In the process of white wine production, the grapes are pressed immediately after stalking and no later than the next day if the white mash is macerated cold. The red mash goes to press after the maceration, which, depending on the style and category of the wine, can last from three days to a month or more. Sometimes we press white and red grapes almost at the same time. So, it’s important to emphasize that grape press for wine making must be easy to clean.
The solid (pomace) is separated from the liquid (must) phase during compression. As the pressure increases, the unwanted substances increase in the liquid phase. These problematic substances are allegedly found in stalks, seeds, and strawberry skin. Injuries increase not only coarse yeast but also the proportion of unwanted substances. The quality of the wine is declining as a result. The extent to which the grapes are damaged also depends on the elasticity and resistance of the strawberry skin.
Basket Grape Press for Wine Making
The presses are based on various technical solutions—pneumatic, large horizontal capacity, and vertical, smaller capacity. Pneumatics are the most sought after due to their large capacity and easy cleaning, which is very important in the short harvest season. Sometimes red mash and white are squeezed alternately, and practical cleaning is also a great advantage from this point of view.
The most classic press, which until recently was widespread in all basements and is still in use, is the “basket” press. Initially, the drive was manual; later, it was upgraded with hydraulics, and after, it was driven by an electric drive.
Pneumatic or Air Pressure Presses
The development of presses has been very intensive in the last 30 years. For some time, pistons were the most widespread, but air-pressure presses have successfully supplanted them. The pressure in the drum is up to two bars. Most of the must is drained at a pressure of up to 0.2 bar.
Grape Press Equipment and Operation
The press is filled through the door on the drum or central. During the central filling, the mash drains at the same time. It is also possible for the drum to rotate during central filling, which allows a larger amount of mash to be filled. But the simultaneous central filling of the mash and the rotation of the drum increase the sediment and thus have a negative impact on the quality of the wine.
This is not such a dangerous procedure if the grapes are healthy. However, if the grapes are rotten or overripe, there is additional damage to the tissue of the strawberry cells, which increases the proportion of colloids that hinder the outflow of must from the drum.
The filling of the press should be carefully planned, taking into account the specifics of the variety, year, degree of maturity, and degree of rot. Preliminary processes in grape processing, such as stalking, pumping, and maceration time, affect the pressing result to a greater extent than the pressing program itself, including pressure, cycle, and crushing of the pomace.
Summary of Grape Press for Wine Making
Grape processing machinery and equipment are very sophisticated. Knowing the composition of grapes and understanding the processes that take place during processing allows safe and lenient handling of grapes. It is not enough to have the most expensive machines if we buy them for prestige. New machines are making technical changes that require changing old work habits. However, the new equipment does not automatically guarantee higher wine quality. There is a lot of new knowledge that needs to be mastered. It is even more critical to respect the grape berry’s composition, the wines’ established character, and subordinate machines and procedures to this.
Questions for Your Reflection
- Based on which requirements do we decide when buying new equipment: stalkers, crushers, pumps, presses, Vinificators?
- Is accessible equipment cleaning important? Why?
- To what extent the hourly capacity of machines important is?
- How do you imagine the harmony between the performance of individual machines, and where is the coordination of performance key to wine quality?
- Is manual or machine grape processing better for wine quality?