RS1: Physically inaccessible starch
RS1 is entrapped in the protein matrix or cell wall material and is physically inaccessible
for enzyme hydrolysis. For example, starch granules in the vitreous endosperm of cereal
grains are embedded in a dense protein matrix (Figure 6). The protein matrix is relatively
water-impermeable, which retards starch swelling during cooking and acts as a barrier for
amylase hydrolysis (O'Dea et al 1980, Rooney and Pflugfelder 1986, Correa et al 2002).
Grinding of raw grains or seeds increases the susceptibility of starch to enzyme hydrolysis
because the starch granules are free from the protein matrix (O'Dea et al 1980, Jenkins et al
1988). RS1, however, is not observed in the floury endosperm of cereal grains because the
protein matrix is weak and discontinuous (Figure 6) and the starch is more accessible for
enzyme hydrolysis