Lid on or off during boiling?

[Wynne]

An interesting article that introduces taste thresholds and loss of other aroma chemicals into the argument. The paper though does incorrectly state that the DMS is easily boiled off rapidly which while strictly correct it ignores the constant production of it from precursors and while the wort is hot which goes some way to explain the findings of higher DMS in the beer than in the hot wort. What hasn't been measured in their data is the DMS in the cooled wort.

One of the things I found really interesting about this is the influence of a warm hop stand which would increase the DMS.

Anna

@DocAnna You are right, for example, DMS continues to be formed during whirlpooling. I read somewhere that a very long boil (several hours) would be required to convert all SMM in wort to DMS and remove it.
If I were designing a brewhouse from scratch, I would be inclined to use CO2 stripping immediately prior to wort cooling to remove undesirable volatiles, unfortunately, my shed is too small for a stripping column.
I think your suggestion of increasing the vigour of the boil towards the end is interesting - perhaps holding wort at 99c and only boiling for the last 20mins would be effective.
Having said all that, I am not aware of ever having tasted DMS.

 

[micklupulo]

I do not understand the chemistry behind all this but what I do understand is that my marriage would be in grave peril if I ever again created a situation whereby the garage and its contents were showered with boiling wort and hops! On a thread about safety I described how over 30 years ago this happened to me because seemingly the sharp end of a hop cone got stuck in the vent hole of the lid causing the inevitable whilst I was elsewhere. The majority of respondents boil with the lid off but a couple with it half on and half off which I thought I would follow next time I do a boil. Plus it sounds like a good old fashioned British compromise.

 

[DCBC]

Could you connect your extraction duct directly to the top of the kettle?

I might be able to but it would mean making a new condenser hat for my BK. Worth looking into certainly. Looking at this thread, I think what's telling is the suggestion that I should be looking at about a 4% boil-off rate per hour. I'm up at 13% at the moment. Maybe my interpretation of what is a vigorous boil is different to other people's! If I were to take it down to <10% I could save energy and put less moisture into the air.

 

[Cheyne_brewer]

My Hopcat has quite a gentle rolling boil even at full power with the lid off. To get any kind of real mechanical action I leave the lid on for half the boil and keep an eye out for boil over.

 

[Wynne]

@DCBC I think its a trade-off between the cost of energy and the cost of malt. I know of a craft brewery that employs a boil-off rate of 5-6%. I’m tempted to try @DocAnna’s suggestion of a vigorous boil for the last 20mins although it will probably mean using a little more malt, stopping the sparge earlier and foregoing some extract efficiency to reach the desired post-boil gravity.

 

[DocAnna]

@DCBC I think its a trade-off between the cost of energy and the cost of malt. I know of a craft brewery that employs a boil-off rate of 5-6%. I’m tempted to try @DocAnna’s suggestion of a vigorous boil for the last 20mins although it will probably mean using a little more malt, stopping the sparge earlier and foregoing some extract efficiency to reach the desired post-boil gravity.

Having thought about this overnight and that one of the purposes of boiling being the concentration of wort, and that the sparge being the most dilute, I'm wondering about boiling the sparged wort separately more vigorously to concentrate it down. This would mean the boil could be kept to a simmer all but for the last 20 mins of the main wort, so keeping the best of head retention, aroma, and DMS removal, then combining with the now more concentrated sparge?

Theoretically this could be a route to quite high efficiency as you could sparge with more water than usual for improved extraction then boil off to concentrate. Genuinely think I'll try this.

Anna

 

[DCBC]

Having thought about this overnight and that one of the purposes of boiling being the concentration of wort, and that the sparge being the most dilute, I'm wondering about boiling the sparged wort separately more vigorously to concentrate it down. This would mean the boil could be kept to a simmer all but for the last 20 mins of the main wort, so keeping the best of head retention, aroma, and DMS removal, then combining with the now more concentrated sparge?

Theoretically this could be a route to quite high efficiency as you could sparge with more water than usual for improved extraction then boil off to concentrate. Genuinely think I'll try this.

Anna

Great idea! Please report back with efficiencies etc

 

[DCBC]

@DCBC I think its a trade-off between the cost of energy and the cost of malt. I know of a craft brewery that employs a boil-off rate of 5-6%. I’m tempted to try @DocAnna’s suggestion of a vigorous boil for the last 20mins although it will probably mean using a little more malt, stopping the sparge earlier and foregoing some extract efficiency to reach the desired post-boil gravity.

Looking at other things online, including the definition of the desired 'rolling boil' I think I'm not far off where I need to be in fact. I might dial it down towards 10% anyway.

I just about see why a less vigorous boil would require a higher malt bill - if you're not boiling to concentrate, and you need a certain amount of liquor to hit water/grain ratios and sparge volumes. Would it make that much of a difference though? it's hard to tell without extensive calculations and a little trial and error!

 

[strange-steve]

While I find this discussion interesting and I appreciate the thought being put into it, in practice I wonder has anyone here had any DMS issues? Not being negative, just wondering if we're unnecessarily trying to reinvent the wheel here.

The boil is only one aspect of DMS concentration in the finished beer and arguably, rapid cooling is more important for keeping the levels low. Much of the DMS is scrubbed during a vigorous fermentation anyway, and I suspect focusing on ensuring yeast health would be more beneficial overall than adjusting boil strength to cure a problem that may not really be a problem.

 

[Hanglow]

I'd just add more malt or try and improve efficiency through recirculation etc rather than have a separate boil for the sparge. Thermal stress on wort affects colour and taste stability as well. Seems to be creating more problems than you would solve


edit: just to add to strange-steve 's post, beer made with malts kilned higher than pils malt shouldn't have a DMS problem anyway. And modern pils are prepared in a way to minimize smm, plus as you say DMS is often stripped during fermentation.

It's probably only going to be a problem if doing a no boil/short boil beer made with pils

 

[Wynne]

Having thought about this overnight and that one of the purposes of boiling being the concentration of wort, and that the sparge being the most dilute, I'm wondering about boiling the sparged wort separately more vigorously to concentrate it down. This would mean the boil could be kept to a simmer all but for the last 20 mins of the main wort, so keeping the best of head retention, aroma, and DMS removal, then combining with the now more concentrated sparge?

Theoretically this could be a route to quite high efficiency as you could sparge with more water than usual for improved extraction then boil off to concentrate. Genuinely think I'll try this.

Anna

Good thoughts @DocAnna. I am not sure you would even need to simmer, just hold below boiling then boil for the last 20 mins. The chemical reaction times would be virtually the same. I like the idea of separating weak worts, it is moving towards partigyle - a stronger and a weaker beer from the same mash. Personally, I struggle with the idea of adding sparge water to extract the final usable sugars from the mash only to have to use energy to evaporate it off again. It may improve extract/brewhouse efficiency but it isn’t very energy efficient. I wonder if there would be a more energy efficient way to concentrate weak worts e.g. using reverse osmosis/dialysis to concentrate them before or after the boil?
How is your separating funnel for yeast recovery working? I like the idea but I would prefer a funnel in plastic or s/s - the glass ones look a bit fragile for me to use!

 

[Buffers brewery]

And there was me thinking that by boiling for an hour with the lid off I was just reducing the wort volume, concentrating the sugar solution and increasing the OG by a few points!

My process produces about 2 gallons of wort from first mash (high SG). Two subsequent mini mashes produces another 4.5 gallons of wort (lower SG). I boil without lid for an hour to reduce volume down to around 5.5 gallons which, after fermentation and transfer losses yields 5 gallons of beer.

 

[DocAnna]

Personally, I struggle with the idea of adding sparge water to extract the final usable sugars from the mash only to have to use energy to evaporate it off again. It may improve extract/brewhouse efficiency but it isn’t very energy efficient. I wonder if there would be a more energy efficient way to concentrate weak worts e.g. using reverse osmosis/dialysis to concentrate them before or after the boil?
How is your separating funnel for yeast recovery working? I like the idea but I would prefer a funnel in plastic or s/s - the glass ones look a bit fragile for me to use!

Yes I've been thinking about the concentration issue too and about a freeze concentration as possibly more energy efficient way of extracting the water from the sprage. I am though with @strange-steve here that this is interesting theoretically but there is a bit of wheel reinvention going on. For me I feel this is a gentle stretch outside of recipes and standard methods as I understand a bit more. More than likely I'll come back to the tried and tested methods, but it might be worth a wee excursion if only for the journey... and hopefully a nice drink to come back to. I don't have a lot of spare time, in fact it's only in recent years the concept really existed for me and I'm still enjoying the novelty!

Anna

 

[Buffers brewery]

it might be worth a wee excursion if only for the journe

I’m a great believer in looking at different ways of doing thing things even if it confirms that the way you’ve always done “it” is the best way!

 

[strange-steve]

I’m a great believer in looking at different ways of doing thing things even if it confirms that the way you’ve always done “it” is the best way!

Reminds me of this quote: "Engineers like to solve problems. If there are no problems handily available they will create their own problems."

 

[Cheyne_brewer]

It is my understanding that a good mechanical action is required in the boil to maximise protein coagulation, not just a chemical reaction. Hence the calandria- bringing boiling wort to the surface in quite a violent fountain. Commercial boil off rates are around 8% per hour so the calandria is mostly contributing a vigorous movement of the wort, not just heating. Unless you have a high wattage setup or a big gas ring the next best way to achieve this is to have the VENTED lid on for at least some of the time.

 

[Hazelwood Brewery]

I tend to boil lid-on but offset so as to leave a gap - like you do with the pan on your hob. I figure this allows to boil off anything I don’t want and reduces the risk of a boil-over. I don’t use evaporation as a mechanism for managing the gravity because as a home-brewer I don’t mind that my latest batch of beer is a little different (I also interfere far too much with the recipe for this to even be a factor!). The mostly closed lid also reduces the energy required to maintain the boil.

No science here, just my rationale for what I do.

 

[foxy]

I posted this a few weeks ago when someone asked a similar question.
Tim O'Rourke is a British brewer who teaches brewing to pro's across Europe.
http://www.ibdlearningzone.org.uk/a...g=the+function+of+the+boil&category=&keyword=