Functional Properties of Some Non-conventional Treated Starches

Starch is one of the most widespread and used biopolymers in different applications such as in the paper, textile, food, pharmaceutical and cosmetics industries (Richardson & Gorton, 2003). Even starch is useful in various industrial fields, its use as a native form has been restricted by some limitations (high viscosity, low solubility in cold water, paste instability, etc.) in specific applications due to its structure. Taking into account this aspect, starch is frequently submitted to the chemical, physical and enzymatic treatments or their combination in order to modify it and to obtain some functional properties suitable in specific industrial applications. The most used way to obtain modified starch is by chemical methods which are most of the time complex, expensive and time consuming. Modern, non-conventional methods of starch modification are generally physical techniques (e.g., ionizing and non-ionizing radiation treatments, plasma treatment) which are fast, low cost and environmentally friendly because they do not use pollutant agents, do not allow the penetration of some toxic substances in the treated products and do not generate undesirable residual products, do not require catalysts and laborious preparation of sample. There are reported several studies related to starch treatment with ionizing radiation, especially with gamma radiation (MacArthur & D’Appolonia, 1984; Sokhey et al., 1993; Kang et al., 1999; Wu et al., 2002; Ezekiel et al., 2007). Recently, information regarding starch treatment with electron beam (e-beam) in different irradiation dose range, either at low or relative high doses (0 – 25 kGy) (De Kerf et al., 2001; Pimpa et al., 2007) or at very high doses (> 50 kGy) (Kamal et al., 2007; Shishonok et al., 2007) were reported. The studies concerning the effects of ionizing radiation were performed on starches extracted from various vegetal sources such as corn (Kang et al., 1999; De Kerf et al., 2001; Adeil Pietranera & Narvaiz, 2001), wheat (MacArthur & D’Appolonia, 1984; Koksel et al., 1996), potato (Ezekiel et al., 2007; Shishonok et al., 2007), barley endosperms (Faust & Massey Jr., 1966), rice (Wu et al., 2002; Bao et al., 2005) or sago (Pimpa et al., 2007). The reported data showed that ionizing radiation treatment generates free radicals on starch molecules that can alter their size and structure (Raffi et al., 1980; Ciesla et al., 1991; Grant & D’ Appolonia, 1991; Sabularse et al., 1991; Sokhey et. al. 1993). Therefore, the hydrolyze of the chemical bonds occurs by cleavage of starch macromolecule into lower fragments of dextrin, which can be either electrically charged or uncharged as free radicals (Kang et al., 1999). This type of treatment may change the functional and physicochemical properties of starch leading to the increase of solubility (Bao & Corke, 2002), the reduction of swelling power (MacArthur & D’Appolonia, 1984) as