Research On The Changes In Physicochemistry Characteristics And Nutritional Quality Of Camellia Oil During Frying

Camellia oil,one of China's unique woody grease,is quality edible oil favored by our market,which is of high nutritional value due to its high oleic acid,VE,squalene content,etc.In addition,Camellia oil is rich in polyphenols which have anti-oxidation,anti-virus,anti-inflammatory,antibacterial effects and other effects such as improving human immunity.And polyphenols is one of the main nutritional components which gives Camellia oil high nutritional value.The results show that the endogenous phenolic compounds have good safety at room temperature,but during high temperature frying,the oil is prone to loss of value or degradation,which leads to the decrease of oil quality and even the risk of food consumption.Therefore,study on the frying characteristics of Camellia oil and the oxidation characteristics of endogenous phenolic compounds during frying is of great significance to nutrition preservation as well as food safety.In this paper,in view of the habitual use of frying of Chinese cooking oil at high temperature,experiments on the changes of physical and chemical properties and nutritional quality of Camellia oil during high temperature frying were carried out,and analysis of the law of loss of the phenolic compounds in Camellia oil at high temperature were conducted,with a view to providing basic support for scientific advice on proper consumption and full use of the nutritional value of Camellia oil.The main research results are as follows.(1)Study on the change of main physical and chemical properties of Camellia oil during frying.Measured by GB method,changes of index including the acid value,iodine value,peroxide value,carbonyl value,anisidine value and polar component of Camellia oil during frying were studied.It proved that during frying process,with prolonged frying time and elevated frying temperature,the acid value,peroxide value,carbonyl value,anisidine value and polar component of Camellia oil increased while iodine value displayed a decrease.And the change rate of each index at 200? is larger than that of 160? and 180?.The contents of saturated fatty acids(SFA)increased and monounsaturated fatty acids(MUFA)did not change significantly,while the contents of polyunsaturated fatty acids(PUFA)decreased during frying.Through solid-phase headspace microextraction and gas chromatography analysis,the volatile components of Camellia oil during frying were explored.The results showed that the volatility of Camellia oil was stronger with more unsaturated aldehydes content;And there were more volatile components of Camellia oil with the extension of the frying time.(2)Establishment of separation and purification and detection methods about polyphenols of Camellia oil.After degumming through enzymatic method and oil extraction of Camellia seeds,on the basis of single factor experiment,the optimal technological conditions of liquid phase extraction were determined as follows: ethanol as extractant,extraction time 15 min,liquid ratio 1:4,ethanol volume fraction 70%,extraction 3 times,and the total phenol content up to 537 ug/g.Solid phase extraction was extracted positive phase silica gel extraction column and eluted by methanol;the total phenol content reached 580.95 ug/g.However,the second extraction effect was only 50% of the original extraction and could not be reused.Effects of extraction and purification of the total polyphenols conducted by two methods,that is,liquid extraction and solid phase extraction,were compared.In contrast,liquid phase extraction is more economical,so liquid extraction is chosen.After Comparing phenolic colorimetric method,ultraviolet spectrophotometry and recovery rate experiments,the best detection method for the phenolic is colorimetric method.(3)Study on the loss of representative nutritional components of Camellia oil during frying.The changes of polyphenols,sterols and VE content in Camellia oil during frying were investigated.It was found that the total phenolic content decreased with prolonged frying time and elevated frying temperature;After 20 h,the total phenols content decreased quickly at 160 ?,180 ? and 200 ?,and at 32 h,the loss ratio of the total phenols content was 82.93%,85.22%,92.13%,the loss ratio of VE content 77.13%,85.90% and 97.61%,the loss rate of sterols content 87.93%,89.53% and 94.90%.Therefore,Camellia oil suffers more loss of nutrients with prolonged frying time and elevated frying temperature.(4)Study on effects of antioxidation and free radical scavenging of Camellia oil during frying.Through three systems of in vitro antioxidant tests,including determination of DPPH free radical scavenging ability,total reduction ability,hydroxyl radical scavenging ability.The results showed that the antioxidant capacity of Camellia oil decreased with time extension and temperature rise.