Concentrating raw milk at the dairy farmsrather than at the dairyreduces energy consumption and CO 2 emission, due to less road transportation of the milk. This study demonstrates whether it is possible to use either reverse osmosis or ultra-filtration for milk concentration at the farm without harming the milk quality, regarding lipolysis and proteolysis. Filtration at low temperature (4°C) secures a good milk quality. Despite reverse osmosis operating at much higher feed pressures, the effect on lipolysis is small, which makes this technology the most applicable, as lactose is withhold in retentate.

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Implementation of reverse osmosis filtration at the dairy farm will reduce the volume of milk, which has to be transported, and thereby potentially reduce energy consumption and CO 2 emission. The aim of this study was to examine the quality of whole milk powder produced from reverse osmosis retentate concentrated at the farm. Whole milk powder prepared from reverse osmosis retentate, with a volume concentration factor of 2, was compared to powder from non-concentrated milk, as well as to a range of commercial whole milk powders. A storage experiment of the stability of retentate powder for up to 12 months at room temperature was conducted and evaluated for quality parameters, including proteolysis, oxidation, furosine and colour. The results showed that concentration of the oxidation products hexanal, heptanal and nonanal increased during storage of both retentate powder and powder from non-concentrated milk, but not to a higher extent than found in commercial powder of similar storage conditions. Detectable furosine was higher in powder prepared from non-concentrated milk than that in powder from pre-concentrated milk, and further no changes in colour was found during storage. However, high variation in powder composition between produced powders, especially with regard to moisture content, could have affected some quality parameters. In conclusion, pre-concentrating milk by reverse osmosis at the farm did not have significant effects on the overall quality of the produced milk powders in this study.