Effect of Holder pasteurization on nutrient and immune component retention in human milk: a comparison between water and dry pasteurizers

Holder pasteurization (HoP; 62.5 °C, 30 min) is the method used most frequently in human milk banks to reduce the risk of infection transmission through donor human milk (DHM), but it has the disadvantage of potentially affecting the contents of some bioactive milk components. Dry pasteurizers avoid water handling and are easier to operate than water pasteurizers; however, the effect of dry pasteurization on human milk quality has not been fully elucidated. The aim of this study was to determine the effect of HoP by water or dry pasteurization on the nutrient content of human milk. Milk samples were assigned to 4 groups: No-HoP (untreated milk), Sterifeed (water pasteurizer), Barkey (dry pasteurizer), and Racoon (dry pasteurizer). The processing temperature of each machine was measured over time. Levels of macronutrients, minerals, secretory immunoglobulin A (sIgA), lactoferrin, and human milk oligosaccharides (HMOs) in DHM were analyzed before and after HoP. The mean plateau temperature and the highest temperature of the water pasteurizer was more than 0.5 °C lower and more than 1 °C lower, respectively, than for the dry pasteurizers. Macronutrients, minerals, and HMOs were unaffected or minimally affected by the HoP process in experiments conducted using each type of pasteurizer, whereas sIgA and lactoferrin levels were decreased significantly. The losses of sIgA and lactoferrin through dry pasteurization were more than 10% greater than the losses incurred by water pasteurization. The respective reductions in sIgA, calculated from median values, were 23% for Sterifeed (P < 0.05), 42% for Barkey (P < 0.001), and 44% for Racoon (P < 0.001). The reductions in lactoferrin were 75%, 86%, and 86%, respectively (all P < 0.001). After the cooling process in the two dry pasteurizers, energy decreased by 6% and calcium decreased by 2% in Barkey (all P < 0.05), while lactoferrin increased by 3% in Racoon (P < 0.05). No other components showed significant changes. These results show that dry pasteurization causes a higher reduction in immune components than water pasteurization, suggesting that dry method is not suitable for processing DHM.