## 1 Introduction  
The maceration process is one of the most important steps in red winemaking since the extraction of phenolic compounds and to a lesser extent, of some aroma compounds is dependent on this step. Given its importance, many studies have dealt with the influence of different macation conditions on the content of the final wine phenolic composition [1, 2]. Traditionally, enologists have used variables such as maceration length, temperature, or the use of enzymes, among others, to achieve the best extraction. Nowadays, new technologies are being developed to optimize this phenolic extraction and/or for reducing the length needed to achieve the best results. These new methods include pulse electric fields [3, 4], high power ultrasound [5, 6, 7], thermovinification [8, 9], or the use of microwaves (MW).  
Many techniques in food processing (pasteurization, sterilization, drying, thawing, blanching, and stunning) are assisted by microwave energy [10, 11]. Microwave-assisted extraction uses electromagnetic waves in the frequency spectrum between 300 MHz and 300 GHz, which causes the crushed grapes to heat up due to two main mechanisms: ionic conduction and dipole rotation. Grape skin cells, where most of the phenolic compounds are located, undergo changes under the electromagnetic field created by microwaves since, and according to several authors, the rapid oscillations of the electric field may exceed the elasticity of the cell wall and cause the destruction of the cell membrane, facilitating the phenolic compound extraction [12; 13; 14]. Moreover, it seems clear that although a thermal effect may be present, this is not the most important effect. [PERSON] et al. [15] conducted a histological examination of grape skins and they found more substantial intracellular damage in microwave-maccrated skins than in heat-maccrated and control skins.  
The studies found in the literature on the use of microwaves applied to red wines are mostly coincident with the fact that they facilitate the extraction of phenolic compounds during maceration [14; 15; 16; 17]. However, some studies have also shown that a varietal effect may exist since the application of MW to different varieties (Cabernet Sauvignon, Merlot, and Syrah grapes) led to different degrees of success. It has been reported that MW treatment failed to increase color in wines from Cabernet Sauvignon and Merlot treated grapes, but it did so in Syrah [18] and in Pinot Noir, with a reported fourfold increase in tannin concentration [16].  
Another advantage of the use of microwaves during the prefermentative phase of vnification could be a shortening in the length of maceration time needed to achieve a high phenolic content, improving, in this way, the efficiency of winery operations.  
In this study, our objective is to determine if previous negative results of the application of MW to Cabernet Sauvignon grapes before the skin maceration step could be related to a varietal effect or operational effect and determined if, in our conditions, we could improve the phenolic extraction and, therefore, the wine chromatic characteristics, and if this technology could be useful for reducing the time needed to get a certain phenolic content in the final wines.