| 摘要: |
| 【目的】比较牛、羊乳热处理后蛋白质变性程度，探讨牛、羊乳蛋白质热稳定性差异机理。【方法】采用离心沉淀法、全自动色差仪和SDS-PAGE电泳法，以未热处理的常温（18～20 ℃）牛、羊乳为对照，测定不同温度（95，121 ℃）处理15 min后牛、羊乳蛋白质沉淀率、红值（a*）和酪蛋白的组成；并采用考马斯亮蓝法、菲林试剂法和激光粒度仪测定牛羊鲜乳蛋白质、还原糖质量浓度及蛋白质粒度大小。【结果】羊乳蛋白质沉淀率显著高于牛乳（P＜0.05），牛乳酪蛋白的红值显著高于羊乳（P＜0.05），牛、羊乳酪蛋白主要均为β-酪蛋白和αs1-酪蛋白2种，分子质量分别约为34和26 ku；羊乳蛋白质质量浓度（（37.67±1.67） g/L）显著高于牛乳（（20.33±1.20） g/L）（P＜0.05），还原糖质量浓度（（421.77±10.17） mg/L）显著低于牛乳（（525.67±14.98） mg/L）（P＜0.05）；牛乳蛋白质粒度大小主要集中在1 nm以下，羊乳蛋白质粒度只有少部分在1 nm以下，主要分布于1～1 000 nm。【结论】牛、羊乳蛋白质粒度和还原糖质量浓度分别是影响其蛋白质沉淀率和羰氨反应程度大小的主要因素。 |
| 关键词: 牛乳 羊乳 蛋白质 热变性 变性机理 |
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| 基金项目:陕西省农业科技创新与攻关项目(2016NY-212) |
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| Comparison and mechanism analysis of protein thermal denaturation degree of cow milk and goat milk |
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LI Linqiang,ZHU Lili,WAN Wei,et al
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| Abstract: |
| 【Objective】Thermal denaturation degree of protein from cow milk and goat milk was compared to investigate mechanisms in thermal stability of protein. 【Method】Protein precipitation rate,redness value (a*),and casein composition of cow milk and goat milk after 15 min treatment with different temperatures (95 ℃ and 121 ℃) were analyzed using centrifugal sedimentation method,full automatic colorimeter,and SDS-PAGE.Fresh cow milk and goat milk at room temperature of 18-20 ℃ were used as control.Protein content,reduced sugar content,and size of protein particle from fresh cow milk and goat milk were measured by Kaumas coomassie brilliant blue method,Fehling reagent method,and laser particle size analyzer,respectively.【Result】Precipitation rate of goat milk was significantly higher than that of cow milk (P<0.05),while a* of cow milk was significantly higher than that of goat milk (P<0.05).Both cow milk and goat milk mainly had β-CN and αs1 CN,with molecular weights of 34 and 26 ku,respectively.The protein content of goat milk (37.67±1.67) g/L was significantly higher than that of cow milk (20.33±1.20) g/L (P<0.05),while the content of reduced sugar of goat milk (421.77±10.17) mg/L was significantly lower than that of cow milk (525.67±14.98) mg/L (P<0.05).Particles of cow milk protein were mainly in 1 nm or less,while that of goat milk protein mainly distributed in 1-1 000 nm.【Conclusion】Particle size of milk protein and reduced sugar content were the main factors affecting protein precipitation rate and maillard reaction,respectively. |
| Key words: cow milk goat milk protein thermal denaturation denaturation mechanism |
