Langmuir, Freundlich, BET, Harkins and Jura, Halsey, Smith, Henderson, and Chung and Pfost equations were used to fit experimental moisture sorption data at 20°C for kudzu, sweet potato, corn, potato, rice, wheat, and snake gourd starches. Goodness of fit (from calculated average residue), standard deviation, and standard error and range of water activity indicated Henderson and Chung and Pfost equations fitted the data well over a wide a, range to 0.85. The large value of constants in Henderson and Chung and Pfost equations indicated stability of the microporous structure to moisture sorption. For larger constants, the microporous structures were more stable.

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Moisture sorption characteristics of kudzu starch and sweet potato starch were investigated based on the results of moisture sorption isotherms at ll"C, 20°C and 3o"C, thermal analysis, isosteric heat of sorption and entropy of sorption. The water of crystallization in sweet potato starch was strongly retained compared with that in kudzu starch. Differences in amount of moisture sorbed between kudzu starch and sweet potato starch seemed to be attributable to the stability of the microscopic structure. The interaction of moisture-sweet potato starch was stronger than that of moisture-kudzu starch. Amount of moisture sorbed and strength of moisture-starch binding of the starches, preheated to llO"C, decreased compared with those of the starches vacuum-dried at 20°C because of release of water from the amorphous part of the starch granule.

The effects of filtering through bleaching media on decrease of peroxide value (PV) of autoxidized soybean oil were investigated to improve its quality. Sixteen kinds of filtering and bleaching media were employed. The standard activated clay was the most effective in decreasing the peroxides in autoxidized soybean oil. The relations between the decrease of PV and the physical or the chemical properties of the media were examined. It was found that peroxides are reduced in proportion to the amount of acid at the highest acid strength range + 1.5--5.6 rather than amount of acid at the lower acid strength range, total amount of acid or specific surface area of medium.

Adsorption characteristics of methyl orange were investigated on kudzu, sweet potato, corn, rice, wheat, potato and snake gourd starches. No adsorption of methyl orange, an anionic dye, was observed on potato starch and snake gourd starch because of the presence of phosphate esters. Adsorption isotherms were found to fit both the Langmuir equation and Freundlich equation in a11 others. The degree of adsorption by kudzu, sweet potato, corn and wheat starches was related to the number of hydroxyl groups. We suggested methyl orange was confined to a monolayer on surface hydroxyl groups of the starches. sorbed on starch was calculated from decrease in absorbance of the supernatant. Specific surface areaSpecific surface area of starch was measured by the method described previously . Water and nitrogen surface areas of starch were calculated from the moisture sorption isotherm at 20°C and the nitrogen adsorption isotherm at liquid nitrogen temperature, respectively. INTRODUCTIONSTARCH can adsorb dyes, and adsorption capacity depends on the species of starch (Fujii et al., 1986). Adsorption of dye on starch is important in staining colors on bean-jam cake and starch confectioneries. The extent of adsorption of anionic dyes on starches was related to the ratio of amylopectin to amylose (Zografi and Mattocks, 1963;Carroll and Cheung, 1962). Schoch and Maywald (1956) showed potato starch did not adsorb anionic dyes because of the presence of phosphate esters. Vickerstaff (1954) proposed adsorption of dye occurred at the hydroxyl groups of starch.Estimation of starch content in kudzu starch products by a methyl orange adsorption method was reported by Boki et al. (1989). Amount of methyl orange adsorbed on sweet potato starch was greater than that on kudzu starch. The purpose of our study was to elucidate factors responsible for the difference in amount of methyl orange adsorbed on kudzu starch and sweet potato starch. Adsorption characteristics of methyl orange on corn, wheat, potato and snake gourd starches were also studied on the basis of specific surface area, neutral hydrophilic sites, pore volume, pore size distribution, phosphate content and amylose content.