In the last two weeks, I did not write any posts because I was preparing for this important conference, ACS Spring 2023 by American Chemical Society, one of the greatest annual conference in Chemistry. I presented my work here, and had the opportunity to know other fellows’ works. Their works were really impressive and thorough, which provided insightful information to my current research. And that was the “joy” of attending a conference: to learn and be inspired by other research.
Aside from that, I also found an entire session dedicated to research on coffee. In the lens of general understanding, coffee is just brewing the ground, roasted beans in water. In the lens of a scientist, there is some phenomenal chemistry in our daily cups of coffee, which I would like to summarize here. Appreciation to the effort of those researchers!
NMR spectroscopy to control the authenticity of coffee
Let’s start with the coffee beans! The first work I would like to show was from Dr. Bunzel’s group. His group has employed NMR spectroscopy to control the authenticity of coffee, namely species, origins, cultivation and roasting levels.
(Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy, is a spectroscopic technique to observe local magnetic fields around atomic nuclei.)
By analyzing the characteristic peaks in the NMR spectra, coffee species and different roasting levels could be differentiated. Origins of the coffee could be differentiated to some extent, yet it was unable to point out the difference of organic and non-organic coffee. The screenshot below summarized the highlights from their work.
Chemistry in your cup: Chemical characteristics of cold brew coffee
Now to the brewing methods. The work I would like to talk about was “Chemistry in your cup: Chemical characteristics of cold brew coffee” by Dr. Niny Rao and her research group from Thomas Jefferson University. Their work provided scientific proof for some observations we found on cold brew and hot brew, such as acidity.
pH scale (0 – 14) is used to estimate acidity. The lower the pH value, the more acidic the substance is.
Titration is a common laboratory method to determine the concentration of an identified analyte by slowly adding a known reagent (titrant) until it reaches neutralization/equivalence. In this case, the acid content in coffee is determined by titration with NaOH. The more NaOH used, the more acidic it is.
- pH test is not sensitive enough to point out the difference in acidity of hot brew and cold brew among various beans, but a simple titration with NaOH can.
- By performing pH test and titration with NaOH, it shown that coffee extract from light roast (R1) beans is more acidic than medium roast (R2) and dark roast (R3).
And what about caffeine as well as other bioactive contents? It has shown that caffeine is insensitive to the brewing temperature. Note that the coffee-to-water weight ratio in these experiments was 1:10. If you have known the solubility of caffeine in coffee from my old post (Some “research notes” on caffeine quantification in coffee), you could anticipate that the maximum amount of caffeine was already achieved regardless of roasting levels and brewing temperature.
- The general trend here is that the caffeine content decreases with increased roasting level. There is not much different in the concentration of caffeine between cold brew and hot brew.
- The amount of chlorogenic acid (CQA) in light roast is double than that in medium roast, and four times more than dark roast. Brewing coffee in hot water releases more water-soluble bioactive components.
Anti-obesity and anti-aging effects of coffee components
Now that we have our cups of coffee. It has been “rumored” that drinking coffee helps losing weight. Is it true? Well, Dr. Yeonhwa Park and her group from University of Massachusetts Amherst might have the answers for us in thier work on “Anti-obesity and anti-aging effects of coffee components”. The anti-obesity was quite thoroughly discussed. Briefly, her research showed that drinking coffee helped reduce lipid digestion and formation of fat (lipogenesis), promote lipolysis (i.e. breakdown of fat) and beta-oxidation of fatty acid (a pathway to break down fatty acids). On the other hand, it was still unclear on the connection between lipid uptake and transport as well as the anti-aging bioactivity. The screenshot below summarized the highlights of their work.
Wow, these works really blew my mind. The research using NMR to control the authenticity of coffee would be potentially contribute to the consistency in quality of coffee. The research on basic chemistry of coffee provides quantitative analysis to the qualitative observation between cold brew and hot brew. The work on the anti-obesity of coffee shines a light to one of the many “rumored” benefits of drinking coffee.
In addition to that, caffeine is insensitive to brewing temperature, and somewhat consistent among roasting levels. Yet the antioxidants content is vastly different. Nevertheless, I like Dr. Niny Rao’s conclusion: at the end of the day, enjoy the coffee however you want (because it’s your cup of happiness).
That’s it for the short updates on coffee research! Hope you would also enjoy this super nerdy post like me!
P.S. ACS Spring 2023 has come to an end, and I am already looking forward to ACS Fall 2023 this August to learn more from others! Cheers to the science (and food)!
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