【摘要】：反式脂肪酸(Trans fatty acids，TFA)是不飽和脂肪酸的異構(gòu)體，其結(jié)構(gòu)中一般含有至少一個反式構(gòu)型的雙鍵。TFA過多攝入，可能對人體健康造成不良影響。主要表現(xiàn)：影響必需脂肪酸的消化吸收、導(dǎo)致心血管疾病發(fā)生、可能引起大腦功能衰退，影響嬰幼兒的生長發(fā)育，也是老年癡呆癥的主要誘因之一等。在國內(nèi)外，關(guān)于TFA的相關(guān)研究已被學(xué)界高度重視，在餐飲業(yè)和食品加工方面已有大量研究報道。 反芻動物（如牛、羊）的乳、脂肪組織及其制品中一般含有少量天然TFA成分，，其中體脂中的TFA含量比較多，占到總脂肪酸含量的4%-11%；牛乳和羊乳中的TFA含量占到總脂肪酸的3%-5%，一般不會對人體造成危害。牛乳脂中的TFA通常是不飽和的單烯鍵結(jié)構(gòu)，雙鍵一般在Δ6與Δ16位置之間比較多，含量最多的單烯酸一般是C11T-C18T之間，以C16T和C18T為主。不恰當(dāng)?shù)臒崽幚砉に嚳赡茉斐膳Ｈ橹蠺FA含量的升高，甚至可能達到危害人體健康的程度。 目前，關(guān)于各類食品中TFA含量和組成的研究已經(jīng)較多，但是乳品加工過程中TFA的相關(guān)研究鮮見報道，特別是牛、羊乳在不同熱處理工藝加工后產(chǎn)品中TFA的含量變化是否對人體造成危害，未見相關(guān)研究報道。 本研究采用羅茲-哥特里法提取乳中脂肪，經(jīng)三氟化硼-甲醇甲酯化反應(yīng)后進行氣相色譜分析，對牛乳中的TFA含量進行分析比較。旨在探討牛乳中反式脂肪酸（TFA）在不同熱處理條件下的變化規(guī)律，為牛乳加工熱殺菌工藝參數(shù)確立提供參考依據(jù)。主要結(jié)論如下： 1.三種甲酯化方法檢測乳脂中C16T含量的對比研究。結(jié)果表明：對于同一樣品，采用氫氧化鉀-甲醇常溫甲酯化的方法效率最低，C16T含量為0.050±0.003mg/mL；加熱回流方法檢測出含量為0.052±0.002mg/mL，比常溫法效率稍高；采用三氟化硼催化-甲醇加熱回流的方法甲酯化效率最高，為0.060±0.001mg/mL，與氫氧化鉀-甲醇常溫甲酯化方法相比差異顯著（P0.05），結(jié)論：樣品甲酯化采用三氟化硼催化-甲醇加熱回流的方法最優(yōu)。 2.氣相色譜檢測條件的優(yōu)化研究。對甲酯化的脂肪酸分別采用三種氣相條件進行檢測，最終檢測條件優(yōu)化為：色譜柱：Rtx-1701毛細管柱(30m×0.25mm×0.25μm)；載氣：N2，柱流量0.8mL/min，恒流模式；進樣口溫度250℃；檢測器溫度280℃；升溫程序：180℃保留5min，4℃/min升至200℃，再以1℃/min升至210℃，最后以20℃/min升至230℃。此條件能夠全面表征牛乳中脂肪酸及反式脂肪酸組成與含量。 3.不同熱殺菌處理條件下TFA的含量變化研究。結(jié)論：①巴氏殺菌（85℃）條件下，隨著加熱時間的延長，牛乳中C16T和C18T的含量均處于上升趨勢（P0.05）。當(dāng)加熱時間延長到90s時，乳中C16T和C18T含量達到檢測峰值，分別為0.15±0.01mg/mL和1.82±0.04mg/mL，比原奶中有顯著升高(P0.05)；②超高溫條件下（T133℃），熱處理時間（4s）不變，隨著加熱溫度的升高，C16T含量0.056±0.002mg/mL-0.066±0.005mg/mL間波動，無明顯的變化差異；C18T含量在0.8±0.04mg/mL-0.95±0.08mg/mL間波動，無明顯差異，但其含量均高于原料奶。即超高溫處理對乳中TFA含量存在影響，但其作用效果不明顯(P0.05)。③高溫條件（130℃）保持不變，延長滅菌時間，乳中TFA含量顯著上升。當(dāng)加熱至300s時乳中C18T含量已高達2.11±0.2mg/mL，接近對人體造成危害的限量。高溫條件下時間對TFA含量的影響差異顯著(P0.05)。因此，UHT滅菌工藝應(yīng)嚴(yán)格控制滅菌時間。 4.不同生產(chǎn)季節(jié)對產(chǎn)品中TFA的影響。通過對不同月份的產(chǎn)品中TFA含量進行分析比較，結(jié)果表明：十月份乳中TFA含量最低，其中C16T含量為0.056±0.002mg/mL，C18T為0.82±0.04mg/mL；C16T含量在七月份達到最高，為0.068±0.002mg/mL，C18T含量在八月份最高，為0.95±0.03mg/mL。七、八月份與4月和10月間牛乳中TFA含量存在顯著差異（P0.05）其它各月份間TFA含量的差異并不明顯（P0.05），結(jié)論：季節(jié)對產(chǎn)品中TFA的含量也有一定影響，但不明顯。
[Abstract]:Trans-fatty acids (TFA) are the isomers of unsaturated fatty acids, which generally contain at least one double bond in the trans configuration. Excessive TFA intake may have an adverse effect on human health. The main performance is that the absorption of essential fatty acid is affected, which leads to the occurrence of cardiovascular diseases, which can cause the function of the brain to decline, which can affect the growth and development of the infant, and is one of the main causes of the senile dementia. At home and abroad, the related research on TFA has been highly valued by the academic field, and a large number of research has been reported in the field of catering and food processing. The milk, adipose tissue and its products of ruminants (such as cattle and sheep) generally contain a small amount of the natural TFA component, in which the TFA content in the body fat is much higher, accounting for 4% to 11% of the total fatty acid content; the TFA content in the milk and the goat milk accounts for 3% to 5 of the total fatty acid %, in general, will not cause danger to the human body The TFA in the milk fat is usually an unsaturated monoethylenically unsaturated structure, and the double bond is generally more abundant between the position 6 and the position 16, and the most content of the monoenoic acid is typically between C11T-C18T, in the order of C16T and C18T. The improper heat treatment process may cause an increase in the content of TFA in the milk and may even reach a range of harm to the health of the human body Degree. At present, there are more studies on the content and composition of TFA in various foods, but the relevant research of TFA in dairy processing has been reported, especially whether the content of TFA in the products after the processing of different heat treatment processes has been made to the human body. As a hazard, no relevant research is found. In this study, the fat in milk was extracted by the Roz-Gothic method, and the content of TFA in the milk was determined by gas-phase analysis after the reaction of the boron trifluoride-methanol methyl ester. The purpose of this study was to study the change of trans-fatty acid (TFA) in milk in different heat treatment conditions, and to establish the parameters of heat sterilization process for milk processing. for reference. Main The conclusion is as follows:1. Three methyl esterification methods to detect C16T in milk fat The results showed that, for the same sample, the efficiency of using potassium hydroxide-methanol at normal temperature was the lowest, and the content of C16T was 0.050 to 0.003 mg/ mL, and the content was 0.052 to 0.002 mg/ mL, and the ratio was 0.052 to 0.002 mg/ mL. The efficiency of methyl esterification with boron trifluoride catalyst-methanol was the highest, which was 0.060 and 0.001 mg/ mL, and the difference was significant (P0.05). the best method of the reflux method.2. Gas chromatography The detection conditions were optimized. Three gas-phase conditions were used to detect the methyl ester, and the final detection conditions were as follows: column: Rtx-1701 capillary column (30 m, 0.25 mm, 0.25. mu.m); carrier gas: N2, column flow of 0.8 mL/ min, constant current mode; injection port temperature of 250 鈩

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