Experimental Values and Correlations for Characteristic Variables and Thermophysical Properties of Osmotically Dehydrated Stone Fruits

ANABEL RODRIGUEZ; MARIA M. RODRIGUEZ; ANA M. PAGANO; RODOLFO H. MASCHERONI

Stellenbosch

Simposio; 7th CIGR International Technical Symposium "INNOVATING THE FOOD VALUE CHAIN" y 2nd International Conference on Postharvest Technology & Quality Management; 2012

Partial osmotic dehydration (OD) of food materials, especially of fruits and vegetables, is often used as a pre-treatment to further conservation procedures as it assures a better final quality and less energy use. The wide diversity of source food materials, with their different compositions and structures, sizes and shapes of pieces and of working conditions determine the need of extensive experimental work to characterize each particular case (food, piece, solution, working condition). It is important to develop general relations between those variables relevant to the dehydration process (water content WC, soluble solids content SS) independent of product characteristics and process conditions. It is also of high technical value to develop simple general equations to predict the variation of thermophysical properties like heat capacity and enthalpy with temperature and water content and initial freezing point with water content, valid independently of the fruit and vegetable used. Based on our experimental determinations on different stone fruits (peaches, plums and nectarines), dehydrating solutions and working conditions and on an extensive search of literature on osmotic dehydration of those fruits, in this work we developed: - A general linear correlations between WC and SS for stone fruits dehydrated in sugar or alcohol solutions that allows to characterize both properties with only one rapid determination (of any of both); - General correlations between heat capacity and enthalpy with water content and temperature for fresh and osmotically dehydrated stone fruits; - A general correlation for initial freezing temperature of fresh and osmotically dehydrated stone fruits as a function of water content.