Fatty acid profile determination in fresh and freeze-dried donkey milk

Donkey milk is the most appropriate milk in cases of cow milk protein allergies; it is produced in small amount, so use of thermal treatments to prolong its shelf life have been investigated: freezing, pasteurization, condensation, High Pressure Processing and spray-drying. The aim of the present study was to investigate the effects of freeze-drying on donkey milk fatty acid profile. Fresh donkey milk samples were collected in duplicate from 18 Ragusana breed asses, the two aliquots were named: sample A, fresh milk, sample B, to be processed for obtaining freeze-dried donkey milk. Fatty acid composition was determined in fresh and in reconstituted donkey milk, identification was made by comparing gas chromatographic retention times with the anti-oxidant standard BHT. Donkey milk is characterised by large amounts of polyunsaturated fatty acids, including essential fatty acids (n-6 and n-3) which counteracting with the oxidative stress, diminishing the inflammatory response in allergic disease. Both fresh and lyophilized donkey milk show a valid MUFA and PUFA content, with a ratio UFA/SFA respectively of 0.88 in fresh and 0.91 in freeze-dried milk. The most abundant fatty acids in both milks are: among the saturated fatty acids, palmitic acid (24% in fresh milk and 26% in lyophilized milk), among the monounsaturated fatty acids, oleic acid (38% in fresh milk and 36% in lyophilized) and among the polyunsaturated fatty acids, linoleic acid (10% in fresh and 9% in lyophilized). PUFA also showed small amounts of eicosapentaenoic (EPA, C20:5 n–3) and docosahexaenoic acids (DHA, C22:6 n–3) in both fresh (0.32 %) and freeze-dried (0.28 %) donkey milk.