Abstract
Donkey milk has functional properties of great interest to human nutrition. The effects of ultra-high pressure homogenization (UHPH) at 100 MPa, 200 MPa and 300 MPa in comparison with different pasteurization treatments of 70 °C for 1 min and 85 °C for 1 min on the physicochemical quality and shelf-life of treated and raw (untreated) donkey milk were studied. Gross composition and pH, total mesophilic counts, lysozyme activity and physical stability were studied during storage at 4 °C for 28 days. The compositional profile showed resemblance to that of human milk characterized by high lactose, low fat and low protein content and was least affected by the treatments. UHPH treatments at 200 MPa, 300 MPa and 85 °C were able to maintain steady pH during storage whereas the low intensity treatments showed a significant decrease. The observed lysozyme activity in the samples was generally high and appeared to have been enhanced by the applied UHPH and pasteurization treatments with no significant change during storage. Although the raw milk showed good initial microbial quality, extensive growth of mesophilic microorganisms occurred after 7 days of storage, unlike the treated samples which were able to maintain significantly low counts throughout the storage period. The physical stability of milk was negatively influenced by the higher UHPH treatments of 200 MPa and 300 MPa which exhibited sedimentation phenomenon, while creaming was insignificant.
Highlights
Milk from non-ruminant species for human consumption is recently receiving much attention as an alternative to cow milk due to a number of nutritional and health concerns
Due to the bioactive components contained in donkey milk, the use of highly destructive thermal treatments normally applied to cow milk are probably not suitable if its special functional attributes need to be maintained
Donkey milk was characterized by a lower dry matter content comparable to dry matter values reported in the literature by Ivankovic et al (2009) and Salimei et al (2004) who both worked on different donkey breeds
Summary
Milk from non-ruminant species for human consumption is recently receiving much attention as an alternative to cow milk due to a number of nutritional and health concerns. Donkey milk chemical composition is very close to human milk, due to its similarity in nutritional composition, and its therapeutic purpose has been known centuries ago for the curing of several diseases (Conte et al, 2004) It is characterized by high lactose and low fat and protein contents. Due to the rich nutritional value of donkey milk and its strict seasonal production variability, its processing and preservation is essential Thermal treatments such as pasteurization and high temperature sterilization are the commonest ways of milk preservation to obtain products of longer shelf life with good microbial quality. The objective of this study was to explore the response of UHPH technology application in comparison to pasteurization of donkey milk The effects of those treatments will be studied in terms of microbiological, physical and functional evaluation, and determining the shelf life of treated milks
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