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Konjac glucomannan flour, which mainly consists of glucomannan, is an indigestible dietary fiber. Therefore, it has been broadly used as low-calorie food ingredient in various kinds of foods, beverages, and pharmaceutical products. In this study, the production of dried konjac noodles was evaluated by studying the effects of alkalinity using limewater versus calcium hydroxide and the gelling agent sodium alginate on textural properties of konjac noodles. Drying and rehydration conditions were studied to evaluate the optimum conditions for producing dried konjac noodles. By considering the springiness and cohesiveness of the konjac noodles, the results indicated that using 3% konjac glucomannan flour with limewater and an incubation time of 30 min were the most suitable conditions. In addition, hot air drying at 80 • C for 55 min and soaking in hot water for 9 min were the optimum drying and rehydration conditions.

Puffing technique is the process that can improve texture and volumetric of crisp fruit and vegetable. However, the effect of chemical composite in foods on puffing characteristics is still lack of study. Therefore, potato and apple slices were comparative study on their physical properties. Potato and apple were sliced into 2.5 mm thickness and 2.5 cm in diameter. Potato slices were treated by hot water for 2 min while apple slices were not treatment. After that, they were dried in 3 steps. First step, they were dried by hot air at temperature of 90°C until their moisture content reached to 30, 40, and 50 % dry basis. Then they were puffed by hot air at temperature of 130, 150, and 170°C for 2 min. Finally, they were dried again by hot air at temperature of 90°C until their final moisture content reached to 4% dry basis. The experimental results showed that chemical composite of food affected on physical properties of puffed product. Puffed potato had higher volume ratio than those puffed apple because potato slices contains starch. The higher starch content provided more hard texture of potato than those apples. Puffing temperature and moisture content strongly affected on the color, volume ratio, and textural properties of puffed potato slices. In addition, the high drying rate of puffed product observed at high puffing temperature and higher moisture content.

Crisp banana processed by hot air drying combined puffing provides low volumetric shrinkage and high crisp texture, but crisp product has more brown colour. The hot water blanching and steaming pretreatments could reduce brown colour of puffed product. From previous reports, the comparative study of effects of hot water blanching and steaming pretreatments on crisp banana qualities were limited. Therefore, this work was interested in a comparative study of the effects of hot water blanching and steaming pretreatments on crisp banana. The fresh bananas were cross sectional sliced to 2.5 mm and then they were pretreated by hot water or steaming. After that, it was dried by hot air and puffed by hot air. The experimental results showed that both pretreatments by hot water and steaming could reduce the firmness of raw material structure, resulting in the larger volumetric and lower hardness of pretretment product than that of the non-pretreatment banana product. In addition, the both pretreatment also retarded browning reaction of crisp banana product as compared to non-pretreatment product. However, it was not observed the difference in qualities of both pretreatment crisp banana methods. Increasing puffing temperature provided lower hardness of product, however, the color of puffed banana was more browning. Therefore, the banana should be pretreated by hot water blanching or steaming before processing and using of puffing temperature not exceeding 170 oC.