A novel method for determining the dissolution kinetics of hydrocolloid powders

Food hydrocolloids are sold as powders so they must be dissolved before use. In modem manufacturing practice, rapid dissolution can be an important specification. However, quantifying dissolution kinetics is a problem, because when lumps form the process becomes irreproducible, partly because lumps tend to stick to the stirrer. This paper presents a simple method for determining the dissolution kinetics of soluble polymer powders which solves these problems. The dissolution kinetics were followed using a modified rotational viscometer. The key modification is that when the powder is added, there is a vortex below the axis of the rotor, so that the powder cannot stick to it. The amount of hydrocolloid dissolved is followed via the torque on the viscometer. Measurements were performed under both dispersing and non-dispersing conditions. Under dispersing conditions each powder grain dissolves individually, and it is shown that the dissolution rate is proportional to the amount of powder surface. Under non-dispersing conditions, grains can stick together, forming lumps. The reproducibility of the method under both conditions is demonstrated using pectin. It was used to quantify the empirical observation that reducing the powder grain size increases the dissolution rate, but it also greatly increases lump formation. (C) 1999 Elsevier Science Ltd. All rights reserved.