WO1998026041A1

WO1998026041A1 - Beer processing

Info

Publication number: WO1998026041A1
Application number: PCT/GB1997/003415
Authority: WO
Inventors: Malcolm Mckechnie
Original assignee: Brf International
Priority date: 1996-12-11
Filing date: 1997-12-11
Publication date: 1998-06-18
Also published as: GB2320256A; GB9625764D0; AU7847598A

Abstract

A method for single stage processing of beer in which green beer from a fermenter passes directly to filtration. The filtration step produces beer of sufficient clarity and colloidal stability that there is not requirement for separate conditioning of the beer.

Description

BEER PROCESSING

The present invention relates to a method for processing beer and more particularly to a method for filtering beer using cross flow microfiltration.

In the brewing process beer is produced using the following general procedure. Barley seeds are encouraged to begin to germinate and before the seeds start to grow,

germination is stopped by a gentle heating process. This is the so-called malting process. The germinated barley or malt is then ground up and mixed with warmed water to allow enzyme activity to proceed. This is the wort production step and hops or their extracts are generally added at this stage. A yeast starter culture is then added and the fermentation process begins.

Beer run off from a fermenter (often termed "green beer") is not ready to drink; it must first go through a period of maturing or conditioning and then filtration, unless cask conditioned ale is being produced.

The conditioning process is conducted at or below about 0°C and has several objectives. Firstly, it produces beer with good colloidal stability. This is achieved by removing haze forming materials. Secondly, it clarifies the beer prior to filtration thereby helping improve filtration runs. Thirdly, it provides flavour stable beer and helps ensure no undesirable off flavours develop during and after packaging. Fourthly, it allows for adjustment of critical beer parameters so that the product is within the required specification following filtration and dilution.

During cold conditioning, the bulk of the suspended solids (yeast, carbohydrate and proteinaceous material) settle in the cone of the cylindroconical vessel that is typically used. These "tank bottoms" are removed and processed separately, usually by centrifugation or filter pressing. The most significant effect however is the formation of chill haze (protein -polyphenol complexes).

Proteins and polyphenols are essential for the formation of hazes and therefore removal of one or both of these constituents will reduce the possibility of haze formation. One of the best ways to combat haze is to chill the beer to as low a temperature as possible, preferably below 0°C before the final filtration. This will cause a major proportion of the protein-polyphenol complexes to come out of solution and thus be removable. The chill haze will re-dissolve if the temperature of the beer increases above about 0°C and therefore it must be removed during the cold conditioning stage. If the chill haze is not completely removed, it may persist on into the finished, packaged product. This is undesirable since it could precipitate out at a later stage causing an unacceptable level of turbidity within the predicted shelf life of the final product.

A complementary approach for removal of protein-polyphenol complexes is to use absorbents which are insoluble. The insolubility makes it possible to stir them into the tank and to allow them to settle after reaction. Alternatively, they can be added in dose form into the beer line upstream of the filter. A further alternative is to pack the absorbents into a filter bed for filtering the beer. A common polyphenol absorbent is polyvinylpyrrolidone (PVPP). This material is very expensive and is often re-generated for re-use. It is either packed into a filter or dosed into the beer line prior to filtration. Other absorbents include silica hydrogel such as Lucilite ™ which adsorbs proteins. These can be added either directly to the conditioning tank or dosed into the beer line before it reaches the filtration stage. These adsorbents settle readily and have little effect on beer foam.

Beer run off from the conditioning tank (commonly referred to as "rough beer") is then

filtered at or below 0°C in order to remove the haze particles precipitated during cold conditioning and any remaining yeast or other solid materials. The low temperature is very important since above about 0°C the protein complexes go into solution and pass through the filter. Kieselguhr or diatomaceous earth filtration is still the most popular means of filtering rough beer, however, problems in disposal of the used filter and associated environmental issues have lead the Applicants to look for a better and cleaner alternative.

Alternative filtering methods have been proposed and examples include regenerable filters such as sand beds, ultrafiltration techniques wherein large molecules and other material are removed from a liquid and cross-flow microfiltration techniques wherein filtered particles are maintained in suspension in rapidly re-circulating liquid.

It has been previously proposed to use cross-flow microfiltration to recover beer from fermenter bottoms and tank bottoms. The cross-flow microfiltration technique filters to a very high degree and results in the removal of essential beer components such as head retention proteins and bitterness compounds. The result is a filtered "beer" which is outside the required specification. Since the technique is only utilized in the beer recovery steps the amount of "below specification beer" produced represents only a small percentage of the total beer volume. Accordingly, when the "below specification beer" is added to the rest of the stock, it is diluted out of significance. Because the cross-flow microfilter removes many of the desirable beer components it has not been used as a filtration technique for "rough beer" from the conditioning tank. Furthermore, cross-flow microfiltration techniques were generally considered to fail economically because of low filtration rates which resulted from fouling by proteins and other materials on the microfilter surface. It should be noted that these reasons for the failure of applications of crossflow microfiltration for beer do not appear to apply to cider production.

The cold conditioning step is regarded as an essential stage of the brewing process since the "green beer" from the fermenter must be chilled to precipitate out the chill haze materials and allowed to settle to remove the bulk of the particulate matter. The length of the conditioning period varies from brewery to brewery but is typically between four days to four weeks.

It has long been the conventional wisdom that cold conditioning is essential prior to filtering since without a settling stage unacceptably high additions of filter aid would be required to remove all of the particulate matter. Moreover, without the chilling stage the chill-haze materials remain in solution and thus pass through the filtration stage into the final packaged product. The requirement to store the beer at a low temperature for a period of time makes the cold conditioning step one of the most expensive in the brewing process.

It is an object of the present invention to provide an alternative filtration technique for filtering rough beer.

It is a further object of the present invention to significantly reduce or eliminate the cold conditioning period in beer production.

As stated above, following cold conditioning, the bulk of suspended solids settle to form the "tank bottoms" which are processed separately. It is another object of the present invention to provide a method for processing beer wherein there is no need to process tank bottoms separately.

It is yet another object of the invention to provide a method for processing beer to remove chill haze wherein cooling to below 0°C is not required.

According to the present invention there is provided a method for single stage processing of beer wherein the beer passes directly from fermentation to filtration, the said filtration being effective to produce a beer having colloidal stability and clarity such that the requirement for separate conditioning is substantially avoided.

The present invention also provides a method for single stage processing of beer wherein the beer is filtered using a cross-flow microfilter. The present invention further provides a method for single stage processing of beer wherein the filtration step can be conducted at above 0°C.

Accordingly, the Applicants have developed a method for processing beer that not only substantially avoids the requirement to cold condition the beer but also allows the beer to be filtered at temperatures above 0°C. The present invention utilises a surprising and unexpected technical effect which is completely contrary to the prejudice in the art

The exact mechanism by which the claimed filtration method works is not fully elucidated however, it is believed to result from the formation of a fouling layer or secondary membrane which develops during a cross-flow microfiltration run. The membranes used in the filtration system are selected to have pore sizes sufficient to allow the desirable beer components through however, the fouling layer has structural characteristics such that chill haze material is retained in or on the fouling layer, even at temperatures where the chill haze materials are in solution, whilst allowing the desirable beer components to pass through.

Processing the beer at temperatures above 0°C where the chill-haze materials are in solution has the advantage that the viscosity of the beer is decreased allowing the flux through the filter system to increase significantly. Furthermore a higher filtration temperature substantially avoids the need for chilling. This saves energy since the temperature does not need to be maintained by refrigeration and less heat needs to be removed from the circulating retentate. The following non-limiting examples are intended to describe the nature of the invention more clearly: -

Laboratory scale crossflow microfiltration trials at BRF International and on site were conducted on the "Ceramem" ceramic membrane module shown in Figure 1, however,

similar results are obtained using other membrane types. The physical characteristics and operating conditions of this membrane are given in Table 1 and Table 2 respectively below. The trials were conducted using BRF International's laboratory crossflow rig.

TABLE 1

TABLE 2

Operating Conditions.

Warmer Filtration

In order to investigate the effect of filtering at elevated temperatures on filtrate productivity, crossflow trials were performed at < 3°C (which is representative of that commonly practised), 10°C, 15°C and 20°C. Runs lasting an average of 5 hours were performed at a transmembrane pressure of 1.3 bar and crossflow velocity of 2.2ms^"1. A commercial rough beer type was used in all trials.

Colloidal stability (the period of time that a beer can be stored until its haze value becomes unacceptable) was investigated by forcing hazes in filtrate samples ie chemically inducing any haze forming material. An ethanol forced haze was used; 3ml of 96% ethanol are added to 100ml of beer which is then stored for 24h at 0°C and the haze is then read. The lower the haze reading the more stable the beer.

Site Trials

Runs lasting an average of 12 hours were preformed at approximately 10°C using the Ceramem membrane module in order to investigate the effect of warmer filtration on filtrate throughput and product quality. A control trial at 3°C was also undertaken. Samples were taken throughout the course of each filtration trial performed and analyzed typically for chill haze (haze that forms at 0°C but redissolves at 20°C), ambient haze, colour, present gravity (PG), head retention values (HRV) and bitterness. HRV values relate to the foaming potential of a beer, the higher the better.

Warmer Filtration Trials

The results showed that filtrate productivity increased as the temperature progressively increased. An example is given in Figure 2. This flux increase certainly has a very positive impact on the economics of crossflow microfiltration, however, the crucial point is the filtrate quality. "Ethanol Forced Haze" analyses were used to investigate colloidal stability of the filtrates and typical results are presented in Table 3. Filtrate stability appears acceptable at 15 °C but not 20°C. No evidence for damage to sensitive foam proteins was observed when filtering at these elevated temperatures. TABLE 3

Typical haze values achieved when filtering at 15 and 20°C

Site Trials

Trials were all performed for 12 hours at 10°C using the same batch of ex-fermenter beer. It can be seen from Table 4 that with the exception of Trial 5 the average fluxes achieved did not vary significantly. TABLE 4

Data for Ceramem.10°C

The results of the analyses undertaken on samples from these trials showed that in all trials there was a slight reduction in colour due to filtration but the values were still acceptable and did not vary significantly during the course of a run. There was also a slight but not significant drop off during some trials in present gravity, original gravity and HRV. Bitterness, pH and alcohol remained stable throughout the runs. An example

of the results obtained are given in Table 5.

TABLE 5

Quality analyses on samples taken during Trial 4 (Ceramem. 10°C).

Key Rough - Rough beer

Sample 1 - Sample taken at start of run (after 10 minutes)

Sample 2 - Sample taken 6 hours into run

Sample 3 - Sample taken at 11 hours into run

For each trial approximately 501 of filtrate (bright beer) was collected. Since the least volume that could be canned was 4001, it was decided to combine the filtrates from trials, dilute with deaerated liquor (water) to sales gravity and then can. Results of analyses on these cans are shown in Table 6. All values are within specification. TABLE 6

Results of analyses on cans from CeraMem filtration tπals undertaken al 10°C (Brewery QC)

A control run at 3°C was performed in order to compare product qualities at the higher and lower temperatures. The trial was performed using the same batch of rough beer as used previously. The average flux achieved over a nine hour period was 15.5 L.m ^"2h^"' (Figure 3). This is considerably lower than the fluxes achieved at 10°C using this batch of beer thereby confirming that increasing the temperature increases filtrate throughout.

Analyses again showed that filtration resulted in a slight but not significant reduction in colour and that the colour then remained stable throughout the run. There was a slight loss of original gravity and alcohol at the start of the run as a result of dilution by water held within the membrane but this self rectified during the remainder of the run. All other variables remained stable throughout the run. It can be seen that analytical results from the control trial were not significantly different from the 10°C results indicating that warmer filtration does not affect colour, present and original gravity, alcohol, bitterness, HRV and pH. Data for the control trial are shown in Table 7 TABLE 7

Quality analyses on samples taken during the control run.

Key : Sample 1 - Start of run. Sample 2 - after 4.5 hours, Sample 3 ■ after 9 hours, Sample 4 - cumulative

Claims

1. A method for single stage processing of beer wherein the beer passes directly from fermentation to filtration, the said filtration being effective to produce a beer having colloidal stability and clarity such that the requirement for separate conditioning is substantially avoided.

2. A method for the simultaneous filtration of beer from a fermenter and recovery of beer from sediments in the fermenter to yield a beer of similar quality.

3. A method as claimed in Claim 1 or Claim 2 wherein the beer is filtered using a cross-flow microfilter.

4. A method as claimed in Claims 2 or 3 wherein the filtration step an be conducted at above 0°C and below 20°C.

5. A method as claimed in Claim 4 wherein the filtration step is conducted at between 5°C - 15°C