本文研究了不同因素对崂山奶山羊初乳和成熟乳蛋白质稳定性的影响，分析了温度、pH值、柠檬酸、钙离子、蔗糖及超高压处理下，羊乳蛋白质离心沉淀率的变化，并以此衡量乳液的稳定性。结果表明，第1~3 d的乳对热最为敏感，第1 d的乳65 ℃加热15 min即变得极为粘稠，70 ℃加热15 min第1、2 d的乳均出现凝固结块；第3 d的乳85 ℃加热15 min出现凝固结块。第4~7 d的乳加热到95 ℃未出现凝固结块。可见，随着泌乳期的延长，乳的热稳定性增强。pH6.9的羊乳蛋白质的稳定性最好；蔗糖添加量低于1.0 mg/100 mL时，降低乳的稳定性；高于1.0 mg/100 mL时，随着蔗糖浓度的增加，酪蛋白胶束的稳定性增强；羊乳蛋白质的稳定性随柠檬酸和钙离子浓度的增大而降低。300 MPa以下压力处理对蛋白质沉淀率的影响不大；500 MPa超高压处理时，沉淀率明显增加，作用15 min沉淀率达最高值7.35%。超过500 MPa的压力处理会导致蛋白质的稳定性明显降低。

This study examined the effects of various factors on protein stability in the colostrum and mature milk of Laoshan dairy goats. The centrifugal sedimentation rate of goat milk proteins was analyzed under various conditions, including a range of temperatures and pH values, citric acid, calcium ion, sucrose, and ultra-high pressure, to evaluate the stability of the milk proteins. The results showed that colostrum was the most sensitive to heat during the first 1~3 days. On the first day, milk samples became extremely thick when heated up to 65 ℃ for 15 min, and both first-day and second-day milk samples caked and solidified when heated up to 70 ℃ for 15 min. The third-day milk samples caked and solidified when heated up to 85 ℃ for 15 min, and milk at 4~7 days did not cake or solidify when heated at 95 ℃. Therefore, as the lactation period was extended, the thermal stability of goat milk increased gradually. The goat milk had the highest stability at pH 6.9. When less than 1.0 mg/100 mL sucrose was added, the stability of the emulsion containing milk proteins was reduced, and when greater than 1.0 mg/100 mL was added, the milk stability increased with an increasing sucrose concentration, and the stability of milk casein micelles increased. The stability of goat milk protein decreased with increases in the citric acid and calcium ion concentrations. There was little effect of ultra-high-pressure processing at 300 MPa on the protein precipitation rate. At 500 MPa, the sedimentation rate significantly increased, reaching a maximal value of 7.35% after treatment for 15 min. Treatment with greater than 500 MPa caused a significant reduction in protein stability.

山东省科技发展计划项目（2013GNC11306）；山东省博士后创新项目（201303051）