two-row malt | The Oxford Companion to Beer

is made from two-row barley, which is distinguished by having two rows of seeds along the flowering head. Two-row barley clearly differs from six-row barley, which has six rows of seeds. A number of generalizations apply to six-row and two-row malts: the latter generally have larger kernel sizes, lower protein levels, lower enzyme activity, and lower huskiness (tannic astringency). Two-row malts also have a higher starch-to-protein ratio because of their smaller aleurone layer compared with the endosperm. Only 2 of the approximately 30,000 genes of barley determine whether a plant became a two-row versus a six-row individual. Therefore, it is possible to breed for a specific malt profile regardless of the row type.

The difference between these two malts arises from different growth patterns of the seeds. Two-row barley varieties produce only a single fertilized seed at each seed point, or node, on their flowering head. The position of the corns alternates at each node, resulting in two-row barley having two rows of seeds along its length. Six-row barley varieties, by contrast, have three fertilized corns develop at each node and thus produce six rows along the length.

Typical differences in protein levels between two-row and six-row malts result in different applications. This relates to the protein in malt containing hydrolytic enzymes used for the modification of starches and proteins. See modification.

The usually higher protein level in six-row malt makes them more suitable for beers that are made with greater proportions of adjunct levels or with poorly modified malts. This is because their relatively high enzymatic power assists in the conversion of the added material. Alternatively, well-modified two-row malt tends to be more suitable for all-malt beers. As a general rule, six-row malts are preferred by large mass-market breweries in the United States and Mexico, whereas two-row malts are preferred almost everywhere else.