Brewing today....

[UserDeleted]

There is nothing wrong in boiling with the lid up to 90% on at all.

Yes DMS is formed from S Methyl Methionine in the from the malt during the boil. However UK and European Malts are MUCH lower in SMM than US Malts so its not as obvious here in the UK.

Also the boiling point of DMS is 35C, so during the boil it most certainly is driven off, it is unlikely to condense on the lid of the boiler and drip back in as the boiler lid is quite likely to be more than 35C after a few minutes of boiling. We have lids on the kettle (with 10% open area) and after a few minutes of the boil starting there is very little if no condensation (OK so the lids are insulated but even so)

Of course what you do need to do is to ensure that you remove the lid from the boiler when you are cooling the wort, as then you will get condensation that can cause undesirables to drip back in. (SMM continues to be converted to DMS until the wort drops below50Cish)

The other thing to be aware of is that keeping the lid on to reduce evaporation does not reduce the thermal load on the beer, While your apparent evaoration rate is around the 10% mark your actual evaporation rate is probably considerably higher than this. The only way to truly reduce the evporation rate is to turn down the amount of energy being applied to the wort.

[steve_flack]

However UK and European Malts are MUCH lower in SMM than US Malts so its not as obvious here in the UK.
.

Some European Pils malts are quite high in SMM also. It's a fairly common minor flavour component in german pilsners and helles. Pale malt rarely has high levels due to the higher kilning. I've not really noticed it during the boil when brewing with UK lager malt though there has been quite a lot of farty smells from the yeast!

[steve_flack]

What sort of nasties?

There are some volatile, unpleasant tasting compounds driven off from the hops during the boil. If you leave the lid on, they condense on it a drip back into the wort. I've had to ditch a whole batch due to leaving the lid on during the boil.

Mycene is a very volatile hop component that doesn't have the nicest flavour or aroma in the world - to me the pure chemical smells a bit hydrocarbony (like parafin or petrol). Hops that are a bit rough (for example Target) usually have high levels of myrcene and aroma hops have lower levels. It is very volatile and usually boils off but will probably condense back if you boil with the lid on.

[J_P]

All may not be lost chaps, for all I boiled with the lid on it wasn't snapped shut and I pull the lid forward so the condensation doesn't drip on the power cable allowing steam to escape. I also remove the lid to stir, add hops and check on the boil etc.

So far in all my samples I have not detected anything even remotely cabbage like, I did get a TTL "biscuitty" flavour on my first brew but I thought that was due to caramelisation of the small wort volume.

On the plus side I found this in the fermenter this morning.



That's the best AG yeast head I've had!

[SteveD]

Hops that are a bit rough (for example Target) usually have high levels of myrcene and aroma hops have lower levels. It is very volatile and usually boils off but will probably condense back if you boil with the lid on.

And yet, Target makes a very good dry hop. High levels of oils mean that hop flavour & aroma get into the beer much faster than, say, Goldings, making it ideal for dry hopping in the fermenter or secondary.

[steve_flack]

I'd heard that and it's odd as you'd expect it to be awful because it's not a good late hop in the boil.

[UserDeleted]

If for any reason the boil gets too vigorous and evaporation is excessive then adding small quantities of excess wort from the sparge or small quantities of cold water help keep the boil and evaporation rate in check.

No, Adding liquid back to the boil does not keep the evaporation rate in check you are replacing what has been removed/lost through evaporation

If you boil 30L of wort for 60 Minutes and end up with 20L thats 10L of evaporation (16% per hour). If you boil 30L of wort, add 10L During the boil and end up with 25L thats still 10L lost through evaporation and still 16% per hour.

You still haven't reduced the thermal load (Total amount of energy added to the kettle) applied. High thermal loads can have undesirable effects on beer stability . . . and also can have some wonderful effects on beer flavour eg extra malt profile due to higher production of melanoidins being one. . . . This may or may not be an effect you are trying to achieve

[SteveD]

I'd heard that and it's odd as you'd expect it to be awful because it's not a good late hop in the boil.

I think Target is a maligned hop. It's fine if used carefully. Some notably good beers are brewed with Target. London Pride, for one - I think.