Mass transfer kinetics and quality attributes of osmo-dehydrated candied pumpkins using nutritious sweeteners.

Abstract

The aim of this study was to investigate the mass transfer and quality properties changes during the osmotic dehydration (OD) step of the candying process in pumpkins. The goal was to obtain nutritious, low calorie candied pumpkins improving the time-consuming and inconsistent traditional technique. The osmotic agents were sucrose, oligofructose and mixture of sucrose-oligofructose (1:1), while the concentration of each solution was constant (70° Brix). The process temperature varied in three levels (75, 85 and 95°C) and the duration was 180min for sucrose and 240min for the other osmotic agents. The determined parameters during OD include solid gain, water loss, water activity, chroma, hardness and compression work. An empirical model based on a first-order kinetic equation was developed to predict the products' properties, in which the rate constant is a function of the process temperature. The process temperature (Tosm ) had a significant effect on the water loss and solid gain as well as on the physiochemical characteristics of processed pumpkins. The chroma of osmo-dehydrated pumpkins was affected significantly by process parameters. Both hardness and compression work decreased until an equilibrium value was reached as time and temperature of the process increased, regardless the osmotic agent used.