Appears in
On Food and Cooking

By Harold McGee

Published 2004

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The first step in converting barley grain into malt is to steep the dry grain in cool water and then allow it to germinate for several days at around 65°F/18°C. The embryo restarts its biochemical machinery and produces various enzymes, including some that break down the barley cell walls, and others that break down the starch and proteins inside the cells of the food-storage tissue, the endosperm. These enzymes then diffuse from the embryo into the endosperm, where they work together to dissolve away the cell walls, penetrate the cells, and digest some of the starch granules and protein bodies inside. The embryo also secretes the hormone gibberellin, which stimulates the aleurone cells to produce digestive enzymes as well.