Stopping Juice from natural fermentation

[menace]

I have a wild fruit (from the ficus family) that I would like to make alcohol from. The juice seems to ferment immediately after extraction. The ambient temperature here is high 20s C +.

1. Is there any advice on how I can extract juice and stop fermentation so that I can collect sufficient volume of juice to process in one hit?
2. Is there any additive that will stop fermentation without impacting taste?
3. Is there any way of neutralising wild yeasts? Hopefully this will allow me to use standard yeast to ensure consistency.