Just got TPA's sour and sweetener. The sour is 20% malic acid in PG. Wondering what a good percentage to start with is. Going to try to make some sour fruit juices. I know sweetener is to be used sparingly. I tasted a drop of the sour, and it was really bitter. I'm hoping it makes my juice tangy without the bitter taste I got from one drop on my tongue. I noticed on one of the older threads about using citric/malic acid that a few people stated no matter how much they added to their liquid, they never got a sour taste. I guess I will find out!