What pressures are used and will this damage my wine?
The typical operating pressure of the system will vary according to the application and will range from 2,000 to 7,000 kpa.(or 20 to 70 bar). Over many years of operation and many millions of litres of wine processed, we have never observed any damage to wine as a result of pumping to these pressures. The process takes place in a closed loop and normal cellar practices are used to minimise the uptake of oxygen.
How long does the process take?
The time taken to process the wine will vary according to the treatment being used. For example the most rapid treatment is wine concentration. As the wine passes through the system somewhere between 10 and 20% of its volume passes through the membrane as permeate. In many cases this is sufficient concentration for the winemakers purposes so the process is complete after just one pass of wine through the plant.
With alcohol correction the alcohol level is typically reduced by about 0.7% to 1.5% as the wine passes through the plant. The processes of volatile acidity removal and taint reduction generally take considerably longer because the offending compounds are removed much more slowly. For example, to halve the volatile acidity in a wine might require five or six passes because VA is reduced by only 10% at each pass. The Brett taint removal process is even slower – analyses of samples show that 4-EP is reduced by about 7% on each pass. The time taken for each pass will vary according to the model of RO being used. An 8 membrane Memstar RO408 processes wine at the rate of 3,500 litres per hour and a 16 membrane Memstar RO416 operates at 7,000 litres per hour.
How much does the process cost?
Each job is priced differently according to the extent of processing required and whether quantity discounts are applicable. As an indication, reducing the alcohol content by 1% would cost about $0.10 per litre. For volatile acidity removal the base cost of halving the volatile acidity from say 1 g per litre to 0.5 g per litre would be about $0.50 per litre. Please contact Memstar for full details or a quotation.
How much VA can be removed?
In theory it is impossible to completely remove VA from a wine because on each pass it is reduced by about 10%. So after one pass it would be reduced to 90% of the original level; then on the second pass, 90% of 90%; then 90% of 90% of 90% etc. In practice most winemakers are satisfied to reduce the VA to about 0.5 to 0.6 g/l.
Can I over-treat just a portion of my wine and back blend?
Because it takes as long to reduce the VA from 1g/l to 0.5g/l as from 0.5g/l to 0.25g/l, there is no benefit in trying to over-treat a portion. In general it is preferable to remove a little VA from a lot of wine compared to taking a lot of VA from a little.
Can the process remove ethyl acetate?
Yes, the high pH conditions in the anion exchange column hydrolyse the ethyl acetate ester into ethanol and acetic acid. The ethanol passes through the column and returns to the bulk of the wine and the acetic acid is adsorbed in the resin and so removed. This process takes place more slowly than the reduction of acetic acid because the ethyl acetate passes through the membrane more slowly.
What is the smallest quantity that can be treated?
Practically it has been found that it is possible to successfully treat some batches as small as 1,500 to 2,000 litres. Below this, problems of dilution arise because of mixing in the system. In any case, the real problem is the inefficiency of trying to treat such small batches. It takes as long to travel to the site; set up; clean the equipment and lines before and after then pack up for small and large jobs. Therefore a minimum fee applies and this can make the treatment of small batches unattractive.
What condition does the wine need to be in prior to treatment?
The equipment will not tolerate any significant levels of grape or other solids in the wine. Otherwise it is reasonably tolerant of wines in a wide state of preparedness. To aid efficient processing we require that wines have turbidity no higher than 50NTU and are as warm as the winemaker is prepared to accept but certainly no less than 15 oC. Preferably (but not mandatory) they should be heat, cold and pectin stable and have been polish filtered. The better prepared the wine, the faster and more effective is the processing.
What special facilities will be required at my site?
There are a number of utilities and other facilities required for the timely and efficient processing of wine when we are on-site. Full details are available from Memstar – please call +61 (0)3 9564 7089 or contact Memstar.
What effluent does the process generate?
The cleaning of the RO generates a waste stream of a few hundred litres of water and trisodium phosphate plus several hundred more litres of rinse water. The ion exchange columns used for VA reduction are charged with sodium or potassium hydroxide. In the process, each recharge (once or twice a day) generates between 300 and a 1,000 litres of high pH sodium or potassium acetate solution plus another 2,000 litres of caustic solution rinsed from the column. The alcohol correction process generates a stream of alcoholic strip water. This is about 6% to 10% in alcoholic strength and is produced at 600 to 1500 litres per hour. This may be discarded if permitted or it may be sent away for distillation as it produces high quality spirit.
Can I purchase my own equipment?
All Memstar equipment is available for sale; however some processes are subject to technology licensing arrangements so as a condition of the sale, a licence would need to be negotiated.