Crushing-maceration-pressing

Crushing—Maceration—Pressing Operations. Fundamental to making any type of wine is the conversion of sugar to ethyl alcohol by the enzymes present in living yeast cells according to the equation established by Gay-Lussac,... 

Table 12.19 compares free run and press juice composition for traditional (crushed grapes) and carbonic maceration winemaking. In carbonic maceration press wines, the alcohol content is higher (caused by ethanol fixation) and the acidity lower (due to malic acid degradation). These wines also have lower concentration of phenolic componnds and other extracted components their dissolntion is diminished. 

Caxignan tanks (110 hi) of conventionally produced (CP) wines vinified with crushed grape harvest and carbonic maceration (CM) wines. After pressing F, free-run juice, P, pressing juice FP, assembly of F and P. Total potential alcohol = produced alcohol + alcohol corresponding to the residual sugars (Andre et al, 1967). 

Skin Contact. Skin contact (also called pomace contact or maceration ) is a system of holding the crushed must for a period of two to thirty-six hours prior to dejuicing and pressing. The grapes are crushed into... 

For the production of white wine, it is almost universally accepted that a relatively clear juice of 0.5-2.0 percent suspended solids is desired for fermentation. This is achieved by separating the juice from the skins, pulp, and seeds. Many of the small wineries use a horizontal basket press to receive their fresh must. These presses utilize either an inflatable bladder or a movable piston to press the crushed grapes. In many cases, the must is pumped directly to these presses from the crusher-stemmer. An exception to this method of operation in small wineries is the case where skin contact is desired. Several wineries will allow maceration for from four hours to twenty-four hours for V. vinifera cultivars Chardonnay and Gewiirztraimer. 

As made at Fernham, Ragland, it ooQsisU ol finely divided or macerated gun cotton compounded with about the same weight of nitrate of baryta. The gun cotton itself Is mainly common cotton waste stet ped in nitric acid, and on the excess being forced out by a hydraulic press or otherwise, it is left some time for digestion In vessels of clay. While moist, it is macerated between crushing rollers and then washed ... 

Nevertheless, the dissolvent effect of sulfiting, with respect to phenolic compounds, is obvious in the case of limited maceration. This operation is not recommended for crushed white grapes before must extraction by pressing. The sulfiting of grapes also has an impact on the color of rose wines. 

The transformation of grapes into juice can be obtained by different methods. Juice extraction can be immediate or preceded by a skin maceration phase. It can be continuous or in batches, with or without crushing and destemming. Continuous and immediate juice extraction processes (very widespread until recently in high-volume wineries, despite its disastrous consequences on juice quality) are fortunately being abandoned they will therefore be covered only briefly. Immediate whole or crushed grape batch pressing and skin maceration will be described in more detail. 

If press capacity permits, crushing and destemming shonld be avoided and the grapes should be hand-harvested and pressed immediately. These operations are only necessary when the grape undergoes skin maceration before pressing. 

Skin maceration consists of voluntarily permitting a contact phase between the skins and the juice in controlled conditions. An adapted tank is filled with moderately crushed, destenuned grapes. Several hours later, the drained juice is collected and the drained pomace is pressed. 

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