Can unripe grapes be a source of acidulant for food preparation? Obviously it was being used for creating tart taste in foods before the advent of lemon juice which has high concentration of citric acid. The active ingredient in grapes that imparts tartness is Tartaric acid which was known as far back as 800 AD though it was extracted in pure form only in 1769. Credit goes to the French chefs in recognizing the usefulness of green juice obtained from unripe fruits like grapes, crab apples, plums etc in creating special taste and flavor when added to preparations like sauces, condiments, stews, meat products etc and the juice preparation commonly refereed to as verjuice was a standard item in most French pantries.
Tartaric acid is one of the acidulants used by the food industry along with acetic acid, citric acid, fumaric acid, lactic acid, malic acid and phosphoric acid. Acidity is critical for food processing as well as preservation. The famous sugar-acid-pectin gels, which created jams , jellies and preserves, are the basis of an important segment of food industry that processes fruits. Emergence of citric acid as the most important acidulant, probably because of its cost has led to decline of tartaric acid though its role is still critical in specialized preparations like baking powder, emulsifiers as bread improver etc. Besides being an organic acid like other similar ones, tartaric acid in natural form is known to have special inhibitory power against gram negative and gram positive bacteria including Salmonella paratyphi, Bacillus subtilis, Salmonella typhis and Staphylococcus aureus.
The old Verjuice of Midieval times is reported to be resurfacing during the last couple of years with many western cooks rediscovering its special effect in creating highly acceptable taste and flavor profiles in food preparations. Probably sourness was the major taste popular at that time giving Verjuice its prominence in foods. Verjuice is to day made by processing unripe fruits obtained during the thinning process in the vine yards and these half matured fruits have the necessary tartness desired by the cooks. Now it is available in bottles manufactured using modern processing technology to give longer shelf life.
Though green grapes are invariably the raw material most commonly used, in a few cases red varieties are added to create a more attractive product. Like lemon juice, verjuice adds a bright tartness to a wide range of dishes. But it has an advantage over its far more popular competitor. It's a more gentle, subtle tartness, with a faint but definite undercurrent of vegetal sweetness. Because of this, it is more adept at complementing rather than masking other flavors in dishes where it's used. Because of all this, verjuice is considered a good choice for deglazing the pan after sautéing fish or chicken as it adds just the right touch of tart, with no harshness in the background.
In India Tamarind fruit is the most commonly used acidulant and same tartaric acid contributes to the acidity of this food ingredient. Tamarind is grown in Asia, Africa and American continent, leading producers being India, Brazil, Mexico, Costa Rica, Guatemala, Cuba, Puerto Rico etc. While in most cases ripe fruit after shelling is extracted for its juice for use in hundreds of culinary preparations, there are also commercial products based on the pulp. In India dried tamarind pulp, powder and juice concentrate are commercially made and find wide acceptance. Presence tannins, saponins, sesquiterpenes, alkaloids, phlobatamine and other phytochemicals makes tamarind a most potent health protecting food adjunct, especially recognized by indigenous medical practitioners in India. Its reported effect in reducing serum cholesterol and blood glucose levels is especially noteworthy. Probably food industry in India can make tamarind juice popular in western culinary preparations also through effective promotional programs. If color is not needed, green tamarind fruit can be considered for extracting juice through pectinase enzyme intervention and subsequent stabilization.