The infusion obtained from coffee beans gives energy to more than half of Poles every day. In Poland, about 3 kg of coffee is consumed per capita per year. For comparison, the Finns, who drink the most coffee, consume 12 kg per person per year. Surprisingly, Italians, famous for their coffee culture, drink 'only' 5 kg of coffee per person.

In the coffee production process, the pulp is mechanically removed from the ripe coffee fruit, and the obtained green seeds are dried and roasted. Roasting takes place at a temperature of 180 to 250 degrees C and takes from two to 25 minutes, depending on the desired degree of roasting. 

Coffee roasting, like other food thermal processing methods, leads to a change in the chemical composition of the product. There is also a process called the Maillard reaction. The products of this non-enzymatic reaction between simple sugars and amino acids include melanoidins, responsible for the browning of roasted beans.

However, in addition to the positive effects of coffee roasting, such as improved taste and aroma, there are also unfavourable phenomena - molecules with potentially harmful properties are formed, such as acrylamide or 5-hydroxymethylfurfural (5-HMF).

Dr. Joanna Grzelczyk from the Faculty of Biotechnology and Food Sciences of the Lodz University of Technology, with a grant from the National Science Centre (NCN), conducted research on the health-promoting compounds in green and roasted coffee beans.

'I am a coffee lover and I have always wondered if there is a grain of truth in the myths about coffee. Research on coffee absorbed me. A grant from the National Science Centre allowed me to conduct interesting experiments and present the results at conferences, and gain new cooperation, which resulted, among other things, in a fellowship at McGill University in Canada', Dr. Grzelczyk tells PAP - Science in Poland.

Coffee is a product rich in compounds from the group of polyphenols, which have a number of health-beneficial activities. They improve the functioning of the immune system, they are anti-mutagenic, neuro and cardioprotective, anti-diabetic. Roasting negatively affects the content of polyphenols in grains. These compounds in the free have a higher biological activity than in the bound form.

As part of her research, Dr. Grzelczyk prepared extracts from arabica and robusta coffee beans - from both green beans as well as light and dark roasted ones, and then subjected them to in vitro digestion in an artificial digestive system. It turned out that the content of free polyphenols effectively increased during digestion, especially in the part of the system simulating the large intestine, and the presence of intestinal microorganisms had a positive effect on this process.

Dr. Grzelczyk analysed the binding of substances contained in coffee extracts with receptors and enzymes. She proved that these extracts could inhibit the activity of monoamine oxidase A and regulate the activity of the PPARγ receptor. The first of these molecules is responsible for the breakdown of serotonin in the body, and its inhibitors are used as antidepressants. In particular, robusta green coffee extract blocked the activity of monoamine oxidase A. Green coffee may therefore have potential antidepressant properties. The researcher adds that blocking monoamine oxidase activity also reduces the desire to consume carbohydrates.

The role of the PPARγ receptor is known in the pathogenesis of type 2 diabetes. Dr. Grzelczyk's research shows that active substances contained in coffee extract, especially green coffee, can positively affect tissue insulin sensitivity, and thus have a preventive effect against type 2 diabetes. In a roasted coffee, the content of these active substances decreases.

Dr. Grzelczyk also studied the influence of coffee on the development of neurodegenerative diseases. She proved that the tested coffee extracts had the potential to prevent them, because they inhibited the activity of certain enzymes and had a protective effect on model nerve cells. Coffee also counteracts the formation of beta-amyloid deposits associated with Alzheimer's disease.

Dr. Grzelczyk determined that all tested coffee extracts protected epithelial cells of the small intestine, i.e. enterocytes, against oxidative stress, which is conducive to carcinogenesis. Green coffee extracts also protected the liver, and the higher the degree of roasting the beans - the weaker this effect was.

Although Grzelczyk focused mainly on the health-promoting effects of drinking coffee, she also determined the content of acrylamide in coffee extracts. This compound is formed during the processing of food products at high temperatures (e.g. roasting) and promotes the formation of gastrointestinal cancers. 'There is more of it in lightly roasted coffee, and less in dark roasted coffee. However, these are not the amounts that would cause cancer with daily consumption of coffee,’ she says.

Summarizing her research, Dr. Grzelczyk tells how - and which - coffee to drink to make the best use of its health-promoting potential: 'Green or dark roasted at a temperature of up to 230 degrees C. Of course, without additives such as sugar,’ She adds that green robusta coffee contains more compounds beneficial to health than green arabica.

'To people who tell me about the harmful effects of coffee, I repeat an important sentence: everything we consume, we must consume in moderation. Even excess water can be harmful,’ she says, adding that we can consume 3 to 4 cups of coffee a day (a cup is about 150 ml),’ she says. 

Dr. Grzelczyk used the results to develop a food product with a potential health-promoting effect - ice cream with the addition of green coffee extract - for which a patent application has been submitted.

PAP - Science in Poland, Dominika Cieślak

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