A review of the recently reported moisture diffusivity experimental data in food materials is presented in this work Values are classified and analysed statistically to reveal the influences of temperature and moisture content Empirical models relating moisture diffusivity with the above variables, along with relevant graphs for various materials, are included Other factors affecting moisture diffusivity prediction are also discussed

Moisture Diffusivity Data Compilation in Foodstuffs

CONTENTS
18.1 Introduction 40418.1.1 Background of Drying 404
18.1.2 Mode of Preservation 404
18.1.3 State of Water in Foods 404
18.1.4 End Point of Drying 405
18.1.5 Heating Methods in Drying 40518.2 Drying Methods 405
18.3 Thermal Drying 405

Drying and Food Preservation

Heat and mass transfer modeling in air drying of foods

The purpose of this investigation is to compare various drying models with respect to (a) the accuracy in calculating the material moisture content and temperature versus time and (b) the computation time required. Mechanistic as well as phenomenological heat and mass transfer models are considered. The mechanistic models are formulated by considering different combinations of mechanisms between (1) moisture diffusion in the solid towards its external surface (2) vaporization and convective transfer of the vapor into the air stream (3) convective heat transfer from the air to the solid's surface (4) conductive heat transfer within the solid mass. The phenomenological model incorporates the drying constant while the mechanistic models incorporate the mass diffusivity, the mass transfer coefficient in the air boundary layer, the thermal conductivity, and the heat transfer coefficient in the air boundary layer. The proposed methodology is applied to experimental data of four vegetables, namely, pota...

Model selection in air drying of foods

Inhibition of enzymatic browning and decay on cut surfaces of Golden Delicious apple using ascorbic acid, cysteine, sodium chloride, calcium chloride, citric acid and sodium ascorbate alone or in combinations was investigated at 4 and 10 °C for a storage period of 0, 7 and 14 days, in an attempt to find the most effective treatment. Apple segments immersed in ascorbic acid and citric acid alone showed visual traces of browning after 7 days storage at 4 °C. After 14 days storage, only ascorbic acid and ascorbic acid plus sodium chloride had moderate browning, while all other treatments were severely affected. However, at 10 °C, only ascorbic acid was effective in reducing the level of browning, although its effect was minimal after 14 days storage. Browning was more severe at 10 °C than 4 °C in all solutions. The browning measurement (a* value) became increasingly positive from 7- to 14-day storage. Microbial decay was absent in all treatments within 7 days at 4 and 10 °C. However, three test solutions showed microbial decay after 14 days storage at 10 °C in addition to the control solution, which showed decay at both 4 and 10 °C storage temperatures.

Prevention of enzymatic browning of apple cylinders using different solutions

The ultimate goal of the project is to develop procedures, techniques, data and other information that will aid in design of cost effective and energy efficient drying processes that produce high quality foods. This objective has been sought by performing studies to determine the pertinent properties of food products, by developing models to describe the fundamental phenomena of food drying and by testing the models at laboratory scale. Finally, this information is used to develop recommendations and strategies for improved dryer design and control. This report is the executive summary of the program. 27 refs., 5 tabs.

H. Liang

Papers

Design and control of energy efficient food drying processes with specific reference to quality