warm to cold,warm to cold.
I have problem with our package product in the summer, winter is good can get 4 mnth shelf life but in the summer it goes off pretty damn quick, not refermenting in the bottle, just tastes musty and all the hop character has gone.
is there any way to combat this problem?
I suspect it to be oxidation, but dont know how to fix it, any suggestion will be much appretiated.
ps things about the beer:
natural co2 from ferment caught at about 1.020 s.g.
D.E. filtered under pressure 120KPA.
Bottled in brown twist top 330ml bottles, purged with co2 then filled buy h&K 25 head filler (counter pressure).
pasturised at 60c for 10mins.
stored in dark place at about 15c.
Winter here is abuot 10-15c & summer is between 30-45c.
I assume your cold conditioning is OK and you are able to achieve zero or colder with absolute certainty, both summer and winter. If not, then this is a first point of attack. If you are not able to chill and hold chilled consistently, then you will suffer hazes more readily, which will also be accompanied by more rapid staling.
However, from 12000 miles away, I would agree that the most likely cause is oxygen pickup prior to or during bottling. Firstly you need to ensure that all tanks and connection hoses, rigid pipe, pumps, filler etc are thoroughly purged with inert gas, either CO2 or nitrogen being normally used, prior to any beer transfer.
Normally you can purge the hoses and pipes through with fast flowing water until all air bubbles are removed. If you can use deoxygenated water, even just cold boiled water, all the better.
The tank can be purged from the bottom with CO2, or, rather expensively, filled with water, then pushed out with CO2.
Similarly the filler bowl prior to filling with beer should be water flushed and CO2 purged.
The bottles themselves should ideally be flushed with CO2 before filling, as part of the pre filling sequence incorporated into the filler. After filling, the space between the beer and the crown should be filled with dense foam, generated by the beer. This is normally achieved by a tapper, literally a little hammer mechanism that taps each bottle and causes the beer to foam up, or a very fine high pressure jet of sterile water, which has the same effect.
The foam should be just overflowing the bottle as you put the crown on it. To tellif you have low air in headspace (as it is known), as soon as a bottle has been crowned, turn it on its side, and look at the quality of the foam. If you have one or more large bubbles, these are generally air. The faom should consist of small bubbles only, say one or two mm diameter max, and be very consistent in size. If you have large bubbles, increase the time between filler discharge and crowner, or increase the jetter pressure, or increase the severity of the knock or a combination as appropriate.
Oxidised beer is oftern descibed as tasting of chewed paper or cardboard, and / or sometimes has a blackcurrant smell / flavour.
Hope this helps
are you measuring your DO through the filtration and/or packaging process - perhaps you are picking up oxygen through the filter? also, are you measuring air in heads?
I would first like to say that you have received some excellent advice from Dick ans Alex. I can't help the feeling that there is more to this, however. Oxidation knows no season and the fact that you are pasteurizing would expose the oxidation problem throughout the year. Testing the dissolved oxygen content of your beer at every stage of the process on a regular basis would uncover the source of oxidation, if indeed this is the problem. In the absence of good testing equipment you may want to take a case of beer from the line prior to pasteurizing it and a case post treatment. Store them in the usual manner for finished goods and taste them side by side at say 10 days and 30 days after packaging. If oxidation is the root cause, it should be evedent in the flavor difference.
I think there needs to be some more focus on things that are different from winter to summer. Outside temperature is a big one here. 45C is hot. Does this affect your refrigeration? Does it make your pasteurization more intense? Does it affect your ambient water temperature (maybe bottles don't cool down as much as you think after the pasteurizer)? We have found that even the difference between storage at 15C vs. 17C takes a bite out of shelf life.
Are the flavor problems you experience at the brewery or out in the trade? Perhaps your beer is not being refrigerated out in the trade? Elevated summer temperatures can accelerate degradation of the product logrithmically.
There can be other seasonal influences as well. How are your hops stored? Are they kept at cold temperatures?
Could you write back with more information. I agree that oxidation is a likely source based on what you have said, but I think it goes beyond being process related.
Last edited by BAugust; 11-12-2004 at 08:31 PM.