Tamarind is very sharp-tasting because of its high tartaric acid content, and is one of the most popular souring agents used in dishes in the majority of tropical countries. Although it may often seem very moist, tamarind should never go mouldy as its high level of acidity acts as a preservative.
Recipes will generally call for a quantity of tamarind water, typically two tablespoons to a cup, to be added during cooking. To make tamarind water from the hard tamarind block, break off a walnut-sized piece (a 2 cm diameter ball) and put it into half a cup of hot water. Stir it around with a spoon and leave for about 15 minutes. Strain the liquid off, squeezing the remaining pulp as dry as possible before discarding it. Tamarind water can be made in large batches and frozen into ice cubes to drop into cooking whenever the fruity tang of tamarind is required.