Oat Malt – Better flavour with a higher pH steep

Raising the pH of the steep water with Sodium Hydroxide has almost eliminated the bitter grassy flavours I was getting when malting oats. Please read this post first on my malting process. This beer is waaaay better than the last oat beer which made me give up on oats, I even state in my book that when malting oats, off flavours are unavoidable. I reached this conclusion after trying different sources of oats and hulless oats as well. I kept getting grassy flavours developing a few days into the malting process. I’m still not 100% sure what the source of these flavours are but according to these articles it could be the oxidation of lipids.

In Optimization of Enzymatic Activities in Malting of Oat by E. Hosseini, M. Kadivar and M. Shahedi …”Unlike other types of cereals, fat exists throughout the grain that possesses much lipase activity in its neighborhood and its native condition. During germination, the level of free fatty acids (FFAs) rises remarkably and the subsequent oxidation of these acids in storage of malt produces hydroxy acids which result in development of bitter taste.” Also in this article  Role of lipid reactions in quality of oat products. by Pekka Lehtinen and Simo Laakso  “In oat, a lipoperoxidase (EC1.11.1.-) activity is responsible for the conversion of hydroperoxides to relevant hydroxyacids (Biermann and Grosch 1979). These hydroxyacids are suggested to be partially responsible for the bitter taste associated with the enzymatically active oat (Biermann et al. 1980).”

If I’m understanding it correctly, the first article suggests that by reducing Lipase activity one can reduce this oxidative effect. Further on in the article there’s this . “Liukkonen et al [15] reported that lipase activity is sensitive to alkaline pH above 8 and it subsequently dropped.” However, the experiments in this article only show the effects of pH between 3 and 8. So this is why I thought I’d try increasing the steep pH to 8 or above to see if it would have any positive effect. It only took 0.4 grams of lye added to 4 Litres of water to change the pH from 6.3 to 9.5. It’s a minuscule amount but if you’re going to try this be careful when handling lye as it can burn your skin, always where gloves and always add the lye to the water never the other way around. I wonder if it’s the Sodium Hydroxide that has an effect on lipase or is it just the pH level and would naturally alkaline water have the same effect? I guess this will be my next experiment.

The beer is sort of yellowy brown. It’s got a nice head and mouthfeel and a creamy chocolatey sort of flavour. If I’m really looking for it, I can taste just a hint of the grassiness but it’s very faint and disappears as soon as I detect it. I can drink this beer without noticing it at all. I did a step mash for this one with an hour at 107F, 45 minutes at 125F and then an hour at 153F. My pre-boil gravity was pretty low at 1.036 which I think was due to my low germination rate of 70-75% and the fact that oats do not have the same diastatic power as barley. So I boiled for 2 hours to up the gravity 1.053. Had I only boiled an hour the gravity would be 1.045. Final gravity was 1.012 for an A.B.V. of 5.36 but a final volume of only 4 gallons. The colour comes from some of the roasting I did, it’s got 10 oz of toasted oat malt (biscuit)  1 hour at 350F.  4 oz of a chocolate oat malt +30 minutes at 425F and 4 oz of roasted oat malt +45 minutes at 450F. The malt itself was kilned quite high with an air-on temperature of 195F but the malt temp only reached 190F. This high kilning may also have contributed to my low numbers.

 

Oat malt- Promising results with a higher pH steep

I’m very surprised and excited about the results of this experiment. If you’ve read my past experiments with malting oats then you’ll know the trouble I’ve had with it. Even though I’ve tried different brands and hulless vs. with hulls I’ve always noticed a grassy flavour to it, and by grassy I mean like freshly cut lawn clippings or even green corn husks. I still do not know what causes this but it seems to appear only 1 or two days after steeping. It has been suggested in this article by  E. Hosseini, M. Kadivar and M. Shahedi that rancid bitter flavours are due to the oxidization of free fatty acids and they show that increasing the pH of the steep water has a positive effect on enzyme activity which may have an affect on the development of rancid flavours. Though, I’ll admit I found this article confusing, maybe you guys can make better sense of it. The folks from Breiss malting suggest in this podcast that bacteria present on the oat husk is what caused off flavours to emerge in their trials.

Germination was not great at about 70% for all three batches

Steeped for only 4 hours to achieve a 42% moisture content.

So whatever the reason, I wanted to see if adjusting the pH of the steep water would have any effect on flavour. The first batch of malt would be my control using regular filtered water. The second batch had the steep water adjusted to a pH of 9.5 (only because I couldn’t hit 8 due to the small amount of Sodium Hydroxide used). The third batch was subjected to a 1 hour steep in a .2% lye solution which had a pH of around 13 in order to disinfect the grain from any mold or bacteria. Then it was rinsed and steeped for another three hours in regular filtered water.

0.4 grams of lye was added to 4 Litres of water to change the pH from 6.3 to 9.5
8 grams of Lye per 4 Litres was used for the third batch.

 

And the winner is … the 9.5 pH batch. Within a few days of steeping I noticed that it was not developing as much grassy aroma as the other two. Even after mashing this malt it’s tasting much more like a bowl of oatmeal than a bowl of cut grass. I still have to brew with it as a final test to see if this is actually working but I’m very optimistic. Also the brix of the 9.5 batch after mashing small 4 oz. samples was 13, both the normal batch and the disinfected batch were just 10. Of course these mash results could have been different had I adjusted the pH of the mashes.

 

All three batches were steeped at 12C 54F and germinated for 5 days at 16C 61F.

All three batches were also dried and kilned the same; 12 hours at 21C 70F with fan. 8 hours at 30C 86F with fan. 8 hours at 50C 122F no fan. 4 hours in the oven at 185F

Tomorrow I’ll start to malt another 10 lbs. in order to make another attempt at a 100% oat malt beer.

 

Mini-mashing 4 oz. batches.

After mashing for two hours it still did not pass the iodine test.

After mashing, before boiling. The 9.5 pH batch in the center had a brix of 13, the other two 10

 

 

Hulled Oat Malt

I really did have high hopes for malting oats. I like oats, I eat them for breakfast. I also like putting them in beer, in their raw state or toasted. So I’m very disappointed in this grassy, green corn husk flavour that I’m getting as soon as the oats germinate. This experiment has at least proven that the flavour is coming from the oats and not the husk as I previously suspected. I’m not going to give up on oats completely just yet, I’d like to try a few more things with them, like a caramel for example but as a base malt it’s not a grain I’d recommend. If you’re curious, my process went as follows:

• Steeped for 8 hours at 10C in filtered water to reach a 40.6% moisture content. Hulled oats absorb water very fast.
• Germinated at 16 C for 10 days spraying with water once a day after day 5.
• Kilned for 12 hours at 30-35C with a fan on
• Then 8 hours at 50-55C without the fan (my hot-plate stays on the same setting)
• Cured in my oven starting at 170, 180,190,200F for one hour each.

 

Oat malt lager, kinda nasty, gets better, but still weird.

I’ve avoided malting oats after reading in the “Homebrewers Garden” by Fisher and Fisher that germinating oats attract “butryfying bacteria” and that the butanol isomers that these bacteria can produce are poisonous as are the microbes themselves. But I still can’t find any other sources of information to back up this claim, and please correct me if I’m wrong here but I don’t think butryfying is even a word. If you have any information on this subject please let me know, you could be saving my life! What does give me some cause for concern is Ergot which is found most often in rye and oats, but ergot is easy to spot in whole grains because it’s black and looks like a mouse turd. It’s impossible to spot once it’s ground up though.

Ergot in barley

 

I recently picked up a 40 lb bag of oats at a feed store for $13. It was surprisingly clean, much cleaner than any feed barley I’ve bought. I only rinsed it twice and that seemed sufficient. What I soon discovered with oats is that they absorb water much faster than barley. I discovered this by actually overshooting my target moisture content twice!

I started by finding out the initial moisture content by drying out a ground  1 ounce sample in the oven at 225F for 3 hours. The initial moisture content was 12%. I also tested the germination rate between some damp paper towel and I got a 95% germination rate which was pretty awesome. For the first batch I made mathematical errors while weighing it and I ended up steeping it for too long. It reached 47%  which I malted anyway but I got a surprisingly low germination rate at 62% The malt was very wet for a long time during germination, the surface of the grains just wouldn’t dry out like barley does. So I did another batch and after only two steeps at 8 hrs with an 8 hour rest in between, it was still too high at 44%. The germination rate improved to 72% So why not try again. It turns out you can reach 40% with just one steep at 11 hours and my germination rate improved yet again to 81.5% which is ok, not great, but I’ll take it. Makes me wonder what say 36-38% would produce. The added advantage to steeping just once is less risk of mould forming. This third batch did not have any visible mould by the end of germination whereas the other two had some ( not a lot, I picked out most of them). The oats had an unpleasant smell throughout the process and it should be noted that it was present even before germination, and before any visible mould forming. When oat husks are wet they smell exactly like green corn husks and it’s quite strong too, so much that I almost chucked all three batches. This green corn husk smell is very similar to and can be mistaken for a musty odour – like a mouldy wet basement. Having that show up in my beer well, that’s kind of a deal breaker. It also made me kind of paranoid to think that I could be ingesting something poisonous. I’m not sure why I got such a high germination rate without steeping in the test sample compared to the steeped batches. Perhaps oats do better with spraying water during germination instead of steeping.

I ended up making a lager malt since I planned to make a lager out of these oats using the second and third batches of malt. It’s not something I’ve seen before and I thought it would be a good way to really find out the flavour characteristics of oats. What I soon discovered is that people don’t make oat lager for a very good reason, it’s gross. I added some lightly toasted oat malt to the recipe and those tasted great. It made me think that perhaps dark beer made with a Vienna oat malt as a base would be able to mask the corn husk flavour. I’ll try this next.

After primary fermentation the corn husk flavour was still there but decreasing slightly. I threw in some Citra hops in an attempt to mask some of the flavour and it kind of worked. Needless to say this beer is not what I expected at all so I’m not quite sold on it yet. It’s an acquired taste, but if someone gave me this beer and said that it’s made using the ancient Mayan technique of filtering through green corn husks I would say ” WOW, this beer is AMAZING, you can actually taste the corn husks!” But there is no ancient Mayan technique, so I can’t even lie about it. The first thing you notice is the Citra hops, which are always nice, then for me, the husk flavour starts at the back of my throat – I know gross -perhaps due to the tannins? not pleasant. Once it rears it’s ugly head the husk flavour kind of takes over or this could be just a mental thing – as in, I can’t get away from tasting it when I really don’t want to. But like I said before, if you can embrace the husk flavour (perhaps you also like eating grass) then this beer is fantastic!

The recipe:

• 11 lbs. Oat malt
• .5 lbs Oat biscuit malt
• 5 oz acid malt (store bought)
• 1 oz Goldings (5%) 60 min
• 1 oz. Goldings 15 min
• 1 oz. Centennial (10%) 5 min
• 1 oz Mandarina Bavaria last minute
• 1 oz Citra last minute
• 2-3 oz (can’t remember) Citra dry hopped 7 days

Mashed in at 105F at 1.0 qt/lb and added direct heat to 130F for 20 min. Then added an infusion of 1 gal. to get to 145F at 1.42qt/lb for about 30 min. I then decocted a gallon to get to 154 for another hour and a half.

Original gravity was 1.050 Final gravity was 1.0064 for 5.5% abv.