Drying by desorption: a method to determine the water availability in dairy concentrate to dry and in non-fat cheese
Résumé
The most frequently used technique for dehydration of dairy products is spray drying. The aims of this study were to evaluate the ratio of bound to unbound water availability by using a drying by desorption [1]. Typical curves were registered with a water activity meter on water, dairy and food concentrates . With these data, more than 80 experiments to correlate calculated and measured parameters in a pilot plant (Bionov) and industrial plants have been performed. The results show that the difference between the calculated and measured inlet air temperature was below 5%. The economic interest of this system is obvious, because it is easy to anticipate the spray-drying parameters by using a controller integrating the water availability of the concentrate and certain thermodynamic parameters. Software based on this step was developed (SD2P®, Spray Drying Parameters Simulation & Determination). The combined results provide more precise determination of spray-drying parameters (including inlet/outlet air temperature, mass/powder flow rate, powder temperature, etc.), powder state during spray-drying (stickiness) and the cost of spray-drying with respect to weather conditions. This method has recently been adapted for cheese.