Trans fatty acids are fatty acids that exist in foods made by some animals under natural conditions. When vegetable oils are concentrated to make other products such as margarine, trans fatty acids are also formed. Among them, the content of margarine and crisp oil is the most. Most people think that animal oils contain more saturated fatty acids than vegetable oils, but after years of research shows that trans fatty acids in vegetable creams are also harmful to humans, and may be more harmful than animal oils.
The harm of trans fatty acids (TFAS) to the human body has caused widespread concern. The United States and eight EU countries have begun to issue standards to restrict the content of trans fatty acids. At present, China's understanding of trans fatty acids has just begun, and foreign research on it has entered a stage of mandatory rectification. Because trans fatty acids are 10 times more harmful to humans than saturated fatty acids. Therefore, China has also begun to take action, and relevant standards and test methods are being researched and in progress. The Changzhou City Product Quality Supervision and Inspection Institute of Jiangsu Province also conducted a discussion on the detection of trans fatty acids based on relevant data. The author will talk about the practical experience of trans fatty acids and testing.
Fat consists of saturated, polyunsaturated, unsaturated and monounsaturated fatty acids. EPA and DHA are two kinds of polyunsaturated fatty acids. They are also called eicosapentaenoic acid and docosahexaenoic acid according to their chemical structure. EPA and DHA are important fatty acids that make up phospholipids and cholesterol esters.
Saturated fatty acids in food are mainly derived from animal products and certain vegetable oils (including coconut oil, palm oil and cocoa butter). The unsaturated fatty acids in food are mainly cis, and a small part of animal fatty acids are trans. When chemically processing oil, people sometimes add hydrogen atoms to polyunsaturated fatty acids through hydrogenation. The newly added hydrogen atoms are located on both sides and become trans fatty acids. The most typical representative of this artificial compound It is margarine or margarine.
Unsaturated fatty acids are essential fatty acids. Unsaturated fatty acids can be divided into monounsaturated fatty acids and polyunsaturated fatty acids according to the number of doubles. Among food fats, monounsaturated fatty acids include oleic acid, and polyunsaturated fatty acids include linoleic acid, linolenic acid, and arachidonic acid.
Trans fatty acids are produced by hydrogenation during processing. After hydrogenation of vegetable oil, cis-fatty acids will become unnatural trans-fatty acids and become solid or semi-solid substances. This fat component may cause cardiovascular disease and endanger health. Trans fatty acids will increase bad cholesterol, while reducing the content of benign cholesterol, interfere with the metabolism of fatty acids, and may cause certain types of cancer.
Trans fatty acids are rarely found in natural foods. The foods containing trans fatty acids that people usually eat basically come from foods containing margarine. Foods containing hydrogenated vegetable oil may contain trans fatty acids, the most common are baked goods (biscuits, bread, etc.), salad dressing, and fast foods such as French fries, fried chicken, onion rings, as well as Western-style pastries, chocolate Pie, coffee mate, hot chocolate, etc. It's just that the names of trans fatty acids are different, and they are generally marked on the product packaging as "hydrogenated vegetable oil", "plant shortening", "margarine", "margarine", "vegetable cream", "wheat cream", "Short butter" or "milk fat", which may contain trans fatty acids.
Before, there was no detection method for trans fatty acids in China. Recently, TFA detection methods have been "born" in Hangzhou. National standards are also expected to be promulgated before the end of this year. In addition, we learned from the National Aquatic Products and Processed Food Supervision and Inspection Center (Hangzhou Quality and Technical Supervision and Inspection Institute) that the subject of "Transfatty Acid (TFA) Testing Method Research" completed by the center has now been approved by experts. The completion of this subject ended the passive situation in China where there is no industry standard for TFA content and no detection method. This move will take the lead in the world. We provide according to the literature of Jiangxi Food Industry Qinglong High-tech Co., Ltd., according to its parameters and operating conditions. The pretreatment of the sample, the choice of chromatographic conditions, and the technical parameters were explored. Taking trans-palmitic acid and trans-octadecenoic acid as examples, this method is fast and effective. specific method:
1. Experimental part
Equipment: Varian GC3800.
Chromatography column: EC-1000 (30 × 0.32 × 0.5).
Detector: FID.
Standard products: trans-palmitic acid (C 16: 0), trans-octadecenoic acid (C 20: 0).
2. Experimental procedure
1. Test requirements
The reagents used are all chromatographically pure or analytically pure, test water (ultra-pure water or distilled water).
1.1 Qualitative comparison with standard products, use fatty acid methyl ester mixed standard to explore the effective separation conditions before sample detection.
1.2 Sample methylation
Weigh 0.5g of oil sample in a 100ml pear-shaped bottle with a stopper and add 10ml of a mixed solution of 11 petroleum jelly and benzene to dissolve the oil. Add 20 ml of 0.4 mol KOH-methanol solution, shake well, let stand at room temperature for about 15 minutes, add 30 ml of pure water, make the puzzle layer and the nail fat and water layer, extract twice, if necessary, add a few drops of ethanol to make The solution is clear. The supernatant was collected and made up to 50 ml, and analyzed by gas chromatography.
3. Test conditions:
Detector temperature: 300 ° C.
Inlet temperature: 250 ° C.
Column oven temperature: temperature programmed (120 ℃ -1min-15 ℃ / min-200 ℃ -5min).
Flow rate: 0.7mL / m.
Diversion: 50.
4. Method accuracy and recovery rate
High and low concentration samples were selected for precision and recovery test. The results are shown in Table 1 and Table 2.
V. Results analysis
The test results show that the average recovery rate of the determination method is 93%, and it has good accuracy and precision. This method has the advantages of good repeatability, high recovery rate, simple operation and high sensitivity, and is particularly suitable for the determination of low content of samples. According to the spectrum results, the separation effect of the components is also satisfactory, which can ensure the accuracy and reliability of the data.
6. Conclusion
This method can be used well in the determination of trans fatty acids.
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