%0 Journal Article
%T Thermal, Structural, and Physical Properties of Freeze Dried Tropical Fruit Powder
%A K. A. Athmaselvi
%A C. Kumar
%A M. Balasubramanian
%A Ishita Roy
%J Journal of Food Processing
%D 2014
%R 10.1155/2014/524705
%X This study evaluates the physical properties of freeze dried tropical (guava, sapota, and papaya) fruit powders. Thermal stability and weight loss were evaluated using TGA-DSC and IR, which showed pectin as the main solid constituent. LCR meter measured electrical conductivity, dielectric constant, and dielectric loss factor. Functional groups assessed by FTIR showed presence of chlorides, and O¨CH and N¨CH bonds in guava, chloride and C¨CH bond in papaya, and chlorides, and C=O and C¨CH bonds in sapota. Particle size and type of starch were evaluated by X-ray diffraction and microstructure through scanning electronic microscopy. A semicrystalline profile and average particle size of the fruit powders were evidenced by X-ray diffraction and lamellar/spherical morphologies by SEM. Presence of A-type starch was observed in all three fruits. Dependence of electric and dielectric properties on frequency and temperature was observed. 1. Introduction Guava (Psidium guajava L.) and sapota (Manilkara zapota) are native of tropical America and grow well in tropical and subtropical regions and are widely cultivated in the tropics including India, Guatemala, and Mexico [1, 2]. Papaya (Carica papaya L.) is also an important fruit crop grown widely in tropical and subtropical countries in the world. The relative humidity and temperature are the more critical variables to extend the shelf-life of the fruit and to preserve its sensory, physical, and chemical properties. Thus, dehydration processes may be an efficient alternative for fruit storage, because the reduction of water activity is related to the decline of chemical and enzymatic reactions responsible for the deterioration of foods. Dehydration is based on the extraction of water contained in foods up to a minimal level which is enough to their conservation for long time. The hot air-drying is one of the most used methods for preservation of fruits since long time ago; however the main problem is the possibility to lose or change some of their properties due to the thermal treatment. Hence, gentle drying techniques, such as osmodehydration or lyophilisation (freeze-drying), have also been used in fruits. With the aim to find new alternatives for the commercialization of tropical fruits and to reduce the difficulties for its handling and transport, freeze-drying techniques were used to obtain added-value solids from tropical fruits. The International Confederation for Thermal Analysis and Calorimetry (ICTAC) has defined thermal analysis (TA) as a group of techniques that allow us to study the relationship between
%U http://www.hindawi.com/journals/jfp/2014/524705/