To improve the characteristics of low-fat butter produced with only milk components, a preliminary study was carried out using freeze-dried milk whey added to commercial low-fat butter (5, 10 and 20 per cent whey/water). Thus, the effects of whey protein emulsifying properties and the effects of the soluble whey components on water activity were evaluated. Low-fat butter produced in laboratory-scale equipement and commercial low-fat butter spreads were considered; in all samples the composition, water activity, colorimetric characteristics and the emulsion Stability Index (SI) were determined. Increasing the quantity of freeze-dried whey in the composition of low-fat butter decreased at the water activity values but not sufficiently to be meaningful in microbiogical terms. The colorimetric parameters were influenced by the quantity of freeze-dried whey employed. Freeze-dried whey addition could improve the emulsion stability, the best results being achieved with 5 per cent w/w addition, probably for the limited supplementing of whey soluble components.
