One bacterial amylase unit is defined as that quantity of enzyme which will dextrinise one milligram of starch per minute at pH 6,6 and 30 °C.
This α-amylase product is a liquefying diastase supplied as a dry, free-flowing powder having high uniformity and excellent storage stability.
The general procedure for the enzymatic liquefaction of starch is the same, regardless of the nature of the end product. The degree of conversion is followed by measuring the viscosity. The ultimate viscosity is controlled by the level of enzyme and the time which elapses after gelatinisation. The usual conditions are 0,03 to 0,06% a-Amylase based on weight of starch for 15 to 30 minutes.The starch is suspended in cold water with agitation sufficient to assure uniform dispersion. If vigorous agitation is provided, the dry solid enzyme may be added directly to the suspension. A safer practice, however, is to dissolve the dry enzyme in a little water before charging. The reaction mixture is then heated to the gelatinisation temperature and held there (or slightly hotter) until the required viscosity is reached. Potato, tapioca, sago, arrowroot, and cereal starches other than those obtained from maize or rice are gelatinized at 70 to 75 °C. Maize and rice starches require a temperature of 80 °C. When the conversion is complete, the mixture is heated quickly to 100 °C and held 10 minutes to inactivate the enzyme. Additional heating at 100 °C is sometimes done to effect further reduction in viscosity by the action of heat alone.
