Effects of roasting and ultrasound-assisted enzymatic treatment of Nigella sativa L. seeds on thymoquinone in the oil and antioxidant activity of defatted seed meal.

Background: Black cumin seeds (black seed; BS) contain various bioactive compounds, such as thymoquinone (TQ). Roasting and ultrasound-assisted enzymatic treatment (UAET) as pre-treatments can increase the phytochemical content in the BS oil. This study aimed to investigate the effects of pre-treatments on the TQ content and the yield of the BS oil and to profile the composition of defatted BS meal (DBSM), followed by evaluating antioxidant properties of the DBSM.

Results: The extraction yield of crude oil from BS was not affected by the roasting time. The highest extraction yield (47.8 ± 0.4%) was obtained with UAET cellulase-pH 5 (enzyme concentration of 100%). Roasting decreased the TQ content of the oil, while the UAET cellulase-pH 5 treatment with an enzyme concentration of 100% yielded the highest TQ (125.1 ± 2.7 μg mL ). Additionally, the UAET cellulase-pH 5 treatment increased total phenolics and flavonoids of DBSM by approximately two-fold, compared to roasting or ultrasound treatment (UT) alone. Principal component analysis revealed that the UAET method might be more suitable for extracting BS oil with higher TQ content than roasting and UT.

Conclusion: Compared to roasting or UT, using ultrasound along with cellulase could improve the oil yield and TQ in the oil from BS and obtain the DBSM with higher phenolics, flavonoids, and antioxidant activity. © 2023 Society of Chemical Industry.