Deamidation of wheat-flour gliadin with ion-exchange resin
2001
Kumagai, H. (Nihon Univ., Tokyo (Japan)) | Norimatsu, Y. | Hashizume, N. | Sakurai, H. | Kumagai, H.
Gliadin in wheat-flour gluten was deamidated by cation-exchange resins in order to enhance the affinity for water ; four kinds of cation-exchange resins with functional groups of -N=(CH2COO sup-) sub2, -COO sup- and -SO3 sup- (Amberlite, IRC718, IRC50, IR120B, and XT1006) were used. The affinity of untreated and deamidated gliadins for water in the region of low water content were evaluated by water sorption measurement and thermodynamic analysis. In addition, the solubility of the samples to water and salt solutions was measured, as an index of affinity of the samples for water in the region of high water content. The gliadin of the largest amount of deamidation was obtained by using IRC 50 which was referred to as CE (COC sup-) in this paper, the cation-exchange resin with a functional group -COO sup-. The degree of deamidation of the gliadins reached about 28% using CE (COO sup-) at the optimum conditions (amount : 0.2g/g-solution, treating time : 6hr). Water sorption isotherms of the gliadins were obtained ; the amount of sorbed water on the deamidated gliadin was larger than that of the untreated one. The integral Gibbs free energy, delta G supS, on the basis of solution thermodynamics was calculated. The enhancement of the affinity for water by deamidation was quantitatively evaluated by delta G supS. The solubility of the deamidated gliadin to water and NaCl solution was higher than that of the untreated one.
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