Determining sugar addition of a homemade adjunct?

[witko]

Let's say one was to take some home made fruit jam and add a good portion of that to a beer, any ideas on how to get a reasonable calculation of the sugars you'd be bringing to the party?

I've got this amazing Quince paste that I recently made and I was thinking of adding a cup or two to simple ale, to try to bring out some of those wonderful floral notes that the jam has. Problem is, I'm not really sure how to calculate that addition. Was thinking I'd either add to last 10 minutes of boil, or even just drop into fermentation after high krausen.

Would it be as simple as just looking back at my recipe and dividing the total amount of sugar used in the recipe by the portion of jam I use in my brew? So for example, if I used 4 cups of sugar and made 8 cups of jam, and put 2 cups in my brew, for the purposes of my recipe calculations should I just put 1 cup of sucrose? I realize there would be some fructose there from the fruit as well, but from what I understand Quince is relatively low in fructose and the long cooking process would also get rid of a lot of it.

Thoughts?

 

[daksin]

I'm not really sure. I would just make a beer with the characteristics you want, ignoring the jam addition, and then just add jam to it. The fruit won't make a big difference. You're right though, the sugar will be evenly distributed among your jam jars so you can assume that 1 jar equals whatever fraction of the sucrose you added. Fructose doesn't go away with cooking though.

Anyway, unless you absolutely need to know the exact ABV of this brew, I'd just add it. I'd go after fermentation slows down- heating the jam may cause the pectins to set giving you a nasty haze.

 

[zmanzorro]

Don't forget to take the water in the jam in account as well. If you have a refractometer, I'd mix in a known amount of water with the jam and take a reading.

 

[Calder]

I'm guessing it has already been boiled when you made the jam. You can add it to the boil and check gravity in the fermenter.

OR you can add it after kraeusen is done, and then use an hydrometer AND a refractometer to measure FG, and back calculate your OG.