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.

Milk Products from Minor Dairy Species: A Review

“…The effectiveness of in-vat pasteurization at +65 °C for 30 min and storage at refrigeration (+3 °C ± 2 °C) and freezing temperatures (−20 °C ± 5 °C) on some hygienic characteristics of donkey milk was investigated. The treatment ensured compliance with EC Regulation No 1441/2007, as Enterobacteriaceae were never found in the milk, and TBC at 30° never went beyond 1 log cfu ml (initial load was 4.84 log cfu mL −1 ) [ 55 ]. A study on 101 half-udder milk samples showed very low values of TBC (<250 cfu/mL) and a minor presence of pathogens: Staphilococcus aureus was isolated from only five milk samples (three animals), Streptococcus equi from two samples, and Streptococcus equisimilis from a single sample.…”

Effects of donkey milk on oxidative stress and inflammatory response

“…However, very recently, scientific research has shown its value and importance in many fields. Several studies support the idea that donkey milk could be helpful for babies and patients suffering from cow’s milk protein allergy (Martini, Salari, et al., 2018), and play a significant role in improving the health of certain healthy individuals (e.g., elderly people, some subhealthy people with dyslipidemia and obesity) as well in individuals with a certain disease (e.g., fatty liver, diabetes, and IBD). In the past, the consumption of donkey milk was mainly due to the higher abundance of vitamin B and vitamin C. With the development of technology, especially omics, more bioactive and antimicrobial properties of donkey milk (such as proteins and bioactive peptides) were observed (Aspri et al., 2018; Brumini et al., 2016; Cunsolo et al., 2017).…”

Potential Hazards Associated with Raw Donkey Milk Consumption: A Review

“…Coagulase-positive staphylococci were found in the raw donkey milk, with an average count of 1.7 × 10 2 cfu/ml [13].…”

“…The raw milk for human consumption can be sold directly at farms; it is also pasteurized (rarely, UHT-treated or freeze-dried), packed, and sold in shops, pharmacies, or it is sold online [12]. It is not always or easily available on the market and domestic milk freezing of donkey milk is a common practice [13].…”