Randi Group products, among which tartaric acid, are all of natural origin.


The production process has its roots in the most ancient tradition of re-working wine residue.


Grape marc, lees, barrel tartrate are the raw materials used for the extraction and purification of natural tartaric products.


Grape marc is the solid and semi-solid residue of grapes after the pressing: it’s made up of grape seeds, stalks, and skin. It contains potassium bitartrate and ethyl alcohol: its composition, as well as its worth, varies depending on the grape’s nature and ripening, but mainly on the wine-making system. It’s used for the production of calcium tartrate and ethyl alcohol; with the residue product, spent marc, thermal and electric energy is produced.


Lees, that wine settles during its fermentation, contains potassium acid bitartrate and ethyl alcohol; it has a sludge-like texture and it comes in a cream or red color, depending on the color of the grapes from which it comes from. It’s used for the production of calcium tartrate and ethyl alcohol.


Barrel tartrate, or raw tartrate, settles in the wine storage tanks: it’s the richest tartaric material, it contains 60% to 90% of potassium bitartrate and it’s normally used for the production of cream of tartar.


Tartaric acid history: Louis Pasteur’s experience


At Paris’ Ecole Normale, already as a student, Louis Pasteur studied the feature some composites, including natural tartaric acid, have that makes the polarized light field rotate. A Polaroid lens lets through only the radiation whose magnetic field has an intensity that oscillates on a single plane, called polarization plane.


However, if this polarized light meets, after the lens, an optically active substance, the plane rotates of a certain angle around the propagation axis. Among the composites studied by Pasteur there were tartaric acid and its salts (tartrates), extracted from the tartrate in the wine-makers barrels that contains potassium acid tartrate (cream of tartar). Frenchman Biot and German Mitscherlich had demonstrated that watery solutions of natural tartaric acid and of tartrates in general made the light polarization plane rotate clockwise. At the time in some factories another acid was isolated, that had the same composition, but had to be a different composite, because it was optically inactive. It was then called differently than tartaric acid: paratartaric acid or, more commonly, racemic (from latin racemus, grape bunch). In 1844 Mitscherlich had written that one of the salts derived from it, ammonium and sodium racemate, was identical to the corresponding tartrate even in the crystal from.


That article stimulated Pasteur: he felt annoyed by the coincidence of so many properties with such a distinct difference in the optical activity.


Observing the crystals of 19 derivates of tartaric acid, he noted that they all had facets that made the asymmetrical: a bit like a series of all left or all right hands. Convinced that optical activity and molecular asymmetry were connected, and thinking that the latter had to reflect in an asymmetry of the crystals, he was very surprised finding out, in 1848, asymmetrical crystals also in the inactive salt subject to Mitscherlich work. At the moment he thought that his theories were wrong, but then he realized that those crystals had opposites asymmetries, like a series of pairs of left and right hands.


With patience he separated the tartaric acid’s right and left crystals: the former had the same optical activity of the corresponding tartrate, while the latter made the light polarization plane rotate in the same intensity but with opposite direction; racemic acid was made up of tartaric acid molecules and their mirror images: the two optical activities counter-balanced. Pasteur’s finding led to the understanding of the structure of organic composites.