Hot-air drying

Torringa, E., Esveld, E., Scheewe, I., van den Berg, R., and Bartels, P. 2001. Osmotic dehydration as a pre-treatment before combined microwave-hot-air drying of mushrooms. J. Food Engineer. 49,... 

The conversion processes are shown schematically in Figure 6. Softboards or insulation boards are cold-pressed and hot-air dried to specific gravities of 0.2 to 0.5. Air temperatures of 200-250C are used to evaporate residual water. 

Wet/Dry - wet formed mats are hot-air dried to anhydrous condition and hot pressed between two smooth plates to form a smooth-two-sides board. 

It is difficult to obtain mesoporous RF drygels by hot air drying. The mesopores of RF xerogels are collapsed by pyrolysis. 

In retained heating methods (dry heat), a simple hot air drying reduces the moisture content to 3-4%. The bran must be kept dry in moisture-proof containers, or the rehydrated bran will regain its lipase activity. If the bran is heated in the presence of moisture, the lipase is permanently denatured. 

Removal of 95% or more of the water from a material, usually a foodstuff, by exposure to high temperature by various means. Its primary purpose is to reduce the volume of the product, increase its shelf life, and lower transportation costs. Special equipment for dehydration includes tunnel dryers, vacuum (shelf) dryers, drum dryers, etc., in which the bulk product is exposed to a hot-air environment. Another method is spray drying, in which a liquid product is ejected from a nozzle into hot air dried milk and egg white are prepared in this way. The term dehydration is not applied to loss of water by evaporation or sun drying. See drying. 

It has been established that in many edible mushrooms such as Agaricus campestris and Agaricus bisporus, the C8-compounds are formed enzymically during the oxidation of linoleic acid (16-20). In the present study, the identification of l-octen-3-ol and 2-octen-l-ol as major C8-compounds in macerated fresh Shiitake mushrooms suggested a similar biosynthetic origin. The amount of C8-compounds (primarily l-octen-3-ol and 2-octen-l-ol) in the blanched (97°C, 8 min) or the hot-air dried (commercial process)... 

These are usually made from a two-component system which when mixed has a short life. Uses involve the screen printing of polythene containers, with either air drying or hot air drying. 

This process can use either solid stencils or screen (mesh) stencils (see Figure 16.12). The latter is called screen printing and was originally known as silkscreen, as silk-type screens were employed. Present day screens are made of nylon, polyester or steel and are relatively low in cost, 45-75. Each screen may give 15,000 to 50,000 impressions. The ink is forced through the screen by a squeezer. Prior to this action the screen is separated from the item to be printed by a lift-off gap. This gap is reduced by the pressure of the squeezer whereby contact is made between the screen, ink and item. Screen inks are relatively thick, and are either air or hot air dried. The screen process can produce coarse half tones with thin inks. 

LUNING P A, EBBENHORST-SELLER T and DE RIJK T ROOZEN J P (1995), Effect of hot-air drying on flavor compounds of bell peppers Capsicum annuumf, J Sci Food Agric, 68, 355-365. 

Chiewchan, N. and Morakotjinda, P. 2009. Effect of acetic acid pretreatment and hot air drying on resistance of Salmonella on cabbage slices. Drying Technology 27 955-961. 

FIGURE 39,7 Spray-drying process scheme (one stage). Hot air drying/drops cocurrent = ao high T for dry product. Residence time 10 s, continuous process). (Adapted from Pisecky, J., Handbook of Milk Powder Manufacture, Niro A/S/, Copenhagen, Denmark, 1997, 261p.)... 

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