As coffee lovers, we have all read many articles about the beneficial / harmful effects of coffee on health.
One day, if we feel like it, we can talk about the harms of excessive amounts of consumption, but the purpose of this article will be to convey from a scientific perspective how its beneficial effects on us can be increased or decreased by roasting. And of course, we will be talking about scientific studies.
Coffee, in addition to being our favorite drink, has many beneficial effects on our body, such as energizing, stimulating, fat burning, improving physical performance, and protecting against diabetes.
These properties are the result of beneficial components and compounds hidden in coffee beans. Coffee is considered an important source of substances characterized by strong antioxidant activity. This property is mainly affected by the content of polyphenols and melanoidins. Coffee drinks, along with fruits and vegetables, contribute significantly to the daily antioxidant intake in the diet of consumers. Phenolic compounds play an important role in the nutritional, organoleptic and commercial properties of agricultural foodstuffs, as they contribute to the sensory properties of coffee, such as color, astringency, bitterness and aroma, due to the interaction between phenolics, especially procyanidins in saliva, and glycoprotein. Polyphenols and chlorogenic acid are compounds related to the antioxidant properties of coffee. The antioxidant activity that represents the important beneficial effect of coffee on health, the ability to inhibit the oxidation process, is related to the chlorogenic acid and polyphenolic compounds such as ferulic, caffeic and n-coumaric acids it contains. In this article, we will examine how antioxidant levels in coffee change with roasting parameters and the relationship between them.
Brown pigments known as Melanoidins are synthesized in roasted coffee. These compounds are believed to be powerful antioxidants, as well as caffeine and trigonelline. Phenylalanines and heterocyclic compounds with high antioxidant activity are formed during the roasting process. When processing natural coffee, the roasting stage is considered necessary to reveal changes in bioactive compounds such as polyphenols. Roasting temperature plays an important role in affecting both sensory and antioxidant properties. These can be affected by compounds produced during the Maillard reaction. In the study; Colombia El Colibri Amarillo, Yellow Caturra, Colombia El Colibri Rojo Red Caturra, India Bababudangiri Kents, Catimor, India Malabar, Ethiopia Sidamo Heirloom,
7 arabica varieties including Ethiopia Yirgacheffe Heirloom, Ethiopia Yirgacheffe Kochere Heirloom and 1 robusta variety called Vietnam Queen Coffea canephora were used.
The beans in the study were roasted in 3 different ways, light-medium-dark, in a Behmor 1600, model TO9500T machine suitable for home baristas. The roasted beans were ground at 10,000 rpm. The moisture content of the coffees was determined as 8.99% when green, 1.99% as a result of light roasting, 2.52% as a result of medium roasting and 2.36% as a result of dark roasting, respectively.
The Folin-Ciocalteu spectrophotometric device, which is a very frequently used method for the determination of total polyphenols, was used. This method works with the reaction mechanism based on single electron transfer (SET). In this method, readings are made at 750-765 nanometers while determining total phenol.
For the determination of total antioxidant capacity, radical scavenging test was performed using DPPH (2,2-diphenyl 1-picrylhydrazyl) according to Brand Williams.
Without boring you with more chemical and technical analysis, let's examine the results of this extensive study.
According to the results, while polyphenol values in Green Arabica coffees ranged between 49.19 ± 0.70 and 74.05 ± 0.28 g GAE.kg-1, the highest polyphenol content was found in the Vietnamese Queen Coffee sample with a value of 74.05, yes yes you heard right, in a robusta, and the lowest in the Ethiopian Sidamo sample. This result may surprise some of you, but in the next article we will present our study on the reasons for this.
Let's put this topic on hold and continue with the results...
If we look at the values of the same bean at different roasting degrees, considering the Ethiopian Yırgacheffe Kochere coffee, the total polyphenol value in the green state was recorded as 55.45 GAE.kg-1, the total polyphenol value in the light roasted state was 50.15 GAE.kg-1, the total polyphenol value in the medium roasted state was 51.93 GAE.kg-1 and the total polyphenol value in the dark roasted state was 42.36 GAE.kg-1. The differences in the total polyphenol values of the beans from different regions at the same roasting degree can be examined in two different region beans, Colombia El Colibri Rojo bean and India Monsooned Malabar bean. According to the results, the total polyphenol value of Colombia El Colibri Rojo bean roasted at the same roasting degree is 41.90 GAE.kg-1, while India Monsooned Malabar bean is 48.01 GAE.kg-1.
A coffee growing region has a significant effect on the development of polyphenols in coffee beans, as seen. Roasting is very important in preserving polyphenols in coffee, and a statistically significant difference (P˂0.001) was found in the polyphenolic levels between the green state and all three roasting stages of coffee beans. The study revealed that longer roasting, namely the dark roasting style, caused a significant decrease in polyphenol compound levels (from 7.3% to 32.1%) in all coffee varieties. Similarly, it was observed that as the roasting temperature and duration increased, the total antioxidant level, as well as the total polyphenol level, decreased. Depending on the method used, the roasting degree, which we call light-medium and medium roast, reveals the optimum antioxidant amount for coffee.
There are numerous publications investigating the relationship between coffee antioxidant activity and roasting:
– Comparison of antioxidant activity in roasted and green coffee beans;
– Dependence of antioxidant activity on roasting temperature and time;
– Relationship between antioxidant activity and the roasting method used (convection and microwave roasting).
Based on previous publications, the differences in antioxidant activity between different coffee types, composition and also different molecules produced during roasting can also be attributed to their varying polyphenolic content. In addition to the obvious color change from green to brown depending on the degree of roasting, many unknown and unidentified complex physical and chemical changes occur. The content of chlorogenic acids, the main antioxidants in green coffee beans, decreases significantly after roasting, while polymeric compounds such as melanoidins (which are powerful antioxidants) and other compounds are formed after roasting.
This study addressed the measurement of total polyphenol and total antioxidant levels after roasting coffees from different regions with different parameters.
The main issue in this study is the roasting effect.
In summary, in order to achieve the highest antioxidant and polyphenol levels and to obtain the highest health-friendly efficiency from coffee; dark coffees other than light roast, light medium and medium roast coffees that have completed their formation should be avoided as much as possible.
DUYGU KURTULUŞ
Co-Founder / Chemist / Nanotechnology Engineer / Hazardous Chemical Consultant / Chemical Evaluation Specialist