In this text, we are going to discuss the carbohydrates present in coffee beans, their composition and their importance. In addition, we will discuss what carbohydrates are and their importance for coffee.
Does coffee have carbs in it?
No, coffee does not have carbs in it.. Arabica coffee beans (approximately 8%) have twice as much sucrose as Robusta coffee beans (approximately 4%), most of the time. However, there’s not even a drink.
There are several types of carbohydrates, more complex and simpler ones. Each species contains different amounts of carbohydrates. In addition, during the roasting of the beans, several changes in carbohydrates occur, forming aroma, flavor and body compounds.
What are carbohydrates?
Carbohydrates account for more than 90% of the dry matter of vegetables, that is, after removing the water, it is the component present in the greatest quantity in vegetables.
They are divided into monosaccharides, oligosaccharides and polysaccharides. Monosaccharides are free sugars with low molecular mass and when they come together they form oligosaccharides and polysaccharides. Polysaccharides are the most complex carbohydrates and are found in greater amounts in foods.
What is the importance of carbohydrates for coffee?
Carbohydrates are important for the development of coffee flavor and aroma and the formation of pigments and other high molecular weight products. In coffee, they are made up of polysaccharides (40-50%), low molecular weight sugars and carbohydrate derivatives such as pectin and lignin.
Among the low molecular weight sugars present in coffee, sucrose is the main one. Sucrose is a disaccharide (composed of two monosaccharides), formed by a molecule of glucose and a molecule of fructose. It is table sugar, which we use daily to sweeten our recipes. Our table sugar is produced by sugarcane, but in other countries, it is produced by beetroot.
Carbohydrates are important in the formation of pigment, flavor and aroma in coffee because they participate in a reaction that occurs during roasting, called the Maillard reaction. This reaction occurs whenever there is the presence of reducing carbohydrate and protein or amino acid at high temperature.
Exactly what happens to coffee beans when subjected to the roasting process. During this reaction, which occurs between the reducing sugar and the protein or amino acid, the formation of compounds responsible for the aroma, flavor and browning of the grain occurs.
The browning formed by this reaction is classified as non-enzymatic browning, since the reaction takes place without the action of enzymes.
Another reaction that occurs with carbohydrates at a high temperature is caramelization. In this case it doesn’t need to have proteins and/or amino acids. Caramelization is easily observed when cooking table sugar, which turns into caramel. As seen in sugar, browning occurs during this reaction.
The same happens with coffee during roasting. Caramelization causes browning and formation of flavor and aroma compounds. This reaction is facilitated in the presence of acids and salts.
The polysaccharides present in greater amounts in coffee are: mannans, galactomannans, arabinogalactans, cellulose and xyloglucans. Polysaccharides influence the beverage’s body attribute, since they are the main responsible for the viscosity of coffee extracts.
However, coffee brewed at home does not extract as much polysaccharides, while espresso coffees achieve greater extraction, since they are extracted with high pressure. They are also responsible for the stability of the espresso coffee foam and the retention of volatile compounds.
The volatile compounds that form the coffee aroma compounds, so polysaccharides are important in preserving the coffee aroma as they bind to the volatile compounds.
What happens to carbs during roasting?
We saw that arabica coffee has a higher amount of sucrose, but it has a lower amount of total reducing sugars (approximately 0.1%) compared to robusta (approximately 0.4%). The reducing sugars present in coffee are glucose and fructose and traces of stachyose, raffinose, arabinose, mannose, galactose, xylose, ribose and rhamnose.
During roasting of a coffee bean, sucrose is quickly lost, whereas in lightly roasted coffee, only 3-4% of its original sucrose content is retained. In a dark roast, sucrose is lost completely.
The reducing sugars will be formed during roasting by hydrolysis of polysaccharides or oligosaccharides. Despite the formation of reducing sugars on roasting, their quantity is not greater in roasted coffee, as they are also degraded by the roasting heat.
Among the reducing sugars, glucose is less susceptible to losses on roasting and arabinose is more susceptible. Polysaccharides are more resistant to the roasting process, with an average of 75% of their initial composition remaining in roasted coffee.
It is not possible to say which type of coffee has the greatest amount of polysaccharides, since the difference between these compounds is minimal.
How are carbohydrates determined?
The determination of carbohydrates can be done using a refractometer, obtaining the measure of °Brix. °Brix is used to measure the amount of soluble solids present in the solution, more specifically the amount of sugars.
Another method is using a spectrophotometer, which measures the absorbance value of the sample in relation to a source of radiation at a specific wavelength. To use this method it is necessary to perform a calibration curve with a carbohydrate standard. This method will quantify the total carbohydrates in the sample.
If the interest is to know which carbohydrates are present, it is necessary to use other techniques. The gas chromatography technique is widely used for the determination of monosaccharides. But liquid chromatography is also used.
In this text, we discussed the carbohydrates present in coffee beans, their composition and their importance. In addition, we discussed what carbohydrates are and their importance for coffee.