Water transfer during rehydration of micellar casein powders

Abstract

Rehydration is an essential quality attribute of a dairy powder, as most powders are dissolved before use. However, there can be problems associated with the different stages of the rehydration process: i.e. wettability, sinkability, dispersibility and solubility. Many sensors and an- alytical methods such as the insolubility index, NMR spectroscopy, turbidity, viscosity and particle size distribution can be used to study water transfer in dairy protein concentrates during rehydration. Micellar casein (MC) powder, obtained by tangential membrane microfiltration of milk followed by spray-drying, is an interesting dairy powder due to its high protein content, and it is a valuable model of milk micelles. However, enrichment of milk in micellar casein decreases water transfer during rehydration of MC powder. The slow water transfer during MC powder rehydration is time- consuming. Some studies have shown that insolubility is related to a decrease in the water transfer during rehydration and not to thermal denaturation. Other studies have also shown that the decrease in water transfer might be related to the micellar structure. In the present study, the destructura- tion of micelle induced by addition of phosphate or citrate solution to MC increased water transfer during rehydration. Water transfer in the dairy protein concentrate during rehydration was found to be related to the aqueous environment, the nature of the mineral salts, the structure of the dairy proteins, the size of the powder particle and the rehydration conditions. micellar casein / powder / rehydration / wettability / dispersibility / solubility