Grape pressing is an important stage in the winemaking process because it extracts the juice from the grapes that will be fermented to make white and rosé wines. Because the pressing process has a major influence on the quality and character of the finished wine, winemakers must understand the best procedures for pressing grapes.
The pectic polysaccharides of the berry skin epidermis cell walls and of the cell layers immediately beneath serve to maintain the integrity and continuity of plant tissue. Their molecular structure gives them chemical and physical properties suitable for this purpose, such as water retention capacity and gel formation. All these characteristics are obstacles when white grapes are processed, in the pre-fermentation extraction and must clarification stages, and for the diffusion of aromatic compounds and their precursors in the must.
Pectins are essentially made up of main chains called homogalacturonans, rhamnogalacturonans, arabinans, and arabinogalactans, found particularly in grapes that are considered difficult to process, like Muscat. The action of a balanced set of different enzymatic activities is necessary to break down their particularly complex structure.
A few years ago, we, Oenobrands, developed Rapidase® Extra Press, an enzymatic preparation suitable for improving the release of juice from grapes by weakening grape skins. Its use increases juice yields and allows for faster pressing cycles, preserving grape must from oxidation.
For clarification, in addition to pectolytic activities (pectin lyase, polygalacturonase, and pectin methyl esterase), Rapidase Extra Press contains activities able to hydrolyze both homogalacturonan chains and side chains (arabinans and arabinogalactans). Cellulase and hemicellulase activities are kept at low levels to avoid excessive skin maceration and the formation of an excess of solid particles in suspension that are difficult to remove.
Numerous tests conducted by us, Oenobrands, in various harvests and on numerous varieties around the world demonstrate the effectiveness of Rapidase Extra Press in white grape processing, whether added to the crushed mass in the press or during the pre-fermentation maceration phase.
The addition of Rapidase Extra Press enzyme directly in the press, with a contact time of 2–3 hours, or during maceration for 6–10 hours, leads to an increase in yield that increases according to the length of the enzyme action on the skin and the pulp (Figures 1 and 2).
The results show an increase in pressed-must yields using Rapidase Extra Press versus the control without enzyme. The trials’ findings included directly adding the enzyme to the press during filling.
Using Rapidase Extra Press allows winemakers to get more juices and qualitative juices compared to a reference enzyme used in pre-fermentation skin maceration.
In particular, the greatest increase can be measured in the must fraction, obtained from the draining of the crushed grapes treated before pressing cycles start. This not only leads to a better yield but also to a better quality of the must, especially due to softer and shorter pressing cycles.
We applied Rapidase Extra Press directly during the filling of the press at various doses for various grape varieties. The dose rate was chosen according to the reference enzyme used in these wineries. Each time, we have noticed an increase in the total yield when applying Rapidase Extra Press.
Chardonnay France, Languedoc, enzyme dosage 1 g/100 Kg, maceration 6 h at 10 °C. Muscat 1, USA, California; enzyme dosage: 1,1 g/100 kg; maceration at room temperature; free-run juice. Muscat 2, USA, California, enzyme dosage 1,3 g/100 Kg grapes, maceration at room temperature, 7h for Rapidase Extra Press and 12h for competitor enzyme. Pedro Ximenez Moscato rosado Chile, Pisco, enzyme dosage of 2 g/100 kg grapes, maceration at 16–18 °C for 6 hours, free run juice.
From an operational perspective and looking at process efficiency, the systematic addition at the crusher facilitates cellar operations and reduces the work required and the possibility of error in the grape and must processing stages. The use of Extra Press will also help in the cleaning process, allowing the winemaker to decrease or even eliminate the enzyme used for flotation or settling.
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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