Fermenting Fruit Juice

[JohnDemallow]

I am new. My "prior experience" is limited to ginger beer, sauerkraut and "graduation" with one exploded bottle. Sanitation is by liquid detergent and then boiling water. Where I live it is always between 27-30 degC. I work with small 250ml-500ml batches. I have some manually juiced, 1) apple 2) pineapple 3) pommegranate 4) red grapes happily fermenting, airlock bubbling, for past 2-3 weeks. Tannins are extracted from black tea, cardamom, clove. I have not used potassium metabisulphate, no added sugar, not aiming for alcohol but (back sweetened) taste and carbonation. welcome comments questions from experienced brewers.

 

[RM-MN]

When you ferment fruit juices without adding sugar the fermentation stops when the yeast has eaten all the fruit sugars. Adding sugar at that time trying to back sweeten simply restarts the fermentation and the yeast eat that sugar until it is all gone. If you have the wine in a stoppered bottle the CO2 produced by that restarted fermentation will cause the bottle to burst.

If you add sugar to the juice (and yeast nutrient, fruit juices lack it) the amount of alcohol increases. If you add a sufficient amount the alcohol concentration will kill the yeast before it consumes all the sugar and you get a sweet wine. To get carbonation and the sweet wine you have to figure out when to bottle so you get the right amount of carbonation without bursting the bottles. That isn't easy. The other way to get carbonation is to calculate the amount of sugar to add to the completed wine for carbonation and use a non-fermetable sweetner like Stevia.

 

[JohnDemallow]

Thankyou ! I understand your point about fermentation restarting when back sweetening with table sugar. Once the juice has cleared I intend to rack it, add sugar, babysit to ensure no runaway carbonation/re-fermentation and pasteurize the bottle at 80 degC in hot water bath. That should finish off the yeast leave residual sugar and some carbonation. My volumes are small 200ml/400ml so amount to sugar to generate one/two volumes of CO2/carbonation are too small. ( assuming 1mol sugar -> 4mol CO2; 1mol CO2->22.4liter at STP and 80psi limit for bottles)

 

[Shaika-Dzari]

I'm not sure what you mean by "babysit" but the pasteurization will kill the yeast so you can just ferment, rack if you want something a bit clearer, back sweet to you taste and pasteurize immediately.

 

[JohnDemallow]

Thankyou Shaika-Dzari, I babysit by having a "plastic" coke bottle as "control unit" and normal glass/beer bottles with flip top.
I add sugar and wait for the plastic bottle to go firm and then I put the glass bottles in water and gradually heat up to 80 degC
and separately cold crash/freeze the plastic bottle.