Scientists find a way to brew sour beer faster

The same flavours found in Belgian-style sour beers can been obtained with a shorter brewing process if brewers use the sugars found in peas.

According to a new study in the Journal of Agricultural and Food Chemistry led by scientists from the Norwegian University of Life Science, field peas, as well as beans and lentils could start to save brewers time when creating sour beer styles.

Speaking about the findings, report co-author Bjørge Westereng of the Norwegian University of Life Science said that the breakthrough for beer would be good news for beer fans because in many ways “sour beer is the beer enthusiast’s alternative to Champagne”.

Westereng explained that the process was also relatively simple and by “using sugars derived from peas that yeast cannot metabolise, we promote the growth of bacteria essential for producing sour beer”.

Recent scientific reports on the topic highlighted how even though sour beer has been around for centuries, it has risen in popularity among craft brewers and flavour obsessives in recent years, but, despite the rise in interest, the brewing process has always been both time-consuming and somewhat unpredictable.

While brewers usually carefully control the strains of yeast they use to ensure other microbes don’t alter the flavour during fermentation, brewers of sour beers have long been interested in using wild yeasts to let them grow freely in the wort, sometimes adding fruit for acidity and gaining an array of enticing flavours.

Historically, the process has been considered to be time consuming, but well worth the wait. For instance, brewing sours often saw the wort transferred to wooden barrels before being matured for months or even years to give the microbes time to contribute to the resulting beer’s flavour. Additionally, brewers also made pains to add in extra mashing steps in separate vessels in some cases in a bid to ensure the beer gained a characterful flavour.

“The whole process is tricky to control, and brewers don’t always know exactly which compounds end up in the final product or how it will impact the overall beer,” the reports outlined. But, despite these hurdles, Westereng and his collaborators have insisted that they have found a way to reduce the multi-step brewing process.

Previously, sour beer brewers have typically use starch from raw wheat as a carbon source for the specialty yeasts they used. Also, Westereng admitted that he has already experimented with using wood-derived xylo-oligosaccharides (prebiotic sugars) instead as a carbon source for lactic-acid brewing bacteria (LAB) since brewers’ yeast doesn’t degrade those carbohydrates. But, after trialling this, he revealed that the resulting experimental sour beers “weren’t perfect but nonetheless were reasonably comparable to commercial sour beers”.

Now, the scientists have turned to peas, part of the pulses plant group, because pulses contain sugars called raffinose-family oligosaccharides (RFOs) that are equally appealing as a carbon source for lactic acid-brewing bacteria.

As part of the experiments, the team extracted the sugars from field peas and brewed four experimental sour beers using three different LABs. According to the report, two of those beers contained the RFOs and two did not, and all four were fermented for 19 days.

Following this, the scientists then performed a chemical analysis, and a panel of trained testers sampled each of the sour beers. The report results showed that “the lactic acid-producing bacteria scarfed up all the pea sugars despite the shortened brewing time”. It also showed that “the sour beers brewed with pea sugars (RFOs) had more lactic acid, ethanol, and flavour compounds than those brewed without them”.

One extra benefit was that “the sour beers brewed with pea sugars were rated as having fruitier flavours and higher acidity” with the sensory panelists noting that the taste intensity was “comparable to that of commercial beers”.

Even with these strides, the best result was that the panelists detected no trace of undesirable flavours that have thus far limited the use of pea-based ingredients in brewing. The report assured that strides had been made in any case and that “the beany flavour of pulse-derived ingredients is often considered a hurdle.

Thus, the results of this study indicate that pea-derived RFOs can be exploited in unconventional ways to generate products with acceptable sensory properties” – a discovery that may well change brewers’ approach to recreating beer styles in more economical and indeed sustainable ways for the future.

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