Studies on Spray-dried Citrus Unshiu Juice

Part I. Characteristics of water adsorption properties of spray-dried Citrus Unshiu juice

Abstract

Citrus Unshiu juice with various contents of pulp (10 to 25%) were dehydrated by spray drying to form powder. The equilibrium moisture contents were determined by the saturated salt solution-desiccator method at 25°C.
The equilibrium moisture contents of the spray-dried Citrus Unshiu juice decreased at low relative humidity, whereas sharp increase was seen at high relative humidity. The equilibrium moisture contents of the powder became larger with decreasing the contents of pulp.
As the relative humidity increased, the powder required longer period to reach the equilibrium moisture contents.
The unilayer adsorption water (4.8 to 6.1%) and adsorption area (171 to 220mm²/g) of the powder became larger with decreasing the contents of pulp.
Isosteric differential heat of adsorption of the powder was 12.2Kcal/mol at low equilibrium moisture contents.