Starch - Beer, Wine, Mead, & Cider Brewing Discussion Community.

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Starches are complex carbohydrates used by many plants, including grains, to store energy. The individual grains of barley or other brewing grains are seeds; each is composed mostly of starch. The process by which starch is turned into sugar during the mash is known as conversion. An iodine test is used to test for the presence of unconverted starch.

For a complete overview of all of the processes which happen during the mash, see The Theory of Mashing.