is barley developed and grown specifically for brewing beer. Barley was originally domesticated independently in ancient Mesopotamia and Ethiopia; in both areas it was used for beer brewing. Modern malting barley may be either two rowed or six rowed. Two-rowed barley gives a higher extract yield, whereas the six-rowed types have a slightly higher enzyme activity. The flavor and finish of beers produced from either type also differ somewhat, with the six-rowed types being slightly drier in the finish.

Malted barley grain has the potential to provide the perfect balance of carbohydrates and proteins for feeding yeast—and ultimately making beer. “Potential” is the key word. A prerequisite is that the barley has the right genes to produce the necessary compounds in the proper ratios for brewing. For 10,000 years, people have bred barley to achieve this. Simply put, varieties with the right genes for brewing are considered “malting varieties” and those with the wrong genes become “feed varieties.” There are stringent testing and approval systems in place to ensure that malting varieties have the traits necessary to meet the needs and expectations of farmers, maltsters, and brewers. Although the needs of each profession differ, there is some general agreement about what the right traits are in a malting variety. Malting barley varieties need to be high yielding, their grain kernels must be of a specified size, the malt extract percentages need to be high, and the wort beta glucan levels need to be low. However, specifications for grain protein and levels of enzymatic activity vary tremendously between brewers. Of particular importance in this regard is the amount—and type—of adjunct used in brewing. Brewers adhering to the Reinheitsgebot find the malting varieties used to brew “low-carb” lagers entirely unacceptable. Brewers of “light” beers despair at the low enzymatic activity of a malt perfect for an all-barley craft beer. Thus, differentiating malting and feed varieties is possible for some traits, but not for others.

These differences in the definition of malting quality lead to elusive targets for plant breeders and geneticists attempting to determine which of the 30,000–40,000 genes of barley are “right” and “wrong” genes for malting. To add yet another variable to this already complex equation, the environment plays a huge role in malting quality. The best available malting variety will produce malt of abysmal quality if grown under conditions of extreme temperature and/or moisture or if it is afflicted by any of the multitude of bacterial, fungal, viral, and/or insect plagues that can attack barley. When things go wrong (as they are increasingly likely to do with climate change), the “malting” barley grown under poor conditions will sorely tax the skills of the maltster and brewer and some of it may have to be sold as lower-value “feed barley.” The feed market thus provides a safety net for rejected malt barley, leading to the maxim that “a good malt barley is a good feed barley.” The reverse is never true because a variety selected only for grain yield will malt about as effectively and efficiently as gravel. Beta-glucans are good for the human diet, but terrible for beer, turning mashes gummy and the resulting beers hazy.

In actuality, there is no single and simple definition of “malting barley,” except to say that it is barley that produces a target profile of characteristics when subjected to malting—a process of controlled germination and subsequent processing for flavor, color, and aroma. Despite many advances in barley breeding, a number of traditional barley cultivars are still used in malting because of their good brewing and flavor characteristics, the British Maris Otter being a prime example of this.