Resistant starch (RS), produced in vitro by hydrolysis of retrograded
pea starch gels and amylose gels by porcine pancreatic alpha-amylase,
was characterised by X-ray diffraction, size exclusion chromatography
and methylation analysis. These techniques showed that RS in vitro con
sisted of semi-crystalline, mostly linear material that was present in
two main molecular size subfractions (DPn > 100 and DPn 20-30) with a
third, minor subfraction (DPn less than or equal to 5). The extent of
retrogradation of amylose was found to be of primary importance in de
termining the RS content of starch. Analysis of in vivo RS, recovered
during an ileostomy study, produced results that were similar to those
obtained from RS in vitro. An in vitro model for the structure of res
istant starch is proposed. (C) 1996 Academic Press Limited