Comparison of supercritical CO<inf>2</inf> and screw press extraction methods for producing oil from Camellia sinensis var. assamica seeds: Physicochemical properties and antioxidant activity

Abstract

The quality of Assam tea seed oil obtained by supercritical CO2 extraction was evaluated and compared to that of tea obtained using a screw press. Supercritical CO2 extraction produced a higher oil yield (12.94–16.53 % w/w) compared to the screw press method (9.96–12.18 % w/w). Using a higher temperature for supercritical CO2 and screw press extraction caused a decrease in the saponin content from 32.12 to 25.07 mg saponin equivalents/g oil and from 39.28 to 35.60 mg saponin equivalents/g oil, respectively, and for supercritical CO2 extraction also increased the flavonoid content from 0.84 to 1.75 mg/mL quercetin equivalents but did not affect the flavonoid yield for screw press extraction (1.02–1.07 mg/mL quercetin equivalents). The tannin content obtained from supercritical CO2 and screw press extraction was not significantly different (31.67–36.30 and 29.49–32.12 mg/mL tannin equivalents, respectively). Increasing the temperature of supercritical CO2 extraction resulted in a decrease in acid value and free fatty acids. No significant differences in acid value or free fatty acids were observed for oil extracted using the screw press method. Iodine and saponification values of oil obtained by supercritical CO2 extraction decreased when the extraction temperature increased, and screw press oil had higher iodine and saponification values when the temperature was increased. All of the extracted Assam tea seed oils, obtained by both methods, overwhelmingly contained oleic acid (48.55–50.14 %), linoleic acid (24.14–25.52 %), and palmitic acid (18.74–19.95 %). In addition, an increase in temperature promoted the extraction of phenolic compounds for both extraction methods (9.21–22.01 mg GAE/100 g oil), resulting in an increase in the antioxidant capacity of the extracted oil. These results indicate that supercritical CO2 extraction could be competitive with the screw press method, providing an environmental approach and enhancing the quality of the oil obtained.