Chapter 1: Barley Malt

1: Barley
Barley (Hordeum vulgare. L) is a monocotyledonous cereal belonging to the genus Hordeum, the tribe Triticeae (Briggs, 1978) and is a member of the grass, Gramineae, family. In terms of global production, barley ranks as the fourth major cereal crop (after wheat, maize and rice) with over 133.85 million tonnes being produced annually worldwide (USDA, 2008). Of this global production, more than three quarters is used for animal feed with the remainder being used mainly by the brewing and distilling industries (Morris & Bryce, 2000). As well as its significant economic importance, barley is of considerable nutritional significance to the human diet contributing a significant portion of the global human diet (Finnie & Svensson, 2009) by way of both direct consumption, in the form of beer or bread for example, and indirect consumption, in the form of animals fed on barley feed. This global reliance on barley is primarily due to its ability to adapt to a wide range of environments leading to its cultivation in diverse areas such as the sub – arctic, cooler tropical highlands and the sub – tropics, temperate regions, high altitudes and the saline soils of maritime area. Indeed, one of the few places on Earth that barley is not found is the more hot and humid regions such as the tropical lowlands.

1. Cultivated Barley – Its Origins and Main Varietal Classification
There are many different varieties of barley grown around the world today, all of which can be separated in two main groups depending upon the number of rows of grain that can be observed when looking at an ear of barley from above. These groups are referred to as the two – rowed and six – rowed barleys (Briggs, 1978). Evidence suggests that the modern day barley arose from a common two – rowed ancestor in the “fertile crescent” of the Middle East about 8000 years ago to form the progenitors of today’s barley (Briggs, 1978).

2. Anatomy of a Barley Grain
A mature barley grain is oval in shape, tapering at each end (Fig. 1) and has a furrow or crease running the full length of its ventral axis (Briggs, 1978). While the majority of barley grains have a protective outer husk surrounding the grain, huskless varieties can also be found but are not as widely cultivated for malting due to the inability of huskless malt to form a natural filtration bed (as they lack the husks to do so) during wort (liquid containing carbohydrates, small peptides and amino acids that the yeast uses as a source of nutrition during fermentation) separation (Briggs, 1978).

The barley grain itself consists of five distinct tissues (Fig. 1.1); two living and three dead. In mature grains the living tissues comprise of the embryo or germ and the aleurone layer, while the endosperm, pericarp and testa (or seed coat) composes the dead tissue (Palmer, 1991). The pericarp (the wall of the grain) can be found just beneath the husk and on top of the testa. Both of these structures cover the entire length of the grain up to the awn (Fig. 1.1) and function not only as extra layers of protection for the seed, but also as semi permeable membranes allowing the passage of some substances such as water into the grain, but restricting the flow of others, such as hormones, out of the grain.