低温保存对人乳营养成分和免疫物质的影响

Effect of cold storage on nutrients and immune substances in human milk

目的探讨新鲜母乳的最佳保存方法。方法采集30例新鲜母乳,每例分为12份,分别在3个温度点的不同时相,即4℃的24、48、72 h,–18℃的72 h、7 d、14 d、4周、8周、12周,–80℃的12和24周,检测和比较新鲜母乳与11份保存母乳中宏量营养素脂肪、蛋白质、碳水化合物、干物质和能量值,免疫活性成分水平s Ig A、乳铁蛋白,IL-6、8、10,TNF-α,以及细菌菌落数。结果不同低温保存条件下母乳宏量营养素、免疫活性成分以及细菌水平总体差异有统计学意义(P均<0.05)。其中,4℃保存至72 h时人乳脂肪、IL-6和TNF-α下降,细菌总菌落数和革兰阳性菌落数上升,与新鲜母乳差异有统计学意义(P均<0.05);–18℃保存时,各时间点的脂肪、蛋白质、干物质、能量和IL-6普遍下降,与新鲜母乳差异有统计学意义(P均<0.05),碳水化合物和s Ig A则分别在保存4周和8周时下降,与新鲜母乳的差异有统计学意义(P<0.05);–80℃保存时,24周时的脂肪、蛋白质、干物质、能量和IL-6的下降,与新鲜母乳差异有统计学意义(P均<0.05)。结论低温保存对母乳宏量营养素、免疫成分和细菌水平有明显影响,其中4℃保存不应超过72 h,保存72 h以上建议应–18℃冷冻保存,而保存2个月宜以–80℃保存。

Objective To explore the optimal storage standard of fresh human milk, and to observe the influence of different cold storage condition（time-temperature） on macronutrients（fat, protein, carbohydrates, TS and energy）, immune substances（s Ig A, lactoferrin, IL-6, 8, 10 and TNF-α） and bacteria indicators of fresh human milk. Methods Fresh milk samples（n=30） were divided and stored at three temperature and nine time points, which are 4℃（24 h, 48 h, 72 h）,-18℃（72 h, 7 d, 14 d, 4 w, 8 w, 12 w）, and-80℃（12 w, 24 w）. At each time point, the macronutrients, immune substance, and bacteria colony counts of each milk sample were measured and compared with fresh milk. Results Compared with fresh milk, all indicators with the exception of lactoferrin in stored human milk showed significant difference（P〈0.05）. Under 4℃ refrigeration condition, fat, IL-6, and TNF-α decreased, bacteria colony counts and Gram-positive colony counts increased over 72 h storage（P〈0.05）. Under-18℃ freezing condition, fat, protein, TS, energy and IL-6 decreased from 72 h to 12 w storage（P〈0.05）; carbohydrates and s Ig A also decreased from 4 w and 8 w storage, respectively（P〈0.05）. Under-80 ℃ freezing condition, fat, protein, TS, energy and IL-6 decreased over 24 W storage（P〈0.05）. Conclusions The macronutrients, immune substance, and bacteria indicators of human milk were affected obviously by cold storage. Refrigerated at 4℃ should not be longer than 72 h,-80℃ freezing condition should be chosen for more than two months storage.