that enzyme susceptibility is influ

that enzyme susceptibility is influenced by several factors, including the ratio of amylose/amylopectin, the crystalline structure and
the size of the particles. Amongst these factors, the crystalline
granular structure is the most important.
The high-, medium- and low-amylose rice starches treated by
the HMT 25% had a higher concentration of reducing sugars at all
times during the hydrolysis, as compared to HMT 15% and HMT
20% and their respective native starches. These results are similar
to those ofKweon, Haynes, Slade, and Levine (2000), who observed
a trend toward increased digestibility of the starches with an increase in the moisture content of the HMT.
Lorenz and Kulp (1982)reported that the changes in the HMT
probably occur in the amorphous regions of the granules that are
more accessible to the hydrolysis. According toGunaratne and
Hoover (2002), the HMT promotes a crystalline disruption and dissociation of double helical structures in the amorphous region.
These authors studied the hydrothermal treatment (30% moisture/100C/10 h) of taro, cassava and potato starches, and concluded that there was an increase in the enzyme susceptibility of
heat-moisture treated starch. The possible disruption of the crystals near the surface of the granule can facilitate the attack of the
a-amylase within the granule.
The HMT 25% starches had a higher enzymatic susceptibility in
the first two hours of digestion as compared to the native starches.
As reported by some authors (Jacobs, Eerlingen, Spaepen, Grobet, &
Delcour, 1998), the amorphous areas of the starch granules are
more rapidly degraded by bacterial and pancreatica-amylase than
the crystalline areas. The rearrangement caused by the hydrothermal treatment facilitated the accessibility of the amorphous areas
by the enzyme. This may explain the fact that HMT 25% starches
show a high concentration of reducing sugars in the first two hours
of hydrolysis as compared to the native starches