Studies On The Heating Stability Of Camellia Seed Oil

Camellia seed oil,a natural woody edible vegetable oil,rich in oleic acid and a variety of anti-oxidative micro-components,becomes the high-level edible oil that can be comparable to olive oil.However,consumers have a lower overall awareness of camellia seed oil,so vigorously carry out the basic characteristics of camellia seed oil are needed to provide the basic theoretical and scientific basis for improving the market influence of camellia seed oil.At present,the research on the quality of camellia seed oil is mainly focused on the oxidation stability in processing and storage,and the thermo-oxidative stability under the high temperature process is relatively small.In this paper,two kinds of high temperature treatment methods were adopted to study the thermo-oxidative stability of camellia seed oil from the initial substrate loss and the primary/secondary oxidation product formation.The results provide scientific theoretical basis for improving the processing technology of camellia seed oil,monitor the high temperature quality of camellia seed oil,expand the application range of camellia seed oil and improve the awareness of camellia seed oil.(1)The optimum chromatographic conditions of camellia seed oil triacylglycerols analysis by ELSD-HPLC are as follows:mobile phase consisted of acetonitrile(A)and isopropanol(B),flow rate 1.2 mL/min,column temperature 25?,Gradient elution conditions:0-1 min,60%A,40%B;1-15 min,60-70%A,40-30%B;15-60 min,70%A,30%B;60-75 min,70-60%30-40%B;75-88 min,60%A,40%B.ELSD detector parameters:drift tube temperature 80?,air flow rate 2.8 L/min,gain of 1.Camellia seed oil consists of 12 kinds of triglycerides measured under this optimization conditions.The temperature have a significant influence on camellia seed oil OSI among Rancimat operating parameter(P<0.01).Compared with the sample size,the air flow rate had a significant effect on the OSI of camellia seed oil(P<0.05).The temperature coefficient and Q10 of camellia seed oil were-3.02 � 10-2 and 2.02,respectively.There is a significant difference in the constructed shelf life(OSI at 20?),indicating that there may be a misleading in the evaluate shelf life of oil and fats by accelerated oxidation.(2)Sensory evaluation showed that the higher the temperature,the deeper deterioration of camellia seed oil sensory quality,and camellia seed oil could maintain good sensory quality during the high temperature treatment compared with rapeseed oil.Analysis of physical and chemical indexes in accelerate oxidation experiment showed that the total oxidation level of camellia seed oil was higher than 180? at 120?,while the formation rate and the cumulative amount of nonvolatile carbonyl compounds and secondary oxidation product contained conjugated diene or triene are higher than 120? at 180?.The results obtained from deep frying experiment show that the primary,secondary and total oxidation degree and the cumulative amount of secondary oxidation product such as nonvolatile carbonyl compounds in camellia seed oil are lower than that of rapeseed oil,indicating that camellia seed oil characterized by good thermal stability can be used as an excellent frying oil.In addition,the frying material has a certain effect on the oxidation degree of frying oil,but has a significant effect on the of hydrolysis degree of frying oil.During the high temperature treatment,the increase of the polar component content in camellia seed oil was significantly correlated with the time(R2>0.98).The higher the temperature,the more polar compounds were accumulated in camellia seed oil,and the accumulation degree of camellia seed oil were lower than rapeseed oil in deep frying experiment.(3)The results obtain from accelerate oxidation experiment showed that the effect of temperature on the unsaturated fatty acids of camellia seed oil were significant,the higher the temperature,the more unsaturated fatty acid were degraded and the loss rate increased gradually with the unsaturation degree.In addition,high temperature treatment at 180? results in the formation of trace trans oleic acid in camellia seed oil.The results obtain from deep frying experiment indicated that differences in fatty acid composition of camellia seed oil and rapeseed oil resulted in a different degradation models in the fatty acids of two samples significantly,indicating that fatty acid composition was a key factor affecting the thermal stability of oils and fats,compared with rapeseed oil characterized by higher polyunsaturated fatty acids,camellia seed oil with high oleic acid were more thermally stable.The trace trans-oleic acid were detected both in deep-fried and control-heated Camellia seed oil and rapeseed oil,which were lower than the recommended limit(2 g/100g)of trans oleic acid in edible oil regulated in China.Besides,it is worth noting that rapeseed oil may conduct trans linoleic and linolenic acid in this process,so in view of the safety and nutritional characteristics of frying oil,camellia seed oil show good thermal stability.The fatty acid comprehensive index such as C18:2/C16:0,SFA/UFA,MUFA/PUFA and Cox value were significantly correlated with the content of polar components and heating time(R2>0.97),which could be used to evaluate the degradation degree of fats and oils during high temperature treatment.(4)There is a difference in TAG distribution of camellia seed oil with different origin.The results acquired from accelerate oxidation experiment showed that the higher the temperature,the faster the degradation of TAG in camellia seed oil and the degradation pattern were different at two temperatures,besides,TAG content Id also affect the degradation rate.The results acquired from deep frying experimemt showed that the degradation mode of TAG were significantly effected by TAG composition.Rapeseed oil,rich in TAG characterized by high unsaturation degree,were more prone to generate primary and secondary oxidative products that can impair quality of frying oil during the high temperature treatment,otherwise,camellia seed oil showed good thermal oxidation stability.The analysis of PTAG showed that the polymerization degree of camellia seed oil at 180? was higher than that of 120? in accelerate oxidation experiment,and the degree polymerization degree of camellia seed oil was lower than rapeseed oil in deep flying experiment.In addition,the TAG degradation and PTAG formation levels in the deep-fried samples were higher than those in the control-heated samples,indicating that the frying material had some effect on the triglycerides degradation degree.(5)The polar components accumelated in fried camellia seed oil have pro-oxidative ability.HPSEC analysis indicated that the composition of polar compounds and FAMEs were TGO,TGD,ox-TGM,DG,FFA and FAO,FAD and ox-FAM respectively.The results obtained from accelerate oxidation experiment show that the reaction mechanism of camellia seed oil were different between 120? and 180?,the oxidation reaction and polymerization reaction dominate the reaction progress at 120? and 180? respectively,and the hydrolysis degree of camellia seed oil at 120? is higher than 180?.The results obtained from deep frying experiment show that the levels of polar triglycerides and fatty acids produced by camellia seed oil are lower than those of rapeseed oil,which indicates that the low deterioration degree of camellia seed oil and can be used as excellent frying oil.The distribution of oxidative polymerization and hydrolysis products in deep fried and control heated samples shows that the effect of frying material on hydrolysis degree is more significant than on oxidative polymerization degree.The correlation analysis showed that compared with the chemical index,the HPSEC analysis of polar TAG and the polar fatty acid in fats and oils were more accurate in reflect the deterioration progress under high temperature treatment.In addition,the analysis of the recommended indicators for the evaluation of frying life of fats and oils indicates that there may be risks to determine the fried life for vegetable oils according to the current standard(27%TPC)in China.(6)Volatile aldehyde is the main volatile compound produced in camellia seed oil under high temperature treatment,which accounts for about 80%of the total volatile compounds.The results acquired from accelerate oxidation experiment show that high temperature lead to the extensive generation of volatile aldehydes in camellia seed oil,the higher the temperature,the faster the formation rate,and the reaction progress is different between 120? and 180?.The results acquired from deep frying experiment show that except for temperature,fatty acid composition and frying material have a significant effect on the formation of volatile aldehydes during the high temperature treatment of camellia seed oil.The volatile aldehydes derived from oleic acid groups were higher in camellia seed oil than rapeseed oil,while the resulting volatile aldehydes derived from linoleic acid and linolenic acid were higher in rapeseed oil than camellia seed oil.Besides,the distribution of volatile aldehydes were different between deep fried and control heated samples,indicating that frying materials had some effect on the formation of volatile aldehydes in camellia seed oil.It is worth noting that the total level of dienal in in deep fried and control heated rapeseed oil is 7.72 and 7.13 times of camellia seed oil,the dienal characterized by high reactivity and cytotoxicity,in view of safety and nutritional properties camellia seed oil can be used as excellent frying oil.