1 Article title
A Study on the Correlation between oxidation degree and fatty acid ratio of five different plant oils and fats. Ding Jian,Qi Baokun,Wang Limin,et al.
2 articles in the journal
Journal of the Chinese Cereals and Oils Science ;(2019) Composite Impact Factor: 1.214
3 Research objectives and methods
Five kinds of vegetable oils and fats, namely coconut oil, soybean oil, corn oil, sunflower oil and rapeseed oil, were selected as the research objects, and the proportion of fatty acids in different oils and fats was determined in the process of heating oxidation at 180°C, and the correlation between conjugate diene (CDV), P-anisamine (P-AV) and hexalaldehyde content was analyzed.
4 Findings
4.1 The value of lipid conjugate dialne p~AV changes with heating time
The CDV and p-AV of the coconut oil with a heating time of 0 h are very low, indicating that the oil has only a trace amount of oxidation at this time. As the heating time increases, the two show a non-linear change. The CDV value rises within 0~6 h, the CDV value decreases slightly during the 6~12h process, and when the conjugated diene value increases rapidly to 12~18h, the CDV value begins to decrease in the late oxidation period; the p-AV value has a similar change trend with the conjugate dialne value with the change of heating time.
Soybean oil CDV has been increasing at 0 to 18 h, showing a rapid increase at 0 to 6 h, and CDV began to decline at 18 to 24 h. The P-AV value basically tends to be stable at 6 to 18 h, and the P-AV value begins to decline slowly at 18 to 24 h. Soybean oil has a higher CDV and P-AV value than coconut oil, due to the higher content of unsaturated fatty acids, which are rearranged by the double bonds when they come into contact with oxygen during heat oxidation.
Corn oil CDV rose slowly after 0 to 6 h and decreased slightly at 18 to 24 h. The P-AV value of corn oil rises rapidly at 0~6 h and decreases at 6~12h, while the P-AV value tends to be stable during the 12-24h process. It can be seen from the change law of CDV and P-AV values that the CDV value changes after 18 h, the change of P-AV value is closely related to the heating time of the grease, and the secondary oxidation product of corn oil reaches its maximum at 6h heating, and the unstable degradation occurs with the extension of the heating time.
Sunflower oil CDV value 0 ~ 6 h slightly decreased, 6-18 h CDV value continued to rise, in 18 ~ 24 h there was a rapid decline, mainly due to the early stage of oxidation, unsaturated fatty acids between the formation of conjugates, the reaction to the formation of peroxides, to the middle and late stages of the decomposition of peroxides, when the oil oxidation to a certain degree of peroxide formation of aldehydes and ketones.
The CDV value of rapeseed oil increased at 0 to 18 h, the fastest increase at 12 to 18 h, and the process of 18-24 h tended to be stable. In the process of 0-6h, the P-AV value of rapeseed oil increases rapidly; when it is 6~12h, the P-AV value decreases; in the process of 12~18h, it gradually increases, and the 18-24h tends to be unchanged.
4.2 Determination of hexanal content
After the oxidation of oil and fat, the content of hexanaldehyde gradually increases with the increase of heating time, and the increase of hexanal is related to the oxidation of unsaturated fatty acids in oils and fats to form fat oxides. Almost all 5 kinds of oils and fats accumulate to the maximum after heating for 18h, and sunflower oil and rapeseed oil have the most hexalaldehyde content at this time.
4.3 Changes in fatty acid content during oil heating
Heating affects the saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids of the five oils and fats. After heating for 6h, the content of palmitic acid and stearic acid of the five oils was significantly increased, while the content of oleic acid, linoleic acid and linolenic acid was reduced; among them, the oleic acid, linoleic acid and linolenic acid content of sunflower oil and rapeseed oil decreased significantly during the heating process, while the degree of decline of soybean oil and corn oil was lower; the content of saturated fat of the five oils was increased.
4.4 Correlation analysis between fatty acid ratio and oxidation of fats and oils
Different fatty acid ratios in different oxidation stages and the detection of oxidation index are positive correlation, but the correlation is not completely consistent, coconut oil fatty acid ratio only SFA / UFA and CDV, P-AV and caprolaldehyde content correlation R value of 0.9 or more, the other 4 kinds of lipid hexanal content and each fatty acid ratio parameter between the correlation coefficient R is mostly above 0.8, indicating that the accurate headspace analysis method of oil and fat is better than CDV and p-AV in characterizing the degree of oxidation of oils and fats.
5 Conclusions of the study
5.1 The heating time and the oxidation of oils and fats have a good linear correlation, cdV and P-AV heating fluctuate at different times, and the proportions of oil fatty acids selected by the five plants C16:0/C18:1, C18:0/C18:1, C16:0/C18:2, C18:0/C18:2, C18:l/18:2, SFA/UFA and the detection indicators are positively correlated.
5.2 The correlation R value between the SFA/UFA ratio of coconut oil and the content of CDV, P-AV and hexaldehyde was above 0.9, and the correlation between the C18:0/C18:1 and C18:1/C18:2 fatty acid ratios of soybean oil and corn oil was above 0.8;
5.3 The degree of oxidation of oils and fats can be described by the fatty acid ratio parameters with good correlation, but the fatty acid ratios with different characteristics can be selected for different oils and fats to evaluate the oxidation of oils and fats.
6 Reader Reflections
6.1 Differences in oxidation rates between animal and vegetable fats and oils?
7 Extended topics
7.1 "Differences in oxidation rates between animal and vegetable fats";
7.2 Oxidation rate of fish oil, soybean oil, rapeseed oil;
7.3 "Effect of Oxidized Oils and Fats on Liver and Pancreatic Metabolism"
Literature Learning Summary (Part 14)