Enzymatic hydrolysis of starch by salivary α-amylase, its time dependence and influence on plaque acid production was investigated. Analysis of the composition of starch digests was performed with gel filtration chromatography. Wheat starch in solution, in bread and in biscuit was hydrolyzed rapidly mainly to maltose, maltotriose and limit dextrins. In vivo enzymatic degradation of wheat starch caused marked drops in interdental plaque pH to 4.75 measured by intraoral plaque pH telemetry, most probably as the result of the fermentation of low molecular weight maltodextrins by plaque bacteria. On this basis starch may contribute to cariogenesis.

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The time dependent α‐amylolytic degradation of different wheat starch products was investigated in vitro. Starch digests were analysed by gel filtration chromatography and measurement of reducing end groups. The hydrolytic activity of crystalline porcine pancreatic α‐amylase was compared to that of human salivary α‐amylase in cell‐free pooled saliva. With conditions similar to those of the human oral cavity wheat starch solutions, whole wheat bread and wheat starch biscuit were hydrolyzed rapidly to mainly maltose, maltotriose and limit dextrins. The distribution of the main degradation products was different depending on the source of the α‐amylase. Independent of the enzyme source the rate of hydrolysis decreased from wheat starch solution to bread and biscuit.

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