The format for the day at Falkirk was fairly open, however we
felt that the day would be best with some structure to it, so we asked some
of the members to introduce each topic and then lead the discussion. There
was a great exchange of information (and beer !) with a variety of members
giving talks and demonstrating equipment:
·
Sterile
techniques Robin Jones
·
Mashing
discussion Ian McAnally
·
Equipment
John McGarva / Dave Laurie
STERILE TECHNIQUES
Robin Jones
INTRO - The
elimination of contamination is the most important factor in brewing; the
one a brewer cannot afford to get wrong.
No matter how good
the recipe, how efficient the mashing, how high the quality of ingredients,
if the brew is contaminated it's all for nothing. Poor sterile technique is
the one factor that can undermine all the others and ruin a lot of hard
work. The only microorganism in your beer should be the fermenting yeast.
If only this were always so.
WHAT IS
CONTAMINATION? - May sound obvious, after all, we know when a pint is off,
but I believe that contamination can be quite insidious. What about lower
levels of contaminants that, while not sufficient to be seen as such, are
manifested as a taste that lacks the 'usual flavour', or is an 'average
pint', or 'nothing special?' Its easy to put it down to a poor mash or
recipe, but it might also be that some contamination got in between
sterilising and using the fermenter bin, or before a vigorous fermentation
got going - especially if there was a long cooling period, and was the wort
boiled soon after mashing? Boiling may destroy any contaminants, but even
dead bacteria and the compounds they produced while the wort was sitting at
cool temperatures, might still taint the brew.
METHODS - The essence
of good sterile technique is to minimise the opportunity for contamination
and incubation. Always use equipment as soon as sterilised on the
assumption that something will always get into containers and onto stirrers
etc. as soon as they are free of sterilant. We all have our own sterile
methods and each considers their's to be fine or wouldn't use it. However
it is likely that we all have our own 'lazy moments' or 'blind spots' as
well as sound methodology, which it is important to share, and is why I want
to start a discussion on sterile techniques.
An illustration -
albeit from an absolute beginner. [Anecdote about beginner who dried
sterilised bin with dishcloth].
Brewing equipment has
to be microbiologically clean, not the same thing as just physically clean.
I repeat, sterility
is the most important factor in producing a good beer. In fact I would say
that the drop in quality due to contamination off tastes is likely to be
greater than the gain in quality from full mash brewing. Anyone noticing
off tastes should put on a kit or use malt extract. Any problems with
mashing can then be eliminated. If there are still off tastes, there is a
sterility problem and one may just as well stay with kits until it is sorted
out.
STERILANT - I use
Sodium Metabisulphite, which does not need to be rinsed, unless dirty, then
Chempro. There are equivalents eg. bleach (1 cup per gal.). Don't forget
boiling water, always have a kettle handy for a sterile rinse and
emergencies.
UTENSILS - Have a
large bowl into which will fit the largest utensil. Addis make good square
bowls with close-fitted lids. All utensils that will make contact with the
wort or sterile surfaces are kept submerged in sodium met. in the bowl with
lid fitted, until used, then returned. This includes stirrers, thermometer,
hydrometer, funnels etc. and tubing (get all air out). Sod. met. does not
need rinsing off, but if using Chempro or bleach (why?) utensils can be
rinsed with boiled water before use. Do not just sterilise utensils once,
then leave them on the draining board etc. to gather bugs.
FERMENTING BIN &
BARRELS - Microorganisms and spores are falling out of the air constantly
and will rapidly contaminate any exposed surface. Anyone who has studied
microbiology will have done the experiment exposing agar plates for 30sec,
1, 2, 5, 10 min. etc and incubating. This gives a frightening measure of
the rate of microbial 'fall-out.' Sterile surfaces must be kept covered.
Keep the lid on the fermenting bin with sterilant in until it is used. Only
remove the lid to empty sterilant and put in wort and water and then replace
the lid. Wort can be stirred by lifting the lid on one side only with a
sterile spoon left inside until the yeast has been pitched. Then clip the
lid 2/3 around the fermenter, just enough to allow excess CO2 out and cover
with a towel. Resist the temptation to keep lifting the lid every day or so
to see how its doing, only open when necessary eg. skimming, stuck
fermentation etc. In the home, contamination cannot be eliminated, only
minimised.
Do the same with
barrels. A spare barrel cap with the valve hole sealed with tape can be
used while sterilising, to prevent sterilant damaging the valve of the valve
cap. After filling the barrel, the valve cap can be sterilised with boiling
water.
SIPHON TUBING - is
removed from the bowl and emptied of sterilant and fitted into bin and
barrel without it touching anything else. A sterile short piece of tube can
be fitted to the siphon end and used to suck on and removed as liquid starts
to flow down. This avoids putting your mouth on the siphon tubing.
BOTTLING - Bottles
are cleaned and sterilised by 1/2 filling with fresh sod. met. Eight are
filled, sealed and left for 20+ minutes. Then emptied into 8 more bottles
and left to drain. I have one batch sterilising, one draining and one being
filled. In this way the same 4 pints of sod. met. can be used to sterilise
40 pint bottles. Before filling, the drained bottles have caps removed and
are shaken to remove excess sod. met. I use a conditioning tank with a
Boots flip-top spout (sadly no longer available) which fits into the
bottle.
PRIMING SUGAR - is
from a clean batch. Do not use sugar from the general household stock. Buy
a fresh bag of cane sugar and keep sealed or in a sterilised jar with a
label threatening anyone who touches it, puts wet coffee spoons etc. in it,
with death, or worse. Better still, keep the jar under lock and key and
labelled potassium cyanide.'
After being careful
thus far, you do not want to add contamination at the final bottling stage.
The sugar bag or jar is kept on its side to prevent 'fall-out' getting in.
A teaspoon is sterilised with boiling water (which evaporates) and kept
under a clean, folded kitchen towel at all times when not being used to
transfer sugar.
A plastic funnel is
sterilised inside and outside with boiling water, fitted in a bottle and
sugar added. Once some beer has washed the sugar in, the funnel is removed
and the bottle is filled with the tap nozzle. The funnel is inverted and
left to drain on kitchen paper. Every 8 bottles the funnel is re-sterilised.
DRY HOPPING - Put
hops in a muslin bag and place in small saucepan. Add priming sugar and
just cover with boiling water. Simmer briefly. In this way hops and sugar
are sterilised together before adding, with water, to the barrel or
conditioning tank.
STERILE TECHNIQUE -
SUMMARY.
1. Sterility is the
most important factor in brewing, since contamination can undermine
everything else.
2. Low level
contamination, not necessarily perceived as such, can make a potentially
great beer, mediocre.
3. We can't eliminate
contamination, only minimise the opportunities for infection and incubation.
4. Sterilise every
container and utensil that will touch the wort.
5. Use wort and
equipment immediately after sterilisation, they won't stay sterile.
6. Do not allow
anything non-sterilised to touch sterilised equipment.
7. Sterilise with
sodium metabisulphite solution, which does not need rising and helps
preserve beer, or with chlorine-based products such as Chempro or bleach
which do. Don't forget boiling water, always have some to hand.
8. Sodium met. only
sterilises. Use Chempro, bleach etc. to clean and to remove the few
contaminants against which sodium met. is less effective.
9. Keep utensils
submerged in Sodium met. in a bowl with a lid, between use.
10. Keep the lid on
fermenting bin and barrel between sterilising and filling, stirring etc.
11. Put a few pints
of sodium met. solution into sealed barrels, bins etc during storage to
prevent mould.
12. Buy a spare
barrel cap (with hole covered with Sellotape etc.) to use during
sterilisation and storage as sterilants corrode the valve. Sterilise valve
cap with boiling water.
13. A rapid start to
fermentation reduces contaminant growth. Use an active yeast culture or
pitch dried yeast at 80oF/27oC.
14. Clip the bin lid
3/4 around and cover bin with a towel or blanket. Only lift lid when
necessary eg. to skim yeast, check gravity.
15. Submerge siphon
tubing carefully to fill the inside with sterilant.
16. To start
siphoning, use a sterilised 5ml auto pipette tip, short piece of tube etc.
to attach to the end of the siphon to avoid touching it with your mouth.
17. Sterilise 8
bottles with half a pint of sodium met. for 15-20 min. Then pour into the
next 8. In this way 4 pints sterilises 40 pint bottles.
18. Priming sugar
should be kept purely for brewing and separate from the household supply.
Dispense from a container on its side or covered against "aerial fall-out."
19. Regularly
sterilise spoons and funnels for putting sugar into bottles during bottling.
20. For dry hopping,
put hops in a muslin bag and blanche in a minimum of boiling water and add
water with hop bag to barrel, conditioning tank etc.
