Hefeweizen: How long should I leave it in secondary?

[BackshoreJake]

Today I racked my hefeweizen to secondary. I am aware that many people prefer to bottle directly after primary fermentation, and skip secondary as this will further clarify a beer that is supposed to be cloudy. I felt that I wanted a slightly lighter taste in my hef , and thought that getting it away from the yeast cake for a few days would maybe be the best thing to do for that.

My question is: now that I have racked to secondary, how long must I keep it there? I don't want any damage done to my beer from oxygen exposure, so I am not inclined to bottle any sooner than a week. The beer sat in primary for 2 weeks, and I had planned to keep it in secondary for a week.

If I was to bottle in 4 or 5 days- would all the oxygen exposure harm the beer?

I guess my biggest questions is HOW does oxygen exposure harm the beer? How much is too much?

Jake

 

[daveooph131]

Not at all...I wouldn't worry about oxidation as long as you racked to the secondary without disturbing the beer to much. Oxidation will only really occur if you really agitate the brew while moving vessels. I would bottle at 3 weeks from pitch, maybe sooner b/c Hefes are better young. I keg and am drinking hefes about 4 weeks after pitch.

 

[bmsteele]

...maybe sooner b/c Hefes are better young.

Word! Do it to it yo!

 

[Challenger440]

My question to the OP- What is the difference, in terms of oxygen exposure, if you bottle a beer after it has been sitting in the secondary for 2 months vs. a beer that has been in the secondary for 2 days?

 

[BackshoreJake]

I feel that when you allow oxygen to come into contact with the beer- you are taking away the anaerobic environment for the beer. Thusly no further fermentation may occur until the oxygen has been replaced with CO2. At this point in my brew I don't think there is a whole lot of respiration going on in the first place, that is I think fermentation is done. So I guess there would be no difference?

My main concern was if it was important to make sure that the O2 was not absorbed by the beer, and to make sure that it has been completely replaced by CO2 in the carboy. I'm still foggy as to why it is important to make sure that beer does not get much contact with oxygen once fermentation is done. After the advice on this thread I'm anticipating bottling on Saturday now. Just to let some residual proteins and things settle out- and into the glass the beer goes.

 

[Challenger440]

I feel that when you allow oxygen to come into contact with the beer- you are taking away the anaerobic environment for the beer. Thusly no further fermentation may occur until the oxygen has been replaced with CO2....

I think you might be misunderstanding how yeast work. Yeast need and aerobic environment to perform fermentation. This is why we aerate the wort when we pitch the yeast.

My main concern was if it was important to make sure that the O2 was not absorbed by the beer..... I'm still foggy as to why it is important to make sure that beer does not get much contact with oxygen once fermentation is done....

The reason we don't want oxygen to get absorbed by the beer after fermentation is if it happens then over time an off flavor will develop that we don't want. The off flavor that it will develop is a cardboard taste, nobody wants to drink cardboard.

 

[Challenger440]

For a more in depth look at yeast (Warning, science mumbo jumbo ahead)

Yeast use the oxygen present in the wort to make sterols and fatty acids for cell membranes before budding takes place.

Here is a rundown of the chemical reaction formulas for yeast during carbohydrate metabolism:
Activation: Sugar + 2ATP ---> Fructose 1,6‐bisphospate + 2ADP
Oxidation: Fructose 1,6‐bisphospate + 2 NAD + 2 phosphate ---> 2 diphosphoglycerate + 2 NADH
Energy Capture: 2 Diphosphoglycerate + 4 ADP ---> 2 Pyruvate + 4 ATP
NAD Regeneration: 2 Pyruvate + 2 NADH ---> 2 Ethanol + 2 Carbon Dioxide + 2 NAD

So here is the net chemical reaction for carbohydrate metabolism by yeast:
NET: Sugar + 2 ADP + 2 phosphate ---> 2 Ethanol + 2 Carbon Dioxide + 2 ATP

 

[BackshoreJake]

MORE SCIENCE MUMBO JUMBO

My understanding: Yeast need oxygen to initially bud, and perform glycolysis. During this process CO2 is created- slowly replacing the O2 that is dissolved in solution and is being used during glycolysis. Once the oxygen has been fully replaced, the yeast will be forced to perform fermentation instead of glycolysis because of the anaerobic environment. Once fermentation is complete, the yeast have either died and or used the majority of sugars in solution- So O2 exposure is not all that important for the yeast, however, prolonged exposure to oxygen may give beer a bad flavor. I'm assuming some sort of ester is created, though I'm not sure.

So, long story short: I should not be worried about bottling soon after racking to secondary as the oxygen exposure is not enough to harm the integrity of the beer. Looks like I'll be havin hef in 2 weeks.