1.  Gunaratne and Hoover (2002) proposed that

HMT might cause the occurrence of additional interaction between

amylose–amylose and/or amylose–amylopectin chains.

The decrease of soluble amylose content could be attributed to

a strengthening of the molecular bonds. Consequently, during

HMT an increase in the interaction between amylose molecules,

amylopectin molecules and lipid molecules (forming a more stable

structure) occurred which contributed to the change of soluble

amylose and insoluble amylose.

2. Li and Gao (2010) postulated that, it is likely

that augmentation in amylose formation was susceptible to form longer or more ordered helical segments by amylose–amylose (AM–AM) and/or amylose–amylopectin (AM–AMP) interactions formed on HMT, which resulted in increased colour of the iodine solution during colorimetry determination.

There is no reason to believe that HMT may cause a change in Am/Ap-ratio. A higher Am content is likely to be an artifact. The observed effect probably has its origin in preferential aqueous leaching of amylose from the granule in combination with incomplete dissolution of the starch granules.

It has to be ensured that the starch sample is completely solubilized. This is done by slurrying the sample in water and adding an equal volume of 2 M NaOH with stirring. An aliquot is withdrawn, then diluted and neutralized, and then analysed for amylose (e.g. blue value). An untreated starch is taken as a reference. The solution has to be checked for absence of granular remnants, e.g. by phase contrast microscopy or by analysing the carbohydrate content of the supernatant after high-speed centrifugation.   

Starch have amylopectin and amylose units together and during analysis apparent amylose is estimated. Amylose leaching (AML) depends upon the type of binding between amylose, amylopectin and lipid fraction of starch. (Reference; Hoover R. 2010). During heat and moisture treatment (HMT), organization and re-organization of amylose and amylopectin structural  modification into amorphous and crystalline regions on the granules takes place, result, amylose leaching (AML). The magnitudes of AML found to be dependent upon the moisture content during heat treatment and the source of starch.

It is likely that the extent of AML is influenced by the magnitude of interaction between amylose and amylose and amylose and amylopectine-chains and their interaction with lipids content in the amorphous domains of the native granule.

Secondly, if lipids fraction in starch is high, it binds with amylose chain during moisture treatment and subsequent heating of starch reduce the tendency of amylose to leach out.

The reason may that native starch, amylose-amylose (AM-AM) and amylose-amylopectin (AM-AMP) interactions within native granules of native starch are slightly stronger than in HMT starch. Since the extracted native starch don’t have lipid fraction, and would not bind with amylose fraction of starch. (Hoover & Vasanthan, 1996). So, an increase in AML after heat-moisture treatment has been attributed and associated with two factors:

ü  interaction between free starch lipids and the amylose helix, and

ü  interaction between starch chains.

      Loss of amylopectin in process occur only due to fact that amylose adhered to branched chain of amylopectin initially contribute towards amylopectin but after treatment it is responsible for increasing the amylose content of starch.

during heat processing amylose undergoes dextrinization, than amylopectin and the amylose starch dominate the amylopectin