冷冻贮藏对喷雾干燥羊乳粉品质特性的影响

Effect of Frozen Storage on Spray-Dried Goat Milk Powder Quality Characteristics

摘要:

本研究中对新鲜羊乳、低温冷冻（-16~-18 ℃）和超低温冷冻（-76~-80 ℃）贮藏3个月的常温解冻（20~25 ℃）羊乳进行喷雾干燥，制备了鲜羊乳粉、低温冷冻常温解冻（CFHT）羊乳粉和超低温冷冻常温解冻（UFHT）羊乳粉，对其品质进行比较分析。结果表明：喷雾干燥羊乳粉的水分质量分数符合国家标准，水分活度（A_w）均小于0.2，总色差（ΔE）均小于0.3，具有良好的贮藏特性；3组羊乳粉复水后多分散性指数（PDI）均小于0.3；激光共聚焦显微镜（CLMS）图像显示3组羊乳粉复水后组间脂肪球与蛋白质颗粒无明显差异。相比于鲜羊乳粉，CFHT和UFHT羊乳粉的脂肪损失较严重（P<0.05），蛋白质和乳糖质量分数损失10%~19%（P<0.05）；而UFHT羊乳粉的蛋白质和乳糖高于CFHT羊乳粉，水分质量分数和A_w低于CFHT羊乳粉。因此，冷冻贮藏可用于喷雾干燥羊乳粉的制备，且UFHT羊乳粉的品质优于CFHT羊乳粉。

Abstract:

In this research, fresh goat milk was frozen at cryogenic temperature(-16~-18 ℃) and ultra-cryogenic temperature(-76~-80 ℃) for 3 months, and thawed at room temperature(20~25 ℃). Then, the stored samples were subjected to spray drying to prepare fresh goat milk powder, goat milk powder that was cold-frozen and thawed at room temperature(CFHT), and goat milk powder that was ultra-low-temperature frozen and thawed at room temperature(UFHT). And the quality of resulting powders was compared and analyzed. The results showed that the moisture content of spray-dried goat milk powder met the national standard, with water activity(A_w) below 0.2 and total color difference(ΔE) below 0.3, indicating good storage characteristics. In addition, PDI values of all goat milk powders after rehydration were all below 0.3. Confocal laser scanning microscopy (CLSM) images revealed no significant differences in both fat globules and protein particles among the three groups of rehydrated goat milk powders. Compared with the fresh goat milk powder, CFHT and UFHT goat milk powders exhibited more severe fat loss(P<0.05), as well as protein and lactose losses of 10%~19%(P<0.05). Furthermore, UFHT goat milk powder had higher protein and lactose content than CFHT goat milk powder, while its moisture content andA_w were lower than those of CFHT goat milk powder. Therefore, frozen storage can be used in the preparation of spray-dried goat milk powder, and the quality of UFHT goat milk powder is better than CFHT goat milk powder.