超高压及加热处理对羊乳脂肪酸组成的影响

    Effect of ultra-high pressure and heating treatment on fatty acid composition of goat milk

    • 摘要: 为了研究超高压处理及加热处理对羊乳中脂肪酸组成的影响,该文以崂山奶山羊乳为研究对象,通过氯仿-甲醇法和碱催化法分别对乳脂肪进行提取和甲酯化,采用气相色谱-质谱(gas chromatography-Mass Spectrometry,GC-MS)方法分析在100、200、300、400 MPa超高压条件和65℃/30 min、75℃/15 min、90℃/1 min、煮沸加热条件下羊乳中各脂肪酸组成的变化,结果显示:经超高压处理,羊乳中的短链脂肪酸、饱和脂肪酸和不饱和脂肪酸含量的变化均不显著(P>0.05),而经加热处理羊乳中的短链脂肪酸和饱和脂肪酸含量均显著升高(P<0.01),不饱和脂肪酸的含量显著降低(P<0.001)。经超高压处理羊乳中C6:0、C8:0和C10:0含量的变化均不显著(P>0.05);C12:0、C14:0含量显著增加(P<0.01),C16:0变化不显著(P<0.05),C18:0含量显著降低(P<0.05);C18:1含量的变化不显著(P>0.05),C18:2和C18:3含量显著降低(P<0.01,P<0.05),C20:4含量变化不显著(P>0.05)。而经加热处理羊乳中C10:0含量显著升高(P<0.01);C12:0、C14:0和C16:0含量也均显著升高(P<0.05),C18:0含量的变化不显著(P>0.05);C18:1、C18:2、C18:3含量均显著降低(P<0.001,P<0.05,P<0.001),而C20:4为检测出来。研究结果表明超高压处理能够更好的保持羊乳中脂肪酸的含量及组成,进而为超高压技术和加热处理在乳品中的应用及羊乳资源的开发提供了理论依据。

       

      Abstract: Abstract: Goat milk has more nutrition advantages compared with bovine milk, and its fat contains a large number of fatty acids, some of which are very important for human health such as anti-carcinogenesis, anti-atherosclerosis and strengthening immunity. In addition, the specific flavor of goat milk is mainly influenced by free fatty acid of short-chain, such as octanoic acid (C8:0) and decanoic acid (C10:0). Therefore, the purpose of this paper was to study the effects of ultra-high pressure and heating treatment on fatty acid compositions in goat milk from Laoshan dairy goat. The samples were treated under the ultra-high pressure conditions of 100, 200, 300 and 400 MPa and heating treatment of 65℃ every 30 min, 75℃ every 15 min, and 90℃ every min. Then, composition of fatty acid was analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that with the treatment of ultra-high pressure and heating processing, the content of short-chain fatty acid (SCFA) and saturated fatty acid (SFA) increased, while unsaturated fatty acid (USFA) decreased, and there were no significant differences under ultra-high pressure processing, but significant differences were observed under the treatment of heating (P<0.01, P<0.01 and P<0.001). Under the heating treatment of 90℃ every min, SCFA increased to the highest, which was 64.91% (P<0.05) higher than the raw milk, respectively, while the content of USFA decreased to the minimum under the treatment of boiling, which was 35.85% (P<0.01) lower than raw milk. For the SCFA, with the treatment of ultra-high pressure, the differences of caproic acid (C6:0), C8:0 and C10:0 were not significant, however, the significant increase (P<0.01) occurred in C10:0 after heating. For the SFA, significant differences were observed in lauric acid (C12:0), myristic acid (C14:0) and stearic acid (C18:0) under various pressure conditions (P<0.01, P<0.01 and P<0.05), while there was no significant difference for C16:0. The contents of C12:0, C14:0 and palm acid (C16:0) increased with ultra-high pressure treatment and up to the maximum at 300, 200 and 100 MPa respectively, which were enhanced by 179%, 54%, and 26% respectively (P<0.05, P<0.05, P>0.05) compared with raw milk. However, the content of C18:0 decreased with the treatment of ultra-high pressure, and it was the lowest at 200 MPa, which decreased by 65% compared with raw milk (P<0.05). The contents of C12:0, C14:0 and C16:0 were increased with heating treatment and up to the maximum under the boiling condition, which were enhanced by 91%, 74% and 21% respectively (P<0.05) compared with raw milk. For USFA, there was no significant difference in oleic acid (C18:1) with the treatment of ultra-high pressure, but the changes of linoleic acid (C18:2) and flax acid (C18:3) were significant (P<0.01 and P<0.05). The contents of C18:1, C18:2 and C18:3 all decreased with the treatment of ultra-high pressure, and under 300 MPa the contents reached the minimum and reduced by 27%, 60% and 58% respectively compared with raw milk (P>0.05, P<0.05 and P<0.05). The contents of C18:1, C18:2 and C18:3 all decreased with the treatment of heating (P<0.001, P<0.05 and P<0.001), and under the treatment of boiling the contents were the minimum, which were reduced by 33%, 66% and 64% respectively compared with raw milk (P<0.01, P<0.05 and P<0.01). The results of this study reveal that the effect of ultra-high pressure on fatty acids in goat milk is slighter, and it is helpful for the applications of ultra-high pressure technology and heat treatment in the dairy and provides theoretical basis for the development of goat milk resource.

       

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