making dessert/sweet wine

I am making a gallon of dessert/sweet raspberry wine. I know the basic tecnique is to add sugar until you kill the yeast.
At which point in time do you stop adding sugar?

Why would you add sugar to kill the yeast ? You need the yeast to make the alcohol. I don't think you have it right. Or either you asked your question wrong and I am not understanding. Just to clarify though, you never kill the yeast when making wine for no reason.

sashurlow said:

I am making a gallon of dessert/sweet raspberry wine. I know the basic tecnique is to add sugar until you kill the yeast.
At which point in time do you stop adding sugar?

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By continuing to add sugar until the yeast dies, you'll end up with a high alcohol wine. It may work well with a sweet dessert wine.

If this is your goal, keep adding sugar until you see no more fermentation activity.

Once the fermentation activity stops do you add more sugar to make it sweet or will it be sweet enough at that point in time?
After adding another cup of sugar recently its bubbling but just barely, so I'm pretty sure I'm at that point now.

sashurlow said:

Once the fermentation activity stops do you add more sugar to make it sweet or will it be sweet enough at that point in time?
After adding another cup of sugar recently its bubbling but just barely, so I'm pretty sure I'm at that point now.

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That is something you will have to taste to determine. As pointed out previously you are gonna add enough sugar to get the alcohol high enough that the alcohol will kill the remaining yeast at which point there will be some residual sugar remaining. Is that sweet enough? Only your taste buds will know for sure.

Adding sugar is fine if you're using a sweet/medium yeast (they have lower alcohol tolerance so you don't end up with ridiculously alcoholic wine). If you use a champagne-yeast or anything similar, this method is a bad idea.

The more reliable method is to let it ferment-out, then add stabiliser (meta and sorbate) to kill-off the yeast. Then you're free to add sugar without it being fermented.

I'm using a combination of Montrachet and Cote des Blancs. I have two gallons of "real" raspberry wine, this is the yeasty stuff left over from primary fermentation, so its an experiment wine. I've also read that raspberry wine is better done dry, so that makes this even more of an experiement.

I have yet to enjoy a dry raspberry wine as I find residual sugar brings the fruit forward. But I am sure there are those who enjoy dry raspberry wine. As far as knowing whether or not your method will result in dry, semi-sweet..you must rely upon your hydrometer. You should take measurements after you add your incremental sugar and monitor. Bubbles really are a poor indicator of end point of fermentation.

When you say you have two yeasty gallons of 'real' wine leftover from primary I do not really know what you mean.

What was the startingSG of this wine and how much sugar has been added since the start of fermentation? The technique of stepfeeding with sugar to reach alcohol toxicity and not typically done with the everyday batch.

I have three (and a half) gallons. Two gallons are off the top of the primary. I also tried to reuse the fruit for another gallon (per directions) but it is definetaly less concentrated. The yeasty gallon came from the bottom of the primary and topped off with the dilute second batch. This gallon is my dessert experiment. It would have normally been thrown out, so why not try something with it.
I didn't use a hydrometer this year. I may be nuts but I'm not going to be overly scientific this year. I'm following directions and/or just going with it.
Next year I am expecting an over abundance of raspberries and blackberries, so I will try new things next year.

sashurlow said:

I have three (and a half) gallons. Two gallons are off the top of the primary. I also tried to reuse the fruit for another gallon (per directions) but it is definetaly less concentrated. The yeasty gallon came from the bottom of the primary and topped off with the dilute second batch. This gallon is my dessert experiment. It would have normally been thrown out, so why not try something with it.
I didn't use a hydrometer this year. I may be nuts but I'm not going to be overly scientific this year. I'm following directions and/or just going with it.
Next year I am expecting an over abundance of raspberries and blackberries, so I will try new things next year.

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Wine lees don't taste good, and yeast that have been in the wine already have experienced some alcohol poisoning. I never reuse wine yeast due to that, except for rare stuff like if I was making "skeeter pee".

I've also heard of the 'add sugar slowly until the yeast can't take anymore' method, but being inexperienced personally, I would be fearful that the yeast were still processing slowly - perhaps too slowly for me to see. Isn't there risk of bottle bombs from gradual pressure increase after corking? Better living through chemistry, I say - add the sorbate and sulfite.

Or from another perspective, I just had a port kit chew through a total gravity point change of .147 before I stabilized it and added sweetener (1.132 -> 1.010 + .015 after extra sugar, down to 1.000 ). Just how much alcohol are you willing to have in your final product to make it sweet? In this case the kit was designed for that, but another wine might not be drinkable.

airving said:

I've also heard of the 'add sugar slowly until the yeast can't take anymore' method, but being inexperienced personally, I would be fearful that the yeast were still processing slowly - perhaps too slowly for me to see. Isn't there risk of bottle bombs from gradual pressure increase after corking? Better living through chemistry, I say - add the sorbate and sulfite.

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This is why you use a hydrometer, track the chaptalization and have patience. If there are any live yeast when you bottle, sorbate and k-meta will not prevent them from eventually utilizing any residual sugar. You may think all is well and months down the road you have corks pop...a classic reason to bulk age...IMHO

I thought that was the purpose of adding k-meta and sorbate: to stop any live yeast from starting further fermentation. Note that I'm not suggesting trying to stop an active fermentation: everything I've read says to add those prior to back-sweetening and you should be safe. Is that not your experience?

airving said:

I thought that was the purpose of adding k-meta and sorbate: to stop any live yeast from starting further fermentation. Note that I'm not suggesting trying to stop an active fermentation: everything I've read says to add those prior to back-sweetening and you should be safe. Is that not your experience?

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It is safe as long as your ferment is complete. It is a fine line. If you have live yeast in the wine, and fermentable sugar...they will use the sugar and then die off in the presence of k-meta plus sorbate. K-meta and sorbate does not kill the yeast, just stop them from reproducing. Hence the recommendation of fermenting dry, racking, then allowing to clear, degas, stabilize with k-meta and sorbate, backsweetening and monitoring with hydrometer checks to confirm it is stabilized. Or if you chaptalize you can aim for a planned for residual sugar plus yeast die off due to alcohol toxicity..it works once you get the hang of it.

I actually had an entire case of commercial wine bottle ferment six months after I bought it. Turns out it was not dry when stabilized and backsweetened. The cool storage temp kept things at bay, but when I grabbed one bottle and it warmed up in transport...well let me just say my car trunk needed major cleaning. Lost the rest of it for same reasons. It was sparkling when opened cold but nasty stuff. Refund given.

How long will yeast live under normal circumstances? If you are simply preventing them from reproducing then they will eventually die without replicating.

sashurlow said:

How long will yeast live under normal circumstances? If you are simply preventing them from reproducing then they will eventually die without replicating.

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The yeast will be active as long as there is sugar or live until it reaches its alcohol limit.

One the sugar is used up, the cells will die off. At this point you can add k-meta and sorbate, then back sweeten.

When back sweetening do you need to use both campden and sorbate? Or just one?

Nwa-brewing said:

When back sweetening do you need to use both campden and sorbate? Or just one?

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They need to both be used together because they do different things, but it has been found by many that if you add sorbate without the presence of adequate campden/k-meta then the wine may start to referment. They complement each other.