Corn Flavour?

[Blackfish]

Hi all

I am getting back to basics in order to recognise flavours etc.. so, this is meant to be a simple 'get to know you' for some staple ingredients.

20L Batch
Expected Pre-Boil Gravity: 1.042 SG Expected OG: 1.050 SG
Expected FG: 1.012 SG Apparent Attenuation: 74.9 %
Expected ABV: 5.0 % Expected ABW: 3.9 %
Expected IBU (using Tinseth): 28.2 IBU Expected Color (using Morey): 7.2 EBC
Mash Efficiency: 75.0 %
Boil Duration: 90.0 mins
Fermentation Temperature: 18 degC
Fermentables
Australian Export Pilsner Malt 4.396 kg 90.0 % 2.7 In Mash/Steeped
Australian Wheat Malt 0.488 kg 10.0 % 0.4 In Mash/Steeped
Hops
Variety Alpha Amount IBU Form When
NZ Hallertauer Aroma 9.0 % 16 g 18.9 Loose Pellet Hops 60 Min From End
NZ Hallertauer Aroma 9.0 % 12 g 7.0 Loose Pellet Hops 15 Min From End
Czech Saaz 4.0 % 12 g 2.3 Loose Pellet Hops 10 Min From End
Other Ingredients
Whirlfloc Tablet 10 g In Boil
Yeast
DCL US-05 (formerly US-56) SafAle

After 10 days in primary the flavour is what I can describe as 'Corny'.
Its quite distinctive, like you steeped some cobs or tipped the water from your steamed corn into the mix.
Its not unpleasant, just very noticable. Sanitation was good. I thought the initial mash temp was a few degs high but it settled out to 66 degs after a few minutes and a bit of a stir.

Ferm temps have been at 19 to 20 degs under the house.

Have I made some sort of mistake or Is it just 'green' ?

any help is appreciated

FHG

 

[Adamt]

I think you'll find the taste is DMS (Dimethyl sulfide). This compound is common in pilsner malts and requires a strong, uncovered rolling boil for at least 15 minutes before hop additions to drive off.

You boiled for 30 mins before hop additions... so did you cover your pot during the boil and/or not boil rapidly?

Could also be a mild infection, but I doubt this as you say it isn't unpleasant.

 

[mickoz]

I agree with Adam. Make sure you have a vigorous boil and make sure the pot is uncovered - this will allow DMS to boil off.

I had this with a couple of my first brews that I did on the stove top. Got a NASA burner now and boils are huge

Edit: Added extra detail

 

[dr K]

When you malt garin the pre-cursors to DMS are created.
Ale malts are kilned a tad higher than pils and much of these compounds are eradicated.
DMS forms (due to the presence of the pre-cursors) in the boil, a vigorous uncovered boil will drive it off.
Slow cooling may result in the formation of DMS if the precursors have not been eliminated during the boil, fermenatation itself may result in DMS as a by-product, some infections result in DMS.
A general guide will be that a canned corn aroma is DMS from your malt and boiling, cooked vegetables is an infection.
I would not worry too much, just boil somewhat more vigour next time !!

K

 

[Blackfish]

Thanks guys
The Boil rolled well uncovered for the whole time. I evaporated a heap more than I thought actually.
I haven't got a chiller worked out so I ice bathed the pot & it took over an hour to get down to 25c. I was scared of infection so I sealed it with foil and put the lid on.
Base malt for my other beers has always been Ale & I've never had this before so I think it makes sense. Either chill faster or stay away from the Pils
Cheers B)

 

[dr K]

I haven't got a chiller worked out so I ice bathed the pot & it took over an hour to get down to 25c. I was scared of infection so I sealed it with foil and put the lid on.

So there is your answer..DMS has been formed during the slow chill..at least you have not got an infection that caused DMS by the sounds of it, a bit of DMS is better than infection but best of all is a fast chill....

K

 

[jjeffrey]

Dimethyl Sulphide (DMS) is mainly formed in the wort above temperatures of about 70C. It has a very low sensory threshold, so humans can pick up even a little bit present in the beer. DMS is very volatile, and once formed from the pre-cursor it tends to evaporate with bubbles of steam. Pre-cursors are the chemicals naturally present in the malt that react to form DMS, predominantly S-methylmethionine (SMM) and dimethyl sulphoxide (DMSO).

When you stop boiling but let it sit at high temp, any precursor present continues to convert to DMS, but the DMS gets trapped in the beer because there is no steam to strip it. That's why you need to chill that puppy down to about 60C as soon as possible, if you want to avoid that corn flavour.

DMS=normal in lagers and pilsners because the malt used is not kilned at high temps, =not normal in ales which tend to use malts that have been kilned at higher temps. It tends to be viewed as a flaw in ales.

 

[geoffi]

So the no-chiller's guide to Pilsener malt is: boil the bloody hell out of it.

I did a brew with Weyermann Pils recently and gave it about an 80 minute boil (fairly hard, no lid) but I'm sure I pick up DMS in the beer.

Next time it's a 100 minute boil.

 

[mesa]

Slightly off topic, but the boiling point of DMS appears to be 37C. I wonder then if you no-chill to just above 37C then start aerating, would the bubbles from aerating carry away the DMS? This assumes that hot side aeration is not a problem at 37C (at what temperature does HSA become insignificant?). Or maybe you just need to hold it at 37C and release the seal on the no-chill cube?

 

[geoffi]

My understanding is that the rolling action of the boil keeps it moving up to the surface where the steam can carry it off.

Slightly off topic, but the boiling point of DMS appears to be 37C. I wonder then if you no-chill to just above 37C then start aerating, would the bubbles from aerating carry away the DMS? This assumes that hot side aeration is not a problem at 37C (at what temperature does HSA become insignificant?). Or maybe you just need to hold it at 37C and release the seal on the no-chill cube?

 

[ozpowell]

I think you'll find the taste is DMS (Dimethyl sulfide). This compound is common in pilsner malts and requires a strong, uncovered rolling boil for at least 15 minutes before hop additions to drive off.

Adam,

Just curious why you stipulate that the wort should be boiled for 15 mins prior to hop additions - I've never heard that before. Are you implying that the removal of DMS is inhibited in some way by the addition of the hops? I've always added hops to my kettle within about 5 minutes of reaching a nice rolling boil (never had a problem with DMS either that I've been able to detect).

Cheers,
Michael.

 

[jjeffrey]

I wonder then if you no-chill to just above 37C then start aerating, would the bubbles from aerating carry away the DMS? This assumes that hot side aeration is not a problem at 37C

Pure DMS boiling point may be 37C, but it is soluble in water so it will want to stick in solution at that temperature. You may get some stripping with aeration, but the higher the temperature you aerate the faster you oxidise lipids. I think any DMS removal via aeration would be (by far) out-weighed by cardboard flavours caused by oxidation.

 

[mesa]

Thanks jjeffrey that makes a lot of sense.