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Analytical Chemistry

Old-fashioned brewing and an easy way to age hard liquor

by Manny I. Fox Morone
March 20, 2017 | APPEARED IN VOLUME 95, ISSUE 12

A good old-fashioned beer

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Credit: Stanford News/Kurt Hickman
Sip of history: Learn how to make beer the way they used to.
Credit: Stanford News/Kurt Hickman
Sip of history: Learn how to make beer the way they used to.

Any seasoned home brewer will tell you that it can take a while to perfect a recipe. Five thousand years after one recipe’s heyday, Stanford University students are still working it out.

Li Liu, a Stanford archaeologist, teaches a course titled “Archaeology of Food: Production, Consumption & Ritual.” This year, students got to re-create a boozy beverage based on Liu’s research on Neolithic Chinese artifacts. Liu says that’s what archaeology is all about: “You’re not just reading books.”

Starting in 2012, Liu, Jiajing Wang, and coworkers investigated the composition of residue scraped from millennia-old pottery found in Xi’an, China. These fragments of pottery stoves, wide-mouthed pots, funnels, and narrow-necked vessels piqued the archaeologists’ interest because the shapes and styles of the vessels suggest three stages distinctive to the beer-making process: brewing, filtration, and storage, the team claims. They published the list of the brew’s likely ingredients last year (Proc. Natl. Acad. Sci.USA 2016, DOI: 10.1073/pnas.1601465113).

Ion chromatographic analysis showed that the residue contained oxalate, which the archaeologists attribute to beer stone—sediment composed of primarily calcium oxalate that collects on the surfaces of brewing equipment. Plant material, however, was too degraded after 5,000 years to identify other ingredients using cells or DNA. Instead, the researchers sifted through microscopic starch particles and mineral structures called phytoliths, which are found in plants and can stay intact for thousands of years, to try to match their shapes with those of modern-day species.

So if you want to make beer the way they used to, your shopping list might include the following: millet, barley, and Job’s tears—also known as Chinese pearl barley—all of which fill the usual role of grains in beer. You would also need roots and tubers from snake gourd, yam, and lily plants, which add more starch and might have imparted a sweeter flavor to the brew. Whether Neolithic people in China added yeast or whether they relied on airborne yeasts and enzymes in the plant material was not clear from the analysis.

When making their brews, Liu’s students could choose their own combination of grains, which they sprouted, milled, heated, and finally left to ferment. After a week, the students’ jars developed a moldy coating and a range of odors. One student remarked that her beer had a fruity smell and a citrusy flavor. But Liu tells Newscripts that the brews were “a bit sour, with low alcohol level,” and ultimately, “I cannot say I like it.”


A sound approach to aging spirits?

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Credit: Manny Morone/C&EN
Hints of notes: Ultrasound makes wine spirits better.
Credit: Manny Morone/C&EN
Hints of notes: Ultrasound makes wine spirits better.

According to the U.S. Alcohol & Tobacco Tax & Trade Bureau, if a wine spirit wants to be called brandy, it has to have been “stored in oak containers for a minimum of 2 years.” But if you can’t wait that long to get your fix of that sweet, sweet nectar, researchers at the University of Cádiz might have the thing for you.

The scientists have developed an accelerated technique that ages spirits in only a few days. The process involves pumping wine spirits through a tube containing oak chips and pulsing the tube with ultrasound (Ultrason. Sonochem. 2017, DOI: 10.1016/j.ultsonch.2016.11.031). The ultrasound waves create bubbles in the liquid that collapse with enough force to rupture the cell walls of the oak, releasing flavor compounds such as vanillin and furfuraldehyde.

After just three days of accelerated aging, eight trained judges reported that, in general, the ultrasound treatment gave the spirits better looks, smells, and tastes. Sounds good, but the judges compared the ultrasound-aged samples with unaged spirits rather than with commercial brandy, and that feels a little off.

Manny I. Fox Morone wrote this week’s column. Please send comments and suggestions to newscripts@acs.org.

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