以氣相層析法測定牛奶中脂肪酸含量   全文下載

Quantitation of Fatty Acids in Milk by Gas Chromatography

本研究係以氣相析法探討牛奶中脂肪酸定量之可行性。牛奶以氯仿／甲醇（2：1, v／v）萃取脂肪，以氯化乙醯／甲醇（1：10, v／v）在60°C經90分鐘後，轉酯反應完成，可製成脂肪酸甲基酯。以脂肪酸標準品製成甲基酯其回收率為高濃度組，98.2 ± 3.2%；低濃度組97.5 ± 4.1%。將檢樣注入氣相層析儀分析結果：各額牛奶檢樣中檢出九種主要脂肪酸，佔總脂肪量85%以上。市售主要廠牌之鮮奶與奶粉中，C4-C12短鏈脂肪酸含量略有差異。保久乳中各類脂肪成分大致與鮮奶相同。而調味乳依廠牌不同，皆摻入添加物致脂肪酸含量有顯著差異。牛奶和羊奶較人奶含有較多短鏈脂肪酸。"

This study investigated a reliable method for quantitation of fatty acids (FA) in milk by gas chromatography. Milk samples were treated with CHCl3/CH3OH(2:1, v/v) to extract the fats. A transesterification reaction using fat plus AcCl/CH2OH(1:10, v/v) as a reagent to prepare fatty acid methyl esters (FAME) was carried out at 60oC for 90 min. The recoveries of FAME derived from standard FA were 98.2±3.2% for the high concentration group; 97.5±4.1% for the low concentration group. When FAME derived from each milk sample was injected into a gas chromatograph, a total of 9 corresponding FA were separated and detected. The FA portion was found to constitute more than 85% of total fat. The content of C4-C12 short-chain FA was also found to be slightly different between the various brands of marketing pasteurized milk and milk powder (reconstituted milk). The content of various FA in long-life milk is essentially similar to pasteurized milk; in flavored milk obvious differences were found due to a variety of additives blended. Raw cow and goat milk contain more short-chain FA than human milk.