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Flotation of wine for rapid clarification in cellars

A procedure to clarify must, flotation is a process of separating solids from the liquid (must or wine) in which they are contained. 

 

The goal of the procedure is to prevent the must from retaining undesirable substances that may compromise the quality of the product and adversely affect fermentation, especially in the case of white wines. This is the reason must flotation cannot be ignored. 

What it is used for and how to carry out wine must

Must flotation is carried out using air or nitrogen bubbles and pectolytic enzymes, bentonite, silica sol and protein-based clarifiers which bring the solid parts to the surface so that they can be separated from the liquid. 

 

The various tasks carried out in the vinification process, especially procedures in extracting must from grapes, result in a cloudy product. A product that typically contains soil, stalks, skins or other materials that are left over from processing the vine. If left with the liquid, these substances would affect the fermentation process, giving the wine herbaceous and bitter aromas. 

 

With flotation, therefore, the must is clarified and stabilised with regard to its protein and phenolic substance content. 

 

How is flotation carried out?

The first step is to add pectolytic enzyme to the must – the ‘enriched’ must is kept in motion by the introduction of air into the tank. It is this very enzyme that plays a key role –  as a result of its action, the solid parts that absorb water end up at the bottom of the container, while the parts that absorb air rise to the surface, creating a foam effect (the former have a higher density than the wine, the latter a lower density).  

 

The solid parts deposited on the surface are then removed as appropriate. 

Potential issues with must flotation

Flotation is a chemical-physical phenomenon and, as such, is influenced by a number of parameters. 

 

Firstly, the must has to be at a temperature of no less than 12°C and no more than 20°C, otherwise its density will not be correct. Secondly, the polypeptide chains must be small enough to adhere to the gas bubbles (the pectolytic enzyme must have been acting for at least a couple of hours). Finally, action must be taken before too much lees has settled at the bottom of the container. 

A fundamental aspect is the choice of gas – nitrogen or carbon dioxide are generally preferred, but compressed air may also be used (to hyper-oxygenate the must). The following are then added to the pectolytic enzyme must a couple of hours before it begins to act: 

 

  • PVPP (Polyvinylpolypyrrolidone), to remove oxidised compounds and to make the taste and smell cleaner; 
  • Bentonite to remove protein and oxidative enzymes; 
  • Gelatine to compact the lees. 

 

In order to carry out must flotation properly, it is therefore necessary to observe the correct temperature and choose the most suitable gas and pectolytic enzyme. 

 

Products to be used in must flotation

Specific products must be used in must flotation.

 

E-Flot is a range of flotation equipment that enables musts to be clarified more effectively and rapidly. By implementing more rapid clarification, less use is made of cooling systems, and energy expenditure in cellars is reduced. 

 

The special flotation machine adds a gas (nitrogen or carbon dioxide) to the must with a clarifying adjuvant – the flocculated solids rise to the surface of the tank, while the must remains clear and ready for fermentation in the lower part. The use of specific products and machines for must flotation permits more rapid and more productive clarification by exploiting the principle of incorporating a gas into the solids (responsible for the turbidity in the liquid). 

 

The choice of enzymes is also crucial factor. Pectolytic enzymes optimise clarification of musts and wines, but there are also special liquid enzymes for flotation that reduce process times and increase effectiveness.