Beverage filtration

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Beverage filtration is a term from beverage technology . Different membrane processes are used for this.

Procedure

Cross-flow microfiltration of wine

Here, micro-filters (0.1-0.2  microns is used). In order to avoid a rapid increase in the lees concentration in the circuit within the system (circulation pump and modules), the systems for wine filtration are operated with a concentration device, i.e. H. a small volume of retentate is continuously discharged from the circuit back into the unfiltrate container. A feed pump pushes in product in order to supplement the discharged filtrate and concentration volume.

The two-pump system known from reverse osmosis is designed so that the circulation pump moves large volumes at low pressure, while the feed pump provides the necessary transmembrane pressure. This results in a number of advantages: the closed system prevents aroma and CO 2 losses and avoids the absorption of oxygen , the reduced energy input through the two-pump system results in minimal product heating.

The main task for tangential flow filters in cellars is the filtration of young wines after the first racking ; If the recommended regeneration steps and temperatures are adhered to, almost germ-free filtrates can be achieved. Further areas of application are interrupting fermentation by separating the microorganisms ( Seitz-Böhi process ), filtering depectinized and refined grape juice before pasteurization and sterile storage ( sweet reserve ), as well as sharp pre-filtration of the ready-to-fill blend (pre-filtration).

Cross-flow microfiltration of fruit juices

In addition to modified systems for wine and sparkling wine filtration, special fruit juice filters are also available, which have proven themselves very well in various stages of fruit juice production . The basic requirement, however, is the use of pectolytic enzymes and, if necessary, starch-degrading enzymes as well as fining with gelatine and silica sol . As a rule, it is possible to reduce the amount of fining agent, but it is always advisable to first determine exactly what is needed in the laboratory to ensure that the filtrates are stable.

When processing fresh juices directly or before storage of the KZE, a method with or without retentate concentration is possible. This results in average flux rates of 35 to 90 l / m² h in relation to the juices to be filtered. If the juices are to be concentrated, there is both the option of running at temperatures of around 50 ° C and correspondingly high performance after the aroma separation and hot enzymation, as well as storing the product as a cloudy concentrate and only filtering it when it is diluted back to drinking strength. This way of working is particularly advantageous in apple juice production because the enzymation, fining and filtration take place outside of the labor-intensive pressing season, i.e. shortly before bottling, and the CMF system can be operated according to the principle of periodic water sweetening. A professional MF system allows the following steps:

  • Juice rediluted to approx. 15–17 degrees Brix
  • Pectin and starch degradation (approx. 3–4 h at 15–20 ° C)
  • Gelatine and silica sol fining, bentonite fining as required
  • Tangential flow filtration directly after adding the fining agent
  • periodic sweetening of the retentate with water
  • Mixing the juice to drinking strength
  • Hot filling.

In practical operation, the filtration intervals between the sweetening are around 1 to 3 hours, depending on the sediment content. The process of sweetening takes place automatically via the microprocessor - first, a certain preselectable volume of water is supplied to the system from a water reservoir with the help of the inductive flow meter and in this way the product in the retentate is largely displaced. The filtrate is diluted by <1 to 2 ° Brix while the aqueous retentate then only contains around 3 - 4 g / l sugar, corresponding to approx. 1 ° Brix. In addition to low product losses of <0.6%, the periodic feed-in of water by rinsing and removing the top layer increases performance. With average flux rates of 50 to 60 l / m² h over a period of 10 to 15 hours, volumes of 70 to 90 l / m² h are calculated after redilution to drinking strength.

Characteristic features of the CMF technology are the elimination of filter aids, ie their procurement, storage, handling and disposal, the rapid, labor-intensive and quality-friendly processing.

Candle filter

The candle filter consists of a filter housing and an inserted candle through which the raw drink flows from the outside to the inside. The candle in turn consists of a wound thread made of synthetic or natural material. The combination of a plate filter with a membrane end filter before filling is a reliable variant of the primary clarification, especially when there are products that are difficult to filter. A service filter for the supply media cold water and hot water, steam and lye avoids secondary problems caused by particulate contaminated regeneration and sterilization media and ensures the best possible regeneration.

Two types of candle prefilters have been optimized with regard to effective protection of the downstream membrane filter:

  • a pleated configuration, consisting of glass fiber pre-filter fleece and a 1.2 µm or 0.8 µm membrane,
  • Wrapped, asymmetrical polypropylene matrix with a validated separation rate of 1 µm or 0.5 µm (β value 5000).

Another type, consisting of coordinated, pleated layers of polypropylene fleece, is characterized by mechanical and chemical stability as well as excellent regenerability. It is also used as a validated 1 µm pre-filter cartridge for wines from southern growing areas with low colloidal contamination. There are now a number of areas of application for this candle in the beverage industry:

Seawater desalination

→ see main article seawater desalination

Method without a permeable membrane

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