Rheological properties of yoghurts with 1, 2 and 4% addition of powdered whey, demineralised whey and three lactose reduced whey as an alternative for skim milk powder were studied. The dynamic, apparent viscosity and the hardness of the yoghurts were determined for this purpose. In most cases the decrease of apparent viscosity was occurred in conjunction of increasing whey powders addition. However 1% addition of whey preparations let to obtain yoghurts with higher viscosity than the non-enriched yoghurt (control check). Acidity analysis demonstrated that yoghurts whey powders addition limited the pH decrease in the final product in relation to the control check and yoghurts enriched with skim milk. In a texture examination increasing concentration of applied whey powder additives caused the decrease in hardness in almost all final products. Dynamic viscosity analysis showed that addition of skim milk powder had the best influence on the yoghurt viscoelastic properties, however with 1% additives the differences between the final complex modulus values for applied preparations were slight. Much definite differences were seen in yoghurts enriched by 4% addition of examined preparations. In this case such an addition of demineralised whey powder caused remarkable complex modulus increase in relation to control check. Although the best preparation increasing dry mass content turned out a skim milk powder, however 1% addition of powdered whey, lactose reduced whey as well as 4% addition of demineralised whey caused evident rheological qualities improvement of yoghurts in relation to the non-enriched yoghurt.
yoghurt, rheology, whey powder, texture