What is it?
Tartaric acid is a dicarboxylic organic acid found naturally in many fruits, most abundantly in grapes, tamarinds, and bananas. Commercially it is recovered as a by-product of wine production, where it precipitates as cream of tartar (potassium hydrogen tartrate) on the inside of fermentation tanks. The food-grade form used as E334 is predominantly the naturally occurring L-(+)-tartaric acid enantiomer.
What does it do?
As an acidity regulator it lowers and stabilises pH in food and drink, which inhibits microbial growth and enzymatic browning, and improves the stability of other additives such as antioxidants. Its sharp, clean sourness also functions as a flavouring. In bakery products it reacts with sodium bicarbonate as a leavening acid. In confectionery it provides the sharp 'bite' of sour sweets.
Where you will see it
Found in wine and grape juice (where it occurs naturally and may also be added), sour sweets and confectionery, carbonated soft drinks, bakery powder and baking mixes, fruit preserves, jam and marmalade, and some canned fruits. On a UK label it appears as 'tartaric acid', 'E334', or within the ingredient 'cream of tartar' (E336).