不同保存条件对母乳的影响

摘要

目的 通过观察不同的保存温度、保存时间对母乳pH值、渗透压、白细胞(WBC)、分泌型IgA(sIgA)、维生素C(VitC)及细菌生长的影响,探讨合适的母乳保存条件.方法 采集30例新鲜母乳,每例等分为5份,在0 h(室温)、48 h(4℃)、72 h(4℃)、30 d(-20℃)、90 d(-70℃)检测母乳的pH值、渗透压、sIaA、WBC、VitC及细菌菌落数.结果 不同条件保存母乳的pH值、渗透压、slgA、WBC、VitC及细菌菌落数.差异均有统计学意义(P<0.01).其中,4℃保存母乳48 h和72 h时,pH值、WBC、VitC下降明显,而渗透压在72 h(4℃)下降明显,与0 h(室温)母乳的差异均有统计学意义(P均<0.01);30 d(-20℃)、90 d(-70℃)保存母乳的pH值、sIgA、WBC、VitC也有明显下降,与0 h(室温)母乳的差异均有统计学意义(P均<0.01).4℃保存母乳48 h和72 h时,细菌总菌落数无明显变化,但72 h时,G+菌落数下降,G-菌落数增加,与0 h(室温)母乳的差异有统计学意义(P均<0.01);30 d(-20℃)和90 d(-70℃)保存母乳的总菌落数、G+菌落数、G-菌落数与0h(室温)比较均明显下降,差异有统计学意义(P均<0.01).结论 保存母乳时其pH值、渗透压、WBC、VitC均下降.因4℃保存时G-菌落有增加的趋势,提示母乳4℃保存不宜超过48 h,长时间保存需要选择-20℃或-70℃.%Objective To explore the optimal storage condition of human milk, and to explore the influence of different storage temperature and duration on pH, osmolality, white blood cell counts (WBC) , slgA, vitamin C and bacteria colony counts of human breast-milk. Methods Fresh milk samples (n = 30) were divided and stored at 4℃ for 48 and 72 hours, -20℃ for 30 days, -70℃ for 90 days. At each time point, pH, osmolality, WBC, slgA, vitamin C were measured and the remaining samples were analyzed for bacteria colony counts. Results Compared with fresh milk, all the indicators had significant difference in stored breast-milk under any condition (P < 0.01). Under 4℃ refrigeration condition, pH, WBC and vitamin C decreased dramatically over 48 h and 72 h storage, and osmolality declined over 72 h storage (P < 0.01) . Under -20℃ freezing condition, pH, WBC, slgA, vitamin C decreased remarkably over 30 d storage (P < 0.01) . Under -70℃ freezing condition, pH, WBC, slgA, vitamin C also decreased remarkably over 90 d storage (P < 0.01). Under 4℃ refrigeration condition, there was no change for bacteria colony counts over 48 h or 72 h storage. Under 4℃ refrigeration condition, Gram-positive colony counts decreased and Gram-negative colony counts increased over 72 h storage (P < 0.01). Under -20℃ freezing condition, bacteria colony counts, Gram-positive colony counts and Gram-negative colony counts decreased over 30 d storage. Under -70℃ freezing condition, bacteria colony counts, Gram-positive colony counts and Gram-negative colony counts decreased over 90 d storage (P < 0.01). Conclusions pH, osmolality, vitamin C and WBC decline obviously during storage. Because Gram-negative bacteria colony counts increase during storage, human milk refrigerated at 4℃ should be fed best before 48 h. -20℃ or -70℃ freezing condition should be chosen, if long-time storage is required.