The Development And Application For Trans Fatty Acids(TFAs)

Trans-fatty acid is the generic name of a group of unsaturated fatty acids which include trans-configuration double bond. Trans-fatty acids threaten mankind's healthy seriously, such as impacting digestion and absorption of essential fatty acids, leading to cardiovascular disease occurrence, causing brain function decline. The overseas researchers have attached great importance to the trans fatty acids. Attentions on the trans fatty acids are just paied to in home. The universally acceptant method to detecttion of trans fatty acids has not be developed yet in china.In order to establish a fast and effective detection method of trans fatty acids, four esterification methods of potassium hydroxide - methanol, methanol sodium - methanol, boron trifluoride -methanol and concentrated sulphuric acid - methanol were compared on the respond peak areas of the trans fatty acids in butter, and the best esterification method was screened out. Then the concentration and volume of the esterification reagents and methyl esterifacation temperature and hold time were determined. Combined with the optimization of equipment conditions, primary detection method of trans-fatty acids was established. Using the developed detection method, the trans fatty acids in some edible oils and oil foods were mensurated, and content changes of the trans fatty acids in frying oils were explored. The results are as follows:1. Four methyl esterification methods were compared on the respond peak areas of 6 kinds of trans fatty acids in the same quantitative sample butter. It showed that esterification with the method of boron trifluoride - methanol resulted in the greatest response peak areas of the trans fatty acids and that esterification with the method of concentrated sulphuric acid - methanol resulted in the smallest response peak areas of the trans fatty acids.2. Through four esterification methods comparision of the fatty acids, the best pre-treatment conditions of the trans fatty acids were designated as the final sample of 30 mg, 2mll0% BF₃ -methanol solution as derivative reagent, hermetically heating 15 min at 100℃and extraction with 2ml hexane at room temperature.3. The optimized equipment conditions were defined as: Column: Rt-2560 (100m * 0.25mm * 0.2μm); Carrier gas: He, CC mode flow rate: 2 ml / min; Injection port temperature: 250℃; detector: FID, 280℃;Oven temperature: 140℃(hold 2min) to 240℃(hold 10min) at 3℃/ min;Input mode: Split injection, split ratio: 1:50;Gas ratio: nitrogen: hydrogen: air = 45:30:300; Injection volume: 1μ1;4. By internal standard method, the main six types of trans fatty acids in common edible oils and oil foods were identified as C14:1-9t, C16:1-9t, C18:1-9t, C18:1-11t, C18:2-9t, 12t and C18:2-9t, 12c, C18:2-9c, 12t.5. By the developed detection method of trans fatty acid, the trans fatty acid content in edible oils and oil foods was investigated. Among the edible oil, rapeseed oil had the highest trans fatty acid content, reaching 1.2 g/100g. The trans fatty acids in butter reached a maximum content of 3.55 g/100g, followed by puffed food with 2.33 g/100g.6. Monitoring the dynamic change of the trans-fatty acids content in frying oil is another practical application of the developed detection method. It indicated that the content of various of trans fatty acids gradually increased with the prolonging of frying time.