Low-(MPC35, MPC50), medium-(MPC60, MPC70) and high-(MPC80, MPC85, MPC90) protein content milkprotein concentrate (MPC) powders, manufactured at pilot-scale, were evaluated for their rehydrationcharacteristics. Optical tensiometry confirmed that water droplets were imbibed more slowly as proteincontent of the MPCs increased, indicating impaired wetting. Casein micelles comprised only <2% of the particlepopulation by volume in MPC70, MPC80, MPC85 or MPC90 after 90 min of rehydration at 25 C, as primaryparticles which had not dispersed fully remained in suspension. The quantity of sediment, measuredusing analytical centrifugation, increased in the order MPC70 < MPC80 < MPC85 < MPC90 after 90 min ofrehydration at 25 C, with lower protein MPCs forming no sediment. No sediment formation was observedin any of the MPCs after 24 h of rehydration at 25 C, despite the predominance of primary particles in suspensionsof high-protein MPCs. Increasing the temperature of reconstitution from 25 to 50 C during90 min of rehydration caused a 41.4% decrease in sediment height for MPC90 in water; however, reductionsin sediment height of 89.9% and 99.5% were achieved when MPC90 was rehydrated in milk permeateor 80 mM KCl, respectively. It is evident that low ionic strength (confirmed using conductimetry) has astrong negative effect on the rehydration properties of high-protein MPCs, and that the synergistic effectof increasing ionic strength and temperature can substantially accelerate rehydration.
การแปล กรุณารอสักครู่..