Potassium is the most abundant cation in wine. Its concentration depends both on the grape variety, the soil conditions, the collection procedures (presence of scratches) and the methods used in winemaking. High values of potassium in the grapes will lead to more basic musts, which could adversely affect the quality of the wine. Although most of the potassium salts are soluble, potassium bitartrate decreases its solubility as the concentration of alcohol increases, giving rise to precipitates that, although they do not affect the organoleptic properties of the wine, can be perceived as a decrease in quality.
Colorimetric method for total polyphenols measurement
The phenolic compounds of wine (natural phenols and polyphenols) are a broad group of chemical compounds that affect the taste, color and mouthfeel of the wine that come from the skin, pulp and seed of the grape. The specific distribution of the same is that which gives the wine its own characteristics, identifying the type of grape used and the process of elaboration. Its main function is to control the natural oxidation of the wine during the ripening and aging process and increase the stability of its organoleptic properties.
The iron is present in the grapes from both the same grape and from dirt and from contact with the tools used during the elaboration process. Iron is capable of forming complex colored salts and is therefore a critical element when it comes to providing wine with a hue. An excess of iron, in addition to providing a bluish hue, can cause the appearance of ferric phosphate (white) and ferric tanate (blue) precipitates under oxidation conditions.
The color of the wine is the result of the mixture of different colored compounds, mainly of reddish tones (mainly anthocyanins), blue (iron complexes) and yellow (catechins). The color index is an indicator that takes into account absorption at 420, 520 and 620 nm.
The presence of copper in wine is common due to both the phytosanitary treatments carried out on the grapes, as well as the controlled addition of copper salts as part of the winemaking process. Most of the copper is precipitated in the form of sulphides and subsequently filtered. However, a high residual concentration thereof is toxic and can severely affect the alcoholic fermentation process, accelerate phenolic oxidation, cause turbidity and produce precipitates in reducing media. The control of copper concentration is essential to ensure both stability during the ripening process and ensure safe consumption.
