Microwaving Wort

[Bribie G]

Last night's brew I ended up collecting two litres of extra wort into 1 L Schott Bottles.

This was deliberate; it was a Dortmunder lager wort and I brewed a bit more to provide some wort for my next lager yeast starter.

The bottles were taken as last runnings out of the urn, and had settled down to clear wort with about a cm of hot break and a jellyfish of cold break suspended above in clear wort.


To ensure that the wort was sterile I considered reboiling the wort in a pan and freezing in a 2L plastic juice bottle for further use.

Then it occurred to me that borosilicate glass, such as Schotties, should withstand microwaving no problems and by sterilising the wort "in situ" the bottles could then be stored, at ambient if necessary, till next lager brew, a bit like jars of jam.


This is what eventuated and what I observed.

After microwaving for about 6 minutes (bottle top off of course) the cold break seemed to disintegrate into tiny little flakes that started to rain down to the bottom.. and rain down very fast.
Then the wort came to the boil and instead of frothing out of the bottle, that I'd been expecting, it just bubbled away like hot water. Lovely malty smell permeated the kitchen.

On switching off the microwave, the wort was now crystal clear with a layer of something almost as thin as paper on the bottom. I would assume the hot break also got nuked into a more dense state.
Photo shows Schotties re-lidded with boiled then starsan sprayed lids.



This strikes me as a potential absolutely feckin brilliant way of keeping wort for starters.

I'll now chill them to around 8 in my lager fridge and will post pic of the cold result.

 

[MHB]

One to follow with interest.
Will you be adding nutrient to your starters?
Mark

 

[roastinrich]

Where did you get these Schotties BG.

 

[manticle]

Remember what happens to water when it's microwaved.
At no point should you whisper 'hitler' at your wort.

 

[Bribie G]

They came from a Water Engineer guy on the forum about 8 years ago when they were going to bin a heap of them at his workplace :blink: so he rescued them and they went to good homes in Brisbane - mostly to BABBs members.

Similar jars available (well not currently but hopefully back soon) from Craftbrewer at a pretty good price.


Nutrient would be a good idea to add, a bit like Toddler Plus for the widdle yeasties.

 

[Bribie G]

Right, results are quite interesting - I crashed it down in the chest freezer to near freezing.
Cold break has reformed, and the wort is still nice and clear as you can see from the tops of the bottles, but I'd expect the CB to drop fairly quickly on storage.. won't be doing another lager for about three weeks when the conical is free.
I'm wondering what those flakes were that were rapidly settling out in the boil.

However the hot break has been well and truly zapped and, being the last urn runnings there had been a fair bit in the second bottle. Can't see why this shouldn't work to build up a supply of good quality wort for starters, and MHB's suggestion of yeast nutrient should be a winner.

 

[Feldon]

Just thinking for the sake of safety care needs to taken in case the wort gets superheated in the microwave oven.

Probably likely to happen if you are heating to sterilize (eg. the 6 minutes stated above).

The superheated liquid can violently erupt into an active boiling state when it's disturbed, which can be as little as moving the flask out of the microwave. Then woosh - boiling wort in your face or over your hands.

https://en.wikipedia.org/wiki/Superheating

That aside, it seems like a very good way to prepare starter wort for storage.

 

[Mr B]

Off topic as its traditional style, but check these ones. Oooh yeah......

 

[Danscraftbeer]

Just thinking for the sake of safety care needs to taken in case the wort gets superheated in the microwave oven.

Probably likely to happen if you are heating to sterilize (eg. the 6 minutes stated above).

The superheated liquid can violently erupt into an active boiling state when it's disturbed, which can be as little as moving the flask out of the microwave. Then woosh - boiling wort in your face or over your hands.

Yes, and I don't trust myself to think of that when I'm multitasking. Someone recently made a thread about pressure canning. I do that. Its much safer but you need a pressure cooker and the canning jars. But! that can be much cheaper than pain and suffering boil burns.
Be careful.

 

[TidalPete]

Bribie,

For the sake of saving a few minutes I'd give the microwave thing a big miss.
Not a good idea mate.
I've always allowed for extra wort in kettle for future starters, not that I am the be-all\end-all of brewing knowledge but just giving my 2-cents.
Adding nutrients to starters is good & as for the rest I'll be in touch ASAP. B)

 

[peteru]

Any tools is a good tool, but you need know the limits. If you understand how a microwave works you can make it safe. As long as you provide nucleation sites, you should not end up with superheated geysers. A roughed up marble in the wort container would do the trick.

http://www.animations.physics.unsw.edu.au/jw/superheating.htm

BTW: Joe Wolfe was (maybe still is) an awesome lecturer when it came to physics at UNSW - he took a nightmare subject and turned it into fun...

 

[Bribie G]

Must get a roughed up marble.

 

[MHB]

Apart from the concerns about superheating.
What interests me is why the break material behaved so differently. I suspect that the flock is acting as nucleation points or that the protein/tannin complex is absorbing the microwaves and that it is getting denatured (local superheating).
Like I said interesting, also interesting that more cold break formed, means that not all the protein is reacting the same way, perhaps only the trub that had already formed not the protein that is still in solution. Which is good as yeast needs some as nutrient.
Would be good to see what is happening to the lipid and sterol content, yeast needs some of them to, and we know fats get heated by microwaves.

Lots of questions, not many answers yet
Mark

 

[RdeVjun]

Ah, the ol' surplus Schott bottles, they have served us well over the years, thank goodness they were retrieved from the industrial bin!

I freeze surplus wort in PET or other plastic bottles for starters too, so have to thaw, dilute and fertilise, then cook for yonks in Schotts; I've never contemplated simply filling and nuking the Schott instead, seems quite reasonable to me.
I usually aim to prepare starters in Schott bottles well ahead of time to allow them to proof, that way I'm sure it is close enough to sterile. I'll usually cook them on the gas stove in the 19L pot, but for efficient gas consumption, waiting until I have enough to fill it, although nuking them means that I can cook them as I go after each brewday. Will be giving this a whirl Bribie, many thanks for the tip! Horses for courses I reckon though, may not suit everyone.

FWIW, maybe there's a proportion of break that is microwave- sensitive and some that is not, considering the array if issues we encounter with it then it's obvious that its nonhomogeneous, I suppose.

 

[Bribie G]

I'd say the lids are microwaveable as well.I have some spare so will have a go. Just fitted loosely then tightened up when the danger is past.

 

[RobW]

I'd say the lids are microwaveable as well.I have some spare so will have a go. Just fitted loosely then tightened up when the danger is past.

They are microwaveable. I use them for starters with no problems.
As you say, leave the lids loose and let everything settle down before closing.

 

[mofox1]

Kind of on topic - at least with regards to the superheated bizo.

Last night: Boiling some starter wort in a flask (on gas, not in the microwave). Had to go attend the kids so I diligently turned the gas off. It had only been boiling for a minute or two, so when I came back maybe 10 or 15min later I turned the gas back on.

Completely different boiling profile.

First boil: Lots of little bubbles, constant visible boil. Basically everyone's normal Tuesday night boiling up liquids in sexy erlenmeyer flasks.

Second boil: Still. Dead calm. Then BOOM - up it goes (and I am literally right there hovering over the gas knob ready to turn it down - not too much overflow but it was close). Rinse down area and continue, same thing happens but on a smaller scale. It's on a tiny tiny flame at this point, and it will still wait until something gets super-critical before it erupts. Tried giving it a swirl (after it had cooled slightly), tried constantly bumping it as it was heating to try to get the steam to form... after a few more small boil-overs I just gave up sprayed it down with starsan and dumped it into the sink to cool down. I'd managed to get another 5min "boil" out of it, so hopefully most bugs killed.

Curiously, a similair thing happened when I tried to re-boil some extra kettle wort a while ago. Except it had the second boil profile from the get-go. Wondered if it had something to do with the whirlfloc, now not sure. Unfortunately, that one ended with 2nd degree burns that lasted for weeks.

 

[MHB]

It's down to dissolved gas (air), as the temperature rises solubility goes down and you get lots of small bubbles mostly forming on the heated surface (or small irregularities on the surface) the rising streams of small bubbles help the boil to start and establish a roll.

When there is no dissolved gas all the liquid reaches the boiling point at about the same and it all wants to turn to steam at once "BOOM" as you put it.

if you find an old ceramic tile and break a couple of small pieces of (say ~5X5mm), put 1 or 2 in the bottom of the flask before you start heating/reheating a degassed liquid you should get a smooth boil with no "bumping", in labs they use anti bumping granules made of fused aluminium oxide (ceramic) and they work very well.
Mark

Also called Boiling Chips
M

 

[peteru]

As I mentioned in reply #11, you need a source of nucleation sites, which is effectively what MHB is talking about. I mentioned a marble in that post, but a rock that won't leach any minerals, such as a piece of non-polished granite would also do. I guess I should clarify that when I mentioned a roughed up marble, I meant a glass sphere that kids use to play marbles. One with a rough pitted surface. A perfectly smooth glass sphere would not have any effect.