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Volume 20, Issue 138 (August 2023)
Abstract
Many scientific reports have been published about the health effects of black cumin seed (Nigella sativa) oil such as anti-cancer, anti-diabetic, anti-microbial, anti-inflammatory and antioxidant properties. However, one of the main problems in extracting oil from black cumin seed (BS) is the low yield and also the low quality of the extracted oil. Various methods such as microwave treatment, roasting and soaking have been performed to improve the extraction conditions and quality of BS oil before cold pressing. In this study, BS was pre-treated with ethanol (70%) at 0 (control sample), 1, 3 and 6% and then oil extracted by cold press. Extracted oil qualitative characteristics (acid value, peroxide value, chlorophyll content, carotenoid content and total phenolic content) were assessed in production day and every 30 days during 90 days of storage. Also, oxidative stability of BS oil was measured by Schaal test. The results demonstrated that by increasing the level of ethanol in the pre-treatment of BS, acid value and peroxide value significantly (p < 0.05) decreased and oxidative stability, chlorophylls, carotenoids and phenolic contents of extracted oil significantly (p < 0.05) increased. Acid value and peroxide value increased and chlorophyll and carotenoid contents due to decomposition of their contents decreased during storage. Oil extracted from BS pre-treated with highest level of ethanol had the lowest acid value (4.61 mg NaOH/g oil) and peroxide value (7.03 meq O2/Kg oil) and the highest chlorophyll (21.21 mg/Kg oil), carotenoid (3.86 mg/Kg oil) and total phenolic (496.3 mg caffeic acid/Kg of oil) contents at the end of the storage. In conclusion, the results showed that pretreatment of BS by ethanol before cold pressing can be used to improve qualitative properties and stabilize the extracted oil.