The Functional Activity And Key Components Of Coriander Stem Leaves Essential Oil Which Could Inhibit Oil Oxidation

Soybean oil,sunflower oil and other oils,which are rich in unsaturated fatty acids,are prone to oxidation during production,storage and frying,resulting in loss of nutrition,reduction of sensory properties and generation of harmful substances in themselves and in foods containing oil,which seriously affects their nutritional properties and safety.The addition of antioxidants is one of the effective measures to solve the problem.Coriander(fruits and stem leaves)essential oil,as a natural fat-soluble substance,has been widely proven and repeatedly reported in recent years for its antioxidant efficacy and food safety,but its application in oils has not been studied.Therefore,in this study,coriander was selected as the raw material,and its fruits and stem leaves essential oils were firstly extracted and analyzed for their composition,and then the in vitro antioxidant capacity of the two essential oils was investigated by free radical scavenging test and the antioxidant effect of the two essential oils in oils was initially investigated by Rancimat test.Subsequently,one essential oil with better antioxidant capacity was selected to be added to soybean oil and sunflower oil in combination with the test results to investigate its effect on the oxidative stability of oils during storage and frying.Finally,the key components of the selected essential oil to inhibit the oxidation of oils were explored.The main findings were as follows:Firstly,the essential oil was extracted by hydrodistillation,in which the essential oil yield was 0.50±0.01%for coriander fruit and 0.36±0.01%for stem leaves.21 and 23 components were detected from the essential oils of coriander fruits and stem leaves using gas chromatography-mass spectrometry(GC-MS),accounting for 98.21%and 97.81%of the essential oil content,respectively,with the fruit essential oil containing terpenes,alcohols,esters and other compounds,the highest content being linalool(34.28%),followed by geranyl acetate(29.97%)and menthol(9.32%),etc.;The stem leaves essential oil contained terpenoids,phenols,aldehydes and other compounds,mainly decanal(27.66%),(E)-2-dodecanal(19.36%),(E)-2-decanal(13.88%),and also contained 4.89%carvacrol and 2.89%eugenol,which were compared to find a large difference in the composition of the two essential oils,but both contained potential antioxidant components.ABTS,DPPH,hydroxyl radical scavenging assay and total reducing capacity assay showed that both essential oils have certain in vitro antioxidant capacity,and the coriander stem leaves essential oil was significantly better than the fruits essential oil.The Rancimat test showed that both essential oils had antioxidant protective effects on oils,and coriander stem leaves>coriander fruits,which was consistent with in vitro antioxidant.Secondly,the effect of coriander stem leaves essential oil with good antioxidant capacity on the oxidative stability of soybean oil and sunflower oil during accelerated storage(63~oC,25 d)was investigated to further evaluate the antioxidant efficacy of essential oil in oils.The results showed that the addition of essential oil(1.2 g/kg and 1.5 g/kg)significantly delayed the increase of acid value,peroxide value,conjugated diene,p-anisidine value,the content of malonaldehyde and total oxidation value of oils as well as the decrease of PUFA during storage(p<0.05),which proved that it could effectively inhibit the oxidation of oils and improve its storage stability,and the higher the concentration,the better the effect.When the addition amount reached 1.5 g/kg,its antioxidant efficacy exceeded 0.2 g/kg BHT.Then,the effect of coriander stem leaves essential oil on the oxidative stability of soybean oil and sunflower oil during continuous frying(160~oC,30 h)was investigated.The results showed that the addition of essential oil(1.2 g/kg and 1.5 g/kg)significantly improved the oxidative stability of the frying oils and inhibited the deterioration of oil quality during the first 12 h.Moreover,1.5 g/kg essential oil>0.2 g/kg BHT>1.2 g/kg essential oil,which was like its inhibitory effect on oils during storage.However,the oxidation inhibitory effect of essential oil on frying oils decreased significantly after 12 h.This may be due to the breakdown of the key components of the essential oil that act as antioxidants under prolonged high temperature and the chemical reaction of some other components to produce pro-oxidant substances.Therefore,the oils with coriander stem leaves essential oil were more suitable for short-term frying.In addition,sensory analysis showed that the addition of essential oil could improve the flavor and taste of fried products(Mahua),which greatly improved the consumers’enjoyment of their products.Finally,from the previous study,it was found that the antioxidant effect of coriander stem leaves essential oil during oil storage was better than that of frying process,therefore,the key components of coriander stem leaves essential oil to inhibit oil oxidation during storage was investigated.The analysis of the components of coriander stem leaves essential oil initially inferred those two phenolic substances,carvacrol and eugenol,might be the active components for the inhibition of oil oxidation,and then verified them.The results showed that the stability of carvacrol and eugenol was better during storage,and the addition of both carvacrol(1.5g/kg×5.21%≈0.08 g/kg,5.21%is the content of carvacrol in the coriander stem leaves essential oil)and eugenol(1.5 g/kg×3.25%≈0.05 g/kg,3.25%is the content of eugenol in the coriander stem leaves essential oil)significantly improved the oxidative stability of sunflower oil during storage.Meanwhile,the oxidative stability of sunflower oil added with the mixture of carvacrol and eugenol was basically similar to that of coriander stem leaves essential oil(1.5 g/kg)during storage.Thus,the above results provide preliminary evidence that the antioxidant efficacy of coriander stem leaves essential oil in oils can be attributed to carvacrol and eugenol.Through the execution of this study,it provides theoretical support and scientific basis for the macroscopic phenomenon of coriander stem leaves essential oil inhibiting oxidative rancidity of oil and provides new ideas and directions for the product development of coriander stem leaves essential oil as a natural antioxidant.