Effects of pasteurization and storage conditions on donkey milk nutritional and hygienic characteristics

Abstract

Until now there are only few data on the effects of thermal treatments on the nutritional and hygienic characteristics of donkey milk. This Research Communication aims to provide information on the effects of pasteurization (at +65 °C for 30 min) and prolonged storage at refrigeration and freezing temperatures (21 d at + 3 °C ± 2 °C and up to 90 d at −20 °C ± 5 °C) on some nutritional and hygienic characteristics of Amiata donkey milk. The milk was monitored by chemical and microbiological analysis. Pasteurization ensured compliance with EC Regulation No 1441/2007, as Enterobacteriaceae were never found in the milk, or during storage at refrigeration and freezing temperatures. Colony count at 30 °C in pasteurized milk never went beyond 1 log CFU/ml. The heat treatment and the storage did not result in any variations in the main constituents of the milk. Only a decrease in lactose and few variations in some fatty acids at 90 d of freezing were observed. In conclusion, pasteurization was able to achieve and maintain a high hygienic-sanitary quality over time; storage at refrigeration or freezing temperatures did not alter the nutritional quality of fat and the gross composition of the product. These findings are useful to improve knowledge on the milk shelf life in order to guarantee safety and nutritional quality for infants who need small quantities of daily milk.