Modern cross-flow filtration technologies in the winery help winemaker to speed up and improve the wine production process

Membrane filtration – Wine industry

Separation through membrane filtration began in the early 1960s to become, around twenty years later, a technology also used in the wine industry for a wide range of applications. Although the application principle is conceptually simple, the use of membrane filtration involves complex aspects, such as:

• technological knowledge concerning both the product to be treated and the fractions resulting from the separation;
• plant solutions able to achieve the expected industrial performance, guaranteeing the quality of the product resulting from the treatment.

In recent years, membrane separation technologies have found more and more space and increased application in the wine sector, both within the production cycle and in the management of by-products.

SEPRA provides a complete line of membrane elements for food applications, which are used to concentrate, separate and purify in a vast field of applications.

Applications

Membrane separation processes by means of tangential filtration have been used for more than 20 years for the treatment of food solutions of various kinds. Membrane processes in fact have some peculiar characteristics that are well suited to this type of product:

• High flexibility, due to the possibility of using membranes with pores of different sizes and elements of different construction;
• Low energy commitment;
• Sanitation and good microbiological control;
• Modest mechanical and thermal stress on the product.

The type of membranes used obviously depends on the objectives of the specific application. By acting on the porosity of the membrane it is possible to selectively intervene on the different components: the attached "Filtration Spectrum" table exemplifies these possibilities.

Over time, membrane separation technologies have come to the fore in the production of wines and musts. The ability of the membranes to select, within certain limits, the passage and retention of structural elements of the must or of the wine allows effective operation on the product structure, with surprising results.

There are four main separative membrane processes, each of which is specific in allowing the retention or permeation of specific components during the passage through the semipermeable membrane. The following are some of the applications of the technology to the wine sector.

UF - MF pHT Membranes

The pHT series membranes offer exceptional physical and chemical resistance while maintaining the same MWCO ranges as the standard elements.

In particular they allow:

• Hot sanitization, eliminating the need for the chlorine-based phase during CIP;
• High resistance to extreme pH levels and high temperatures;
• High resistance to fouling.

Concentration

With the tangential filtration membranes it is possible to obtain a forced concentration, which allows a natural increase of the sugar degree, of the alcohols or of other compounds; an increase in the colour body is also obtained in young wines.

Partial dealcoholization

By combining a tangential membrane filtration system with other technologies it is possible to obtain a reduction of the alcohol present down to low levels.

Clarification

With ultrafiltration membranes it is possible to filter the must before the fermentation tank to eliminate opacifying substances, tannins or yeasts, accelerating the maturation process and improving its quality.

Discolouration

For reasons of appearance, a partial or total discolouration is sometimes required, which can be pursued with specific membrane systems.

Deacidification

It allows the elimination of a part of the volatile acidity only, maintaining the remaining structure of the wine.

Traditional filtration in the wine industry

Prefiltration

Pleated filtering cartridges with absolute filtration degree

Preliminary filtration after the fermentation phase or between various processing phases eliminates any impurities that can pollute the subsequent phases, as is the case, for example, with tartrate crystals coming from the maturation tank.

0,2 µm	0,45 µm	1 µm	3 µm	5 µm	10 µm	20 µm	30 µm

Final filtration

Sterilizing filter cartridges with pleated membrane with absolute filtration degree

A final filtration of the wine before bottling, with an absolute cartridge with different degrees of filtration (0.1–1.2 µm) to adapt to the characteristics of the wine, guarantees the removal of any microbiological pollution, increasing the durability of the wine.

0,1 µm	0,2 µm	0,45 µm	0,65 µm	0,80 µm	1,2 µm

Ozone in the wine industry

Ozone (O₃, an allotropic state of oxygen) is an unstable gas composed of three oxygen atoms; it is mainly produced by subjecting oxygen to electrical discharges, to ultraviolet radiation and also to some chemical processes.

Ozone is a strong oxidizing agent, capable of reacting with organic substances having a double bond (unsaturated), and this characteristic has been readily used in many water and air treatment processes. Its bactericidal, fungicidal and virus-inactivating effect has been known for a long time (Sonntag, 1890).

Ozone does not alter the characteristics of water, in particular the taste (Viebahn, 1977), and generates a smaller amount of harmful by-products.

To validate the absolute compatibility of ozone, in the right measures, with human activities, since 26 June 2001 the FDA has admitted the use of ozone also in the production processes of the food industry.

Ozone in gaseous form or in the form of ozonized water is ideally suited to the resolution of all sanitizing needs of cellars.

Ozone in a gaseous stage

• Sanitation of stainless steel and concrete tanks
• Barrel sanitation
• Control of microbiological charge in drying rooms

Ozone in a liquid stage

• Reduction of the bacterial load of all cellar surfaces
• Sanitation in bottling plants

Among the main features that make sanitizing with ozone advantageous, we find:

• Absence of residues: once the ozone molecule has ceased its action, it is degraded to the more stable form of gaseous oxygen;
• Reduction of water consumption in rinses: the absence of formation of by-products significantly reduces the quantities of water used in rinses;
• Reduction in the consumption of chemicals and steam;
• Improvement in the quality of waste water: the reduction in the use of chemical products improves the COD (Chemical Oxygen Demand) and BOD (Biological Oxygen Demand) parameters of the water destined for purification.

ORP (Oxidation Reduction Potential)

For generations, winemakers have used pumps and mixers to aerate and shake the wine during fermentation.

Today, technology meets these needs to optimize and create the conditions to produce balanced and colourful wines without the formation of hydrogen sulfide and other products of reductive reactions.

The pumping system is combined with a venturi that creates a vacuum, causing the aspiration of air from the external environment.

The high exchange efficiency allows the oxygen levels in the wine to be considerably increased.

Cleaning of membrane filters

As regards membrane filtration in the oenological sector, fouling phenomena are well known and documented and usually occur after the accumulation of protein and fat matrices on the surface and in the porosity of the membrane, which gradually inhibit their permeability.

The chemical/physical characteristics of the product sent for concentration, the operating conditions to be maintained during processing according to the user's needs, and the sensitivity of the operators managing the plant synergistically determine the speed of fouling of the membranes.

Detergents

Taking advantage of its experience in the use of membranes in tangential filtration systems, SEPRA has developed a line of chemical products aimed at solving the specific problems that occur in them, such as fouling, incrustation, bacterial contamination, sanitization and conservation.

CIP protocols

SEPRA is able to develop, through identification procedures, the best washing procedures dedicated to the cleaning of membrane filtration systems, to be put in place to ensure optimum productivity.

• Restoration of flow rates;
• Plant performance maintenance;
• Cost-effective;
• Action against the development of biofilms;
• Responsible choice.

Integration of the enzymatic phase with the cleaning of membrane filters

An enzyme is defined as a catalyst of a biological process; its role consists in facilitating reactions through the interaction between the substrate (the molecule or molecules participating in the reaction) and its active site (the part of the enzyme in which the reactions take place), forming a complex. After the reaction, the product is removed from the enzyme, which remains available to start a new one.

The enzyme therefore substantially and irreversibly transforms the organic matter into water-soluble, smaller-sized residues that are easily removed.

Depending on the type of substrate on which they act, they are grouped into different families; for example:

• Proteases ⇒ Hydrolytic action on the protein fraction;
• Lipase ⇒ Hydrolytic action on the fat fraction;
• Amylase ⇒ Hydrolytic action on the sugar fraction;
• Cellulase ⇒ Hydrolytic action on the fibrous fraction.

Therefore, the need to integrate the traditional washing protocol based on acid/alkaline detergents with at least one more or less intensive and frequent enzymatic phase, according to what has just been described, is well known.

Water treatment for use and re-use in the oenological area

The production activity of a winery requires large quantities of water, which is used both for processing the product and for washing and disinfecting the premises and equipment.

Falling within the list of food industries, the company must use water for human consumption for its production cycle, which must necessarily meet certain quality requirements.

As an alternative to supply from the public network, the water resource can be supplied by withdrawal from surface or underground water bodies.

To guarantee the potability of the water, SEPRA is able to formulate specific treatments based essentially on the use of:

• Traditional filtration systems;
• Membrane filtration systems (ultrafiltration and reverse osmosis);
• Disinfection and sanitization systems through UV-ray sterilizers and the use of ozone.

• Well water
• Surface water

Water purification in the winery

Membrane bioreactors (MBR)

Grape processing activities generate large quantities of residual liquids and waste water.

Cellar wastewater is completely free of toxic agents or inhibitors of bacterial activity, but due to its high organic content it is not always easy to treat in traditional sewage treatment plants. All this causes difficulties in the management of waste water and often the failure to achieve the limits set by the regulations for discharge.

Solutions promoted by SEPRA

Taking advantage of the experience gained in the field of wastewater treatment, SEPRA proposes approaching the problem of purifying wastewater with membrane technology.

Biological reactors derive from the coupling of traditional suspended biomass processes with filtration processes on porous membranes.

Unlike traditional systems, which base their working principle on the capacity of certain bacterial strains to aggregate into sedimentable flakes, the use of MBR technology allows complete disengagement from the sedimentation characteristics of biomass. This means a considerable reduction in the volumes of the tanks and therefore in the space required for the purifier.

The use of semi-permeable membranes allows the elimination of the sedimentation unit, guaranteeing a fixed and inviolable barrier capable of retaining suspended solids in addition to bacteria and some viruses, ensuring a constantly very high quality effluent.

Pilot plants

SEPRA makes available a complete support service for the feasibility evaluation of innovative processes, guaranteeing the presence of qualified technicians in all critical phases of the process (start-up, washing, change of operating parameters), with the definition in particular of:

• definitive scale-up;
• assessment of fouling and membrane duration;
• tuning of washing cycles.

Plant / Technology	Process
Spiral wound polymeric plant LP	MF, UF
Spiral wound polymeric plant HP	NF, RO
Ceramic tubular plant	MF, UF
Ozone generator	Process
MBR	Waste water
Spiral wound polymeric plant	Washing water
Anaerobic digestor + UF	Biogas

Components

Thanks to the collaboration with the main national and international producers, SEPRA is able to supply all the components necessary for the construction of new plants or for the revamping of existing installations.

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