Forward osmosis concentration of milk: Product quality and processing considerations

摘要

Concentration of milk in the dairy industry is typicallyachieved by thermal evaporation or reverse osmosis(RO). Heat concentration is energy intensive andleads to cooked flavor and color changes in the finalproduct, and RO is affected by fouling, which limitsthe final achievable concentration of the product. Themain objective of this work was to evaluate forward osmosis(FO) as an alternative method for concentratingmilk. The effects of fat content and temperature on theprocess were evaluated, and the physicochemical propertiesand sensory qualities of the final product wereassessed. Commercially pasteurized skim and wholemilk samples were concentrated at 4, 15, and 25°C usinga benchtop FO unit. The FO process was assessedby monitoring water flux and product concentration.The color of the milk concentrates was also evaluated.A sensory panel compared the FO concentratedand thermally concentrated milks, diluted to singlestrength, with high temperature, short time pasteurizedmilk. The FO experimental runs were conductedin triplicate, and data were analyzed by single-factorANOVA. Water flux during FO decreased with timeunder all processing conditions. Higher temperaturesled to faster concentration and higher concentrationfactors for both skim and whole milk. After 5.75 h ofFO processing, the concentration factors achieved forskim milk were 2.68 ± 0.08 at 25°C, 2.68 ± 0.09 at15°C, and 2.36 ± 0.08 at 4°C. For whole milk, after5.75 h of FO processing, concentration factors of 2.32± 0.12 at 25°C, 2.12 ± 0.36 at 15°C, and 1.91 ± 0.15at 4°C were obtained. Overall, maximum concentrationlevels of 40.15% total solids for skim milk and 40.94%total solids for whole milk were achieved. Additionally,a triangle sensory test showed no significant differencesbetween regular milk and FO concentrated milk dilutedto single strength. This work shows that FO is a viablenonthermal processing method for concentrating milk,but some technical challenges need to be overcome tofacilitate commercial utilization.