Effects Of Extraction Methods On Accompaniments And Antioxidant Activities Of Grape Seed Oil

Grape seed oil is an advanced cooking oil.It is obtained through the further processing of grape seed,which is a by-product of wine brewing or juice pressing.Grape seed oil is rich in various bioactive compounds,such as V_E,sterols,polyphenols,and squalene,etc.Therefore,it has a great market potential in food and pharmaceutical fields.In this paper,subcritical fluid extraction and supercritical CO₂ fluid extraction were firstly optimized.After different extraction methods?subcritical fluid extraction,supercritical CO₂ fluid extraction,solvent extraction,cold pressing,and hot pressing?,the accompaniments and in vitro antioxidant activities of grape seed oil were systematically investigated,and the qualitative and quantitative analysis were made on the phenolic compounds of grape seed oil.Finally,the changes in accompaniments of grape seed oil during the accelerated storage were analyzed.The contents of this paper are as follows:The extraction conditions of subcritical fluid extraction of grape seed oil were determined by single-factor experiments:The grape seed/dimethy ether?1:3.5,w/v?were incubated at 30°C for 0.75 h,and the extraction was conducted twice.Under these conditions,the extraction rate and polyphenol content of grape seed oil were 89.39%and 418.56 mg GAE/kg,respectively.The extraction conditions of supercritical CO₂ fluid extraction of grape seed oil were also determined by single-factor experiments:Extraction time 1.50 h,extraction pressure 35 MPa,extraction temperature 40°C,CO₂ flow rate 40 g/min,and 20%?v/v?ethanol/supercritical CO₂ fluid.Under these conditions,the extraction rate and polyphenol content of grape seed oil were 93.96%and 1269.60 mg GAE/kg,respectively.After different extraction methods?subcritical fluid extraction,supercritical CO₂ fluid with ethanol extraction,solvent extraction,cold pressing,and hot pressing?,the quality of grape seed oils were compared.The grape seed oil obtained by subcritical fluid extraction had the highest moisture and volatile-matter content?3.80%?and the highest peroxide value?2.80 mmol/kg?.The grape seed oil obtained by supercritical CO₂ fluid with ethanol extraction had the highest acid value?4.94 mg/g?and the longest oxidation induction time?18.81 h?.The accompaniments of grape seed oil by different extraction methods were significantly different.The polyphenol content of grape seed oils and its antioxidant activities were enhanced by dimethyl ether and ethanol solvent.Proper heating contributed to the increase of polyphenol,sterols and squalene contents in grape seed oil.The qualitative results of phenols indicated that the grape seed oil obtained by subcritical fluid extraction had the largest number of phenolic compounds?totally 20?.The in vitro antioxidant tests?DPPH and ABTS free radical scavenging,ORAC,FRAP,total reducing power and inhibition of?-carotene bleaching?indicated:the phenolic compositions in grape seed oil,which was obtained by supercritical CO₂ fluid with ethanol extraction,had the largest antioxidant activities,followed by subcritical fluid extraction.The correlation analysis showed that gallic acid,catechin,and epicatechin were highly correlated with in vitro antioxidant activities?p<0.01?.Partial least squares regression analysis of the correlation between each bioactive compounds and antioxidant indices of oils showed that gallic acid,catechin,epicatechin and?-tocotrienol had the significant positive correlation with the DPPH,ABTS free radical scavenging capacity and inhibition ability of?-carotenoid bleaching?p<0.01?.Therefore,these accompaniments were considered as important antioxidant fundamental substances of grape seed oil.The changes in the accompaniments of grape seed oil prepared by different proseccing methods during the accelerated storage were investigated.The acid value of grape seed oil prepared by solvent extraction obviously increased;the peroxide value showed an overall upward trend;the polyphenol content sharply declined;the contents of V_E,sterols,and squalene decreased.The decline trend of antioxidant activities of phenolic compounds in grape seed oils were greater than the overall antioxidant activities of grape seed oils.The correlation analysis showed that polyphenol content was the main factor affecting the acid value of grape seed oil;?-tocotrienol and sterols could effectively inhibit peroxygen radicals during the accelerated storage of grape seed oil;total phenols and?-tocopherol were the main substances affecting the antioxidant activities of grape seed oil during the accelerated storage.