Jean-Jacques Bimbenet

Food Drying and Dewatering

ABSTRACT Food drying and dewatering raises a growing interest because of increasing requirements in quality, specially in the production of ingredients and additives for food formulation. Heat and mass transfers, as well as mechanical phenomena and reactions kinetics induced by these transfers must be more and more carefully controlled during drying and storage. This chapter relates recent advances in - drying of solids - spray-drying - drum-dryine - superheateded steam drying - osmotice dehydration - hot oil immersion drying

A COMPARTMENTAL MODEL OF THIN-LAYER DRYING KINETICS OF ROUGH RICE

ABSTRACT Rough rice at about 21% (wet basis) was dried at various conditions of temperatures and evaporating capacities of air. The influence of both parameters on drying rate has been studied. At high temperatures, high drying rates can be achieved with low evaporating capacities. In addition, desorption isotherms of rough rice were measured at 35, 60 and 85°C and the experimental isotherms data were fitted using a modified Pfost equation. A compartmental model was developed to simulate the grain moisture content. Heat and mass transfer coefficients were optimized using a Nelder & Mead method. Internal mass transfer coefficient was written as an exponential function of the average moisture content and temperature of the grain and the external mass transfer coefficient as a function of air temperature. The compartmental approach predicts very well the average moisture content with a mean error of about 5% in static and dynamic conditions.

Dynamic modelling and simulation of industrial corn dryers

This paper deals with a new approach to corn drying models. Due to the specific design of French mixed-flow dryers, a dynamic model had to be built from thin layer to industrial dryer level. The main goal for the model is to simulate corn drying under variable conditions at the grain level as well at the whole dryer level, taking into consideration wet-milling quality as well.

Rapid Method of Determination of Sorption Isotherms and Water Apparent Diffusivity

ABSTRACT In the context of a research on the quality of pasta made from soft wheat, reaction kinetics had to be measured at definite temperatures and water contents. It was chosen to realize such experiments in a pilot dryer. To be able to fix temperature and water content of product for a definite period of time, it was first necessary to determine sorption curves of pasta and a drying model including the values of apparent diffusivity of water at elevated temperatures. This paper presents a method to meet these objectives. It consists in realizing a sequence of plateaux of air relative humidities of decreasing values, at constant temperature, in the dryer. Air-product equilibrium at the end of each plateau would have been too long to attain, therefore equilibrium product water content was calcultated using an exponential model. Apparent water diffusivity was determined by adjustement of a diffusive model, taking in account that the air humidity change from one plateau to the next one was a linear ramp a...

Corn Drying: Modelling the Quality Degradation

Corn is the second largest agricultural produce in France. Nearly 60% of this production is exported (primarily towards the EEC). Thus, its wet-milling quality has become an important criterion since it is strongly affected by the artificial drying which occurs just after harvesting. To preserve the wet-milling quality of the dried corn as well as the energy and the drying rate, a model based simulation tool has been elaborated. For convenience, quality degradation and drying sub-models have been uncoupled. Experimental data were then collected during two campaigns of experiments and a second order reaction has seemed to fit correctly to the results. Due to the numerical adjustment, simulated results seem quite in agreement with commercial trials.