pressurized fermentation

[simon]

I am currently assembling a small brewing plant (300L brewlength) and am wondering if pressurised vessels for fermentation of ales are necessary. Most homebrewers don't ferment under pressure, and I am aware that there has been a long tradition of open fermenting in the industry. I am thinking of buying some 304 stainless steel variable capacity tanks which I will use as fermenters. Is this advisable? I will be relying on the bottle conditioning for most of the carbonation. Any advice?

[Aaron Taubman]

The only brewery i'm aware of that ferments under pressure is New Belgium brewing.. They do it so they can prevent the fermenters from fobbing over and eliminate the beer loss associated with that. You can fill your fermenter higher, and so get a greater yield. If your allow an appropiate headspace and can brew a little bit more often, it probably isnt worth your expense and time. Its more appropriate for breweries who run 24 hrs a day and need to extract the maximum capacity out of their fermenters.

We lose about one bbl out every one of our 21bbl batches to foam. Personally I like to see my fermenters fobbing over, as it is a good visual sign of an happy fermentation.

Cheers
Aaron Taubman
Millstream Brewing Co
Amana IA

[simon]

Aaron,

Thanks for you reply - another question - How can I find out my level of CO2 that remains in my bright beer, if I have racked off and aged for about a week. I am wanting to have better control over my carbonation, so as to not over or under prime. Currently, I am priming with about 5-7g of dextrose per litre, but there often seems to be some carbonation variability between batches. I haven't thoroughly regulated the temperature of my aging tanks. Weather in Melbourne recently has ranged from 40degC to 10degC within 48 hours. Apologies to all Northern Hemisphere folk about the metric thing

Cheers

Simon

[dick murton]

You have pretty well answered the question yourself. You need consistent temperatures throughout cold maturation. However the key to all this is consistent operations, i.e. allow the beer a warm maturation period to mop up diacetyl etc and boil off other less pleasant flavours, and then chill rapidly after a consistent time. Warm maturation time will depend upon your yeast type and oxygenation / aeration condidtions. This will also reduce residual fermentable sugars consistently. If you beer tastes too full bodied with a cloying butterscotch type flavour, extend the warm maturation time a few hours each brew until you get a flavour you like.

You can then sort out the amount of sugar you require for repeatable results. Have a rummage through the other Qs on bottling / CO2 levels - someone gave an indicative amount of sugar usage in one of the recent answers.

The higher the temperature the more likely you are to boil off the CO2. Keep the temperature consistently below 4 deg C (& ideally colder) and you should be able to settle out most of the yeast and protein quite rapidly. For info on temperatures vs pressure and temperature look up the Meheen bottling manufacturing web site, where they have some detailed tables (google seems to find it OK).

Cheers

Cheers

[Chip Tate]

I would also add to what Dick Burton said about the importance of temperature the effects of temperature flux on colloidal stability and premature aging.

Once fermentation is finished and diacetyl has been mopped up, temperatures above 33-36 F are going to do nothing but prematurely stale most beers (many stronger ales take exception to the rule). Further, cycling the temperature up and down is about the best way to colloidally destabilize a beer. The more the cycling goes on, the more easily the beer will throw a chill haze which can eventually become a permanent haze--never attractive on a nice pint In my experience, keeping the temperature relatively stable (at room temperature or below) during maturation can often prove more important to the keeping quality of a beer than keeping the beer cold.

Finally, the easiest way the gauge dissolved CO2 is too keep your beer at a constant temperature in a sealed container for several days. During this time the pressure in the headspace of your vessel will equalize with the CO2 pressure in your beer. A simple read of the beer temperature and the pressure in the head space of the vessel will give you what you need to calculate volumes of CO2 in solution (mathmatically with the universal gas law equation, or on commonly available charts). But again, the key is constant temperature for this method to be accurate.

Cheers,

Chip Tate

[dick murton]

I found some figures for sugar usage to achieve consistent in bottle carbonation levels. I have reworked and simplified these. Obviously they are only guidelines, as they may produce beer which is higher or lower in CO2 content than you like - but it could form a basis for tweaking.

In bottle carbonation may be derived mainly from the fermentation by residual yeast of the fermentable sugar present in the beer when packaged. To achieve the required carbonation level, the amount of fermentable sugar has to be adjusted to around 3.8 by the addition of liquid sucrose prior to packaging.
The sugar addition is calculated from analyses carried out on the pre package beer post fermentation.
1 DEFINITION OF TERMS
PG Present gravity
FG Fermentable gravity or attenuation limit
FR Fermentable residue
PPT Pre package tank

2 CALCULATION OF SUGAR ADDITION
a Measure the PG of the beer in the pre package tank
b Measure the FG of the beer in the pre package tank
c PG minus FG = FR of the beer
d 3.8 minus FR = No of degrees of gravity to be added to achieve FR of 3.8 degrees
e Look up in the table the number of litres of liquid sucrose to be added to increase the PG by the required amount
f Add to tank and mix thoroughly (do not use not air or oxygen)
g Measure the PG of the beer post sugar addition.
h PG post sugar addition minus FG pre sugar = calculated FR
The calculated F.R. must be a minimum of 3.5 before the beer is packaged

SUGAR ADDITIONS

Use the following figures as guide to the amount of liquid sucrose at a specific gravity of 1118 to be added to 1 hl of beer to raise the F.R. by the stated amount

DEGREES INCREASE REQUIRED No OF LITRES OF SUCROSE AT 118 degrees
2.4 (MINIMUM ADDITION) 5.5
3.5 (MAXIMUM ADDITION) 8.0

Example
PG in PPT – 8.0
FG in PPT = 7.0
FR = 8.0 – 7.0 = 1.0
3.8 – 1.0 = 2.8 degrees to be added
Volume of beer = 1 hl
Add amount of sugar indicated in table = 6.4 litres
No adjustment is required for beer volume
FG in PFT pre sugar addition = 7.0
Calculated FR in post sugar addition PPT = 10.7 – 7.0 = 3.7
This is greater than 3.5 and may be packaged.

CO2 levels
2.0 – 3.0 volumes in final pack after warm conditioning of bottles (no pre conditioning level quoted – but anticipate 1.2 - 1.5 vols pre sugar addition)


Hope this helps

[Matthew Letki]

Adding primings can be a great way of inntroducing contaminating microflora to your beer if not done correctly. You can also carbonate naturally by closing your fermenter up at 3 or 4 points of specific gravity above terminal gravity and letiing the pressure build up to roughly 13 psi. You can determine the terminal gravity of the beer by taking a litre or so out just at high krausen and letting it ferment very warm (25 to 30C), it will finish fermenting before the rest of the brew which is fermenting at a lower temp.

You will have to cool the beer considerably to get the CO2 to stay in solutionn during packaging.

Cheers,
Matt

[BigWilley]

It sounds to me like your talking about using open fermentors in an area where you have no control over temperature. If this is right then a lot of what was previously mentioned won't help. You cant bung an open fermentor, nor can you allow the pressure to equalize in an open vessel as you will continually lose CO2. You can definately get away with open fermentation but you would need to research it first and have some kind of temperature control for the fermentation room. You would do well to purchase at least one bright tank capable of being pressurized to 15psi and with a cooling jacket so you can get the beer cold enough for packaging. That way you could open ferment and then transfer to your bright tank for conditioning and Carbonation. It may be extremely difficult to to hit target CO2 levels with no pressurized vessels. Also if you have a pressurized tank with a sample cock you could buy a Zham and Nagle CO2 tester for accurate measurements.