Impact of pasteurization and procedures commonly used to rethermalize stored human milk on folate content

Abstract

Severe heat treatment dramatically reduces milk folate content; however, the impact of pasteurization and rethermalization techniques used by mothers to thaw and warm banked milk is unknown. The purpose of this study was to determine the effect of pasteurization microwaving and warming of milk in a tap water bath (conventional heating) on milk folate content and form. Human milk (n=10) collected by complete breast expression was pasteurized (62.5°C for 30 minutes), microwaved (720 watts, high power for 30 seconds) or conventionally heated (40°C for 10 minutes). Cow ( n=10) and goat ( n=10) milk was pasteurized as above. The folate content of milk samples was determined using a differential microbiological technique with and without added folate conjugase. A 16% reduction in human milk folate content was noted following pasteurization. Microwaving and conventional heating did not cause a reduction in total milk folate content. A similar reduction in milk folate content was noted following pasteurization of cow milk (12%), but goat milk folate content was not significantly affected. Addition of ascorbate (1%) before pasteurization of human and cow milk ameliorated these losses. In a separate experiment, we found that ascorbate added to cow milk at a concentration of 0.01% was sufficient to protect folate against degradation during pasteurization. The mean folate content of human, cow, and goat milk was 113.7±3.7 (mean±SEM), 142.8±6.8 and 21.3±9.0nmol/L, respectively. Results suggest that thermal techniques typically used by mothers to thaw and warm banked milk would provide an infant with the recommended intake of folate. Pasteurization (62.5°C for 30 minutes) without the addition of ascorbate may result in intakes of folate below recommended levels for some infants.