I juiced my crabapples here in UK where they are not very sweet. I left the juice in fridge for a month just with clingfilm on top and a couple of inches of air at top. It now has gunk on top. I’d love your advice. I thought I would use this juice to flavour sauces and to drink, instead of adding loads of sugar to make a jelly as planned. Is it safe to drink? Do I need to heat it first? I have bought book on fermentation but am nervous to use this juice without understanding what has grown on top. I have to be extra careful for my husband. Thank you so much!