Not all raw materials are uniform. Broken or deformed kernels are more prone to molding or poor enzymatic performance, and chaff or weed seeds can negatively impact flavor. Cleaning and sorting are a more modern implementation, brought on by the desire of brewers to have higher quality ingredients. It is likely that, over time, brewers were able to differentiate processing or quality differences between refined and unrefined malts. 

Once a clean crop of barley is attained, the real journey begins. The seed is germinated, which is the first true step to malting. This is where the kernel will undergo enzyme synthesis, emanating from the aleurone layer. Check out other posts for more information on the specific hormones that cause enzyme synthesis in barley kernels, but gibberellic acid (GA) and Abscisic (ABA) are the primary forces.

When the hydrated kernel reaches a certain capacity, hormone levels shift and certain genes become more active. Enzymes are produced, and these begin a sort of lysis, or self-digestion, of the endosperm. Starch reserves are converted into simple glucose molecules, something that can be used as a basic form of energy in many cells. With this energy, more amylase and other enzymes can be produced, leading to an exponential chain reaction. 

If germination is allowed to proceed too far, the embryonic growth will entirely consume the starchy reserves. That is what they are there for. The plant growth by that time should be sufficient for both some foliar exposure (light gathering), as well as root nutrient uptake. From this point onward, the emerging plant should be more or less self-sufficient, providing energy without the aid of the (now spent) seed kernel. 

Growing in popularity over the last few years, un-malted grains like flaked wheat, flaked barley, and flaked oats, are commonly used in New England style IPAs and rich Imperial Stouts. These pre-gelatinized grains are steamed until hydrolysis is achieved, then quickly smashed flat between rollers. This squeezes out the remaining water, and exposes the starchy endosperm for later re-hydration. An increased protein content gives a silky mouthfeel with more body than similar malted offerings. Similarly, for roasted barley, no diastatic power is needed, and the steeping/germination step may be skipped over entirely. 

In base malts, germination techniques are tightly controlled to induce maximum enzyme production. Europe and the United States differ in many ways, and measurement of diastatic power in malt is one of them. Regardless, the ability a malt has to degrade starch into sugar is analyzed by each maltster at the end of processing. Windisch-Kolbach units or degrees Lintner will quantify the value for each given variety. In general, 40°Lintner (about 124 WK), is the minimum average for a successful 60-minute single-infusion mash to fully convert. Premium quality six-row American malt might reach as high as 160°Lintner (544 WK), while dark Munich malts can be as low as 25°Lintner (71 WK). With the information supplied by the maltster, it is the responsibility of the brewer to proportion the malts accordingly. If for some reason information is not supplied, or analysis is needed, it can be ordered from a lab such as White Labs.

After enzymatic development has been maximized by the maltster, a stabilization period occurs. The methods and procedures are not highly secretive, but the finite details are what separates each producer in terms of quality and organoleptic results. For most base malts, a low temperature drying procedure, typically below 120°F, is induced to remove moisture. Once the kernel hydration is around 10-12%, enzymatic activity will cease, freezing the important part of the malting process. If temperatures are above 120°F in the presence of moisture, the enzymes will denature and be rendered ineffective for starch conversion.

Once the drying malt has reached an appropriate moisture level, it can begin the kilning process. This is where the majority of flavor, color, and aroma come from. Green, un-malted barley, will have a raw or earthy character that can be perceived as unpleasant, so temperatures ranging from 175°F to 400°F are used to develop complexity. At the lower end of the spectrum color and flavor development are minimal, producing highly enzyme-active base malts. As temperatures go over 195°F, Maillard reactions occur, imparting rich melanoidin compounds. Holding green malt at 150-170°F for a few hours can covert internal starch into sugar, and “caramelize” it to a degree. This results in a hard, “glassy”, kernel with high levels of unfermentable dextrin, perfect to build up some nice foam lacing. Malts labeled with a prefix of Cara often fall into this category.

Deculming and polishing the kernels takes place at the end of malt processing. Small rootlets and chit are removed, usually by vibration or gentle shaking, leaving behind the brewer's final product. Storage for a brief period allows redistribution of moisture, which at this point should be in the 3-5% range, depending on variety. Now it is possible to bag for redistribution.

Certain maltsters will blend processed malt varieties to create a multitude of options for the discerning brewer. Much like brewing, malting is a merge of science and art. No strict recipe or guideline will guarantee success, and failure is simply objective. If results are not satisfactory, recalibrate and try again!