Quality of oil extracted by cold press from Nigella sativa seeds incorporated with rosemary extracts and pretreated by microwaves

Abstract

Abstract Black cumin (Nigella sativa) seed (BS) oil has high a peroxide value (PV) and acid value (AV). In this study, BS was incorporated with different levels of rosemary extracts as a natural antioxidant source before and after pretreatment by microwaves. Based on the oil extraction yield (33%), PV (8.4 meq O2 per kg oil), and AV (3.2 mg KOH per gram oil), the optimum condition was determined as microwave radiation for 120 s and, after that, moisturizing by the extract at 4% level. AV and PV were lower, and chlorophylls, carotenoids, polyphenols, thymoquinone, and tocopherols content were higher in oil extracted from pretreated BS than oil extracted from control BS. Reduction and loss of bioactive components occurred in oil samples during the 120 days of storage; however, it was higher in the control sample. There were no significant differences (p < 0.05) in the fatty acid composition of oil samples; however, oxidation and reduction of linoleic acid in the control oil sample were higher (4.2%) than the oil extracted from pretreated BS (2.5%). In conclusion, the oil extracted from the pretreated BS had higher oil extraction yield, high bioactive components, and stability; therefore, microwave radiation and incorporation of rosemary extract before oil extraction from BS is suggested.