Étude comparative expérimentale des opérations d’atomisation et d’autovaporisation : application à la gomme arabique et au soja

摘要

Nowadays, the need to achieve long term stability and usability, in addition to greater functionality, implies that many food products and liquid or solid ingredients are dehydrated or mechanically transformed into powder. The manufacturing processes of food powders always require the satisfaction of a series of criteria, such as process performance and product quality. The spray drying technology is always considered the main method used for producing the powders in many varied fields thanks to its preponderant advantages. However, in some cases, the spray drying shows less effective because the initial investment and production costs are too high ; the need to reach a large specific surface area of the powders causes a lot of complex problems relating to the transportation, cleaning, product recovery, explosion risk and thermal degradation of final product. Whereas, many research work on the autovaporization phenomenon by DIC (Instant controlled pressure drop) showed that the DIC technology is able to solve many industrial problems, eventually leading to obtaining the very high-quality finished products and reducing the energy consumption. However, applications of the DIC technology in the manufacture of food powders are still restricted, and the comparison of the properties of the powder obtained by DIC with other production methods is not yet performed systematically. In such a context, this thesis work is performed in order to contribute to solving some problems concerning the control and improvement of the food powder quality as well as the heat transfer efficiency in the spray drying and autovaporization operations (DIC treatment). In order to attain these objectives, two main raw materials consisting of gum arabic and soybean were examined. Five main researches carried out in this thesis consist of : firstly, comparative study of methods for producing the gum arabic powder and the impacts of DIC treatment on the properties of finished products ; secondly, optimization of the spray drying operating conditions for producing the powder mixture of gum arabic (GA) and maltodextrin (MD) as a wall material for encapsulation technology ; thirdly, comparative study of methods for producing the soybean powder and the impacts of DIC treatment on the properties of finished products ; fourthly, optimization of the spray drying operating conditions for producing the soybean powder ; and finally, impacts of ratio (GA/MD) in the manufacture of soybean powder by spray drying. The obtained results showed that the DIC technology can be used instead of the spray drying to produce the high quality powders of gum Arabic and soybean. The properties of these powders were improved and controlled by adjusting the operating conditions of spray dryer and DIC treatment. The optimal operating parameters for each case were found thanks to the process optimization in terms of product quality and heat transfer efficiency in the drying chamber.