Donkey milk powder production and properties compared to other milk powders

In order to adapt the seasonal production of donkey milk to constant market demand, this study was aimed to define the project parameters of a pilot spray dryer for producing soluble milk powder from donkey milk concentrate. The concentrate (23% mean dry matter (wb)) was spray-dried using three different inlet air temperatures (120–150–185 °C). Both cow and goat milk were used as reference in the trials, and ascorbic acid was used as a chemical marker to evaluate thermal damage to the powder. The thermal damage index (IDT) and insolubility index (IINS) were used to assess the quality of the powders produced. Prediction models were developed for each kind of milk to correlate spray-drying operating temperatures to the IINS and IDT. The results of experimental trials were used to determine optimal processing temperatures (both inlet and outlet air temperature) in order to obtain an “extra-grade” milk powder from donkey milk concentrate (the maximum allowed inlet air temperature that resulted was 173.5 °C).