DEHYDRATION OF AN ULTRA-CLEAN MILK AND MI CELLAR CASEIN ENRICHED MILKS

Treatment of raw skimmed milk by the Bactocatch procedure, before its concentration by vacuum evaporation and spray-drying, leads to a high quality milk powder. No heat treatment is required for obtaining a low heat powder with a bacterial count of 3000 CFU/g; a solubility index as high as 99.6%; a dispersibility index of 98.9% and a wettability in dex of 12 s. Such a powder after water reconstitution has the same ren neting time as the original raw milk and can be used as a reference po wder either for industrial or scientific purposes. Enrichment of milk in micellar casein by treatment with a 0. 1 mum pore size diameter mic rofiltration membrane deeply modifies physical properties of resulting powders. According to the volumic concentration factor (VCF), solubil ity and dispersibility indexes decrease. Powder issued from a VCF 6 re tentate has a lowered solubility and dispersibility index by 6% and 71 % respectively. Such a degradation is probably caused by differences i n water permeation during drying and reconstitution. Water transport i s probably modified by the high protein content of the spraid droplet in the atomization tower and similarly when powder granule is dissolve d in water. Lowering both inlet and outlet air temperatures significan tly improves solubility and dispersibility indexes of micellar casein enriched milk powder. These indexes respectively increase with 97.2% a nd 43.3% but they are still lower than the corresponding values of ref erence milk powder. So, more research is needed to obtain satisfactory indexes. Effect of a 100-day storage of powders on physical propertie s at room temperature has been checked.