Flaked cereals are cooked whole grains, parts of grains, or flours that have been pelletized or agglomerated, flattened into a flake, and dried or toasted. A normal process involves blending the grain with a flavoring syrup that may contain sugar, water, malt, or salt as well as other ingredients or combinations thereof. The blend is cooked in a steam atmosphere in a batch or continuous cooker. Cooking conditions involve moistures between 25 and 40%, time between 30 min and 3 h, and steam pressures of 15-40 psig. The cooked material is dried (pelletized and sized if required) to the desired flaking moisture, normally between 12 and 22% moisture. The material is tempered for 1-24 h to equilibrate moisture throughout the grain piece. After tempering, the pieces are fed through flaking rolls to get the desired flake thickness, normally between 0.010 and 0.035 in. After flaking, the wet flakes go to toasting ovens where the product moistured is quickly brought down to 2-3%. At times, grain flakes (especially rice) are oven puffed. This requires that the wet flakes be subjected to a very high temperature (up to 600°F) for a short period of time, often 1 min or less (7). This is done effectively in a fluidized bed dryer.
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