Fermentation Temperature Question

[Byron]

Been thinking about this a bit recently now I have a digital thermometer on my FV.

I normally make a yeast starter with c.100ml of wort at 30c. I then add this to the rest of the wort when it is about the same temperature.

Now yesterday's brew has taken the best part of a day to get down to the recipe recommended 20c in a fridge. From 31c.

So the question is... is this OK practise or should I cool the rest of the wort to the right fermentation temp before adding my starter.

I've always done the method above and had some great results. It's just now I can see how long it's taken to get to temp (and that's in a fridge) I'm thinking could my process be better?

All input welcomed. Every day's a school day.

 

[terrym]

I think you will find that, for ale, the convention is to pitch at below 24* C tops, better 20*C. Thats what I always do. Something to do with early diacetyl production and higher than advisable core temperatures in the FV.
Others may offer different advice, or may be able to better explain why it's not good to pitch at elevated temperatures.

 

[nigelnorris]

I've been using mainly Fermentis yeasts, partly because they publish a spec sheet [I imagine the other manufacturers do too, but I found Fermentis first] for each one including temps at different stages and the like. It's different between yeasts but the most common recommended temps are rehydrate at 25C-29C for ale yeasts and 21C-25C for lager yeasts then pitch into beer between 20C-25C. Sprinkling yeast direct onto beer is only suggested for some of them but it does specify 20C+ even for lager.

I have no idea why anything ever, I just blindly follow instructions based on the notion that if anyone knows best it must be them. I suppose they could be just picking medium everything in order to guarantee a drinkable product rather than taking risks, but better their advice than my own guesswork.

 

[DoctorMick]

Aside from the temperature, a 100ml starter is pretty small. Do you use a calculator to work out the starter size?

 

[Spapro]

Best to pitch at low 20's ideally.

Are you using dry yeast?

If so for regular 1.040 - 1.050 brews no need to re-hydrate your average dry yeast. I always sprinkled sachets of US05, Gervin or US04 straight into wort (at circa 21°C) and never had an issue with fermentation.

Now using wet yeast which is a different kettle of fish and does benefit from larger starters of 1-2l in size

 

[Slid]

If I recall correctly, Coopers recommend pitching as soon as the wort is down to 27C.

The thinking behind this is that the first thing the yeast will do is multiply in number and whilst this is going on, alcohol production is relatively slow, meaning that by the time there might be a serious risk of off-flavours, the wort has cooled down to nearer ideal ale yeast temps.

Although this is a bit of an over-simplification, I don't remember having issues with either kit or AG beers being pitched at even mid to high twenties C. I do usually use the dry yeasts that are most temp tolerant - US 05, Coopers, Belgian M31 and so forth, not having a brew fridge nor the space to keep one.

 

[ericmark]

If the wort is made by local boiling it then waiting a few hours for it to cool is no problem. But if using tap water then there is a trade off, the wort may have things in it which can start eating the food before you get the yeast into it, so you want to put yeast in at the earliest opportunity.

I have made mistakes using too much hot water to wash the wort out of the tin and started at 24[FONT=&quot]°C I added yeast and set temperature to 19.5[/FONT][FONT=&quot]°C and it took around 3/4 hour to come down, well at least for it to show 19.5[/FONT][FONT=&quot]°C on the STC-1000 display when the sensor was pressed against the fermenter under a sponge. The air in the freezer however dropped to 8[/FONT][FONT=&quot]°C and it was in the freezer compartment of a fridge/freezer so had a motor taking around 70W and of course includes a fan to circulate air, not sure how big the motor is on a fridge, and it is unlikely to have a built in fan.

I expected it to over shoot, however if it did it was less than 0.[/FONT][FONT=&quot]2°C, I did not see any over shoot. I think it restarted twice before settling down, but must be looking at no more than 1.5 hours to get down to set temperature.[/FONT]

 

[strange-steve]

Two things, firstly yes you should pitch the yeast at fermentation temperature (or even a couple of degrees lower then let it rise).
Secondly, it sounds like you are making a starter with dry yeast? You're not really doing any good by doing that, you might as well just sprinkle it straight into the wort, or even better, rehydrate it in boiled water cooled to the appropriate temperature (this temperature is strain dependant and important).

 

[nigelnorris]

it sounds like you are making a starter with dry yeast? You're not really doing any good by doing that, you might as well just sprinkle it straight into the wort, or even better, rehydrate it in boiled water cooled to the appropriate temperature (this temperature is strain dependant and important).

I don't doubt you but how come? Why can't you make a starter from dry yeast?

 

[Norfolk79]

I don't doubt you but how come? Why can't you make a starter from dry yeast?

From my understanding dried yeast has more viable yeast cells than liquid yeast and so making a starter to increase the number of cells isn't necessary as there should be enough straight out of the packet.:thumb:

 

[strange-steve]

I don't doubt you but how come? Why can't you make a starter from dry yeast?

You can make a starter with dry yeast but you should rehydrate it in water first, however it's usually cheaper and easier to just buy an extra packet rather than faff with starters.
Adding dry yeast straight into wort isn't too good for the health of the yeast, but you can counter that by using a higher pitch rate.

 

[nigelnorris]

You can make a starter with dry yeast but you should rehydrate it in water first, however it's usually cheaper and easier to just buy an extra packet rather than faff with starters.
Adding dry yeast straight into wort isn't too good for the health of the yeast, but you can counter that by using a higher pitch rate.

Except that when I look at the Brewers Friend pitch calculator for the last batch of lager [nothing special, 20L @ 1050 OG] I made it was telling me to chuck not one but four 11g packs of dried yeast in there. That's fifteen quid's worth of S-23, surely it's worth the faff trying to build one or two packs up to save that sort of amount of money.

 

[strange-steve]

That's why I said usually, lager is a special case because it requires double the standard pitch rate. The other thing to bear in mind is that there is a lot of different figures regarding cell density of dry yeast, so if you used J Zainasheff's figure of 20B/g then 2 packs would be enough.