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Berrypie:
Please, does anyone know of a proven method that can be used to preserve Zobo drink and Pineapple juice? In other words, how can I prevent my pineapple juice or Zobo drink from fermenting? How can I maintain the taste without the drink's taste going bad/sour?

freeze it

Generally, the activities of fermentation microbes are inhibited when the degree of temp is aggresively lowered. Although some microbes are on the other hand activated by that. That said, cooling or even freezing will help preserve the juices for few more days.

Go to the market and buy preservative.apply and hope it preserves the taste for 3days.if you freeze zobo,it still loses its taste.

You can use lemon juice.

ThePost:
Generally, the activities of fermentation microbes are inhibited when the degree of temp is aggresively lowered. Although some microbes are on the other hand activated by that. That said, cooling or even freezing will help preserve the juices for few more days.

Thanks, although freezing is out of the option. I am actually looking for other proven methods.

NoToPile:
You can use lemon juice.

In what proportion please?

Jafar1:
freeze it

Thanks but I don't want this option.

Lalasticlala please I need the help of professionals on this topic. Google isn't forthcoming.

Flash pasteurization.
I worked on this sometime in 2012. IMO, it's a better route if you don't want to go through the preservative path ie sodium benzoate.