What is starch? Starch is carbohydrates from grains. Starch is used to break down into sugar. Sugar is used to ferment in beer.
You need enzymes to convert starch to sugar. To do this, your grains need to be malted, as that’s when these enzymes exist naturally to convert the starch to sugar, for the zest to eat the sugar to turn into alcohol.
Starch is basically what plants use as energy. Plants store their energy as starch. Inside a grain, it has starch. When the grain begins to root, it creates enzymes that turns the starch to sugar. Brewers kiln the grains to stop the malted grain from growing.