| Edible vegetable oil is an essential nutrient substance in our daily life.The value of vegetable oil is different because of its different nutritional composition.Camellia oil has a high content of oleic acid,which is comparable to olive oil,and its selling price is expensive.At present,there are two main types of adulteration of camellia oil,The first type is adulterated with traditional low-value vegetable oils such as soybean oil and corn oil,the other type is adulterated with a new type of high oleic vegetable oil,this kind of vegetable oil has the same oleic acid content as camellia oil,but its low price makes it easy to be sold as camellia oil.At present,adulteration of camellia oil has seriously hindered the development of China’s tea oil industry.It is urgent to excavate the characteristic differential compounds in camellia oil to distinguish from the above two kinds of low-value vegetable oil adulteration.The main research object of this study is camellia oil with high quality and characteristic of Jiangxi Province,and compared with the traditional low-cost vegetable oil(soybean oil,corn oil,peanut oil,rape seed oil,sunflower oil,rice oil)and the new high-oleic vegetable oil(high oleic acid corn oil,high oleic acid rape seed oil,high oleic acid sunflower oil),the triterpenoids and fatty acid components of camellia oil were studied to establish a method for the identification of adulterated low-value vegetable oil.The main research contents and results are as follows:(1)Two-Dimensional Gas Chromatography-Mass Spectrometry method was developed for the qualitative analysis and relative quantitative analysis of triterpenoids in different types of vegetable oils,the results showed that camellia oil was different from other vegetable oils because of β-Amyrin,lupeol,lanosterol.To further determine the content of these substances in camellia oil,the Gas Chromatography-Mass Spectrometry method was further optimized,and accurate qualitative quantitative analysis of these characteristic substances were obtained with reference materials.(2)To establish a quantitative method for the determination of triterpenoids by GC-MS,and to further determine the types and contents of triterpenoids in different vegetable oils.It is further proved that β-Amyrin and lanosterol are the unique triterpenoids in camellia oil,it can be used as a marker of difference between camellia oil and other vegetable oils.In addition,the content of campesterol in common low-value vegetable oil is much higher than that of camellia oil,which can be used as the index to identify the adulteration of low-value vegetable oil.(3)Gas Chromatography-Flame Ionization Detector was used to qualitatively and quantitatively analyze the fatty acid components in camellia oil and low-value vegetable oil,the fatty acid composition of different plant oils has different species characteristics,such as camellia oil has the highest oleic acid content,about 79%,sunflower seed oil has the highest linoleic acid content,rice oil has the highest palmitic acid content,sunflower seed oil has the highest stearic acid content;The oleic acid content in the new high oleic vegetable oil is higher than that in the common vegetable oil,which shows the characteristics of fatty acid profile of different vegetable oils.At the same time,the fatty acid composition database of vegetable oil was constructed,and the partial least squares regression-discriminant analysis was used.It was found that the high content of oleic acid in camellia oil was different from the traditional low-value vegetable oil,this is consistent with previous reports,but compared with high oleic vegetable oils,oleic acid is no longer the characteristic substance that distinguishes camellia oil from high oleic vegetable oil,behenic acid can distinguish camellia oil from traditional low-value vegetable oil and high-value vegetable oil at the same time,which can be used as a characteristic index to distinguish camellia oil from two kinds of low-value adulterated vegetable oil.(4)From the above conclusion,β-Amyrin and behenic acid are the markers of the difference between camellia oil and other vegetable oils,the difference ratio ofβ-Amyrin and behenic acid in different vegetable oils was amplified byβ-Amyrin/campesterol,cis methyl oleate/methyl behenate.It was found that the ratio of cis methyl oleater to methyl behenate in camellia oil was higher than 1400,but the ratio of other vegetable oils was much lower than that of camellia oil,the results show that the ratio of β-Amyrin/campesterol in camellia oil is higher than 50,which is much higher than that of other kinds of vegetable oils.By simulating the adulteration of5%-20% of other oils,it was found that when the ratio of cis methyl oleate/methyl behenate was less than 1200 and the ratio of β-Amyrin/campesterol was less than 40,other vegetable oils could be identified in camellia oil The feasibility of this method is verified.From the above conclusion,β-Amyrin is a differential marker between camellia oil and low-priced common vegetable oil(soybean oil,sunflower oil,etc.),in addition to oleic acid,behenic acid can also identify camellia oil and high oleic vegetable oil,the ratio of β-Amyrin/campesterol,cis methyl oleate/methyl behenate was used to enlarge the difference ratio between β-Amyrin and behenic acid.and behenic acid is a differential marker between camellia oil and high oleic vegetable oil.By comparing the ratio of between different kinds of vegetable oil fatty acid methyl esters,we can see that the ratio of cis methyl oleate/methyl behenate in camellia oil are all higher than 1400,the ratio of other vegetable oils is much lower than that of camellia oil.Therefore,this ratio can be used to determine whether camellia oil adulterated with other vegetable oils.Comparing the ratio of β-Amyrin/campesterol between different kinds of vegetable oils,it can be seen that the ratio of β-Amyrin/campesterol in camellia oil is more than50,and much higher than that of other kinds of vegetable oils,therefore,the identification method of adulteration of camellia oil can be developed by using the ratios of cis methyl oleate/methyl behenate and β-Amyrin/campesterol,and the feasibility of this method is verified by simulating the adulteration of low-price oil with different ratios. |
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