Modelling and improving the spray drying process for whey derivates
Résumé
Spray drying is a well-established technique to convert a liquid solution into individual solid particles. It is widely used in the dairy industry, especially in the whey sector. In fact, the dairy industry has to process huge amounts of whey each year. Because of environmental and economic factors, as well as the potential benefits for health, whey is no longer considered a waste product. It is therefore of the utmost importance to process whey properly to supply the ingredient market with high quality products. However, whey is not an easy product to process because it contains a great deal of free water, lactose, soluble proteins and varying amounts of minerals, especially calcium, phosphate and various monovalent ions. If lactose is not properly crystallised, whey cannot be spray dried correctly without a reduced flow rate and decreased functional properties of the powder. Whey composition is unfortunately highly variable, which makes it difficult to anticipate process optimisation for further processing. Lactose crystallization is a critical step in the processing of whey and its permeates concentrated by evaporation before spray drying. In this overview, we propose several approaches to improve the performance of whey powder processing by using physicochemical and process information. Several examples of process optimization through improved understanding of vacuum evaporation, lactose crystallization and spray-drying are detailed. The final aim of this overview is to contribute to greater understanding of lactose crystallization and to propose an ideal plant to produce whey powders of high value, quality and energy efficiency with a low environmental impact.
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