Flavor characteristics and oxidative stability of supercritical carbon dioxide extracted oil from roasted soybean flakes

Abstract

Supercritical fluid extraction (SFE) method was applied to produce soybean oil with roasting flavor. And the characteristics of the extracted oil were studied. In order to increase the extracted yield, the pressure of supercritical carbon dioxide ($SCCO_2$) should be higher than 4,000 psig and the temperature of extraction vessel should be lower than 50$^\circ$C. When compared with hexane extracted oil, $SCCO_2$ extracted soybean oil was low in phosphorus content and had lighter color while flavoring compounds such as pyrazines were retained in the extracted oil and contributed to the characteristic roasted flavor. The pyrazine level reached maximum after 7 min roasting at 180$^\circ$C. Although roasting process did not affect the fatty acid composition of the extracted oil, it showed a significant effect on the oxidative stability of extracted oil. Roasting the soybean flakes at 150$^\circ$C and 180$^\circ$C increased the stability of $SCCO_2$ extracted oil. However, at 200$^\circ$C, the stability of extracted oil was lower than that of raw control. The $SCCO_2$ extracted oils from the raw and roasted soybean flakes were separated into several fractions according to their polarity. The non-polar compounds such as $\beta$-carotene showed potent antioxidant activity while more polar components showed low antioxidant activity or even acted as potent pro-oxedants. The antioxidation/pro-oxidation balance was varied with roasting temperature. Roasting condition was the most important factor to produce stable flavored soybean oil with $SCCO_2$ extraction.