Reversal osmosis

Reverse osmosis - equipment G.A. KIESEL GmbH

KIESEL reverse osmosis was especially developed for wine making. After many years of testing, modules were created to make economical water removal from grape must possible.

The aim is to balance vintage differences and to enhance good qualities even more via must concentration.

Equipment in the outfit, within the performance range of 50 - 1,000 ltr./h with 1-2% Vol. alcohol enhancement and a must output weight of 75-85 °Oe (~10.0-11.5 % Vol. alcohol), is dependant on a 65 Dalton membrane as a spiral sleeve module, so that the must is available in a micro-filtrated form.

Drainage of liquid causes the product to be concentrated with all its ingredients. That means, with grape most, not only sugar content, but also shares of ingredient, color and aroma content, as well as acidity are enhanced. This is the basic difference from accepted chaptalization of grape must, in that the sugar content would be enhanced through the addition of sucrose.

This technological wine cellar method hasn't been implemented for years in France and Italy for nothing. Authorized trials, which were implemented during the past few years, clearly show that water removal results in content-rich wines.

By the use of reverse osmosis implementation, must water is withdrawn via a fine membrane. Fine pores let the water molecules through, while retaining the must ingredients. The equipments high flowrate keep the pores open, so that a continuous operation is made possible.

An especially high value is set on the careful handling of must. High pressure pumps are used, which must produce overpressure of max. 80 bar. The equipment is designed for max. 20% drainage.

Commodities for reverse osmosis:

• Sodium hydroxide
• Sodium bisulfite
• Citric acid
• Salt tablets

Functional characteristics:

The grape must is pumped, with the help of a primary pressure pump, over a fine filter (100 µ) to a high pressure pump aggregrate. This pumps the juice through a semi-permeable membrane with high pressure. Clean water (permeate) diffuses through the membrane and is collected in the permeate holding tank. Then the increased solvent concentrated grape must is lead back to the storage tank as a concentrate.

The control system monitors and controls all important functions during permeate production.

Control system for reverse osmosis:

Gauges:

• Flow gauge, temperature gauge, conductance gauge
• Error message / Fault report
• Failure confirmation (simple)
• On and Off switch for both pumps (high pressure pump is only allowed to run when the primary pressure pump is running and has more than approx. 3 bar)
• Pressure cut-off / Pressure deficiency failure (when less than 2 bar of pressure is present in the pre-filter outlet)
• Primary pressure pump is not allowed to be turned-on again - Failure confirmation
• Optional: electr. Excess pressure shut-off valve must be shut-off at 90 bar

Market globalization and a very liberal wine standard policy in aspiring viticulture regions and/or nations like South Africa, California, Austrailia, Chile and Argentinia have forced us to have technological conflicts, which are not always compatible with our ethical wine principles. In addition, aroma additives (eg. oak chips) to wine and the main subject of must concentration count. KIESEL had already started tackling these issues in the Autumn of 2000.

The discussion about must concentration and the techniques used in the past few years, have been significantly made by the French. Thereby, the concept of ”self-enrichment” is especially highlighted. The goal is to increase good quality through must concentration and to balance vintage differences; for example, balance through condensation before harvesting.

This technique in France is not called ”de-raining” for no reason. In contrast to improvement with sugar, most concentration makes an effective quality enhancement possible. Thereby, extract, color and many other, quality determining wine ingredients are increased.

However, must concentration can not replace the work which is done in the vinyard. A superior product can not emerge from inferior quality through concentration, because negative content substances would also be concentrated. Only good quality can be choosen for concentration. The rule-of-thumb is: ”Good becomes better and bad becomes worse.”

Presently, two different principles are applied to concentrate must: vacuum evaporation and the reverse osmosis technique. Given that vacuum evaporation was the first to be accepted, it is still more widely prevalent. However, for the last two seasons water seperation through reverse osmosis has shown that it has gained a lot of significance. The advantages are obvious: reverse osmosis outfits are far more effective – and this with more compact designs and significantly less engergy consumption!

During the first years, must concentration was viewed almost exclusively as a tool in red wine business. It shows however, that white wine business want to ensure and improve quality with this technique even more. All the same, whether for red or white, wine-growers should keep the following rule in mind:

All content substances of the must are equally increased by the use of concentration. Therefore, only good qualities are suitable for concentration.

The principle of reverse osmosis

Osmosis is a natural phenomena, which occurs everywhere where solutions with varied concentration (due to a semi-permeable membrane) are seperated:

Example:
A grape gets wet by rain. The berry-skin posesses semi-permeable properties; thereby, water can infiltrate the berry (but sugar can not escape). The sugar concentration in the berry is reduced by water influx. This process continues until a concentration balance is produced or until the grape can not withhold the increased volume pressure and thereby bursts.