Yeast washing?

Forum for all brewing related questions and information

Moderators: triple-oh_six, yeastmeister

Yeast washing?

Postby thebuddrik » Sat Jan 10, 2009 5:07 pm

I just racked an Irish Red to secondary and wanted to try to save my yeast. Not really sure on what to do, I sanitized a small mason jar and just dumped in the yeast and trub. Is washing 100% necessary? How long would it stay good if washed and kept in the fridg?
User avatar
thebuddrik
 
Posts: 391
Joined: Wed Sep 10, 2008 8:36 pm
Location: Lafayette, La.

Postby Imakewort » Sat Jan 10, 2009 11:38 pm

do you really want to be a yeast rancher? Here is a place to start.
http://www.alsand.com/beer/yeast/index_E.html
and then we have this. This part it is a completely different side of brewing, Have fun this is what breweries do, remember bacteria is not your friend. i just make a new batch of yeast every time from my working slants, if needed I make a new working slant from my master slants :)

The New Brewer, September-October 1998
COMING CLEAN
A NEW METHOD OF WASHING YEAST USING CHLORINE DIOXIDE
By Dana Johnson & Katie Kunz

Immersed in the hustle and bustle of a busy brewery, it is easy for one to forget that yeast is a living entity that requires special care, that it is something more than just another brewing ingredient.
Yet even with that yeast-care is a very touchy subject among brewers. Ask ten brewers how they handle their slurries and you'll probably hear ten different answers. Washing yeast is one of the more controversial practices - some breweries rely on it, while others avoid it all together. In this article, we will review the most commonly-used method of washing yeast, and will introduce a new procedure that is being explored at some breweries.

Tried And True
The "tried and true" method of washing yeast utilizes phosphoric acid (H3PO4) to acidify the yeast slurry to around pH 2, where it is held for a given amount of time, ranging from two hours to overnight. In theory, undesirable organisms are destroyed by the low pH and trub is removed from the yeast. The healthy yeast remains suspended and is used for pitching, while dead cells and trub collect at the bottom of the washing vessel.
However, there are several problems with acid-washing. It reduces the populations of most wort-spoiling bacteria, but is less successful with beer-spoilers such as lactic-acid bacteria, and is generally not effective on wild yeasts and molds(1). Further, the low pH tends to stress the yeast, and for this reason most breweries wash with acid only rarely. Recently, a few breweries have begun using an acid-free wash that allows them to wash their yeast on a regular basis.

An Alternative Method
Chlorine dioxide (ClO2) has been used for decades to disinfect drinking water. In this scenario, chlorine dioxide kills by penetrating the hydrophobic region of the bacterial membrane and oxidizing it(2). Chlorine dioxide reacts with sulfur-containing amino acids, which form cell membranes. The proteins get destroyed, the membrane ruptures and the organism dies(3).
Chlorine dioxide is relatively new to the brewing industry. It is gaining acceptance as a post-rinse sanitizer, but is not widely-recognized as a yeast-washing agent. Given what is known about it, however, it makes sense that it might be an effective, economical and safe alternative to phosphoric acid.
Chlorine dioxide has (in theory) over 2.5 times more oxidation capacity than elemental chlorine but does not have a chlorine-like flavor profile. Chlorine dioxide does not form trihalomethanes, as does sodium hypochlorite (household bleach) and iodophors, and breaks down to innocuous compounds, namely table salt and water(4).
Breweries that use chlorine dioxide to wash yeast begin with a measured amount of sodium chlorite solution, which is "activated" to release ClO2 by pouring it into a small amount of acidified water. The activated solution is then immediately added to the yeast slurry and mixed well. In theory, the chlorine dioxide that is released "washes" the yeast in as little as five to ten minutes, depending on contaminant-levels. The yeast can then be pitched immediately or stored refrigerated until needed.
The small breweries currently using chlorine dioxide for this purpose do so without any yeast performance problems. Most, however, do not have the means to check yeast viability and test contamination levels.
Low (1-2) parts-per-million (ppm) levels of chlorine dioxide kill organisms such as wort-spoilers, but not much is known about its efficacy against the myriad contaminants that can find their way into a brewer's yeast. Our purpose here is to begin finding out.
There were two questions we wanted to answer: Does washing yeast with chlorine dioxide reduce the number of spoilage organisms? Does washing yeast with chlorine dioxide have any effect on the viability of the yeast? Testing the long-term stressing effect of chlorine dioxide, such as on the formation of petite mutants, will be the subject of subsequent studies.

Test Procedure
Two different strains of pure ale yeast were propagated using unhopped malt extract and stored at 4° C (39° F) for about two weeks. Just before testing, each was dosed with a mixture of Acetobacter, Lactobacillus, Enterobacter and wild yeast. Six clean and sanitized glass growlers were divided into the following two sets:
• Yeast #1 water-wash (negative control)
• Yeast #1 acid- wash (using Wyeast's protocol, pH 2.2)
• Yeast #1 ClO2 -wash (using tentative brewery protocol, 20-50 ppm actived sodium chlorite)
• Yeast #2 water-wash (negative control)
• Yeast #2 acid-wash (using Wyeast's protocol, pH 2.2)
• Yeast #2 ClO2-wash (using tentative brewery protocol, 20-50 ppm actived sodium chlorite).

One liter of 4° C-water was added to each growler. Each yeast slurry was distributed equally among the three growlers in its set, which were then tightly capped and inverted for good mixing. The viability and cell-counts of each was read using the methylene-blue staining method and hemacytometer. The slurries' cell densities differed by a factor of 1.5, which reflected their distinct growth characteristics in the malt extract.
Contamination levels were tested by drawing a 0.1 ml sample from each and plating onto LMDA medium. All plates were incubated aerobically for 84 hours at 30° C (86° F) and checked for colony forming units (CFUs).
The "water-wash" slurries were stored at 4° C for two hours and inverted every 15 minutes to keep the yeast suspended. After this time, each was tested in the same manner as before for viability and contaminants.
The "acid-wash" slurries were treated with 2.5 ml 85% phosphoric acid each, giving a pH 2.2, and were stored at 4° C for two hours and inverted every 15 minutes to keep the yeast suspended. After this time, each was tested in the same manner as before for viability and contaminants.
The "ClO2-wash" slurries were each treated with 50 ml activated sodium chlorite (0.5 ml of 8.3% sodium chlorite concentrate, added to 100 ml cold water which had been acidified to pH 3), which was calculated to yield 20-50 ppm in the volumes treated. The activated sodium chlorite concentration of each slurry was measured using a sodium chlorite titration test kit.

TABLE ONE: YEAST COUNT AND VIABILITY
Sample Name Initial Cell Count % Viability Before/After
Yeast #1, Water 2.7 x 108 98/98
Yeast #2, Water 1.8 x 108 96/96
Yeast #1, acid 2.7 x 108 98/84
Yeast #2, acid 1.8 x 108 96/92
Yeast #1, ClO2 2.7 x 108 98/98
Yeast #2, ClO2 2.7 x 108 96/96

TABLE TWO: YEAST WASHING EFFICACY
Sample Name Lacto Count CFUs Before/After Aceto Count CFUs Before/After Entero Count CFUs Before/After Wild Yeast Count CFUs Before/After
Yeast #1, Water 1050/1050 520/520 6/3 37/27
Yeast #2, Water 1050/1050 6/6 7/3 41/50
Yeast #1, acid 1055/55 520/0 6/0 82/68
Yeast #2, acid 1050/57 4/0 5/0 36/70
Yeast #1, ClO2 1050/0 520/0 7/0 38/81
Yeast #2, ClO2 1050/0 6/6 3/0 54/69

TABLE THREE: THE TRANSFORMATION OF SODIUM CHLORITE INTO CHLORINE DIOXIDE AND BY PRODUCTS
5NaClO2 + 4H+ ----> 4ClO2 + 4Na+ + Na+Cl- + 2H2O
(sodium chlorite) (acid) (chlorine dioxide) (sodium ion) (table salt) (water)

CONCLUSION
Not surprisingly, washing the yeast with water affected neither viability nor contamination levels.
Phosphoric acid did a good job of removing the gram-negative spoilers tested and reduced the Lactobacillus population by about 20 times. As impressive as this may be, it is unsatisfactory because the levels remaining are 180 times above those generally tolerated. Three CFU's-per-1.0-ml is considered acceptable, as opposed to the 55-per-0.1-ml listed in Table 2.
While phosphoric acid did a respectable job of destroying the bacteria, the viability of the yeast suffered to varying degrees (~14.5% and ~4%). It also seems to have had no effect on the wild yeast.
Chlorine dioxide appears to have cleared both slurries of bacteria quite thoroughly, even at the 13-ppm-levels we achieved, without decreasing the viability of the yeast. This was accomplished inside of ten minutes, rather than over the two-hour period required for the acid wash. The six CFUs of Acetobacter appearing after treatment at ten minutes were gone when the slurry was tested again at 24 hours. Since chlorine dioxide is gaseous and dissipates quickly, this effect may be explained by residual "unactivated" sodium chlorite being "activated" over time by the acids produced by the remaining contaminants. As with the acid-wash, chlorine dioxide had no discernable effect on the wild yeast population.
While our test was not intended to be definitive, it shows that chlorine dioxide may be an effective alternative to phosphoric acid as a yeast-wash. The primary advantages of chlorine dioxide are that it can destroy the tougher spoilers without compromising the yeast's viability, and is safer to handle.
All this having been said, remember that there is no substitute for proper sanitation. The best way to keep undesirable organisms from infecting beer is to keep all the equipment clean, sanitized and unexposed.

Dana Johnson has been with Birko R&D since 1979 and a home brewer since 1989. He is Manager of Birko's CON-TACT-ITâ Bacteria Detection System. Katie Kunz is the owner of The Brewing-Science Institute in Colorado Springs, which specializes in yeast supply and laboratory services for microbrewers. She received her B.A. in Biology from the University of Colorado in 1993, and currently serves as Chairman for the local section of the American Society of Brewing Chemists.

References:
(1) Dr. George Fix, Rocky Mountain Microbrewing Symposium, Colorado Springs, Colorado, February 20, 1998
(2) W.J. Masschelein, Chemical Oxidation, 1992, Technomic Publishing Company, Inc., Lancaster, PA, page 170.
(3) Dave Miller, "The Troubleshooter", Brewing Techniques, March/April, 1998, page 28.
(4) Dana Johnson, "Applications of Chlorine Dioxide: A Postrinse Sanitizer that Won't Leave a Bad Taste in Your Mouth, Brewing Techniques, March/April, 1997, page 76.
Imakewort
 
Posts: 438
Joined: Mon Oct 15, 2007 11:44 am
Location: Afganastan

Postby triple-oh_six » Sun Jan 11, 2009 1:45 am

or you could buy a book on it,
couldn't be longer than the post above :lol:
Sorry, I'm drunk :P
triple-oh_six
 
Posts: 740
Joined: Sat Oct 13, 2007 1:04 pm
Location: Lafayette,La.

Postby Imakewort » Sun Jan 11, 2009 9:11 am

he asked how to do it but I still recommend starting a new batch because of the risk of a bacteria infection. If you want more information on yeast handling go to link below
it also has a abbreviated course on yeast washing you can try which does not use any chemicals.http://hbd.org/brewery/library/yeast-faq.html
Imakewort
 
Posts: 438
Joined: Mon Oct 15, 2007 11:44 am
Location: Afganastan

Postby aleguy » Sun Jan 11, 2009 1:59 pm

I'm told by people who have done it successfully, that you can store your yeast in a sanitized container in the fridge for about two weeks before reusing it and re-pitch the yeast at least six times before the risk of infection becomes too great. this is of course assuming you have excellent sanitation habits.
This was a former member who was once a commercial brewer. Of course, yeast is one of the least expensive ingredients in beer and it's probably best to just use fresh for every batch.
You could also just specialize in lambics and farmhouse ales. In that case sanitation is the enemy and infection is actively sought after. Takes a lot of aging though.
User avatar
aleguy
 
Posts: 2112
Joined: Wed Nov 21, 2007 1:36 pm

not as long this time lol

Postby Imakewort » Sun Jan 11, 2009 2:28 pm

I prefer to start a new batch each time, there are problems with reusing a yeast cake, mainly bacterial infection, no matter how clean you are there is bacteria in your batch. I brew for competitions now.

Don’t reuse yeast that was in beer of greater than 8% ethanol. because of pete mutants

# Acetobacter – requires about 10,000 cells per ml to result in spoilage. They increase 20 fold each fermentation; they don’t die out in ferment.

# Lactobacillus & Pediococcus – require 300-500 cells per ml for spoilage.

I scanned a section of one of my brewing books on this subject for the very long above post All breweries should practise yeast washing

QUOTE "Immersed in the hustle and bustle of a busy brewery, it is easy for one to forget that yeast is a living entity that requires special care, that it is something more than just another brewing ingredient.
Yet even with that yeast-care is a very touchy subject among brewers. Ask ten brewers how they handle their slurries and you'll probably hear ten different answers. Washing yeast is one of the more controversial practices - some breweries rely on it, while others avoid it all together.
Imakewort
 
Posts: 438
Joined: Mon Oct 15, 2007 11:44 am
Location: Afganastan

Postby yeastmeister » Sun Jan 11, 2009 2:36 pm

White brothers on the brewing network tonight. Maybe you could call in and ask them, or submit the question via chat.
User avatar
yeastmeister
Site Admin
 
Posts: 1303
Joined: Fri Oct 05, 2007 6:41 am
Location: Lafayette, LA

Postby Imakewort » Sun Jan 11, 2009 6:26 pm

kool thanks I plan on listening in also. strait from the experts mouth :D
Imakewort
 
Posts: 438
Joined: Mon Oct 15, 2007 11:44 am
Location: Afganastan

Postby aleguy » Mon Jan 12, 2009 11:37 am

I don't care how much Acetobacter you have in your slurry. It won't have any effect on your beer as long as there is no free oxygen present. Yeast activity should have scrubbed the o2 out of the wort long before any vinegar could form. at least not enough to impact flavor. Any acetic acid formed in early fermentation would be scrubbed out from the co2 blowoff.
Know the life-cycle needs of all your bacterial friends, and you can relax a great deal.
All three of the micro-organisms you mentioned are considered very valuable in the right circumstances. By learning what they need to thrive, you can not only cultivate them successfully, but you can also learn to discourage them.
User avatar
aleguy
 
Posts: 2112
Joined: Wed Nov 21, 2007 1:36 pm

Postby Imakewort » Tue Jan 20, 2009 1:30 pm

ugh what happened to the last post so if this works out to be a double post oh well, a reply about yeast washing. As stated before I am not a fan of yeast washing or reusing a yeast cake because of the risk of infection or yeast mutations, but top cropping is the way to go, top cropping has been used in breweries in Germany and England since beer was made and is still being used today because your getting almost pure yeast, risk of infection is very small, but the problem of top cropping in a carboy has been difficult up to now, i found a great video on a easy way to do it, the only thing I would add is using low pressure CO2 to help push it out and flush the receiving flask with CO2, Now all I need is 2 stainless tubes for collecting the yeast, you could also use a 2 hole stopper instead of a carboy cap to make hooking up CO2 easier. this is a great way to collect yeast for a starter
http://www.aleiens.com/video/top-cropping-yeast-from-a
Imakewort
 
Posts: 438
Joined: Mon Oct 15, 2007 11:44 am
Location: Afganastan

Postby GuitarLord5000 » Tue Jan 20, 2009 11:17 pm

Northern Brewer sells chlorine dioxide tablets. I've been considering buying some for myself, but have been a bit skeptical. After reading everything above, I think I'll buy some next order and give them a try!

Cheers
Dave
User avatar
GuitarLord5000
 
Posts: 348
Joined: Fri Nov 23, 2007 2:15 pm
Location: Carencro, La

Postby Imakewort » Wed Jan 21, 2009 10:22 pm

let me know how it turns out, and what yeast are you going to try it on, also look at mr. malty to see how much slurry you need to pich so you do not over pitch.
Last edited by Imakewort on Thu Jan 22, 2009 4:25 am, edited 1 time in total.
Imakewort
 
Posts: 438
Joined: Mon Oct 15, 2007 11:44 am
Location: Afganastan

Postby Imakewort » Wed Jan 21, 2009 11:36 pm

here is a great thread from a pro brewer forum discussing this subject about reusing yeast.
http://www.probrewer.com/vbulletin/showthread.php?t=12750
Imakewort
 
Posts: 438
Joined: Mon Oct 15, 2007 11:44 am
Location: Afganastan


Return to DeadYeast Main Forum

Who is online

Users browsing this forum: No registered users and 1 guest

cron