Thanks for the advice! It will be an apple-grape wine with target ABV of around 5%. Thinking more about it, I suppose a heat treatment would be doable after disgorgement and dosage. I've done this before with ciders with good success. I am just not sure how well the bottle would hold up to the heat expansion with 3-4 volumes of carbonation in it at heating. Would that be doable? It would be a 750 mL 29 mm bottle rated to 5.5 volumes with cork and cage.
Apple by itself should ferment dry to yield 5 to 5.5% ABV
Grape by itself should ferment dry to 10 to 14% ABV.
,,, It will be hard to create a 5% alcohol beverage. French traditional methods involve creating a calcium pectate skin floating on the cider and pulling much of the nutrient out of the beverage. By adding grape into the mix you put tartaric acid in the mix which does not Keeve.
,,, A heavy champaign bottle should survive the pasteurization step. The main risk is cracking by quickly cooling the glass.
,,, Factory methods would take a glycol chilled tank to chill the ferment when it is at 5% ABV leaving several percent residual sugar/ kill the ferment by adding acid to get below pH 2,5/ > clean up the beverage as with bentonite fining agent/ or filtration through several stages of coarse to fine filter/ or spin it in a centrifuge. > A US factory would then sterile filter followed by carbonating with a tank of CO
2.
As a personal note I find highly carbonated beverages hard to serve. They really need to be cold or they are messy.
,,, Conceptually a 5% ABV high sugar beverage is hard to produce, especially using tools at home. I could see fermenting in a stainless corny keg and killing the ferment as pasteurizing at target residual sugar. > clean up the lees > bottle. BUT the minute you apply a dosage the work of stopping the ferment would be lost since adding a natural carbonation yeast starts the process up again. ,,,,, I can see a finished 13% ABV beverage with lots of yeast floating in it.
,,, technically you are making a grape/apple cider. Looking at techniques Cider folks have success with is a good place to start.