Valentina Canuti, Paola Domizio, Francesco Maioli, Valentina Civa
Department of Agricultural, Food, Environmental and Forestry Sciences and Technologies (DAGRI) – University of Florence
Color is one of the most important characteristics of wines, not only for defining their suitability, but also for the product consumer’s.
A quick way for color monitoring throughout the entire winemaking process can therefore be really important for the oenologist to better address the process choices.
The evaluation of wine color varies according to the winemaking process and therefore to the type of wine. In white wines production, for example, it may be crucial to monitor the color from the very first stages of grape pressing as well as during the finning and subsequent stages of aging on fine lees or yeast derivates, to protein stabilization, up to filtration and bottling. Instead, in red wines production, the color monitoring is important during the fermentation and maceration phases and, depending on whether it is “ready to drink” wine or a potential long aging wine, the control of it during maturation as well as during clarification, tartaric stabilization and finally filtration, becomes crucial. In fact, each of these phases can deeply affect the wine color and its measure therefore becomes important for controlling the process.
In this context, it also becomes essential to have adequate instrumentation that allows easy execution of the measurements, without the need of specific laboratory equipment or special training.
Color measurements are usually carried out by spectrophotometric, after clarification of the must or wine sample (by centrifugation or filtration). 420 nm, 520 nm and 620 nm wavelengths are used for the determination of parameters such as color intensity (sum of the absorbance at the three aforementioned wavelengths) and hue (ratio between absorbance at 420 and 520 nm). The 420 nm absorbance is also used itself to control the white must or wine browning. However, by evaluating only the three wavelengths, any contributions provided by absorptions in other areas of the visible spectra (380-780 nm) resulted not determined. This is why the official method for evaluating the color of a wine is the CIELab trichromatic coordinates that project the color of a wine into a three-dimensional space, reproducing the perception that the human eye has for that color. Given the importance of this measurement and the parameters that are obtained from some calculations with the three coordinates L*, a* and b*, in recent years, easy-to-use and portable tools have been developed in order to carried out this measurement directly in the cellar.
In the following paragraphs, a series of measurements carried out on different typology of wines, and in different phases of the winemaking process directly in the cellar, using a portable instrument (SMART ANALYSIS, DNAPhone) that measure the CIELab together with the classic parameters of wine color are presented.
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