This work is an overview of the literature in the area of microwave treatment of starch strongly related to changes in its physicochemical, functional and structural properties. The importance of good knowledge of the microwave parameters and starch dielectric properties is highlighted to avoid the improper microwave application on starch or starch-based materials. Future perspectives of microwave processing of starch are suggested.

The properties of starch can be modified by a variety of methods in order to meet desirable technological needs. Electron beam irradiation is able to induce changes in starch properties. The paper deals with investigation of physicochemical and structural modifications of corn starch processed by electron beam up to 50 kGy and evaluation of the technical-economic aspects of starch processing. Paste viscosity, pasting and peak temperatures decreased in a dose-dependent manner, indicating degradation of the macromolecule. Small circular perforations on the granule surface were observed for 50-kGy irradiated sample. Spectral characteristics suffered minor changes, suggesting that the inter-and intramolecular hydrogen bond stability was affected by the electron beam. These modified starches could find applications in foodstuffs requiring low-viscosity starch. A cost estimate of the electron beam processing of corn starch with an average absorbed dose of 30 kGy showed an increase of corn starch price by 16%.

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The paper presents the investigation of the sensitivity and degradation rate of corn, wheat, rice, and potato starches exposed to accelerated electron beam taking into consideration the paste apparent viscosity and MW distribution. The functional radiosensitivity of starch defined by analyzing the apparent viscosity behavior of its aqueous paste as a function of absorbed dose had the following order: potato>wheat>corn>rice. In a similar manner, the structural radiosensitivity of starch based on the degradation rate of the MW fractions was considered. Two slight different orders were found as (1) potato>wheat>corn>rice taking into account the number molecular fraction and (2) wheat>corn>potato>rice considering the weight molecular fraction, assigned to the different structural organization of the investigated starches.

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