Continuous formation of gel structures and stable foams based on a heat treated and acidulated whey protein concentrate
1998
Spiegel, T. | Kessler, H.G. (Technical Univ. of Munich, Freising-Weihenstephan (Germany). Inst. for Dairy Science and Food Process Engineering)
Heating a whey protein concentrate (10 / protein, 13 / lactose) to a temperature of 80 degrees will result in the formation of a compact gel structure if the heat treatment takes place at rest. In a continuous process, however, a highly viscous, but inhomogeneous, gritty product is obtained consisting of large protein aggregates. By means of an intensive shearing load during cooling in a scraped surface heat exchanger, the thermal-induced structure is broken up. The aggregate size declines considerably as the rotational speed of the knife driving shaft increases. At maximum rotational speed a liquid, smooth product is obtained containing aggregates with a volume based median of about 10 micrometers. These aggregates create a creamy, emulsion-like mouthfeel and can be used as a fat substitute. Lowering the pH value by dosing acid into such a heat- and shear-treated whey protein concentrate leads to a gradual increase in viscosity in the pH range around 4.5. This solidification occurs the faster, the higher the storage temperature is. The compact gel structure is formed by hydrophobic interactions between the protein aggregates, of which the negative surface charge is reduced due to the acidulation. The presence of casein and fat in the initial solution results in a further increase in viscosity and an extension of the pH range in which the solidification takes place. The products become spreadable and very creamy, and can serve as a basis for desserts and spreads. If the acidulation is combined with a simultaneous foaming process, it will be possible to form very stable foams without the addition of any non-dairy stabilizers.
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