Clarification of white and rosé grape juice is the process of removing unwanted particles and impurities from the must before fermentation begins. This process is important for winemakers because it helps to ensure that the must is clear, bright, and free from any unwanted flavours or aromas by removing earthy particles, leaf debris, and seeds from the must ; lowering metal and phytosanitary residue concentrations ; and refining the aromatic expression of grape juice while lowering the risk of reduced taste.
There are a few methods of clarification that winemakers use : settling, flotation, and centrifugation. All methods separate the clear grape juice to be fermented from the gross lees and involve the use of enzymes.
The clarification of grape must is essential for white and rosé wine elaboration.
Winemakers can use enzymes that are made for specific techniques or problems to help the must clear up.
Pectinase enzymes help reduce the viscosity of grape must by breaking down pectin, a complex carbohydrate found in grape cell walls. Pectin is responsible for the thick and sticky texture of grape must, and its breakdown leads to a reduction of viscosity. Pectinases are enzymes that specifically target pectin and break it down into simpler sugars. This reduction in viscosity can help improve the flow of juice during winemaking and make it easier to separate the juice from solid particles.
Settling is a method of grape juice clarification in which the juice is allowed to sit in a tank for a period in order for solid particles, such as grape skins, seeds, impurities, and dead yeast cells, to settle to the bottom of the tank, allowing the clear juice to be separated from the sediment. Several factors can influence the settling, like the juice composition, temperature, pH, time, gravity, tank design, the use of fining aids, and enzyme addition.
The addition of enzymes like pectinases to the must can break down pectin and other complex carbohydrates that can contribute to cloudiness, which can help improve the efficiency of settling.
There are various enzyme formulations that can be used for settling, including simple pectinases and those with more side activities.
Winemakers that use Rapidase® enzymes in their white and rosé winemaking processes see more free-run juice and more compact lees, as well as time savings over natural settling.
Rapidase Clear reduces the viscosity and the quantity of lees that must be treated or disposed of during static settling, resulting in clearer musts and wines. This occurs because the enzymes in Rapidase Clear break down the walls of the grape skin. This lets more juice out and breaks down the pectins, which makes for better and faster settling.
We have a long history with Rapidase Clear. Therefore, in some countries, you may come across the liquid version of Rapidase Clear used in flotation due to this past. We invite you to read the following section to understand why we, more recently, formulated Rapidase Flotation.
In order to obtain a fresher, crispier aroma, grapes are picked early, settled at cooler temperatures, and subjected to a cold soak. High amounts of pectin are broken down when skin contact is used to extract aroma precursors, and some grape varieties are known for having complex pectin structures on their own. So, limitations in viticulture, technology, or even climate have pushed commercial enzyme preparations to their limits, making clarification very slow and hard. When it comes to an enzyme with a single type of activity, these limits are especially clear.
We launched Rapidase® Clear Extreme after extensive tests of this new enzyme formulation in both hemispheres to solve these clarifying problems. This formulation has shown its better efficacy in many different circumstances, including temperatures as low as 6 °C, poor ripeness, and cultivars with naturally high or complicated pectin content.
Rapidase Clear Extreme has cryophilic pectinases that work on a wider range of pectins. Pectin is one of nature’s most complicated large molecules. The pecto-cellulosic wall is made up of cellulose microfibrils that are held together by a matrix of xyloglucan, mannan, xylan (also called hemi-cellulose), and pectin. The whole thing is held together by a secondary protein network. Some neutral sugars, like galactose and arabinose, are part of the lateral pectin chains and form macromolecular complexes with proteins. When settling is hard (because of low temperatures, low pH, or hard-to-settle varieties), Rapidase Clear Extreme breaks down the pectin molecule more quickly by hydrolyzing the main chain first, then the side chain. Its application enables quick viscosity reduction and solid particle aggregation, resulting in faster lees compaction and a clearer must.
Flotation is another common way to separate the solids from the juice. This is done by bubbling air or gas through the juice, which causes the solids to rise to the surface and form a foam that can be skimmed off. Pectolytic enzymes, adjuvants like bentonite, silica sol, and protein clarifiers are used. These things help the solid parts rise to the surface so that they can be separated from the liquid.
Before flotation, must depectinization is needed to lower the viscosity and let the particles move to the surface, where they are removed. In acidic must, negatively charged soluble pectin wraps around positively charged proteins. These suspended particles have a negative charge on the outside, so they repel each other and keep the haze stable. When a modified formulation of pectolytic activities is added, the viscosity can drop quickly.
Rapidase® Flotation is the enzyme of choice for fast and efficient flotation of white and rosé grape must. This Rapidase enzyme reduces flotation time by means of a decrease in viscosity, allowing faster flocculation and more compact foam by facilitating haze particle agglomeration.
A pectin test evaluates the residual presence or absence of pectins. A negative pectin test is mandatory for an efficient flotation and a negative glucan test as well.
Click here to get the protocol for pectin and glucan test.
Another method of clarification is centrifugation. This is a process in which the must is spun at high speeds in a centrifuge, which separates the solid and heavier particles from the liquid and lighter. The lees are heavier than the liquid and are forced to the bottom of the centrifuge, while the clarified juice is collected at the top.
The use of enzymes in this process can help improve the efficiency of centrifugation. Enzymes such as pectinases can be added to the must before centrifugation to break down pectin and other complex carbohydrates that can contribute to cloudiness. This results in a clearer juice with less sediment, which can then be more easily separated using centrifugation.
For this technique, we recommend the same as for the settling. Depending on your itinerary and the juice composition, we suggest Rapidase Clear or Rapidase Clear Extreme.
NOTE: For clarification needs outside of wine, please refer to other-than-wine Rapidase products with the link : www.dsm-firmenich.com.
With a highly qualified team of experts in many fields, Oenobrands strives to offer winemakers’ novel and scientifically sound solutions, as well as to highlight the positive synergies between its products.
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