by Mike Retzlaff
I recently read a scientific paper on the subject of brewing beer from 100% oat malt. This paper chronicled a study of brewing beer with malted oats as the sole ingredient instead of as an adjunct.
The study was conducted by a variety of brewing scientists and was a truly global effort. The several facets of these experiments ranged from Finland to Australia; from Ireland to Germany. All of the final testing of the produced beers was conducted using EBC defined methods and all sorts of electronic gadgetry.
Oats have beneficial nutritional properties and are seldom, if ever, used to their potential in the brewhouse. On top of that, there are many of our fellow humans who have to deal, in varying degrees, with celiac disease or gluten intolerance. Gluten is found, unfortunately for them, in most normal brewing grains. There are a number of cereal grains that are gluten free, however. Included in that group are rice, millet, corn, sorghum, buckwheat, and oats. The only readily available gluten-free beer, to my knowledge, is Redbridge by AB-Inbev. I’ve tried it, as I recall its okay, but I’m somewhat thankful that I don’t have to rely on it as a beverage. Kaffir beer is brewed in Africa from sorghum and millet, both gluten free grains, but is not widely distributed.
I think that most of us (including partial mash brewers) have used oats in a number of beers so it can’t be construed a radical idea. However, most users of oats in home brewing turn to the cardboard cylinder packaging with the smiling old Quaker on the label.
Oats have a higher husk content than that of barley which leads to better lautering. The higher husk ratio is a trade-off as the amount of extract, pound for pound, is a bit less than barley. Even without the hulls, the extract from oats is somewhat lower. The protein levels and profiles of other constituents in oats are similar to that of barley.
In this study, the initial mash regimen was designed by mathematical modeling, the formula subsequently modified, and then successfully applied in a pilot brewery. The experiment used a barley malt grist bill as a control. Three oat malt grist bills were brewed varying only in their mashing regimens in order to get the best results.
The pilot brewery set up was as follows:
Batch size 50 L 13 gallons
Grain bill 9 kg 19.8 lbs.
Mash water 32 L 8.45 gallons
Liquor / grist ratio 3.55 L/kg. 1.7 qts./lb.
45 oC 113 oF for 20 minutes as a β-glucanase (cytolytic) rest
62 oC 144 oF for 30 minutes as a β-amylase rest
72 oC 162 oF for 30 minutes as a saccharification rest
78 oC 173 oF for 10 minutes as a mash out
Sparge to collect 55 L 14.53 gallons
Boil to yield 50 L 13 gallons
Ferment @ 11 oC 52 oF using Fermentis Saflager S-23
Lager @ 2 oC 35.6 oF for 3 weeks.
Hallertauer Hercules hops were used @ 18 EBC bittering units (equivalent to IBU)
After lagering, the beer was filtered and bottled. The bottles were stored @ 4 oC (39 oF) until analysis.
Results: OG FG Alc. v/v pH
Barley malt 1.04829 1.0104 4.82% 4.28
Oat malt 1.04492 1.0124 4.30% 4.51
The barley and oat worts fermented nearly identically; the differences being that the oat beer had a bit higher pH and was lower in alcohol content.
The wort provided by oats had a slightly higher β-glucan content and a slightly smaller free amino nitrogen (FAN) content. It was also slightly higher in protein and lipids. The oat wort actually lautered a bit faster than the barley wort but the post-lager filtering was slower.
The oat beer’s flavor showed a strong berry (raspberry, blueberry, yogurt) flavor and a lower amount of staling compounds. The barley beer’s flavor was fruity (apple).
The study showed it is possible to brew a beer from 100% malted oats and the beer is comparable to an all barley malt beer.
This is a good thing to know if you or a family member has celiac disease. This knowledge is also advantageous if you are an adventurous brewer and have a passion for something out of the ordinary.
nota bene –
a. This article and procedure concerns malted oats which already have plenty of husk material. If using malted naked oats, add some rice hulls to the mash as a lautering aid. Naked golden oats are de-husked but are a crystal malt – don’t confuse them.
b. Most malted oats exhibit a diastatic power of at least 25o Lintern. It would be prudent to add some amylase powder to the mash to ensure complete conversion.
c. Even though a β-glucan rest is included in this recipe, a little added insurance against a difficult run-off is adding something like CellarScience Glucabuster. This is a multi-enzyme additive to break down the glucans in the mash.