Our own homemade wines seemed to have an acidic taste similar to the bite you would taste from a grapefruit or a lemon and we suspected that this acid bite was coming from the acid blend.
Upon questioning our wholesaler we learned that their acid blend was a 50-40-10 mix of citric, malic and tartaric acids. Research on the internet told us that years ago acid blend was a 40-40-20 blend of tartaric, malic and citric acids. Comparing the old formula with the new formula showed a 30% increase in citric acid and a 30% decrease in tartaric while the malic acid level remained unchanged. Why the change? I suspect it is economic! Tartaric acid is much more expensive than citric acid.
Although we do not know for sure (we think we do!) that the acid bite was coming from the high citric levels in our acid blend, we have since stopped purchasing pre-mixed acid blend and the acid blend sold at BlueStem Winery (or on the web at http://www.bluestemwine.com/) is a 50-40-10 mix of tartaric, malic and citric acids. Our citric bite has gone away. Our acid blend is a little more expensive but we think the results justify the increased cost.