A Short Coffee Break

20.05.2019

Newspapers and journals often mention antioxidants fight with ‘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 the Swiss food giant was also in fashion. Wonder how? He began to sell a coffee called Green, which reported that it contained naturally polyphenol antioxidants, which could help to prevent destruction body cells from day after day. This coffee contains roasted (green) coffee beans to increase antioxidant levels. Coffee is actually one of the richest phenolic sources in western victu. Sometimes natural mechanisms that potentially protect body cells cannot control the level of reactive oxygen species. Coffee, a powerful source of antioxidants, can seize 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 used to thinking that coffee is bad for our health. Most people are doing their best to skip this guilty pleasure. However, several epidemiological studies suggest that regular coffee drinkers are less likely to contact a variety of cancers, including liver, colon, oral, and esophagus, as well as some magazine articles that encourage people to question daily coffee intake and monitor their health over the years. In 2008, a research team at the Harvard Medical School in the USA and the University of Madrid in Spain evaluated the data of two major US epidemiological studies following more than 125,000 people in 20 years. They concluded that regular coffee consumption is not associated with increased mortality. In fact, considering the risk factors such as weight and special diseases, and the team suggested that people who drink more coffee are at a lower risk of cardiovascular disease. It has been argued that coffee helps to protect from guttan (lowering uric acid levels), tooth decay and gallbladder stones. Also, there is 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 your mind is caffeine. Positive effects to the brain of caffeine have been documented. As for the effects of coffee on our palate, is not it relative? Let’s talk about the abundance of chemical compounds that affect the taste of coffee. Coffee contains more than 1000 aroma compounds and a large number of chemicals. The structure of a limited number of substances were characterized among these chemical compounds. If you are looking for antioxidants, the most abundant phenolic compounds in coffee are chlorogenic acids (CGA) corresponding to 12 percent of the dry weight of green roasted coffee beans. Most of the bitter taste of coffee comes from CGAs which cause the reflux of some coffee drinkers (acid backflow).

CGAs in coffee are formed by the esterification of trans-cinnamic acids (especially caffeic, ferulic and pcoumaric acids) with hydroxyl groups on quinic acid. The resulting conjugated CGA structures are known as caffeoilquinic acid, feruloylquinic acid and p-coulosylkuinic 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. The others are CGAs, melanoidins, plays a role in browning process called Maillard reactions. While toasting, we unintentionally make the Maillard reaction to occur. As a result of these reactions, brown and very bitter taste antioxidant polymers are formed. The CGA concentration ranges from 20 mg to 60 mg per cup in a brewed coffee while it is 20-60 mg in an average tea cup. CGA levels depend on not only the roasting time and temperature, but also the coffee bean - the arabica cores have lower CGA levels than the Robusta- and the brewing method. According to Yi-Fang Chu, who manages the coffee and health research group in the US, decaffeinated coffee contains phenolic levels similar to caffeinated coffee. Even higher levels of phenolic groups can be found by the concentration effect that occurs during the decaffeinated process.3-5

When I was writing this article, I drank as much coffee as I could in my life. But with pleasure… I put a few photos captured by my dear friend Zeynep Özyürek to whet your appetite. It is time to have a break… Make a coffee to yourself and enjoy more than 1000 aromas... You will only notice one or more. I would like to thank my dear friend Zeynep Özyürek who shared her photos with us and our graduate student İbrahim Demirci who supported us with his coffee knowledge.