## 1 Introduction  
Tartaric acid and malic acid are the primary organic acids in grape berries. The concentration of malic acid in wines is reduced during malalactic fermentation because of the ability of lactic acid bacteria to metabolize it into lactic acid. However, tartaric acid can maintain a relatively constant concentration during alcohol and malalactic fermentation because of its microbial stability [1]. The solubility of tartaric acid is usually reduced by low temperature, and then the tartaric acid precipitates as potassium bitartrate crystals [2]. This is a common phenomenon during the bottle storage of wines. Generally speaking, this precipitation does not affect the safety of wine. However, the broken-glass-like appearance leaves an unsatisfactory impression on consumers and reduces the commercial value of the wine. Therefore, some processes are often applied in the winery to avoid the formation of tartaric precipitation and improve tartaric stability [3]. The main components of tartrate precipitation are potassium hydrogen tartrate (KHT) and a small amount of calcium tartrate (CaT) [4, 5]. The formation of tartaric precipitation includes three stages: the solution reaching supersaturation, crystal nucleation, and crystal growth [6; 7]. During the bottle storage of wines, due to the presence of ethanol and the low temperature, the solubility of KHT decreases and tiny crystal embryos grow from the supersaturated solution [8]. After further nucleation to produce crystal nuclei, the ions in the solution continue to bind to the crystal nucleus, and the crystals continue to grow. Finally, the visible tartaric crystal is formed [7; 9]. Besides ethanol and temperature, the wine compositions also affect the crystallization of the tartaric precipitation. Macromolecular compounds, such as the polyphenol rich in red wines and the mannoprotein rich in sparkling wines, can be adsorbed onto the growth site of the crystal surface through the ionic bond, hydrogen bond, or charge-transfer interaction to inhibit the crystallization formation. Macromolecular compounds are fewer in white wines, so white wines are more prone to tartaric precipitation [10]. This means the tartaric stabilization process is essential to produce white wines. At present, wineries improve tartaric stability by reducing ion concentration and inhibiting crystal growth. The former methods include cold stabilization, ion exchange treatment, and electrodialysis. The latter involves adding polysaccharides (hydroxymethyl cellulose, gum arabic, mannoprotein, etc. ), peptides (polyasparatic acid), or metataratric acid (MTA) into wines to inhibit the formation of precipitation, or to modify their properties to be soluble at low temperature [2; 11]. Correspondingly, many technologies have been developed [12; 13]. The effects of ion-exchange treatment and electrodialysis on wine color, tannin content [4], anthocyanins, and other flavor compounds have been investigated in some research [9]. As for additives that have been studied more in recent years, the studies mainly focused on the effects of different additives [14; 15], dosages and temperatures [8], structural characteristics [16], and states (solid or liquid) [14]. However, the additive dosage has been found to be a challenge to determine. Moreover, the legality of applying additives in wine production varies from country to country [9]. Although the International Organisation of Vine and Wine (OIV) has approved the additives mentioned above [17], they are not yet allowed in China [18]. Therefore, the application of additives is not the first choice in production in China. In contrast, although the most traditional cold stabilization treatment takes a long time, it was found to be the most economical approach and wildly used because of its simple operation, the versatility of its equipment, the recyclability of energy during cooling, and the convenience for the batch processing of wine [12].