Pasteurisation - Stopping fermentation in cider

[Jamrozik]

Hey Guys,

I wondered if anyone has advice on what temperature I need to bring my cider up to in order to stop it fermenting while not losing any alcohol to evaporation?

I have just pitched my yeast in 30 litres of apple juice and the OG is 1050. I plan to pasteurise the cider when it drops to 1015 by transferring the cider to a large kettle and heating it up and keeping it at 70 degrees c for about 15 minutes (stirring it constantly). I am then going to keg it and force carb it. I am pretty sure 70 degrees is hot enough to kill the yeast, but will the ethanol start evaporating/ reducing?

 

[timmi9191]

To answer your question no. Ethanol's boiling point is approx 78. Most commercial beer are pasteurised and that doesnt effect alcohol content,

But....

Why would you do it in this way? There would be so many other variables in the flavour profile you would be effecting. IMO a better way to achieve your outcome would be to either

1. Sweeten with maltodextrine or pear juice to raise the FG and allow the yeast to naturally ferment out or
2. cold crash to stop the yeast when the desired FG is reached and keg as you plan or
3. if you are worried about suspended yeast (which you shouldnt be) cold crash, filter and keg as you plan.

All 3 will give you a better end product IMO..

 

[earle]

If you are going to keg it and can keep the keg cold you don't really need to pasteurize.

For a 19L keg, i ferment 18L of juice figuring I will be able to transfer 17L to the keg after crash chilling. I then backsweeten with 2L of fresh juice and force carb. If you can keep the keg cold fermentation will all but stop.

 

[Lyrebird_Cycles]

70 C for 15 minutes will give you 412 PU (Pasteurisation Units)*

25 PU is generally considered adequate.

If you have say 5% wt / wt ethanol in your cider, the vapour above the cider will be about 12% ethanol* so if you evaporate say 1% in your processing your ethanol concentration will go down to 4.93% wt/wt *. I'd suggest that your actual evaporation rates would be lower than this so the loss is too small to worry about.



* I can show you how these results are derived if you are interested but I'm assuming you aren't.

 

[good4whatAlesU]

Don't mention the "P" word.

 

[Vini2ton]

Don't mention the "P" word.

What? Pauline?

 

[tugger]

Please explain

 

[Jamrozik]

Thanks for everyone's response. Unfortunately I can't keep my keg cold. Timmi9191, I might try your first point. On my first cider attempt, I went through 3 micro filters. Each got clogged. I also back sweetened with apple juice, kegged it, but fermentation restarted.

 

[Lyrebird_Cycles]

Never try to get anything through a microfilter filter without prefiltering it.

The reason lies in the ways filters are constructed. To get a defined lower limit and thus ensure sterility, microfilters are a flat surface with very tiny holes punched in them. Any particles larger than the holes (eg the reason you were filtering in the first place) will rapidly lodge in the holes and block the filter. (This doesn't apply if you are using a crossflow, but I assume you don't have a spare $100k for one of those).

Before going into the microfilter you should prefilter using a depth filter with a nominal micron rating at least as small as the rating of the microfilter you will use.

If your solids level is really low you can sometimes cheat by dosing a fine grade of DE or Perlite directly in before the microfilter. It will create a depth bed on the surface of the microfilter and act as a guard against blockage.

 

[good4whatAlesU]

I suppose you could try home made flash pasteurisation, gravity feed the cider through a home made warm magic box (tube running through esky/sink full of 70 c water) if it takes 60sec or so (?) to get through the tube it should be pasteurized (Lyrebird check the calcs?).

 

[malt junkie]

I suppose you could try home made flash pasteurisation, gravity feed the cider through a home made warm magic box (tube running through esky/sink full of 70 c water) if it takes 60sec or so (?) to get through the tube it should be pasteurized (Lyrebird check the calcs?).

You would need some serious heat under your magic box!

 

[Lyrebird_Cycles]

I suppose you could try home made flash pasteurisation, gravity feed the cider through a home made warm magic box (tube running through esky/sink full of 70 c water) if it takes 60sec or so (?) to get through the tube it should be pasteurized (Lyrebird check the calcs?).

Yep, 1 min at 70 oC will give you ~ 27 PU.

The trouble with this is the size of the holding tube required to get a 1 minute residence time at a decent flow rate. If you've ever run a flash pasteuriser, you'll know that they have a bloody great long holding tube between the second and third heat exchangers to achieve residence time.

You can just slow the flow rate down but then you'll drop below the Reynold's number required to ensure turbulent flow. If you have laminar flow a flash pasteuriser it simply won't work as the central flow stream has a lower residence time than any other. This problem is compounded by the fact that the heat transfer across the laminae is compromised.

The usual technique is to combine plate HXs with a tubular holding section, it's easier to maintain turbulent flow in the plate HX but there's still a limited range of flow rates that will work.

 

[good4whatAlesU]

Complicated. I take it back, put in in a pot

 

[Lyrebird_Cycles]

You would need some serious heat under your magic box!

The heat going in would need to be greater than the heat transferred to account for losses. Heating 19 litres from (say) 10 oC to 70 oC is about 5 MJ, assume 50% loss you need to provide say 10 MJ, if the transfer took 10 minutes that's 1 MJ / minute which is about 8 kW.

Flash pasteurisers get around this by having three heat exchangers. The first passes product in against heated product from the holding loop, recovering 90% of the heat. The next exchanges the preheated product against steam (or hot water) allowing trimming to the required holding temperature. The product then flows through the holding loop and back through the other side of heat exchanger #1. The last passes product against chilled water or glycol to get it back to filling temp before it goes to the filling line.

 

[tugger]

Just a quick one for lyrebird.
How many minutes at 62c to get 15 pu.

 

[Lyrebird_Cycles]

About 8.

The formula is PU per minute = 1.398(T-60) where T is the temperature in celsius. Alternatively use 10(T-60) / 25, same result.

For a near enough version that you can do in your head:

if x is the temperature difference between your process temp and 60, halve it then work out 2 to that power (eg 2x/2)

eg for 62 degrees x =2, x/2 =1, 21 = 2 so you get about 2 PU per minute. Real answer is 1.95 PU per minute, good enough for Jazz.

 

[Jamrozik]

70 C for 15 minutes will give you 412 PU (Pasteurisation Units)*

25 PU is generally considered adequate.

Hi Lyrebird, if 25 PU is considered adequate, how long, at 70 degrees, should I keep the temperature at? Excuse my ignorance. I have done little cider brewing.

 

[malt junkie]

Campden tablets and potassium sorbate is so much easier, usually used in sweet/desert wines, Lyrebird may be able to help with dosage as I haven't done it in a year or 2.

 

[Jamrozik]

Campden tablets and potassium sorbate is so much easier, usually used in sweet/desert wines, Lyrebird may be able to help with dosage as I haven't done it in a year or 2.

Yes, I used sodium metabisulfite and potassium metabisulfites when I did my first cider. It did work out well, but I wanted to avoid using them in this instance. I have enough sodium in my diet

 

[Dave70]

Hey Guys,

I wondered if anyone has advice on what temperature I need to bring my cider up to in order to stop it fermenting while not losing any alcohol to evaporation?

I have just pitched my yeast in 30 litres of apple juice and the OG is 1050. I plan to pasteurise the cider when it drops to 1015 by transferring the cider to a large kettle and heating it up and keeping it at 70 degrees c for about 15 minutes (stirring it constantly). I am then going to keg it and force carb it. I am pretty sure 70 degrees is hot enough to kill the yeast, but will the ethanol start evaporating/ reducing?

Have you considered Campden tablets to halt yeast activity, or perhaps using a sweet mead yeast?

If you are going to keg it and can keep the keg cold you don't really need to pasteurize.

For a 19L keg, i ferment 18L of juice figuring I will be able to transfer 17L to the keg after crash chilling. I then backsweeten with 2L of fresh juice and force carb. If you can keep the keg cold fermentation will all but stop.

All but, but not totally. I swear I've had back sweetened kegs still tick over slightly even after ignoring them in the keezer for weeks at 3 deg.