Now that the many options available to food or ingredient processors have been explored, it becomes easier to associate certain products with what to do with them. For most dairy products, nozzle or rotary atomizers can be used, and single to multi-stage dryers are used. The skim milk is concentrated in an evaporator to about 50% solids and dried to about 3.5% moisture before being introduced into the atomizer. Of course skim milk powder can be achieved by rewetting and clumping. Whole milk introduces some additional problems due to its fat content. The electric hammer prevents product deposition on the chamber walls. The product fluid is about 50% solids and dried to about 3.5% moisture.
When the whole milk powder is immediately dissolved, the final agglomerates are finely coated with lecithin, which improves the wettability of the agglomerates. (High levels of fat often prevent adequate wetting of the product.) Fruit juices contain a high percentage of sugar and cannot be spray-dried in their pure form. Often diluents such as maltodextrin or lower D.E. (dextrose equivalent) corn syrup solids can be added. Even with fillers or diluents, a certain minimum cell size is required due to the viscosity of the concentrate, and the solids content of the feed is kept at 30% to 35%.
The design and operating characteristics of spray dryers are as diverse and wide-ranging as the number of food products and ingredients on the market today. Due to unique properties (hygroscopicity, high fat content, granules, multi-phase nature), these products require unique set-up and handling characteristics in order to convert them into the most user-friendly dry form. Energy considerations continue to expand the number of equipment options available for drying, agglomerating, encapsulating and spray cooling novel foods and ingredients, so the potential for new innovative products is limitless.
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