Method for detecting fatty acid content in rice fat

Abstract

The invention discloses a method for detecting fatty acid content in rice fat. The method comprises the following steps of: carrying out base-catalysis methyl esterification and solid phase microextraction synchronously on a rice sample in a headspace bottle by means of a multifunctional sample injector, and then detecting and performing quantitative analysis on the fatty acid content in the rice fat after the rice sample enters a gas chromatography-tandem mass spectrum (GC-MS-MS). According to the invention, the on-line methyl esterification, the solid-phase microextraction and the gas chromatography-tandem mass spectrum technology are adopted, the five steps of methyl esterification, extraction, enrichment, sampling and detection are completed at the same time during one process, the operation is simple, and the consumed time is short; moreover, water acts as a base body during the methyl esterification reaction, so that the competitive adsorption of an extracting head to methyl alcohol and volatile substances is lowered, and the extraction and pre-enrichment of fatty acid methyl ester by the solid phase microextraction are improved effectively; and the minimum detection limit of fatty acid is 0.001-0.049 micro g / L, and is obviously lower than the minimum detection limit, 4.0mg / L, of an internal standard method which is used for performing quantitative determination on oil fatty acid.

Description

technical field [0001] The invention relates to a method for analyzing and detecting fatty acids, in particular to a method for detecting fatty acids in rice fat. Background technique [0002] Fat is an important component of rice, and the main component of rice fat is unsaturated fatty acid. Unsaturated fatty acids have many benefits to the human body, such as alleviating excess cholesterol in the blood, enhancing cell membrane permeability, and preventing myocardial tissue and arteriosclerosis. Due to the rapid deterioration of fat, it is prone to hydrolysis to increase free fatty acids, and unsaturated fatty acids are prone to oxidation to reduce unsaturated fatty acids, resulting in increased acidity and loss of flavor in aged rice. Therefore, the content and composition of fatty acids in rice fat can be used as an evaluation method for rice quality. As an auxiliary material commonly used in beer production, rice has the significance of reducing the cost of beer produc...

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Problems solved by technology

The second method commonly used is boron trifluoride methyl esterification method, alkali method methyl esterification method and acid method methyl esterification method. Among them, boron trifluoride catalyzes methyl esterification rate is high, but its toxicity is strong, it is not easy to store, and it is unfavorable. Used by operators; acid-catalyzed methyl esterification oil has the characteristics of slow reaction, low methyl esterification rate and high temperature requirement, so it is not suitable for solid phase microextraction technology

However, rice has high fat content and few free fatty acids, so the acid-catalyzed methyl esterification method used in this method is not suitable for the analysis of fatty acids in rice

Since methanol as a methyl esterification reagent is volatile, when the methyl esterification reaction occurs in the headspace bottle, methanol enters the headspace, resulting in a decrease in the methyl esterification rate of fatty acids, affecting the extraction effect, and even extraction Competitive adsorption of volatiles and methanol by head against the enrichment of fatty acid methyl esters

In addition, there are few reports on the quantitative detection of fatty acids in the prior art, among which there are articles reporting that the detection limit of the quantitative determination of fatty acids in oils and fats by internal standard method is only 4.0 mg / L (the internal standard method of capillary gas chromatography is used to determine the fatty acids in seabuckthorn oil). , Chinese Journal of Cereals and Oils, 2008, 23(1):198~202)

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