纳滤与闪蒸技术对新鲜牛乳浓缩效果的影响

Effect of nanofiltration and flash technology on concentration of fresh milk

文章以新鲜牛乳为研究对象,通过测定牛乳的感官、色差、酸度、冰点、粒径等特性,及其蛋白、脂肪、乳糖、金属离子、过氧化物酶含量,研究纳滤和闪蒸技术对浓缩鲜牛乳的影响。结果表明,经截留分子质量为1 ku和0.2 ku的纳滤浓缩新鲜牛乳1.35倍时,纳滤膜的膜通量降幅较小,浓缩效率约降低了14.0%和12.0%;经闪蒸技术处理(5 kPa,65℃)后,鲜牛乳色泽和滋味的感官评分较原奶分别下降2.3%和22.6%,且L*值和b*值下降幅度最大为2.8%和2.7%,而纳滤对鲜牛乳感官、L*值和b*值无显著影响(P>0.05)。不同孔径的纳滤膜浓缩新鲜牛乳1.35倍时,其酸度较鲜牛乳分别上升10.1%、9.7%;经膜过滤后,鲜牛乳中蛋白、钙离子截留率分别为98%~100%和97%~99%。结果表明,经纳滤膜技术处理后的新鲜牛乳酸度略有升高,感官和营养物质含量几乎不受影响。

The effects of nanofiltration and flash evaporation on concentrated fresh milk were studied by measuring the sensory properties,color difference,acidity,freezing point,particle size and the contents of protein,fat,lactose,metal ions and peroxidase in fresh milk.The results showed that when the fresh milk was concentrated 1.35 times by nanofiltration with 1 ku and 0.2 ku,the membrane flux decreased slightly,and the concentration efficiency decreased by about 14.0%and 12.0%.After flash treatment(5 kPa,65℃),the sensory scores of color and taste of fresh milk were decreased by 2.3%and 22.6%,respectively,compared with raw milk,and the decreases of L*and b*values were 2.8%and 2.7%,respectively,while nanofiltration had no significant effects on sensory values,L*and b*values of fresh milk(P>0.05).When nanofiltration membrane with different pore size was concentrated 1.35 times,the acidity of fresh milk was increased by 10.1%and 9.7%,respectively.After membrane filtration,the retention rates of protein and calcium in fresh milk were 98%-100%and 97%-99%,respectively.In conclusion,the acidity of fresh milk treated by nanofiltration membrane technology is slightly increased,but it has little effect on its sensory and nutrient content.