Results from a number of studies (B

Results from a number of studies (Berry 1986; Berry et al 1988;
Siljestrdrm et al 1989; Sievert and Pomeranz 1989, 1990;
Czuchajowska et al 1991; Eerlingen et al 1993) led to the conclusion
that resistant starch type III, formed after gelatinization of starch,
consists mainly of retrograded amylose. However, in most studies,
storage conditions were not optimized to favor amylopectin retrogradation,
or else resistant starch was determined after hydrolysis
at 1000 C with a heat-stable a-amylase. At such a high temperature,
retrograded amylopectin is expected to be melted because an endotherm
at -60'C is observed with differential scanning calorimetry
when retrograded amylopectin is heated in water.
Amylopectin consists of 3. 10'-3.106 glucose residues (Zobel
1988). It is highly branched. Three types of chains can be distinguished.
Short S chains with a degree of polymerization (DP)
of 14-18 glucose residues, are organized in a cluster structure
(Robin et al 1975). Inner, long L chains have a DP of 45-55.
A single chain of DP >60 bears the reducing end-group (Mercier
1973, Watanabe and French 1980). Polymodal chain distributions
have, however, also been reported (Hizukuri 1986). Retrogradation
of amylopectin includes a crystallization process of the outer
short branches (DP 14-18). In contrast to what is observed with