GB2475397A

GB2475397A - Secondary fermentation of a beverage using yeast immobilised in support structures

Info

Publication number: GB2475397A
Application number: GB201018928A
Authority: GB
Inventors: Richard Westwood
Original assignee: MARSTON S PLC
Current assignee: MARSTON S PLC
Priority date: 2009-11-09
Filing date: 2010-11-09
Publication date: 2011-05-18
Also published as: GB201018928D0; GB0919507D0

Abstract

A secondary fermentation method for a beverage is disclosed comprising adding to the beverage held in a container a material adapted in use to effect secondary fermentation, for example, yeast, wherein the material is provided with a support, such as a porous gel that immobilises the material. The immobilised yeast may be present in yeast-containing alginate beads. The yeast-containing beads may further comprise a second layer, which does not contain yeast cells, which encapsulates the inner layer containing the yeast. The support beads settle out of suspension in the beverage (e.g. beer) in a set period of time during the secondary fermentation process.

Description

IMPROVEMENTS TO SECONDARY FERMENTATION OF A

BEVERAGE

The present invention relates to an improvement to secondary fermentation in the brewing industry, particularly in relation to cask conditioned beers.

In the brewing industry, particularly in the production of beer, the beverage is produced during a primary fermentation process in which sugars are metabolised into alcohol by yeast. A secondary fermentation step is necessary where the beverage is beer to allow the beverage to mature and be carbonated. This secondary fermentation step occurs in a separate container to the first fermentation step and this container can be the final container from which the beverage will be dispensed, for example a cask, barrel or keg. The container can also be a mini-cask (5-litre), a can or a bottle.

The secondary fermentation step involves the addition of further yeast which ferments sugars still present after the primary fermentation step or added for the secondary fermentation step. The secondary fermentation step produces carbon dioxide which carbonates the beverage. The secondary fermentation step also matures the beer and enhances its flavour and appearance.

However, the secondary fermentation step also gives rise to a beverage containing yeast which tends to be suspended in the beverage. Thus after secondary fermentation it is necessary for the beverage to be allowed to settle for a period of at least twelve hours at a temperature of less than 14°C before the beverage can be dispensed otherwise the beverage dispensed will appear cloudy.

This means that settling time at low temperatures is required after any transportation of the beverage, for example after delivery to an end sales venue or even after moving around within that venue. This can result in loss of sales for the end sales venue if there is a delay in being able to dispense the beverage desired for sale. It also means that such beverages cannot be provided at events where settling cannot occur before dispensing due to time constraints, or the venue not being sufficiently stable to allow settling to occur, for example a boat.

It is usual to add finings to remove organic compounds from suspension in a beverage such as beer; to either improve clarity or adjust flavour/aroma. However, finings do not always ensure complete settling of the yeast and an amount of settling time sometimes of greater than twelve hours at low temperatures is still required.

Therefore, there remains a need in the brewing industry, particularly in relation to beer, for an improved second stage fermentation process that reduces the settling time required before the beverage can be dispensed either after secondary fermentation has been completed or after the container has been disturbed. It would also be beneficial if there could be provided a method of preventing the yeast used in the secondary fermentation step from making the beverage cloudy in situations where the venue is not totally stable and therefore the beverage is disturbed to a certain extent while being dispensed.

According to a first aspect of the present invention, there is provided a secondary fermentation method for a beverage comprising adding to the beverage held in a container a material adapted in use to effect secondary fermentation wherein the material is provided with a support that immobilises the material.

The material adapted in use to effect secondary fermentation may comprise a yeast. As an alternative or in addition the material may comprise one or more enzyme complexes, for example isolated enzyme complexes.

The support may be any suitable support that immobilises the material such that at least a large proportion, preferably substantially all, or all, of the material settles out of suspension in the beverage in a set period of time or less.

A large proportion may be 50%, 60%, 70%, 80%, 85%, 90% or 95%.

The set period of time may be 5 hours or less, preferably 4 hours or less, more preferably 3 hours or less, most preferably 2 hours or less, for example 1 hour or less. The set period of time may be a matter of minutes, for example 50 minutes or less, preferably 45 minutes or less, more preferably 30 minutes or less, most preferably 15 minutes or less, for example 10 minutes or less. The material may settle out of solution immediately.

The support may comprise a porous matrix. The matrix may comprise a natural or a polymeric gel. Suitable natural gels may include alginates, for example calcium alginate, pectates, for example calcium pectate, or k-carrageenan. Suitable polymeric gels may include polyvinyl alcohol (PVA).

The porous matrix may be formed around the material. Alternatively the material may diffuse into a preformed porous matrix.

The porous matrix containing the material adapted in use to effect secondary fermentation may be formed into beads. The beads may have a diameter of 0.3 to 3mm for example 0.5 to 2.5mm or 1 to 2 mm. Where the porous matrix is calcium alginate the most preferred diameter range is 0.5 to 0.6mm.

The beads may each comprise a body comprising a mixture of the material forming the porous matrix and the material adapted in use to effect secondary fermentation, encapsulated by a layer of the porous matrix which does not contain the material adapted in use to effect secondary fermentation, or which contains a significantly lower amount (say, less than 10% of the content of the body) of the material adapted in use to effect secondary fermentation than in the body.

The porous matrix may be secured to the container.

The porous matrix gives a high density support and does not affect the properties of the material adapted in use to effect secondary fermentation nor the level of fermentation that can be achieved.

The support may comprise glass beads, silicon carbide or gluten pellets.

The material adapted in use to effect secondary fermentation may be attached to the surface of the support.

The container may be a cask, barrel or keg. The container can also be a mini-cask (5-10 litre), a can or a bottle.

The use of the method of the invention in relation to casks, kegs, barrels and mini-casks of a beverage allows a quantity of the beverage to be delivered to a venue or moved around within a venue and then served to the customer within a short period of time thus alleviating the problems caused by the need to previously allow settling time. The use of low temperatures is also no longer required with the present method.

In relation to bottles and cans of beverage the present method allows the provision of a cask conditioned beer in a bottle or a can. The method would avoid the need for careful storage and transport of the bottles or cans as settling would occur quickly on arrival at point of sale and without the need to use low temperatures.

The secondary fermentation method should not impact adversely on the carbon dioxide production, resistance to bacterial infection, flavour or ability of the beer to re-fine.

According to a second aspect of the invention, there is provided a method of forming a material adapted in use to effect secondary fermentation in a beverage with a support that immobilises the material, comprising providing a mixture of the material adapted in use to effect secondary fermentation and a precursor matrix material, and dripping the mixture dropwise into a curing solution, the curing solution acting to turn the precursor matrix material into a porous matrix.

According to this method, beads of a material adapted in use to effect secondary fermentation embedding in a porous matrix can be formed.

Typically, they would be used in method according to a first aspect of the invention.

The material adapted in use to effect secondary fermentation may comprise a yeast. Typically, the porous matrix will comprise a gel. In the preferred embodiment, the precursor matrix material comprises sodium alginate, and the curing solution comprises a calcium chloride solution. In such a case, the porous matrix will comprise calcium alginate.

The method may further comprise the step of adding a layer of the porous matrix which does not contain the material adapted in use to effect secondary fermentation, or which contains a significantly lower amount (say, less than 10% of the content of the body) of the material adapted in use to effect secondary fermentation than in the body. Typically, this method may comprise the step of coating the cured beads in a layer of matrix material or precursor matrix material which does not contain the material adapted in use to effect secondary fermentation, or which contains a significantly lower amount (say, less than 10% of the content of the body) of the material adapted in use to effect secondary fermentation than in the body, and then typically using a curing solution to cure the precursor matrix material.

The beads may have a diameter of 0.3 to 3mm for example 0.5 to 2.5mm or 1 to 2 mm. Where the porous matrix is calcium alginate the most preferred diameter range is 0.5 to 0.6mm.

According to a third aspect of the invention, there is provided a yeast bead for use in effecting secondary fermentation in a beverage, the yeast bead comprising a body comprising yeast held within a porous matrix material. The bead may further comprise an encapsulating layer of porous matrix material which does not contain yeast, or which contains a significantly lower amount (say, less than 10% of the content of the body) of yeast.

Typically, the porous matrix will comprise will comprise calcium alginate. The beads may have a diameter of 0.3 to 3mm for example 0.5 to 2.5mm or 1 to 2 mm. Where the porous matrix is calcium alginate the most preferred diameter range is 0.5 to 0.6mm.

Examples

In order to gain scientifically sound results, it is important that the samples subjected to the method of the invention (the trial samples) and the control samples are, as far as possible, treated identically. However in order to obtain bright (not cloudy), cask beer it was necessary to use re-racked beer for the purposes of these examples. This means that the trial samples would have been subject to mobilized yeast for a 24 hour period prior to the immobilized yeast beads being added.

Figure 1 shows the results of the CO2 level test shown in Table 1; and Figure 2 shows the results of the method for drop bright analysis test shown in Tables 2Aand 2B;

Example 1

Preparation of Immobilized Yeast Prepare 4% w/v sodium alginate solution.

Prepare 1.5% w/v calcium chloride solution.

Add brewing yeast (NCYC number RiOl) to 4% sodium alginate solution in equal parts and homogenise.

Draw up the yeast/alginate suspension into a sterile syringe.

Add the mixture drop wise to the 1.5% calcium chloride solution and allow the formed beads to harden for approximately 30 minutes.

Separate the beads from the solution using a strainer.

Store in fridge.

1. Method for the Analysis of CO2 Production Two kilderkins of Banks's Bitter were racked and stillaged and a CO2 sample taken from each for analysis. They were then allowed to settle for 24 hours at which time another CO2 sample was taken from each in order to identify that both casks were fermenting at an equal rate. One kilderkin was then re-racked into a firkin and the immobilized yeast was added (trial). Another CO2 sample was taken at this stage to determine how much CO2 was lost during the rack fining procedure. In order to keep the variables to a minimum the other kilderkin was remixed and re-racked into a firkin (control) and a CO2 sample taken for analysis. These CO2 results represent time zero of subsequent analysis. CO2 samples were then taken every 24 hours for a total of 7 days.

A total of three investigations were carried out using the above procedure to prepare the control and trial firkins. The first of which ascertained how the immobilized yeast (trial) would fair against a control with no additional primings added.

The results of this investigation appear in Table 1 below.

Time of test CO2 Content gil CO2 Content (Day) Control gil Trial 0 1.94 1.99 1 1.96 2.00 2 1.97 2.01 3 1.96 2.01 4 1.97 2.02 1.98 2.03 Time of test CO2 Content gil CO2 Content (Day) Control gil Trial 6 1.99 2.02 7 2.00 2.03

Table 1

The graph for the above data appears as Figure 1.

2. Method for Drop Bright Analysis One kilderkin of Banks's Bitter was stillaged and allowed to settle for 24 hours after which time it was re-racked into a firkin and the yeast beads were added (trial). A firkin of Banks's Bitter from the same rack number (control) was stillaged along with the one containing the yeast beads. A sample from each cask was taken every 4 hours and the haze was measured using a haze meter to give units of EBC.

Two trials were carried out to determine how quickly the beer containing immobilized yeast became bright compared to a control sample.

The tabulated results of these investigations appear below. The results are presented graphically in Figure 2.

Time Haze (EBC units) Haze (EBC Day (Hours) Control units) Trial 1 0 2.80 0.65 4hrs 1.20 0.78 8 hrs 0.80 0.68 2 21 hrs 0.64 0.68

Table 2A

Time Control Haze (EBC Trial Haze (EBC Day (Hours) units) units) 1 0 17.26 0.77 4 9.15 0.66 8 1.32 1.12 2 12 0.86 0.95 16 0.9 0.9 0.72 0.7 24 0.68 0.73 28 0.6 0.78

Table 2B

3. Bacterial Suppression The ability of immobilized yeast to suppress bacterial infection in comparison to mobile yeast was tested. A sample of Banks's Bitter containing mobile yeast was infected with a strain of Lactobacillus (control). Another sample of the same batch was infected after rack fining and adding immobilised yeast, with an identical level of infection.

Six forcing samples for each test (control and trial) were inoculated with approximately l0cfu/ml of Lactobacillus spp. and incubated for ten days at 27°C. The forcing samples were decanted and observed by microscope for growth and recorded using the in house microbiological grading system as detailed in Table 3A.

Sample Number Trial Control Control (no infection) Nil Nil 1 <VSTL <VSTL 2 <VSTL <VSTL 3 <VSTL <VSTL Sample Number Trial Control 4 <VSTL <VSTL <VSTL <VSTL 6 <VSTL <VSTL

Table 3A

The results showed Lactobacillus spp. did not proliferate in either sample type.

The test was then repeated with an increased level of infection. Each forcing was inoculated with approximately 20cfu/ml of Lactobacillus spp.

The results of this test are shown in Table 3B.

Sample Number Trial Control Control (no infection) Nil Nil 1 VSTL STL 2 VSTL VSTL 3 STL VSTL 4 STL VSTL

VSTL VSTL

6 VSTL VSTL

Table 3B

The results showed that a degree of protection from bacterial infection is given whether the yeast is mobile or not.

4. Microbiological Stability Test One kilderkin of Banks's Bitter was stillaged and allowed to settle for 24 hours after which time it was re-racked into a firkin and the yeast beads were added (trial). A firkin of Banks's Bitter from the same rack number (control) was stillaged along with the trial one. To determine the microbiological stability of the trial in comparison to the control a forcing sample was taken from each cask when they had been filled and subsequently every 24 hours afterwards over a 14 day period and incubated anaerobically at 27 for ten days. The samples were then decanted and observed by microscope for any bacterial infection.

Date Trial Control 11/12 Nil Nil 12/12 Nil Nil 15/12 Nil Nil 16/12 Nil Nil 17/12 Nil Nil 18/12 Nil Nil 19/12 Nil Nil 22/12 Nil Nil 23/12 Nil Nil 24/12 Nil Nil

Table 4

A second set of samples were set up and the process was repeated with the addition of a second microbiological sample being taken from each cask sample which was incubated aerobically at 27°C for 7 days to identify any aerobic infection. A similar pattern indicated a similar degree of protection is given whether the yeast is mobile or not.

5. Temperature Tolerance An immobilized yeast bead was added to each of eight samples of pasteurised, bright beer and incubated at four different temperatures, 12°C, 20°C, 27°C and 35°C, in duplicate. The samples were observed daily for signs of deterioration and sediment. On observation of sediment the sample was decanted and observed by microscope to determine the cause of sediment.

Temperature Visual Sediment Observations (°C) 12 (Cellar) No sediment at 9 Slight cast observed at days. six days.

(Ambient) Visible at 5 days Slight cast at 5 days.

27 (Forcing) Visible at 3 days Obvious cast at 3 days.

(Extreme) Visible at 7 days Slight cast at six days.

Table 5

On observation of sediment the sample was decanted and observed by microscope to determine the cause of sediment. The sediment observed in each of the above samples was identified as brewing yeast, indicating yeast cells have broken free of the alginate matrix.

6. Three Glass Taste Trial A three glass taste trial was set 24 hours after re-rack. In this case both samples were re-racked beer and only the trial sample contained yeast beads.

Each participant was given three samples to judge by smell and taste. Some participants would receive one trial and two controls and some would receive two trials and one control. They were asked to indicate which sample they considered to be the odd one out' and which sample(s) they preferred.

A total of 19 individuals took part in the three glass taste trial. All were asked to indicate which sample they considered to be the odd one out.

Below is a table of the results.

Table 6

Correct? Preferred Participant Yes No Control Trial no 1? 8 11 12 10 As can be seen from Table 6, 8 out of 19 participants indicated the correct odd one out. As can be seen some of the participants who indicated the incorrect sample as being the odd one out preferred to other two samples. Of course, the other two samples consisted of one trial and one control sample so they have been included as having a tick on both Trial and Control boxes above.

This being the case, only participants who differentiated correctly can be considered when evaluating which sample, in general, most people preferred.

Out of the 8 participants who differentiated correctly, 6 people preferred the control and 2 people preferred the trial.

Conclusions:

CO2 Production The preliminary CO2 check (Figure 1) produced an equivalent rise in CO2 in both trial and control samples. The initial CO2 levels in the trial being lower than usually found in cask beer, presumably due to the trial sample having been re-racked. The rise in CO2 level in each was very small and may be due to the fact that both trial and control samples had been primed a significant time prior to the commencement of these tests. At this point it is possible that very little primings remained in solution.

Drop Bright Investigations.

Tables 2A to 2C and Figure 2 demonstrate the times taken for each of the trial and control samples to become suitable for sale. A haze of 1.0 EBC or less is taken to be bar bright'. From the tables and figure it can be seen that two of the three trial samples, those mentioned in tables 2A and 2B, were suitable for sale at time 0.

Bacterial Suppression.

Tables 3A and 3B indicate a similar level of infection for both sample types. This would indicate that the trial samples were not notably more susceptible to Lactobacillus spp.

Microbiological Stability.

Table 4 shows no difference between the microbiological stability of the control and trial samples.

Temperature Tolerance.

Table 5 shows that at temperatures above 12°C all of the samples contained a sediment after 7 days. As indicated the sediment was primary yeast indicating that the yeast had broken free from the beads. However at 12°C no sediment was observed after 9 days indicating that the yeast was not active enough to break free from the beads at this temperature.

Three Glass Taste Trial.

As can be seen from the results in Table 6, 8 out of 19 participants identified the odd one out. In order to obtain a significance level of 5% at least 11 people would have had to differentiate correctly. This means that statistically it can be considered that there was no difference between the two samples.

Example 2

In this example, yeast beads as in Example 1 are encapsulated in a further layer of alginate.

Immobilised yeast beads are produced as discussed with reference to Example 1 above. They are decanted from the calcium chloride solution and placed into a fresh calcium chloride solution and then left to cure overnight at room temp. After the overnight cure the calcium chloride is drained off from the beads.

Sodium Alginate (0.5% wlv) is prepared and autoclaved. This autoclaved Alginate can be stored at room temp. The Alginate in a beaker is placed on a stirrer and turned on to a moderate to high speed. The beads are gradually introduced to the 0.5% Alginate. The beads should be added in a steady even stream to avoid "clumping". It has been found that an excess of Alginate is required to prevent "clumping" during this coating procedure.

As the beads are added and the 0.5% Alginate is taken up, the speed of the stirrer will slow. The speed should not be allowed to drop to a level where a layering effect is apparent in the beaker, that is beads at the bottom of the beaker are stirring whilst beads at the top are stationary.

The beads are left in the 0.5% Alginate for no longer than 2 mins and then the excess Alginate is rinsed from the beads with sterile water agitating them to separate the beads. The beads are returned to a fresh calcium chloride solution and allowed to cure for a minimum of lhr 3Omins.

The beads are then rinsed with sterile water as in the method described above in Example 1. Post final rinse excess water is shaken off and the beads stored in sterile containers.

Small-scale laboratory tests have found that the use of these "double encapsulated" bead improves the shelf life of the beer compared to the "single encapsulated" beads of Example 1 by reducing the migration of yeast cells from the beads into the beer. Forcings tests were performed with both beads according to Example 1 and Example 2. Results showed that beads according to Example 1 did leach some yeast into the beer, and so caused a degree of haze, but forcings containing Example 2 beads remained bright.

Claims

CLAIMS1. A secondary fermentation method for a beverage comprising adding to the beverage held in a container a material adapted in use to effect secondary fermentation wherein the material is provided with a support that immobilises the material.
2. The method according to claim 1 wherein the material adapted in use to effect secondary fermentation comprises a yeast.
3. The method according to claim 1 or claim 2 wherein the material adapted in use to effect secondary fermentation comprises one or more enzyme complexes.
4. The method according to any preceding claim wherein the support immobilises the material such that at least a large proportion of the material settles out of suspension in the beverage in a set period of time or less.
5. The method according to claim 4 wherein at least 50%, 70%, 90% or 95% of the material settles out of suspension in the beverage in a set period of time or less.
6. The method according to claims 4 or claim 5 wherein the set period of time is 5 hours, 2 hours, 30 minutes or less.
7. The method according to any of claims 4 to 6 wherein the material settles out of solution immediately.
8. The method according to any preceding claim wherein the support comprises a porous matrix comprising a natural or a polymeric gel.
9. The method according to claim 8 wherein the gel may be an alginate, a pectate, k-carrageenan or polyvinyl alcohol (PVA).
10. The method of claim 8 or claim 9, in which the porous matrix material containing the material adapted in use to effect secondary fermentation is formed into beads.
11. The method of claim 10, in which the beads each comprise a body comprising a mixture of the material forming the porous matrix and the material adapted in use to effect secondary fermentation, encapsulated by a layer of the porous matrix which does not contain the material adapted in use to effect secondary fermentation, or which contains a significantly lower amount of the material adapted in use to effect secondary fermentation than in the body.
12. A method of forming a material adapted in use to effect secondary fermentation in a beverage with a support that immobilises the material, comprising providing a mixture of the material adapted in use to effect secondary fermentation and a precursor matrix material, and dripping the mixture dropwise into a curing solution, the curing solution acting to turn the precursor matrix material into a porous matrix.
13. The method of claim 12, further comprising the step of adding a layer of the porous matrix which does not contain the material adapted in use to effect secondary fermentation, or which contains a significantly lower amount of the material adapted in use to effect secondary fermentation than in the body.
14. The method of claim 13, comprising the step of coating the cured beads in a layer of matrix material or precursor matrix material which does not contain the material adapted in use to effect secondary fermentation, or which contains a significantly lower amount (say, less than 10% of the content of the body) of the material adapted in use to effect secondary fermentation than in the body.
15. A yeast bead for use in effecting secondary fermentation in a beverage, the yeast bead comprising a body comprising yeast held within a porous matrix material.
16. The yeast bead of claim 15, comprising an encapsulating layer of porous matrix material which does not contain yeast, or which contains a significantly lower amount (say, less than 10% of the content of the body) of yeast than the body.1?. A secondary fermentation method for a beverage substantially as described herein or with reference to the examples.