解冻速率和加热温度对人乳中免疫球蛋白 A 和溶菌酶活性的影响。
Effects of the thawing rate and heating temperature on immunoglobulin A and lysozyme activity in human milk.
机构信息
Department of Community Medicine, Faculty of Medicine, Chiang Mai University, 110 Intrawarorot Road, Si Phum Subdistrict, Amphoe Mueang, Chiang Mai, 50200, Thailand.
Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
出版信息
Int Breastfeed J. 2022 Jul 7;17(1):52. doi: 10.1186/s13006-022-00487-4.
BACKGROUND
The percentage of infants receiving frozen human milk (HM) is increasing. The effects of thawing and warming on the secretory immunoglobulin A (SIgA) level and lysozyme activity in frozen HM should be investigated to identify optimal methods for preserving immune factors in frozen HM.
METHODS
Milk samples were collected from 40 mothers with healthy full-term infants who had been lactating for one to six months. The baseline samples were analyzed within 24 h after collection, and the other samples were frozen at -18 °C before analyses. We compared two methods: placing the container overnight in a refrigerator at 4 °C before warming (slow thawing) and immediately thawing in warm water after removing the sample from the freezer (rapid thawing). Additionally, we investigated the effects of the warming temperature by comparing room temperature (25 °C) and physiological temperature (37 °C). The SIgA concentrations and lysozyme activities in the milk samples were determined using ELISA kits and fluorometric lysozyme activity assay kits, respectively.
RESULTS
The SIgA concentrations and lysozyme activity in frozen HM were 16.5-52.1% and 16.8-39.3% lower than those in fresh HM, respectively. The SIgA concentrations in frozen HM were stable during slow thawing at 37 °C (p = 0.072) compared with those in fresh HM. The SIgA concentrations and lysozyme activity were maintained at significantly higher levels during slow thawing than during rapid thawing at 25 °C (p = 0.002 and p < 0.001, respectively). Slow thawing preserved higher SIgA concentrations and lysozyme activity than rapid thawing at 37 °C, but the difference was not significant.
CONCLUSIONS
The SIgA level in HM frozen at -18 °C for two months was stable after overnight thawing in the refrigerator (4 °C for 12 h) before warming to 37 °C compared with that in fresh milk. The thawing of HM in the refrigerator overnight (and then warming to 25 °C or 37 °C for 30 min) has the potential to preserve the SIgA concentration and lysozyme activity to a greater extent than heating immediately after removal from the freezer. Broader temperature ranges should be analyzed to determine the temperature that minimizes the losses in SIgA concentration and lysozyme activity in HM.
背景
接受冷冻人乳（HM）的婴儿比例正在增加。为了确定在冷冻 HM 中保留免疫因子的最佳方法，应研究解冻和加热对冷冻 HM 中分泌型免疫球蛋白 A（SIgA）水平和溶菌酶活性的影响。
方法
从 40 位健康足月、哺乳期 1 至 6 个月的母亲中收集乳汁样本。采集后 24 小时内分析基线样本，其余样本在-18°C 下冷冻，然后进行分析。我们比较了两种方法：一种是将容器在冰箱中过夜放置在 4°C 下进行缓慢解冻，另一种是在从冰箱中取出样本后立即在温水中快速解冻。此外，我们还通过比较室温（25°C）和生理温度（37°C）来研究加热温度的影响。使用 ELISA 试剂盒和荧光溶菌酶活性测定试剂盒分别测定乳汁样本中的 SIgA 浓度和溶菌酶活性。
结果
冷冻 HM 中的 SIgA 浓度和溶菌酶活性分别比新鲜 HM 低 16.5-52.1%和 16.8-39.3%。与新鲜 HM 相比，37°C 下缓慢解冻时冷冻 HM 中的 SIgA 浓度稳定（p=0.072）。与 25°C 下快速解冻相比，缓慢解冻时 SIgA 浓度和溶菌酶活性均保持在更高水平（p=0.002 和 p<0.001）。与 37°C 下快速解冻相比，25°C 下缓慢解冻更能保持较高的 SIgA 浓度和溶菌酶活性，但差异无统计学意义。
结论
与新鲜奶相比，冷冻 HM 在-18°C 下保存两个月后，在冰箱中过夜解冻（4°C 12 小时）后再升温至 37°C 时，SIgA 水平稳定。HM 在冰箱中过夜解冻（然后在 25°C 或 37°C 下加热 30 分钟）比从冰箱中取出后立即加热更有可能在更大程度上保留 SIgA 浓度和溶菌酶活性。应分析更宽的温度范围，以确定使 HM 中 SIgA 浓度和溶菌酶活性损失最小的温度。
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