THESIS

LITERATURE REVIEW
1. Resistant starch functional and properties
1.1 Definition and classification
Resistant starch (RS) is described as starch that escapes digestion in the
small intestine (Englyst and Kingman, 1990; Bravo et al. 1998; Topping and Clifton,
2001). Scanning electron microscopy assessment of ileostomy effluents showed that
some starch escaped digestion in the small intestine and the granules remained intact
(Muir et al. 1995). A EURESTA study defined resistant starch as “the sum of starch
and products of starch degradation not absorbed in the small intestine of healthy
individuals” (Asp, 1992). Experimental data now shows that this definition could be
broadened to indicate that resistant starch is not digested by pancreatic enzymes, and
hence is not metabolized or absorbed in the small intestine, but rather enters the colon
where it is fermented by colonic microflora. On the other hand, dietary fiber consists
mainly of plant cell wall material, notably cellulose, hemicellulose, pectins, gums,
mucilages and lignin. These are generally not digested by enzyme hydrolyses because
of their complex nature.
Classification of four forms of resistant starch and factors affecting their
resistance to digestion in the colon are show in Table 1. RS is further partitioned in
physically inaccessible starch (RS I), in resistant starch granules (RS II), in
retrograded starch (RS III), of which only retrograded amylose is totally resistant
(Englyst and Macfarlane, 1986; Englyst et al. 1987; Englyst et al. 1992; Englyst and
Hudson. 1996) and in chemically modified starch (RS IV) (Brown et al. 1995).
Analyses indicate that RS consists of crystallized, linear, unbranched, short-chain α-
glucans (DP about 60-65) (Berry et al. 1988; Siljeström et al. 1989). Since amylose-
lipid complexes significantly reduce the availability to α-amylase, an interrelation of
complexation with lipids and resistant starch formation is assumed but it is verified
that amylose-lipid complexes are not involved in the formation of RS.
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