I know someone who made a brandy that was chill filtered with a five micron filter before bottling. Then it got warm and cold due to weather and storage issues. Now it has become hazy. How small a micron filter can you go before flavor and color are stripped out?
A 5 micron filter is extremely small. While not small enough to remove flavor molecules, that's below the level you'd usually have issues with cloudiness due to agglomeration at clod temperatures.
The haze you are referring to is mostly clumps of polyphenols. Polyphenols are part of the flavour profile.
If you filter them out, at whatever micron, you will remove some of the flavour.
In theory, the slower the spirit is cooled the larger the clumps or 'crystals" will be, and hence a coarser filter will achieve the same thing.
The Brandy in question may have been chilled too rapidly and many of the clumps could have been too small to be filtered out.
I did some research and couldn't find much more info, except that one of the big scotch distilleries does a 5 micron filtering for char and particles, and 1 micron chill haze filtering.
More info on the brandy. Samples of it were filtered with 2.5 micron and it is clear at room temp., but hazes when very cold, then turns clear as it warms up.
Many bourbons that have been chill filtered will haze when stuck in the freezer and clear up as they approach room temp.
The Scotch example above seems about right.
On a side note, it was good to meet you at the NYISC, Jonathan. I wish we would have had more time to talk....it's hard at those things.
For many spirits the turbidity attributed to chill haze is caused by the esters of the higher fatty acids (flavor), so you are better off selecting a filter that has some asorptive qualities in addition to selecting on the nominal micron rating. You may have to choose which is more important to you, a really bright clear product when chilled or the flavor of a lesser filtered product.
In my experience, we have found great success in brandy using a greater than 2.0 micron nominal filter but you have to filter it really cold (20 F) to keep the haze from coming back. I'm sure I don't have to add that you want to get a acid washed or low calcium and low magnesium filter media or you are just introducing a potential haze producer to your spirit.