| In this study,the different extraction methods of fatty from infant formula for special medical purposes and phytolacca were analyzed,and an analysis of advantages and disadvantages for the different methyl esterification methods was carried out.The detection results of fatty acids and trans-fatty acids by gas chromatography-mass spectrometry(GC-MS)were also systematically investigated,and an efficient and accurate method for the determination of fatty acids in food for special medical purposes(FSMP)and trans-fatty acids in infant formula for special medical purposes(IFSMP)was determined.Based on the above research,this study confirmed the efficient and accurate methods for the determination of fatty acids in FSMP and trans-fatty acids in IFSMP.This study has also optimized the fatty acid extraction and detection method for FSMP,and provided a theoretical basis for the quality control and evaluation of FSMP and IFSMP,which is important to regulate the nutritional properties and safety of FSMP and protect the interests of consumers.The results showed that the extraction method by ultrasound-assisted after solubilization of the sample in water was the best for the isolation of fat from FSMP.The extraction rate of the method is almost the same as that of the hydrolysis extraction method,and the operation is simple,the extraction time is shortened,and fewer reagents are used.Through the comparative analysis of the number of fatty acids and the peak area of the samples to be tested,the results show that the alkaline methyl esterification method is relatively optimal,and can detect up to 13 fatty acids in the samples.The temperature programmed condition of GC-MS was optimized by the mixed standard of fatty acid methyl ester,and the final determination was as follows:initial temperature was 80℃,maintained for 2 min;80℃～100℃,increase 5℃per minute,maintain 5 min;100℃～180℃,increase 10℃per minute,maintain 5 min;180℃～210℃,increase 2℃per minute,maintain 5 min;210℃～230℃,increase 5℃per minute,maintain 2 min;230℃～240℃,increase 2℃per minute,maintain 5 min.Total detection time of the method in this study is only 1 h,which is relatively shortened compared to the previous detection method of fatty acids.When the split ratio is 10:1,16 kinds of fatty acids in the sample can be detected,which further optimizes the detection method of fatty acids in FSMP.The standard curve of the method for the detection of fatty acid in FSMP established in this study has a good linear relationship(R~2≥0.9959),the RSD of precision,stability and repeatability are all less than 5%,and the recovery rate of standard addition is 90.03～107.76%,the minimum detection concentration is 0.263μg/m L.The results showed that the method was accurate and efficient.Aiming at the detection method of trans-fatty acids in IFSMP,this study determined the methyl esterification method by comparing the response values of the detected trans-fatty acids,and the methyl esterification temperature and time were further optimized to obtain the best methyl esterification method.The GC-MS temperature program and transfer line temperature were optimized by the mixed standard of trans-fatty acid methyl ester.According to the peak area,the optimal detection conditions were obtained as follows:170℃for 1min;170℃～185℃,increase the temperature by 10℃per minute,hold for 2 min;185℃～210℃,increase the temperature by 1℃per minute,hold for 5 min;210℃～240℃,increase the temperature by 10℃per minute,hold for 2 min.The transfer line temperature was 270℃.The established method for the detection of trans-fatty acids in IFSMP was validated by standard curve,precision,stability,repeatability and recovery rate.The results showed that the method was accurate and efficient.In this stduy,nine representative samples were collected from the market,and the method established in this study was used to detect fatty acids and trans-fatty acids in the samples.The results showed that the long-chain fatty acids were rich in samples,and the most abundant fatty acid was oleic acid.The detected trans-fatty acid was t C18:1,and the content complied with national regulations.Finally,the standard(draft)method for the detection of fatty acids in FSMP and the standard(draft)for the detection of trans-fatty acids in IFSMP were drawn up. |
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