Colorimetric method for the determination of total acidity in wine
Ascorbic acid (vitamin C) is a powerful antioxidant that is used during the manufacte process to quickly eliminate any presence of dissolved O2 that could oxidize phenolic compounds, especially those derived from cinnamic acid, which produces a darkening of the wine. Ascorbic acid very efficiently converts said oxygen into hydrogen peroxide that is subsequently neutralized by the SO2 present in the wine (thus, it is recommended that the wine contains between 30 and 50 mg / L of SO2 before the addition of ascorbic acid to be effective in the elimination of hydrogen peroxide formed). It also prevents oxidation of iron ions as prevention of iron case. An excess of ascorbic can negatively affect the color of the wine and its subsequent evolution.
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.
Glycerol (or glycerin) is a natural byproduct of alcoholic fermentation, providing body-to-mouth sensation. The glycerol content is directly related to the degree of maturity of the grape, the microorganisms present and the fermentation procedure used (temperature, yeast species, nitrogen source).