RS is highly resistant to mammalian enzymes. In cereal products,
the RS fraction is not digestible both in vitro and in vivo (Bornet
1993). Four different RS fractions have been identified in cereal
products: native starch, retrograded amylose, the amylo-lipid complex,
and encapsulated gelatinized starch. After reaching the large
intestine, the RS fractions are fermented by the colonic flora, resulting
in short-chain fatty acids (SCFA). SCFA profiles derived from RS
are lower in acetate and higher in butyrate than those of conventional
fibers. The SCFA are an energy source for colonic cells (butyrate)
and to the body as a whole (acetate and propionate).