Bleaching efficiencies of bentonites, montmorillonites and sepiolites for alkali‐refined rapesseed, soybean, wheatgerm, safflower, corn, cottonseed and sunflower oils were investigated by a batch method at 110°C. The sepiolites with more acid sites at −5.6 < Ho ≥ −3.0 were the most effective in bleaching of each alkali‐refined oil. Surface area and acidity at −5.6>Ho ≥ −3.0 were highly significant with bleaching efficiency. The sepiolites (numbers 2 and 3) were more suitable than standard activated clay because they were more effective both in retaining tocopherols and in reducing free fatty acids after bleaching.

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.

Adsorption isotherms of pigments from alkali-refined oils (rapeseed, soybean, wheatgerm, safflower, corn, cottonseed and sunflower} were measured to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of pigments on sepiolites and standard activated clay. The Freundlich equation was more applicable to the experimental adsorption isotherms. The equilibrium amount adsorbed, acidity, pore size distribution and inflection of the Freundlich isotherms could be explained by assuming that pigments were adsorbed on the stronger acid sites in smaller pores at low concentration, and then in the larger ones when the concentration increased. The amount adsorbed increased with a rise in adsorption temperatures from 70 to ll0°C, and the heat of adsorption was below 10 kcal/mol. The results indicate that pigments were physically adsorbed on the acid sites activated at higher adsorption temperatures.

Efficiencies of synthetic adsorbents and attapulgites in bleaching alkali‐refined rapeseed and soybean oils ranged from 13–53% and 93–97%, respectively. The Freundlich equation was more applicable than the Langmuir equation to the experimental adsorption isotherms of β‐carotene on attapulgites. Bleaching with attapulgites reduced tocopherols by 12.5–29.5% in rapeseed oil and by 18.9–44.8% in soybean oil. Cosmetic‐grade attapulgite was superior to the others in bleaching efficiency, equilibrium amount adsorbed and removal of free fatty acids.

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.