and become permanently inactive. The time spent transitioning between rests is preferably as short as possible; however, if the temperature is raised more than 1 °C per minute, enzymes may be prematurely denatured in the transition layer near the heating elements. β-Glucanase rest β-glucan is a general term for polysaccharides, such as cellulose, made up of chains of glucose molecules connected by beta glycosidic bonds, as opposed to the alpha glycosidic bonds in starch. They are a major constituent of the cell walls of plants and make up a large part of the bran in grains. A β-glucanase rest done at is practiced in order to break down cell walls and make starches more available, thus raising the extraction efficiency. Should the brewer let this rest go on too long, it's possible that a large amount of β-glucan will dissolve into the mash, which could lead to a stuck mash on brew day and cause filtration problems later in beer production. Protease rest Protein degradation via a proteolytic rest plays many roles: production of free-amino nitrogen (FAN) for yeast nutrition, freeing of small proteins from larger proteins for foam stability in the finished product, and reduction of haze-causing proteins for easier filtration and increased beer clarity. In all-malt beers, the malt already provides enough protein for good head retention, and the brewer needs to ensure the amount of FAN produced can be metabolized by the yeast to avoid off flavors. The haze causing proteins are also more prevalent in all-malt beers, and the brewer must strike a balance between breaking down these proteins and limiting FAN production. Amylase rests The amylase rests are responsible for the production of free fermentable and non-fermentable sugar from starch in a mash. Starch is an enormous molecule made up of branching chains of glucose molecules. β-amylase breaks down these chains from the end molecules, forming links of two glucose molecules, i.e. maltose. β-amylase cannot break down the branch points, although some help is found here through low α-amylase activity and enzymes such as limit dextrinase. The maltose will be the yeast's main food source during fermentation. During this rest, starches also cluster together forming visible bodies in the mash. This clustering eases the lautering process. The α-amylase rest is also known as the saccharification rest. During this rest, the α-amylase breaks down the starches from the inside and starts cutting off links of glucose