assist ultrasound extraction of tocols and γ‐oryzanol from rice bran. Extraction of edible vegetable oils using ohmic heating‐assisted ultrasound is an alternative green process to improve oil quality and produce functional vegetable oils enriched with value‐added compounds.