Oats

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Oats are known for their high contents of protein, fat, and beta-glucan. Since most malted oats have little enzymatic activity compared to barley, they are of little use for beer production. However, special oat types with a reduced beta-glucan content are perfectly suited for brewing. The high husk content facilitates fast lautering. Oats provide increased levels of zinc compared to barley, up to 0.6 mg/L. Oats provide a characteristic taste and good reduction properties (inhibiting oxidation). High percentages of oats may cause a stable haze. Unmalted oats are also sometimes used as an adjunct.

Oats are of special interest due to their physiological properties and the fact that they can be consumed by most celiac patients. Oat beer could be a gluten-free alternative to traditional barley malt beer. Oats supply key cardioprotective micronutrients such as folate, magnesium, vitamin B6, and vitamin E (27).

Oats can cause very foamy fermentation, and haze. The husks from oat malt help with lautering. Small amounts of oat malt are sometimes used to add a toasted biscuit-like aroma and full mouthfeel. Oat malt has relatively low extract, and the high lipid content reduces head retention and causes flavor instability.

Oats are supplied either malted, “toasted” or flaked/rolled. Some flaked oats arrive with husks whereas naked oats get their name from the absence of husk. The starch in oats will gelatinize at standard mash temperatures but flaked/rolled oats are pre-gelatinsed in any case. Oat corn size is substantially lower than barley so in 2- and some 4-roll mills they must be milled on a lower setting than the malted barley. Due to the high levels of β-glucans the amounts used must be kept low unless β-glucanase is to be added to the mash or a protracted β-glucan rest is employed. As well as high levels of gums, oats are also high in lipids. Lipids damage head retention and can lead to rancid off-notes in finished beers. Fashionable opinion has it that oats contribute a silky mouthfeel to beer there is however little scientific evidence that this is the case at present and some even describe them as providing a dry finish.

FAN and soluble-nitrogen analyses were undertaken to monitor the brewing process. The availability of FAN is import for yeast nutrition, whereas soluble higher molecular weight substances influence haze formation, foam stability, and organoleptic characteristics of beer. Final attenuation of barley and oats was similar, reaching 83.2 and 85.1%, respectively, based on the calculation of apparent fermentation using the ASBC method. FAN and soluble nitrogen contents were lower in oats than in barley, indicating fewer oat malt proteins were solubilized during mashing. Extracts of first worts were considerably lower for oats than for barley, showing values of 11.05 and 14.43%, respectively. Yeast growth was similar during fermentation of oat and barley beers and reached its maximum at day 5, with approx. 60 and 70 million cells/mL, respectively. The initial pH values for the worts were 5.48 for oats and 5.40 for barley. These values were comparable to values reported for commercially produced worts (22). Beer pH values were also within the range of standard beers at 4.35 for oats and 4.42 for barley (22).

Oat proteins have some unique features compared with other cereal grain proteins. Oat proteins differ substantially in the distribution of the classic Osborne protein fractions. Prolamin content in oats is low, with estimates ranging from approx. 4 to 15% of total proteins. Albumins, which are considered to be primarily enzymes, are also a minor component, with values ranging from 1 to 12% of total proteins. Most cereals, such as wheat, barley, and rye, have a high percentage of prolamins, which contain most of the storage proteins, but oat is an exception. Its major storage proteins are in the globulin fraction. The consequence of the high-globulin, low-prolamin composition of oat seeds is that oat proteins provide a better balance of the amino acids essential for humans and other monogastric animals. In general, water-soluble proteins and glutelins represent approx. 30% of the total oat proteins; globulins and prolamins are distributed in an approx. 2:1 ratio. During germination, the increase in albumins, which are rich in the essential amino acids lysine and tryptophan, and the subsequent decrease in globulins and prolamins, which are poor in lysine, leads to the increased nutritional value of germinated oats.

Oat groats are the whole intact kernel, with the hull removed. Steel-cut or Irish oats are groats that have been sliced into pieces. Scottish oats are made by milling groats rather than slicing them. Rolled or old-fashioned oats are made by steaming groats, and then flattening them with a roller. Quick oats are steamed and more thinly rolled. "Instant" oats are quick oats that are usually precooked and often are mixed with a combination of added sweetener(s) and flavor(s).

• Effect of unmalted oats (Avena sativa L.) on the quality of high-gravity mashes and worts without or with exogenous enzyme addition
• Brewing with 100% oat malt
• Lyly, M., Salmenkallio‐Marttila, M., Suortti, T., Autio, K., Poutanen, K., & Lähteenmäki, L. (2003). Influence of Oat β-Glucan Preparations on the Perception of Mouthfeel and on Rheological Properties in Beverage Prototypes. Cereal Chemistry, 80(5), 536-541.
• Schnitzenbaumer, B., Kerpes, R., Titze, J., Jacob, F., & Arendt, E. K. (2012). Impact of Various Levels of Unmalted Oats (Avena Sativa L.) on the Quality and Processability of Mashes, Worts, and Beers. Journal of the American Society of Brewing Chemists, 70(3), 142-149.