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View Full Version : How much k-meta and k-sorbate to add?



Ghost99
12-19-2015, 06:50 PM
Hi Guys,

I have two gallons of dry raspberry mead I'd like to stabilize (separated in to two 1-gallon jugs). I have some k-meta and k-sorbate and would like to know how much to add to get this process going? There's currently about a 1/2 of lees on the bottom of jugs and it's clarified really nicely so I figured now's the time.

The recipe was:

7lbs of Clover Honey
2 gallons spring water
1 lb frozen raspberries thawed to room temp (long since racked away)
5 grams ec-1118
1 teasp go ferm
1 teasp fermaid-k.

Current gravity is .092 (very dry!)

I've read a lot of different posts on the subject and all seem to have varying advice.

Thanks for any help

fatbloke
12-20-2015, 05:38 AM
Depends on what form the sulphites are in. It'd normally be 1 campden tablet (crushed) per gallon. Or if you have the K-met as powder, make up a 10% solution (1 powder to 9 water - actual quantity depends on how much you need, I usually make it up a litre at a time, then it lives in a hand spray).

From the powder solution, 5ml per gallon.

For the sorbate, it could depend on the make but usually it's something like a half teaspoon per gallon - check the label though........

And always use both. You can get away with just sulphites for preservation, but if you're back sweetening you need both.

Never just sorbate on its own as that can leave you at risk from geraniols if you get wild MLF bacteria in. The sulphite prevents that........

pwizard
12-20-2015, 01:21 PM
I always use 1 campden tablet and 2/3 tsp sorbate per gallon. I crush the tablet, add the sorbate, mix them up with a little bit of water, and pour the mixture into the aging jug. After that, I let it rest for at least 24 hours to give the chemicals time to work if I plan to backsweeten.

Like Bloke said, sorbate on its own can create funky tastes that may or may not go away over time. Same goes if you add too much.

fatbloke
12-20-2015, 02:23 PM
I always use 1 campden tablet and 2/3 tsp sorbate per gallon. I crush the tablet, add the sorbate, mix them up with a little bit of water, and pour the mixture into the aging jug. After that, I let it rest for at least 24 hours to give the chemicals time to work if I plan to backsweeten.

Like Bloke said, sorbate on its own can create funky tastes that may or may not go away ovber time. Same goes if you add too much.
No, what I was alluding to, is that sorbate will do it's job if used on its own, but if wild MLF bacteria is present, it metabolises the sorbate into geraniols - chemicals that actually smell of geraniums. If that occurs, they won't disappear, the batch is ruined.

If you wanted MLF purposely like with many wines, that needs to complete before stabilising etc. The MLF bacteria is neutralised by the presence of sulphites above 20ppm, and 1 campden tablet per gallon or 5mls of 10% sulphite solution provides 44 or 50 ppm sulphite depending on whether it's imperial or US gallons. Hence if you don't want MLF or the problematic geraniols, you need to use both sulphite and sorbate

Ghost99
12-20-2015, 04:01 PM
Thanks for the advise so far. The packages say for k-meta, use 5 grams and for k-sorbate, use 4 grams. Interestingly, neither say use _grams per quantity, so it's not very helpful! I've got 1 teaspoon of k-meta + 1/2 teaspoon of k-sorbate currently dissolving in a bit of water. I'll add this to the aging jug before racking onto it. Hopefully this is the ticket!

zpeckler
12-20-2015, 06:59 PM
The best reference for sulfite addition I've come across comes from the book "The New Cidermaker's Handbook" by Claude Jolicoeur. It's obviously a book on cidermaking, but there is a ton that was very applicable to me as a meadmaker. The book has a lot of hard science content, which I have found somewhat lacking in other meadmaking resources.

Chapter 14 has a rundown of sulfite. The book goes into the difference between concentrations of free and bound sulfite, which is kinda outside the scope of the home meadmaker as it involves testing with commercial level equipment.

One thing to know is that for complete antiseptic action at the beginning of your batch--prior to yeast inoculation--the needed concentration of sulfite varies by pH. At 3.5 you need 100ppm, at 3.6 you need 125ppm, at 3.7 you need 150ppm, at 3.8 you need 175ppm. He doesn't talk about higher pH's unfortunately, as cider is typically fermented at lower pH's than mead. I have been operating under the assumption that things are probably ok with about 200ppm at a pH of 4 or above.

For sulfite additions after fermentation is complete he recommends about 50ppm. Less is probably ok if you're just trying to protect from oxidation. More if you're trying to prevent a restart in fermentation. I think if you're trying to prevent a fermentation restart you'll probably need the same levels you'd need if you're adding the sulfite prior to yeast inoculation.

So about the doses of sulfite. Campden tablets offer too little leeway to get very specific concentrations of sulfite, so I've stopped using them. I personally prefer potassium metabisulfite in loose powder form. You can't get accurate or precise measurements of powders measuring by volume, so I dose everything by mass (yeast, nutrients, bicarb, and sulfites). The scale I use (http://www.amazon.com/American-Weigh-Scales-ACP-200-Digital/dp/B003STEIYY/ref=sr_1_1?ie=UTF8&qid=1450651523&sr=8-1&keywords=American-Weigh-Scales-ACP-200-Digital) is accurate and cheep.

By mass, 57% of K metabisulfite is sulfite. We can round this down to 50% for simplicity's sake. Basically, 100g of K metabisulfite will yield 50g of sulfite.

Now remember that ppm = mg/L. So for example, if you're trying to get a sulfite concentration of 100ppm, that's equivalent to 100mg of sulfite per liter of must.

To calculate the amount of K metabisulfite to get a desired concentration of free sulfite, use the following equation:
(desired sulfite concentration, ppm or mg/L) x (volume of must, L) x 2 x 1g/1000mg = mass of K metabisulfite in g

You need 200ppm sorbic acid in the must to inhibit yeast division, which corresponds to 257ppm potassium sorbate:
(257mg/L K sorbate) x (volume of must, L) x 1g/1000mg = mass of K sorbate in g


Good luck! Let me know if you have any questions.

Ghost99
12-22-2015, 05:12 PM
Many thanks for these helpful replies and especially to you Zpeckler! Very informative stuff. I'll order up a copy of "The New Cidermaker's Handbook" for good measure.

I ended up adding 1/2 teaspoon of sorbate and 1 teaspoon of K-meta to each gallon, and have let it sit for about 48 hours. Hopefully this did the trick and I can go ahead with backsweetening prior to bottling!

zpeckler
12-22-2015, 06:29 PM
Thanks, man. "The Cidermaker's Handbook" is a really fascinating reference. I've never made cider; I bought it because it's a great book with a lot of fermenty science in it.

You do have to take things with a grain of salt, though. For example: He has a chapter on titratable acidity in cider, which has zero application in meadmaking because honey's acids are different from apples' and has different buffering properties.

I think there are probably more than a few meadmakers out there who would think that the sulfite levels Jolicoeur recommends are excessive. After all, honey has it's own antiseptic properties, which apple musts lack. Apple skins have much higher levels of wild yeasts and bacteria than honey, and those microbes end up in cider must. In my personal meadmaking practices I actually don't add sulfite in the beginning! I rely on the honey's natural properties, meticulous sanitation, and pitching big volumes of yeast to stave off contaminating organisms.

Oh, I almost forgot. If you are using the "full strength" sulfite doses for antisepsis prior to pitching your yeast, wait at least 24hrs after adding the sulfite. Sulfites will also inhibit the activity of the yeast you pitch, and waiting gives them a chance to kill all the spoilage microbes and become less active.