Filtering out ML bacteria

You'd need a 0.45 micron _absolute_ sterile membrane to filter out ML. A

0.5 micron nominal pad won't do it. Same goes if you are trying to remove yeast from a sweet wine.

Tom S

This whole business of filtering out bacteria just doesn't make any sense to me. As a person who has to rely on sterile technique, I can say that there's no half way point with sterility. Things are either sterile or they're growing bugs, though possibly not in as high numbers. When you use a filter, there's lots of leakage and dripping, so even if the filter was 0.45 microns, there would still be contamination.

Add to that the fact that there has GOT to be a variation in the pore size. Even if the average size is 0.45, then there have to be some pores that are much larger.

I think filters do a great job in clarifying wine, but I've never had any luck filtering out organisms.

Lee

I guess this question is for Lum, will the set up he has documented in his manual have the ability to sterile filter the wine with those $25 water filters?

Bob

Lee - I used to deal with sterilization (pharmaceuticals - injectables, preparation of sterile water for mfg. of liquid products, etc.) in my work. We relied on filtration, albeit with 0.22 micron absolute filters, plus an integrity check after filtration. IMO filtration can be used to remove bacteria and yeast cells. Of course most home winemakers don't have the ability to check filter integrity. And in my basement there is great potential for contamination downstream from the filter. Still if you are careful in your preparation, use 0.22 micron filters, sanitize the filter tubing and receiving vessels you can knock the numbers of organisms down significantly if not totally. I would much rather filter a sweetened wine before bottling than just bottle and hope for the best.

Bill Frazier Olathe, Kansas USA

That's true - but sterile filtration is orders of magnitude better than any alternative. IOW, it's pretty damn good.

Things are either sterile or they're growing

Exactly! Orders of magnitude lower.

When you use a filter, there's

Are you assuming that because a filter is leaking that it has also to be backstreaming? Probably not.

Nope. That's why it's called an _absolute_ filter. And let me tell you, those suckers are _expen$ive_!

As far as determining whether the filter is capable of true sterile filtration, it's necessary to run a bubble point check on it. IIRC, you push water through the filter using gas (nitrogen), increasing the pressure slowly until the gas pushes through the membrane and produces bubbles on the other side. The pore size can be calculated from the pressure required to do this, which is a function of pressure and surface tension of water.

You've never used a sterile membrane cartridge filter. They do this quite well. The one thing I don't like about them is that they have a plasticy kind of smell that they impart to the first few gallons of wine - at least when they are new. Run some hot water through first. That helps get rid of it.

Tom S

Hi Bob, the answer is no. Those $25 filter housing do not provide an adequate seal with the membrane filter cartridges. lum

Thanks Lum,

I was thinking about getting the Super Jet Buon Vino but noticed that their "sterile" filter pads are .5 microns . I searched this newsgroup and found another thread pertaining to this very subject. I guess .5 microns isn't "sterile" enough to inhibit MLF so I'm not sure what good the Super Jet is over a plain $25 plastic cartridge filter. Do you or anyone else out there have any suggestions , advice, experience with a fairly inexpensive way of sterilizing 100 gallons of wine? Should I just use sorbate instead? To explain the sitiuation exactly, I have 100 gallons of eastern chardonnay that I'm about to add bentonite to and cold stabilize. I'm looking to make the wine semi-dry( more towards the semi than the dry ) and want to inhibite MLF in the bottle. I am going to add sugar to the wine because it is dry now. Should I just "rough" filter it and address the re-fermentation and MLF in the bottle problem with sorbate and SO2? Any input would be greatly appreciated.

Bob

Sterile bottling involves more than just putting wine through a tight filter. Bottles, corks, corker, etc must all be sterile.

We use the following technique to make an off-dry wine at the winery every year: (1) Add frozen juice (or sugar) and potassium sorbate to the wine. (2) Adjust the molecular SO2 to 0.8 milligrams per liter. (3) Remove as much yeast as possible with a tight pad filtration. (4) Observe the wine for several weeks to be sure it is stable before bottling.

Good luck Lum, Del Mar, California, USA

Thanks Lum. I assume a tight filter is .45 microns or less. Do you have any recommendations for small scale wineries/large scale home winemakers as far as a filtering system goes?? Any input would be greatly appreciated.

Bob

It depends on the amount of wine being made. For small amounts (less than

50 gallons) I would use a $25.00 plastic housing and a $8.00, 0.5 micron (nominal) filter cartridge. That will remove most of the yeast and some of the bacteria, and it will filter 25 to 50 gallons of clean wine.

For larger amounts, I use a 20 by 20 cm pad filter holding four to eight pads. I buy 40 by 40 cm, one micron porosity pads and cut them in four pieces with a box knife. That way, each 20 by 20 pad costs about $0.40 and four pads will filter 50 to 60 gallons of clean wine. BUT, the filter plates for a pad filter will cost about $150.

Lum Del Mar, California, USA

Bob, I have no recommendation at this time. I would have recommended Marcon Filters several months ago, but Mr. Marcon passed away and the filter plates are no longer available.

Lum Del Mar, California, USA