WINETECH Technical Yearbook 2021

OENOLOGY RESEARCH | SEPTEMBER 2021

TARTARIC ACID AND ITS SALTS are important products with commercial and industrial applications in the wine and other industries. INTRODUCTION Tartaric acid contributes to a suitable pH and plays a crucial role in taste, as well as in the physical, biochemical and microbial stability of wine. In addition to tartaric acid existing freely, it is also found as salts (known as tartrates). Tartaric acid and its salts exist in different forms or isomers [D(–), L(+) and DL] of natural and synthetic origin, with different properties. Centuries of extensive use established the safe properties of tartaric acid, confirmed universally in the related food laws. The demand for tartaric acid is increasing due to the growing production of organic acid-containing foods and materials, and new applications thereof in Producers of tartaric acid make use of different processes based on various feedstocks. These include (Hronská et al ., 2017) (1) from grape waste and wine stone (bitartrate) (natural), and (2) from maleic acid/maleic anhydride/fumaric acid derived from petrochemicals, such as benzene and butane (chemical-synthetic). The isomer produced by chemical synthetic processes from maleic acid is DL-tartaric acid, with pharmaceutical industries. ORIGIN AND EFFECTS

equal amounts of L-tartaric acid, and D-tartaric acid as by-product, separated from the mixture. The DL-form gives a much less soluble racemic product which is not suitable for inclusion in foods, because D(–)- tartaric acid in the product is considered to be harmful to human health (Hronská et al ., 2017; Xuan & Feng, 2019). Both isomers have broad industrial and scientific applications. L(+)-tartaric acid is widely used in the food, wine, pharmaceutical, agrochemical and polyester industries, while D(-)-tartaric acid is also important in pharmaceutical manufacturing. In wine, common types of crystalline instabilities, including potassium bitartrate, calcium L-tartrate and calcium DL-tartrate, can be caused by wineries using the racemic (synthetic) forms of tartaric acid and cream of tartar (potassium hydrogen DL-tartrate) during the cold stabilisation process. No toxic effects, including nephrotoxicity (toxicity in the kidneys), were observed in toxicological studies in which the L(+)-form was tested (Younes et al ., 2020). In contrast, nephrotoxicity was reported in studies in which the DL-form has been tested and, therefore, renal effects reported with tartrates were most likely due to the presence of the D(–)-form of tartaric acid. According to the authors, this was due to the DL-form being less soluble than the L(+)-form. Tartaric acid/

Tartaric acid – forms and effects

FRANCOIS VAN JAARSVELD: ARC Infruitec-Nietvoorbij, Stellenbosch KEYWORDS: Tartaric acid, tartrates, forms, effects, synthetic.

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