Fermentation and Yeast

[Loic]

Hi all,

I've just read the book "yeast : the practical guide to beer fermentation" and I would like to share with you my notes and my experiences as homebrewer about fermentation

So please feel free to make any correction or share your experience :)

I would like to start by this tow following points really important for me:

• All yeast will produce most of their flavours in the first 72h.
• Brewer make the work, yeast make the beer.

How to choose the yeast :

• Be creative ! Exploring new strains ! It is like cooking a cake without recipe
  
• Attenuation
• Flavour profile
• Temperature range
• Flocculation

My experience : in accordance with the beer I want to brew, I read every information provided by the yeast supplier, flavours, dry or not...

Firstly how do we rehydrate dry yeast:

1. Use a sanitised container
2. Water ? wort? both ? Sterile tap water (I boil tap water or I use bottled water)
3. how musg water ? 10ml of water /g of yeast - I have to try thisaunsure....
   
4. Between 35 and 41°C :thumba:
5. Sprinkle the yeast on the top and wait 15 min
6. Stir and wait another 5 min
7. Adjust the temperature of the yeast within 8°C of the wort ( I prefere to be within 4 or 5 °C)

What next ? I've just cooled down my wort ! what about oxygen ?

• Prior to fermentation, chill and aerate the wort, it is necessary to promote yeast growth.
• Lager and high in alcohol beer require more oxygen
• Yeast need 10 ppm of oxygen - 5min of shaking aeration is 2,7ppm of oxygen in the wort

Personlly I'm alway afraid by oxydation !!!!!!!!

What's happen in fermentation vessel ?
Lag phase :

• 0 to 15 hours
• 20°C for ale and 13°C for lager
• Acclimating to their environment
• During this phase the yeast will absorb the oxygen to produce compound
• For high gravity beer a second addition of oxygen can make a better attenuation

Exponential growth phase :

• 4 hours to 4 days
• Production of CO2
• Yeast will consume
  • Glucose 14% of the sugar in the wort
  • Fructose
  • Sucrose
  • Maltose 59% of sugar in the wort

• high kraeusen activity

Stationary phase :

• 3 to 10 days
• The beer has not reached the balance of flavours but it I nearly their
• Yeast reabsorb much of the diacetyl and acetaldehyde
• Hydrogen sulphite continue to escape
• At this point we can cool the beer down about 2 to 4°C to force the yeast to floccule and settle

an option if we have a big spare fridge is the Lagering
Process:

• Process to improve beer flavours by cold period conditioning at 4 °C
• Do not drop the temperature more than 5 °C per hour otherwise the yeast can release more ester than usual.

Advantages

• Flocculation
• Improve flavours
• Prevent oxidation

Temperature :

• If we can control the temperature is it interesting to start fermenting the beer at 1 to 2 °C below the final target and raise the temperature over the course of 18 to 36h.
• It is interesting to control the temperature during the first 72 when the yeast make most of their flovours.

Note1 : If we want to cool down the wort, wait until the end of the fermentation net before 4 days
Note2 : at 24 °C acetaldehyde s 10 time higher than the perception threshold.

Ale Yeast : top fermeting between 18 and 21°C
Usually ale fermentation in complete in 4 days and then 4 to 5 more days for the yeast to settles.

Lager Yeast : bottom fermeting between 10 and 13°C

Et voila !

Please forgive my english I've just moved in UK so I'm still learning both brewing and english

Loic

 

[Dutto]

WOW! That's a lot to read!

In view of the many thousands of variables in brewing, I have made a conscious decision to use just two yeasts:

1. Wilco Ale Yeast (aka Nottingham Yeats & Gervin -12 Yeast)
2. Youngs Lager Yeast.

I have often used harvested yeast and also recovered yeast from bottles for experimental purposes.

It's a minefield out there - but good luck with your brewing odyssey!

 

[lancon]

Personlly I'm alway afraid by oxydation !!!!!!!!
oxidation (not good in this environment) is different from aeration,very important to aerate the wort, the yeast needs to grow & multiply, this needs aerobic respiration, once that is complete then it starts the (alcohol producing) anaerobic respiration. I just make sure that the chilled wort splashes into the fermenter from a height, (normally creating a head on the wort showing that it has been aerated?)

 

[divrack]

Yeast nutrient is a good idea for new pitches of yeast. (Although who knows, I'm no scientist)
Liquid yeast will often need a starter for high strength/old packets. Starters are a minefield but plenty info out there.
Mr malty will keep you right.

 

[Loic]

oxidation (not good in this environment) is different from aeration,very important to aerate the wort, the yeast needs to grow & multiply, this needs aerobic respiration, once that is complete then it starts the (alcohol producing) anaerobic respiration. I just make sure that the chilled wort splashes into the fermenter from a height, (normally creating a head on the wort showing that it has been aerated?)

That is correct :). Without oxygen your year won’t produce desired flavours.

By afraid, I mean, I try to be carefully when I’m transferring beer to another vessel for filtration.

Good idea I will try to pitch my next batch with yeast from the previous bottles batch.

Have you ever try yeast from cider or wine ?

I tried to pitch apple juice with beer yeast, actually the result was quite good. But don’t pu to much yeast otherwise you will get to mush gaz !! :)

Cheers

Loïc