drying. Despite its capability of providing a very high quality
dehydrated product, freeze-drying is an expensive method
which limits its wide utilization by the food industry. Thus,
the use of freeze-drying by the food industry is normally restricted
to high value products, such as coffee, crispy fruits
and vegetables, ingredients for ready-to-eat foods and some aromatic
herbs.
Infrared (IR) heating offers many advantages over conventional
hot air drying. When IR is used to heat or to dry fruits,
the radiation impinges on the exposed fruit surfaces and penetrates
to create internal heating with molecular vibration of
the material, and the energy of radiation is converted into
heat (Ginzburg, 1969). The depth of penetration depends on
the composition and structure of the fruits and also on the
wavelengths of IR radiation. When the food is exposed to IR
radiation, the electromagnetic wave energy is absorbed directly
by the dried food with low energy loss. It has been reported
that the drying rate for food materials using IR
heating is higher compared to conventional hot air drying
and increases with increased power supply to a far infrared
emitter (Masamura et al., 1988). The IR heating allows more
uniform heating of fruits resulting in better quality characteristics
than other drying methods (Nowak & Lewicki, 2004;
Sakai & Hanzawa, 1994).
drying. Despite its capability of providing a very high qualitydehydrated product, freeze-drying is an expensive methodwhich limits its wide utilization by the food industry. Thus,the use of freeze-drying by the food industry is normally restrictedto high value products, such as coffee, crispy fruitsand vegetables, ingredients for ready-to-eat foods and some aromaticherbs.Infrared (IR) heating offers many advantages over conventionalhot air drying. When IR is used to heat or to dry fruits,the radiation impinges on the exposed fruit surfaces and penetratesto create internal heating with molecular vibration ofthe material, and the energy of radiation is converted intoheat (Ginzburg, 1969). The depth of penetration depends onthe composition and structure of the fruits and also on thewavelengths of IR radiation. When the food is exposed to IRradiation, the electromagnetic wave energy is absorbed directlyby the dried food with low energy loss. It has been reportedthat the drying rate for food materials using IRheating is higher compared to conventional hot air dryingand increases with increased power supply to a far infraredemitter (Masamura et al., 1988). The IR heating allows moreuniform heating of fruits resulting in better quality characteristicsthan other drying methods (Nowak & Lewicki, 2004;Sakai & Hanzawa, 1994).
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