engleski

Valorization of grape pomaces: Green extraction of grape seed oil using supercritical CO2

The grape pomace obtained after pressing is a valuable by-product, containing about 7-22% grape seed oil. This oil is a rich source of essential unsaturated fatty acids, especially linoleic acid, as well as other bioactive compounds with strong antioxidant activity such as vitamin E active compounds, phytosterols and polyphenolic compounds. In contrast to conventional solvent extraction, supercritical CO2 extraction (SC CO2) of oil from grape seed pomace can be used as an environmentally friendly alternative. Namely, by using green, non-toxic, non-flammable and low-cost CO2 as the extraction fluid, the negative environmental factors of conventional solvents can be reduced. The aim of this research was to study the effect of SC CO2 extraction (pressure, temperature and CO2 flow rate) on the extraction efficiency of grape seed oil and its antioxidant capacity. The extraction process was monitored, and samples were taken every 10 min during the 90-min extraction period, and the extraction yield (%) was calculated for each sampling point. The antioxidant capacity of the extracted oils was analyzed using the lipophilic ORAC method. The results showed that the application of higher pressure (500 bar compared to 300 bar) at 45 °C and a CO2 flow rate of 15 g/min during the first 30 min of SC CO2 extraction contributed to a higher grape seed oil yield. However, the observed trends afterwards tended to disappear, since no significant differences were obtained among samples. Moreover, the same trend was noticed when a higher CO2 flow rate of 45 g/min was applied. Interestingly, the application of a high temperature (55 °C, 400 bar) did not have a favorable effect on the extraction yield, as significantly higher values were obtained when a lower temperature (35 °C, 400 bar) was used. Moreover, the effect of temperature was more pronounced at a lower CO2 flow rate of 15 g/min during the first 30 min of extraction. Finally, the CO2 flow rate of 15 g/ min compared with 45 g/min affected the extraction kinetics and contributed to lower extraction yields at the beginning of the process, but the final trend obtained among counterpart samples depended primarily on the applied pressure and temperature. Moreover, the highest extraction yields were obtained at 400 bar and 35 °C, regardless of the applied CO2 flow rate. However, the highest antioxidant capacity was achieved employing 400 bar, 35 °C, and 15 g CO2/min.

supercritical CO2 ; green extraction ; grape seed pomace ; grape seed oil ; antioxidant capacity

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