Process standardization for microwave and ultrasound assisted extraction of black cumin (Nigella Sativa L.) oil
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Date
2021-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Black cumin (Nigella sativa L.) seed belong to Ranonculaceae family and has been cultivated for use in spices and traditional medicine system of Unani and Ayurveda and has a long history. The seed is known for its oil content but the best method of extraction is still the point of concern. Mechanical expression and solvent extraction are currently used commercially methods of oil extraction of black cumin oil but both of the methods have their shortcomings of less oil recovery, degradation of oil quality and more time consumption. The present research work was thus done to overcome these problems. In the present study, the standardization and optimization of microwave, ultrasound and their combined extraction methods were evaluated to enhance the oil recovery and the quality of extracted oil from black cumin. Experiment were planned using box Behnken design considering parameters of microwave power (320, 480 and 640 W), microwave time (3, 5 and 7 min) and solvent volume (100, 150 and 200 ml/sample) for MAE, ultrasound power (150, 200, 250 W), ultrasound time (15, 30 and 45 min) and solvent volume (100, 150 and 200 ml/sample) for UAE and for combination was done at the optimized value of MAE and UAE. Particle size of 1 mm and the solvent, hexane, were kept constant for all the experiments. As per the results obtained from MAE the oil recovery obtained ranged from 83.27 to 97.45 %, Specific gravity ranged from 0.9 to 0.81, Color ranged from 44.18 to 61.66, DPPH Antioxidant activity ranged from 32.21 to 70.38 %, Free fatty acid ranged from 6.12 to 7.22 % and Peroxide value ranged from 7.54 to 9.37 meq O2/kg. In UAE the oil recovery obtained ranged from 85.51 % to 94.80 % Specific gravity ranged from 0.73 to 0.89, Color ranged from 36.24 to 53.88, DPPH Antioxidant activity ranged from 25.50 to 78.18 %, Free fatty acid ranged from 5.83 to 6.92 % and Peroxide value ranged from 6.63 to 8.24 meq O2/kg. Optimization of these methods was done based on their respective responses by means of Response surface methodology using Design Expert 10.0.1.0 software. The optimized parameters of MAE for black cumin oil gave the maximum oil recovery of 92.26 %, specific gravity 0.81, color 43.11, antioxidant 67.29, FFA 6.46 % and PV of 8.15 at microwave power 320W, microwave time 5.5 min and solvent to solid ratio 10 ml/g. and the optimized parameters of UAE for black cumin oil gave the maximum oil recovery of 87.88 %, specific gravity 0.73, color 38.8, antioxidant 76.32, FFA 6.06 % and PV of 6.92 at ultrasound power 158.1 W, ultrasound time 25.2 min and solvent volume (100, 150 and 200 ml/sample). Combined study was conducted at the optimized condition of parameters from MAE and UAE methods. A single experiment was run at these parameters to find the results. The maximum oil recovery 91.12 %, specific gravity 0.84, color 44.28, antioxidant 58.46, FFA 6.51 % and PV of 8.37 were found at ultrasound power 158 W, ultrasound time 25.2 min and solvent volume 100ml/sample followed by microwave power 320 W, microwave time 5.5 min. Results showed that the microwave assisted extraction proved very effective approach for the extraction of black cumin oil for the better oil recovery and the best quality.