What happens to sour beer… sour (video)

Washington, August 17, 2020-Sour beer, a sour and tangy result of the brewing process used for centuries in Europe, has recently become popular in the United States. Today, scientists say that acids and other flavor compounds evolve as the beverage ages. Their purpose is to help brewers understand the taste of sour beer and gain more control.

Researchers will present results at the American Chemical Society (ACS) Virtual Meeting & Expo in Fall 2020. ACS holds meetings until Thursday. Featuring over 6,000 presentations on a wide range of science topics.

The latest video on ongoing research is http: // www.acs.org/Autumn 2020 sour beer..

Sour beer is an ancient beer that uses freshly brewed beer (wort) to grow and ferment wild yeasts and bacteria. After this stage, wort is often transferred to wooden barrels and aged for months or years. Meanwhile, microorganisms produce many metabolites such as ethanol, acids and esters, providing many of the unique flavors of sour beer. The barrel itself can inject minor components that contribute to the flavor profile such as vanillin and catechin.

“Scientists are very interested because beer, especially sourness, is a very complex system,” says Dr. Teresa L. Longin, one of the project’s principal investigators. “Several studies have been conducted on the ingredients of finished sour beers. The difference between the studies is that we have been able to obtain samples of ongoing beer from different batches.” Has been able to help brewers make better products.

Longin was drawn into her research by her husband and collaborator, Dr. David P. Salisby, both of whom are at Redlands University. When Soulsby started the project a few years ago, he contacted nearby Sour Cellars brewer Bryan Doty. Dotty diligently learned what was happening with his beer and provided a series of samples from the same barrel where the beer was aged.

Soulsby and the undergraduate student Alexis Cooper examined each sample by combining NMR spectroscopy with new analytical techniques for quantifying the data. They used this approach to track the levels of acetic acid, the main constituent of vinegar. Lactic acid that gives sourdough bread a unique taste. Succinic acid contained in broccoli, rhubarb and meat extract. They found that each acid was stable at different concentrations in each batch, even though some batches had greater variability. “These organic acids give sour beers a lot of flavor, and the balance of organic acids produces very different types of sour beers,” Longin says. “It can be like a sweet and sour balsamic vinegar, or it can be a “packery” sour. Therefore, the mix of organic acids is very important for understanding the taste profile. “

Longin worked with one of the lab’s undergraduate students, Emily Santa Ana, to leverage their liquid chromatography/time-of-flight mass spectrometry expertise to contribute subtly to flavor but to detect by NMR. Searched for other compounds that were too low in level.

“This is work in progress, but we can certainly see some trace compounds that change over time,” says Longin. Some compounds start at high concentrations and then disappear. They can be sugars that are consumed by yeast when producing ethanol and carbon dioxide, and by bacteria when forming organic acids. Others “grow” over time. They can be additional organic acids, health-promoting antioxidants known as phenolics, or vanillin that gives beer hints of vanilla.

Researchers use mass spectrometry data to identify trace compounds and determine if they are from barrels or by-products of yeast or bacterial metabolism. “In addition, if the brewer knows that a particular combination of yeast and bacteria produces the desired flavor profile, they can cultivate it more,” Longin says. “Alternatively, if they know that beer with a particular acid combination is particularly enjoyable, they know when to stop aging the beer so as not to lose that balance.”

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A press conference on this topic will be held online on Thursday 20th August at 1pm Eastern time. http: // www.acs.org/Autumn of 2020..

The researchers Redlands University And Hedco Foundation.

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Title

Analysis of organic acids and trace compounds in sour beer using NMR spectroscopy and LC / Q-ToF MS

Overview

Sour beer is an ancient beer in which wild yeast and bacteria colonize fresh beer (wort) and then naturally ferment. Upon cooling, the wort is transferred to barrels and can be aged for months or years. Meanwhile, wild yeasts and bacteria produce numerous metabolites (eg, ethanol, acids, esters, etc.) in varying ratios that provide many of the unique flavors of sour beer. The barrel itself may add minor constituents such as vanillin and catechin, contributing to the flavor profile of the beer. In collaboration with the Sour Cellars brewery in Southern California, we obtained beer samples taken from the same barrel over several months for multiple batches of beer. Quantify metabolites within each batch using quantitative 1H NMR spectroscopy and the CRAFT analysis program and analyze minor constituents within and between batches using liquid chromatography/time of flight mass spectrometry. did. It shows the extent of variability of metabolites and trace components over the same barrel and batch.