A Short Coffee Break

Turkchem 20 May 2019 54 4 dk okuma

TURKCHEM

Newspapers and journals often mention antioxidants fighting 'free radicals'. At first, the most popular foods for these antioxidants were vegetables and fruits. Then dark chocolate and coffee were also included in this group. Have you ever heard of polyphenol antioxidants? One of the Swiss food giants was also in fashion. Wonder how? It began to sell a coffee called Green, which reported that it contained naturally occurring polyphenol antioxidants, which could help prevent the destruction of body cells day after day. This coffee contains roasted green coffee beans to increase antioxidant levels. Coffee is actually one of the richest phenolic sources in the Western diet. Sometimes natural mechanisms that potentially protect body cells cannot control the level of reactive oxygen species. Coffee, a powerful source of antioxidants, can manage this situation. But the story is much more complicated than a simple war between antioxidants and free radicals. Plant-based biochemist Alan Crozier says that all antioxidant-rich products are much lighter in action than previously thought. We are accustomed to thinking that coffee is bad for our health. Most people do their best to avoid this guilty pleasure. However, several epidemiological studies suggest that regular coffee drinkers are less likely to develop a variety of cancers, including liver, colon, oral, and esophageal cancers. Some magazine articles encourage people to question their daily coffee intake and monitor their health over the years. In 2008, a research team at Harvard Medical School in the USA and the University of Madrid in Spain evaluated data from two major US epidemiological studies following more than 125,000 people over 20 years. They concluded that regular coffee consumption is not associated with increased mortality. In fact, when considering risk factors such as weight and specific diseases, the team suggested that people who drink more coffee are at lower risk of cardiovascular disease. It has been argued that coffee helps protect against gout by lowering uric acid levels, tooth decay, and gallbladder stones. There is also strong evidence that coffee provides some protection against type 2 diabetes.1,2 When it comes to coffee, the first chemical compound that comes to mind is caffeine. The positive effects of caffeine on the brain have been documented. As for the effects of coffee on our palate, is it not subjective? Let's talk about the abundance of chemical compounds that affect the taste of coffee. Coffee contains more than 1,000 aroma compounds and a large number of chemicals. The structure of a limited number of these substances has been characterized. If you are looking for antioxidants, the most abundant phenolic compounds in coffee are chlorogenic acids (CGA), accounting for 12 percent of the dry weight of green roasted coffee beans. Most of the bitter taste of coffee comes from CGAs, which cause acid reflux in some coffee drinkers. CGAs in coffee are formed by the esterification of trans-cinnamic acids (especially caffeic, ferulic and p-coumaric acids) with hydroxyl groups on quinic acid. The resulting conjugated CGA structures are known as caffeoylquinic acid, feruloylquinic acid and p-coumaroylquinic acid, respectively. Half of the CGAs in the green coffee bean undergo some conversion during high-temperature roasting. Some of the CGAs are hydrolyzed to form free phenolic acids, or are converted to chlorogenic acid lactones, a bitter sweetener. Others, along with CGAs, form melanoidins, which play a role in the browning process called the Maillard reaction. During roasting, the Maillard reaction occurs unintentionally. As a result of these reactions, brown and very bitter-tasting antioxidant polymers are formed. The CGA concentration ranges from 20 mg to 60 mg per cup in brewed coffee, while it is 20-60 mg in an average cup of tea. CGA levels depend not only on the roasting time and temperature but also on the coffee bean—Arabica beans have lower CGA levels than Robusta—and the brewing method. According to Yi-Fang Chu, who manages the coffee and health research group in the USA, decaffeinated coffee contains phenolic levels similar to caffeinated coffee. Even higher levels of phenolic compounds can be found due to the concentration effect that occurs during the decaffeination process.3-5 While writing this article, I drank as much coffee as I could in my life. But with pleasure… I have included a few photos captured by my dear friend Zeynep Özyürek to whet your appetite. It is time to take a break… Make a cup of coffee for yourself and enjoy more than 1,000 aromas... You will only notice one or more. I would like to thank my dear friend Zeynep Özyürek for sharing her photos with us and our graduate student İbrahim Demirci for supporting us with his coffee knowledge. Faculty Member, PhD. Sultan Funda Ekti Eskişehir Technical University Faculty of Science Department of Chemistry