As new markets emerge and off trade consumption increases, the shelf-life of canned and bottled craft beer has become increasingly important.
Brewers of craft beers carefully select and balance the ingredients to generate the unique and distinctive characteristics of their brand. And as competition between breweries heats up – and drinkers become more adventurous in their choices – the range of flavours available is blossoming. Coffee, chocolate, vanilla and even smoky flavours are joining citrus fruits, sours and high-intensity hops in the battle for beer drinkers’ palates.
Beer’s unique characteristics, which include colour, brightness and taste such as bitterness and sweetness, should remain unaffected by any microbiological stabilization treatment prior to bottling. In a competitive market, it’s vital that a brewery’s products are protected — and that consumers can enjoy their chosen beer’s unique flavours as intended.
Sterile filtration (or cold stabilization) is the final microbial filtration of beer using a microporous membrane to remove yeast and typical spoilage organisms to provide extended shelf life. It’s an alternative to the flash pasteurization of beer, which deactivates yeast and spoilage organisms by heat. Flash pasteurization demands higher relative water and energy consumption, therefore making cold stabilization a more appealing process to craft brewers who wish to keep operational expenditure low and reduce their carbon footprint.
The final stabilization of beer by microfiltration has commonly been accepted as a gentler method of stabilization, generating a cleaner, fresher, more natural flavour when compared to flash pasteurization.
A number of independent tests have investigated the effect on the taste of both flash pasteurization and cold stabilization by Parker’s BEVPOR microfiltration range.
Cold stabilization as an alternative to flash pasteurization, a brewer’s perspective
A trial, conducted by a leading UK brewery, indicated that beer packaged after cold stabilization produced a beer that protected the desirable, crisp and bitter taste profiles when compared to pasteurization in a triangular taste test.
The test, carried out with an experienced taste panel, tested the same batch of beer after cold stabilization and flash pasteurization to identify if the method of stabilization impacted upon the finished product characteristics of the beer. In this case, the data generated helped the brewery to select cold stabilization as their preferred method of microbial stabilization.
The studies performed not only established the immediate characteristic changes of the beer that had been pasteurized, but they also identified that the method of stabilization had an effect upon the beer’s characteristics for the duration of the product’s shelf-life.
The work identified that cold stabilization through BEVPOR filtration increased the time taken for the beer to display a stale/oxidized characteristic. Not only did the oxidized characteristics take longer to develop in the microfiltered beer, but it was far less pronounced over the 12-month trial.
A second brewery in the south of England conducted a trial looking at flash pasteurization and cold stabilization to determine which method would be used in the bottling of a leading premium ale. The same batch of beer was sent to two different contract packagers, one packaged the beer after flash pasteurization and the other after cold stabilization.
The brewing team commented that microfiltration appeared to be a ‘gentle process’ which protected the late hoppy characteristic of the ale. As a result of this process, the brewery installed an integral cold stabilization unit utilizing Parker’s BEVPOR microfiltration cartridges and fabricated housings.
Choosing the right filter materials
Products from Parker’s BEVPOR microfiltration range – such as the BEVPOR BR and BEVPOR PH filter cartridges – utilize a polyethersulfone (PES) membrane which has been carefully selected due to its excellent performance characteristics in beer stabilizing applications.
One of the key performance requirements of the PES membrane was making sure the unique characteristics of the beer were protected while guaranteeing the removal of yeast and typical spoilage organisms.
Microfiltration elements are designed to remove spoilage organisms through size, however, they will also remove other material such as suspended solids, proteins, polysaccharides and colour through adsorption. Depending on the extent of the adsorption, changes to the final characteristics of the beer may be possible.
Studies into the adsorption of head retention protein components during membrane microfiltration were conducted using two commonly used membrane materials: polyetersulphone (PES) and polyamide (PA) for both 0.45 micron and 0.65 micron ratings. Results showed that the membrane material had an effect on the protein content of the filtrate. PES reduced the protein content to a lesser degree than the PA membrane. Micron rating was also shown to affect the adsorption of proteins with 0.65 micron filters having a lesser effect than 0.45 micron filters.
Protecting the unique characteristics of your beer
A further study was carried out in order to demonstrate the low levels of protein adsorption expected with PES membrane compared to other materials used for beer filtration and serves to demonstrate the functional benefits of using PES on a number of levels.
Firstly, due to the lower protein adsorption characteristics of PES, the filtration has a negligible effect on the physical and sensory properties of the first run brew, so qualities such as head retention , colour and taste remain unaffected. Secondly, due to the low adsorption affinity, the PES membrane does not foul as readily as PA and is easily cleaned by clean-in-place processes so the system can be regenerated and used again.
Both of these qualities have been observed by multiple brewers who have reported the associated functional benefits of using BEVPOR filters.
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