This paper presents the development of a new method to measure the main phenolic compounds found in Cabernet Sauvignon red wines. A portable Raman spectrometer was used for this purpose, providing scattering spectra to analyze quantitatively the samples and determining the concentration of the compounds of interest. The Raman spectra were obtained from the wine samples corresponding to different seasons, vineyards, and harvests. The subsequent model calibration was based on reference analytical values obtained using standard laboratory techniques. Several preprocessing and correlation methods were applied to the data in order to adjust models for polyphenols, anthocyanins, and tannins and also to reduce the effect of fluorescence. The optimization of the models was carried out using R² and root-mean-square error of validation (RMSEV) indices. The correlations of R² = 0.895 and RMSEV = 5.55 mg/L were obtained, showing the potential of this technique for field measurements.

The quality of red wine is directly associated with its phenolic composition, which can be controlled using several viticultural techniques that affect the vegetative/productive balance of the plants, such as summer pruning and cluster thinning. However, these techniques may also involve high costs and production losses. This study aimed to evaluate the effects of summer pruning and cluster thinning on the phenolic compositions of grapes and wine over three consecutive seasons. The treatments included long (120 cm shoot length) and short (60 cm shoot length) summer pruning and 50% cluster thinning with control treatments conducted in vineyards with cvs. Cabernet-Sauvignon and Carmenere and located in a warm area (Cachapoal, Chile) and cvs. Cabernet-Sauvignon and Pinot Noir located in a cold area (Casablanca, Chile). These treatments generated differences in the microclimatic conditions (radiation and temperature) and the vegetative/productive balance of the plants. Depending on whether the grapevine vigor was high or low, short summer pruning increased or decreased the phenolic composition. The effects of cluster thinning varied according to the natural productivity of each season, increasing the phenolic composition when the natural yields were high and producing no significant effects when they were low. The decision to make these viticultural practices to improve the phenolic composition of the wine depends on the seasonal vineyard vigor and potential productivity. Thus, measures are only applied when a severe imbalance in the vegetative/productive equilibrium occurs or when the microclimatic conditions of the vineyard must be improved.