**3.5 Spinning cone column**

*Advances in Grape and Wine Biotechnology*

is used as mobile service in wineries.

their prices are much lower.

sensory character of the wine.

**3.4 Vacuum rectification**

offering company.

from the first step.

**3.3 Reverse osmosis/nanofiltration and other process**

Reverse osmosis or nanofiltration alone does not lower the alcohol content of wine. The permeate from that treatment has to be reduced in alcohol content by another step. This alcohol reduced fraction is finally blended with the concentrate

The plant from the company Oenodia (Pertuis, France) is a mobile system that combines reverse osmosis, respectively, nanofiltration with osmotic distillation and

The first step of treatment by reverse osmosis or nanofiltration reduces fouling at the membrane contactor for osmotic distillation as the permeate is free of solids and low in colloid content. In comparison to the expensive and complex membrane contactors, the membranes for the first step can be cleaned more easily. In addition,

The oxygen uptake was measured during several treatments and was between 0.6 and 0.8 mg/l on average for the two-stage process. In comparison to that, the single-step osmotic distillation for alcohol reduction showed on average an oxygen uptake of 1.4 mg/l. So the alcohol reduction by membrane systems can be compared with a common gentle wine filtration. In both cases the strip water was degassed. Without degassing the oxygen uptake could have been 4 mg/l and more [61]. The resulting strip water from the second step had similar alcohol content as in the direct osmotic distillation of wine. The alcohol content was in a range of 5–7 vol.%. Compared to treatments based on distillation, the membrane treatments are compact build and mobile. They just require electricity and water of certain softness. Furthermore small lots can be treated, allowing pretrials to assess the final

Vacuum rectification is a continuous process, and the systems which are used in

The usual minimum quantity to be treated is 1000 l. At the end of the treatment,

For example, if 1000 l wine with 14 vol.% are treated, 135 l of pure ethanol are separated. According to the operation of the column, the spirit fraction has an alcohol content up to 80 vol.% Values above that are not to be recommended as the hazard of explosion increases by such high ethanol contents. Assuming an alcohol content of 80 vol.%, 168 l of spirit are separated. Approximately 830 l of alcoholfree wine are remaining that can be used for diluting the alcohol content of the

Corresponding plants already exist in Germany for more than 100 years. The number of companies offering dealcoholization based on vacuum rectification has grown significantly during the last years. Common systems are designed for flow rates of 1000–5000 l/h of wine. The respective rectification columns are on site, and the legal settlement terms in distillation are in charge of the service-

the beverage industry have a capacity of 300 l/h upward.

the alcohol content of the wine is below 0.5 vol.%.

In the first step, permeate is reduced in alcohol by osmotic distillation. The strip water for the osmotic distillation is not pumped in a closed circuit; there is a continuous flow of heated water through the membrane contactor. These process parameters are chosen so that as much alcohol as possible can be separated with this system per time. The alcohol transfer through the membrane is increased by elevated temperatures, and the vapor pressure difference of the respective substances is significantly higher with continuous supply of new strip water than

with a closed strip water cycle and limited water amounts [14, 27].

**260**

The spinning cone column is generally used for the separation of volatile components from different liquid–solid mixtures.

The universal applicability of this plant explains its widespread use in various areas of the flavor, food, and beverage industries. In the wine industry, it is used for desulfurization, dealcoholization, and partial alcohol reduction.

Similar to vacuum rectification systems, the spinning cone column is due to its size and infrastructure requirements not suitable for mobile use. Already the pilot plant for trials has a height of 4 m and a weight of 5 t. The need for steam is approximately 85 kg/h with required working pressures of 6–8 bar for a problemfree operation. These parameters are very difficult to realize with common steam generators and pipes applied in the beverage industry. For optimal operation a cooling system of 60 kW is recommended. Systems of that size are to be found just in bigger wineries or cooperatives. Corresponding aggregates for cooling and steam can be rented as mobile systems, but this will generate further costs.

The treatment takes place in two passages at different process temperatures. The performance of the SCC is therefore significantly reduced compared to a conventional rectification column. The spirit fraction resulting from the spinning cone column treatment has just an alcohol content of about 50 vol.% For the commercialization in bulk, a further distillation step, to increase the alcohol content, is recommended. This would be easy to realize with another distillation stage directly at the plant. This could also reduce the loss of volume by returning the nonvolatile residue to the wine. The two passages through the spinning cone column allow a recovery of a very volatile fraction that is separated and blended back to the alcohol fraction after the second passage. Due to that practice, the most volatile components are recovered and are not lost in the ethanol fraction. The declaration of that pre-run as aroma is irritating and led to many misinterpretations of the process. The pre-run of the process is not selectively positive. It is coined by descriptors such as pungend, sulfur coined, and solvent.

From a business perspective, the use of the spinning cone column in the wine industry is conceivable above all as a contracted service. Permanently installed it is used for dealcoholization, partial alcohol reduction, and desulfurization.

### **3.6 Water addition**

The dilution of must with water is the simplest and cheapest solution to reduce the sugar content and thus the subsequent alcohol content. The addition of water dilutes all wine components. This concerns the positive and negative sensory aspects. The water used is not really a cost factor. On the other hand, the volume increase by adding water can have a significant impact in terms of sales. In order to avoid possible negative influences on the subsequent wine quality, the amount of water should be minimized and neutral in terms of taste, free of microorganisms and microbiologically active substances.

Similar to sugar reduction by membrane coupling, the key benefits to be seen are improved fermentation kinetics with less residual sugar in the end. In some wineproducing countries, this practice is legal.
