A Study of Native and Chemically Modified Potato Starch. Part I: Analysis and Enzymic Availability in vitro

The availability of native and chemically modified potato starch to α‐amylase was studied in vitro (distarch phosphate, acetylated distarch phosphate and hydroxypropyl distarch phosphate). Enzyme availability was also related to results obtained during analysis of starch and dietary fibre, The degree of substitution (DS) was determined by 1 HNMR spectroscopy and the substitution sites were evaluated by gasliquid chromatography and mass spectrometry. Substitution with acetyl‐ and hydroxypropyl groups reduced the availability of drum‐dried starch derivatives to α‐amylase. In contrast, the susceptibility of raw starch increased after introduction of hydroxypropyl groups. Cross‐linking with phosphate only had but minor effects on enzyme availability. The recovery of starch during analysis depended on (a) degree of hydrolysis to glucose (b) whether or not the substitution groups were removed. The lowest yields were observed when analyzing substituted derivatives after boiling and enzymic hydrolysis (60‐70%). Enzymically unavailable starch was not recovered as dietary fibre when using an enzymic gravimetric assay.