Investigation of the effects of different cold pressing process conditions on the quality of black cumin and mustard seed oils and cold press wastes

In this study, some physicochemical properties of the press cake and oil of black cumin and mustard seed were examined under different temperature and screw rotation speed conditions. PH, moisture content, water activity, color, and Fourier Transform Infrared Spectroscopy (FTIR) analyses were conducted on the press cakes; while free acidity, fatty acid profile, and extraction yield were analyzed in the oils. Mathematical models were created from the experimental data obtained in trials designed using the response surface methodology. The average pH and moisture values of black cumin seed press cake samples were 6.28 and 9.09, respectively. The lowest water activity of black cumin seed cake was 0.531±0.037 at 90°C temperature and 30 rpm screw speed conditions. The average L*, a*, and b* color values of black cumin seed press cake were found to be 16.43, -2.50 and 6.44, respectively. In black cumin oil samples, the average oil yield was 21.96%, and the average free acidity value was calculated as 14.12% (expressed as oleic acid). The average color index of black cumin oil samples was calculated as -12.9. For mustard seed press cake samples, the highest and the lowest pH values were 6.22±0.05 and 5.35±0.02, respectively. The average moisture content was found to be 7.02%. The highest water activity of mustard seed press cake was measured as 0.488±0.031 at 100°C and 25 rpm conditions. The average L*, a*, and b* color values of mustard seed press cake were 36.63, 5.20, and 29.72, respectively. In mustard seed oil samples, the average oil yield was 20.22%, and the average free acidity was calculated as 3.32% (expressed as oleic acid). The average color index of mustard seed oil samples was measured as 11.13. The most abundant fatty acid of mustard seed oil was erucic acid with an average of 57.68%. FTIR analyses results revealed characteristic peaks corresponding to various functional groups in black cumin and mustard seed press cakes. These peaks indicated the presence of biologically active components (oil, protein, carbohydrate, and phenolic compounds) in the press cakes. This study contributes to understanding the effects of different processing conditions on the physicochemical properties of vegetable oils such as black cumin and mustard seed, and how the cold pressing method influences oil quality.