Coffee is one of the most popular beverages in the world, appreciated for its taste and aroma, at the center of real rituals and moments of social gathering. Rich in many different substances, especially caffeine, it has very important effects on the body, which do not end with the simple stimulating effect but which involve various organs and systems, with benefits and even some risks.
Coffee is obtained from the seed of several species belonging to the Rubiaceae family, a family that includes more than 500 genres and over 6000 species. The classification of plants of the genus Coffea is made difficult by the remarkable genetic variability of plants and seeds: the two most important species are Coffea arabica and Coffea canephora or robust.
The origin of the coffee is traced right up to the Ethiopian highlands. Legend has it that a shepherd, after observing the exciting effects that the consumption of leaves and fruits of a shrub, has made a gift to a monk who used them to prepare an infusion to be consumed to stay awake during the long nights of prayer. The infusion must have worked well because the Arabs, trading with the distant lands of Africa, immediately recognized the value and began to cultivate it and exchange it. In the early 1500s coffee was already consumed throughout the Muslim world, and soon European merchants began buying coffee in Yemen to resell it to the courts of the old continent, which were particularly infatuated.
At the beginning of the 1600s the Venetians succeeded in importing the first coffee plants in Italy and, in the course of the century, the cultivation of coffee extended to the East Indies thanks to the Dutch and the Caribbean thanks to the French. Meanwhile the Spaniards began cultivation in the Philippines and Latin America, with an ever-growing production due to the increasing popularity of the drink.
Coffee is currently one of the most traded products on the market and is often an important item for the trade balance of many developing countries. Its quotations move huge capitals, the market is complex and often prone to important speculations, the demand grows constantly and requires an increase in production that, given the volumes, poses many problems from an environmental point of view (the forests do not only cut them down to produce palm oil, it must be remembered from time to time, here detailed information and statistics on the cultivation of coffee in the world). The annual production exceeds 8 million tons, with Brazil alone contributing with 3 million, followed by Vietnam, Colombia, Ethiopia, India, Honduras and Guatemala.
Making coffee for fun and profit
The two species most used for the production of coffee are Coffea arabica and Coffea canephora (robusta). Two other species are grown to a much smaller extent, Coffea liberica and Coffea dewevrei. About two-thirds of the coffee traded on the market is obtained from C. arabica, mainly grown in Latin America, Central Africa and Indonesia, while the other third comes from plantations of C. robusta, a more resistant and vigorous species, grown in West Africa , in Southeast Asia and Brazil.
The height of the plant varies from 5 meters of the arabica to 10 meters of the robust but in the plantation is maintained around the three meters to make it easier to harvest the fruit. Sowing is done using selected grains; the plant becomes productive around the fifth year, after the first flowering. The flowers are white, in groups of two or three, very fragrant, and when fully ripe they give rise to fruits, called cherries, oval shaped and dark red, 1-2 cm long. The fruit pulp contains two seeds covered with a thin silver film, wrapped in a golden film called parchment.
The flowering can take place several times during the year and on the same branch can be found both the flowers and the ripe cherries. For this reason, the collection must be done by hand and with great care. The plant, if well taken care of, can remain productive up to thirty years.
Once harvested, the fruits are freed of the mucilaginous pulp using two different techniques:
- Dry method: it is the oldest and most simple, it does not require any particular machinery. The cherries, after careful cleaning, are left to dry and ferment in the sun until reaching a moisture content of about 12%. At this point a mechanical separation of the skins is carried out. It is the preferred method in dry and sunny areas, from Brazil to Ethiopia; all the Robusta is worked using this technique.
- Wet method: requires special equipment and the availability of large quantities of water. After cleaning in running water the fruits are crushed and the pulp removed. The remaining mucilage is fermented in special tanks for 24-36 hours and then eliminated thanks to a new wash. At this stage of processing the humidity is around 50% and is brought to 12% for drying, in the sun or in special machinery. This method is the one preferred in the processing of Arabica and if well executed allows to enhance the aroma of the coffee, despite the loss of a small amount of minerals and sugars during the washings.
Fermentation takes place by bacteria naturally present on fruits and seeds and does not require any addition of colonies. Generally speaking, bacteria belonging to the genera Lactobacillus and Leuconostoc predominate, which degrade the mucilage present, freeing substances that contribute to the aroma and taste of coffee. The fermented Arabica bean has a green color and an oval shape whereas the Robusta bean is round and yellow or yellow-brown.
The processed seeds are selected, calibrated and packaged in classic 60-70 kg jute bags, shipped and exchanged all over the world, ready for the next stages of processing.
Coffee roastingRoasting is a critical phase in coffee processing during which the hard and compact seeds are toasted and then used in the preparation of beverages. During this phase many compounds present disappear or are degraded, while others are formed, through reactions that are essential for the development of the aroma and taste of the final product.
Toasting takes place at temperatures between 200 and 250 ° C. In this phase the seeds increase in volume, from 50 to 80% compared to the initial one, and darken due to the formation of compounds whose structure is still little known. The final color depends on time and roasting temperature.
In the early stages of the roasting there is denaturation of the proteins present while the still present water evaporates. Above 100 ° C the grain begins to swell, releases the remaining water and increases in volume; as the temperature increases, the reactions between the substances present are progressing faster and faster, until the reactions of Maillard responsible for the darkening and the typical aroma are triggered. After 180 ° C, the grain slits along the median furrow while hundreds of different volatile substances are formed. In the final phase, between 200 and 250 ° C, the humidity is reduced to 1% and there is caramelization and deposition of a film of fatty acids on the surface of the grain. Higher temperatures should be avoided, as the grain starts to burn, producing soot.
Roasting times vary from 2 to 50 minutes, depending on the techniques and machinery used. The temperatures reached also vary: in the USA and Northern Europe, temperatures are around 220 ° C for about ten minutes, while in Italy higher temperatures are preferred, around 240 ° C, which allows to obtain a coffee more suitable for the preparation of espresso.
The roasted beans are very fragile and can be easily reduced to powder, for the preparation of the drink. Each coffee is usually obtained by mixing different varieties, each toasted individually, to obtain the desired taste and aroma. It is still a process in which the craft component has a significant importance, even if in recent years new process control and evaluation technologies have been introduced, to allow the maintenance of a constant quality
Green coffee can be stored for a long time, even more than two years, and some varieties are specially made to age in the warehouse, to increase its quality. Instead, the roasted coffee must be used within three months, keeping it at a low temperature and in the absence of oxygen. The greatest risk is in fact the oxidation of the fats present, the rancidity and the development of unpleasant smells and tastes. The ground coffee has an even shorter life due to the considerable increase of the surface exposed to the air and to the oxidation processes: for this reason vacuum preservation techniques are used which allow to lengthen the storage time of the powders.
Coffee, Caffeine And Health
The WHO has defined coffee as a “component of the non-nutritious diet” even if in reality both the beans and the drink contain nutrients and various biologically active substances. In the bean are present proteins and carbohydrates, fibers such as cellulose and polysaccharides rich in galactose, mannose and arabinose, which are degraded during roasting and tend to react with each other, with a very reduced presence of proteins and free sugars in the powder and in the drink .
The lipids present are much more stable at roasting: free fatty acids, waxes and esters are present. Organic acids are also present, especially acetic acid and formic acid, and to a lesser extent tartaric, malic, citric and derivative lactic acids.
Abundant the presence of chlorogenic acid which during the roasting is degraded with release of its components and formation of derivatives; the presence in the drink varies considerably depending on origin, processing and preparation. In reality it is a family of compounds that in several studies has shown to be able to reduce blood pressure, contribute to a better control of glycemia and to a reduction of insulin peaks. Celebrated by enthusiastic suppliers of supplements as a fat-burning substance, it would seem to have a lipolytic action, but the studies available are few and of poor quality. It is believed that the chlorogenic acid may have a weak stimulating effect, one third compared to caffeine, accompanied by a modest laxative action, given that it could corroborate the stimulating effect that some report after the consumption of coffee.
Another substance present in appreciable quantities is the trigonelline, a betaine that in several studies on animal model has shown an appreciable hypoglycaemic effect. Trigonelline can also help reduce the incidence of caries, in fact it prevents the adhesion to the surface of the teeth of Streptococcus mutans, one of the bacteria responsible for the problem.
Also present minerals such as potassium, magnesium, phosphorus and calcium and a whole series of compounds deriving from the reactions of Maillard between sugars and proteins, melanoidins, whose chemical structure is still under study, responsible for the bitter taste of coffee and the smell of cocoa present in some varieties.
Obviously the most known and studied substance, among those present in coffee, is caffeine, a purine alkaloid that in the Arabica is between 1 and 2.5% of the dry weight, while in Robusta it can be up to 4% . The presence of caffeine in the drink varies considerably depending on how it is prepared: it is very high in the espresso, which is however consumed in small quantities, while it is lower in the American coffee, which is however consumed in massive doses. It is estimated that the per capita consumption of caffeine ranges between 150 and 300 mg / day; obviously not all the caffeine we take every day comes from coffee: in fact, they give a significant contribution to tea, chocolate, some carbonated drinks and energy drinks.
We call it caffeine but the official name is – trimethylxanthine, a very bitter compound, even used in the research field as a standard for bitter taste. It is a very powerful stimulant, it is used by athletes to improve strength and endurance, able to improve alertness and attention, with a strong mental stimulation. The usual consumption of caffeine causes addiction, the effects just mentioned tend to fade to disappear – remains a weak action against sleep – and any increase in the dose consumed does not improve the response, which can be restored only by reducing the consumption of coffee for at least a month.
The effect of caffeine is due to its action of antagonist of adenosine, a substance that modulates the response of neurons to neurotransmitters and that at the level of the Central Nervous System has an inhibitory effect. When caffeine binds to adenosine receptors it actually reduces the inhibitory action giving rise to the well known stimulatory effects.
In the stomach, caffeine can favor the emptying of the gastric contents in the small intestine, thus inducing the gastrocolic reflex, one of the possible mechanisms, together with the action of chlorogenic acid, which could explain the weak laxative effect linked to coffee consumption.
Gastrointestinal absorption is very rapid and complete; the peak plasma concentration is reached within 20-60 minutes from the consumption of the drink. Caffeine is metabolized by cytochrome P450, in particular by CYP1A enzymes, and by a series of other enzymes, with a half-life of 3 to 9 hours. The different rate of elimination of caffeine found in different subjects seems to be due to genetic variations, especially at the level of CYP1A, with several studies that showed different values also between the sexes and between different ethnic groups.
Caffeine is a molecule able to cross many of the barriers present at the level of the human body and therefore tends to distribute itself homogeneously in the various tissues, including the brain.
Caffeine, as well as with adenosine, also interferes with the activity of several other neurotransmitters, elevates serotonin, in acute increases adrenaline and noradrenaline – while a chronic consumption reduces the two substances – stimulates the release of acetylcholine and promotes the action of dopamine, a phenomenon that seems to be reduced with chronic intake. This last effect could be the basis of the weak protective effect that the consumption of coffee and products containing caffeine presents beautiful comparisons of Parkinson’s disease, higher in men than in women, negligible in menopausal women who follow an estrogen therapy. Also interesting are the results of some studies in which caffeine has been used, in addition to targeted therapies, for the treatment of motor disorders related to Parkinson’s.
The consumption of coffee is related to a reduction in the risk for type II diabetes, appreciable reduction with a consumption of two cups a day. These are generally observational studies, although some intervention works seem to confirm what is observed on the population. The effect seems to be mainly attributable to the hypoglycemic effect of chlorogenic acid and trigonelline, while caffeine seems to induce a transient insulin resistance, probably mediated by adrenaline, an effect that tends to shrink to disappear with consumption usual. The consumption of coffee can reduce the concentration of C-reactive protein and oxidative stress and furthermore, by modulating the levels of serotonin and ghrelin, it can help reduce appetite. The effect of increased metabolic activity and lipolysis, essentially due to caffeine, is appreciable even if weak, phenomena in which it is observed a progressive addiction.
A good number of studies show that habitual consumption of coffee can have a protective effect on the liver with a reduction in the risk of cirrhosis and other diseases. The protective effect also extends to hepatic carcinomas and seems linked to the extent of consumption and sex, resulting in greater human activity.
The protective effect linked to coffee consumption also affects several forms of cancer: in addition to the liver, there seems to be also an appreciable risk reduction for cancers of the esophagus, the colon, the prostate and for various forms of melanoma. The results, although positive, are however prone to many confounding factors concerning the methods of preparing the drink, the concomitant consumption of alcohol, smoking and even even particular genetic polymorphisms.
Interesting effects of coffee and caffeine in sports activity. Some studies show an increase in maximal strength with caffeine doses of 6mg / kg body weight. A similar dose seems to improve the ability of repeated sprints in well-trained athletes. Significant effects are achieved on aerobic performance, with an increase in the time necessary for complete exhaustion, an effect that is relevant in non-addicted subjects and becomes negligible in habitual consumers. Increases in sports performance are greater in subjects deprived of sleep, probably due to the stimulating action of caffeine.
Does drinking coffee hurt?
Besides the potential positive effects that we have listed, it is also necessary to detect a series of side effects and contraindications related to coffee consumption.
Most of the studies available show an increased risk of cardiovascular disease associated with coffee consumption. Part of the problem seems to be related to the modest hypertensive action found in some works, part of the problem could be attributed to the increased level of homocysteine in the serum, observed also in clinical studies, for high coffee consumption and finally a significant contribution could be due to hyperlipidemizing action of coffee, with small but appreciable increases of LDL cholesterol and triglycerides, probabilcies due to the action of cafestol and kahweol, two diterpene present in coffee, especially espresso. The results of prospective and intervention studies for pathologies such as myocardial infarction and stroke have however given confusing results, with some works showing weak risk reduction, other small increases: in many cases a protective effect is observed with consumption moderate while the increase is sensitive with high consumption or without any consumption of coffee.
There is also a small increase in risk, related to coffee consumption, with regard to lung cancer, an increase that remains even when the study data have been corrected to compensate for behaviors that may alter the results, such as smoking habits .
Much discussed is the possibility of an increase in the risk of spontaneous abortion in women with high consumption of coffee / caffeine. The results of the studies are mixed, however many authoritative scientific societies suggest that during pregnancy it is better to limit the dose of caffeine taken to a maximum of 200 mg / day (corresponding to about three cups of espresso coffee).
A further restriction of caffeine consumption in pregnancy at doses below 100 mg / day is recommended to avoid a reduction in intrauterine growth of the fetus with a reduced birth weight. Many observational studies indicate a possible correlation between coffee consumption and reduced fetal growth, an effect that seems to be dose dependent, the more pronounced the greater the consumption of caffeine. However, randomized double-blind clinical trials have not produced data to support this hypothesis.
There are data indicating that a high consumption of caffeine during breastfeeding may cause irritability and sleep difficulties for the newborn, however a moderate consumption, less than 200 mg / day would seem to present no particular problems.
Coffee and caffeine reduce the absorption of calcium to the intestinal level, however the effect does not seem to be so significant as to contribute significantly to problems of bone fragility or osteoporosis, particularly when the subject has a good supply of calcium and vitamin D and coffee consumption is not particularly exaggerated.
The phenolic compounds of coffee can reduce the absorption of non-heme iron, the one present in plants for example, therefore subjects with iron deficiency should consume coffee away from main meals.
The consumption of coffee increases the secretion of gastric juices by the stomach and should therefore be avoided or reduced in subjects suffering from gastroesophageal reflux or gastric ulcer.
As we have seen, caffeine is metabolized thanks to the action of cytochrome P450, which is also responsible for the elimination of drugs and other potentially toxic substances. Some antibiotics and drugs can interfere with the processes that lead to the elimination of caffeine, enhancing its adverse effects. In turn, caffeine can interfere with the metabolism of certain drugs such as clozapine, paracetamol and aspirin, enhancing its effects. Caffeine also interferes with the absorption of levothyroxine (Eutirox) which should therefore be taken at a safe distance from the consumption of beverages containing it. It would always be good to check with your doctor whether or not to consume coffee in case of drug therapy, which can give rise to important interactions with the caffeine present in the drink.
The usual consumption of caffeine induces addiction, both to the stimulating action and to some of the effects on biological parameters described above. When a habitual consumer eliminates caffeine intake it can produce withdrawal symptoms, with headaches, fatigue and nervousness, problems that usually resolve within 2-6 days.
Excessive consumption of coffee and caffeine can lead to unpleasant side effects, especially hypertension and palpitations. The toxic dose for humans is about 20-40mg / kg body weight equal to about 1.4 / 2.8g for a subject of 70 kg: the equivalent of about 20-30 cups of espresso, all drunk in one shot. Do not do it at home, it could be dangerous!
A thousand ways to drink coffee
Far be it from me to want to make suggestions on how to prepare a good coffee, a theme which could cause serious conflicts between opposing factions, but I would like to underline some important steps and the main methods of preparation.
The grinding of the roasted beans is a crucial moment because it allows to obtain powders with particles whose dimensions influence the extraction of the substances present. Very thin powders with small particles, offer a high surface and make extraction very fast, while large particles require a prolonged infusion. Ideally the grains should be ground at the time of use, to prevent oxidative processes from occurring that alter their organoleptic characteristics.
The infusion allows the extraction of the substances present in the coffee: from the substances that determine taste and aroma, to pigments, to the carbohydrates that give body to the drink together with the lipids, which participate in the formation of the cream. The amount of powder used and the amount of extracted matter determine the overall quality of the drink. Powders with large particles give an acidic and poor coffee while an excessive extraction, with fine powders, high temperatures and long times, gives an excessively bitter and aggressive drink.
Extraction can take place by prolonged maceration, with coffee in direct contact with water, by percolation, with water passing through the coffee by gravity or pressure, by filtration, as occurs in many of the machines that use enclosed powders in paper or pressure filters, with the typical two-compartment coffee makers.
The water used should have a temperature of 85-95 ° C and should not be chlorinated, calcareous or sulphurous, flavors that could alter that of coffee. Depending on the extraction method, the percentage of coffee solids that we find in the beverage ranges from 1.5% of American coffee to 5% of Italian espresso.
Percolating percolators, typical of Americans, work with long times and temperatures that can reach the boiling point and can give an excessively bitter coffee. Even our moka works at high temperatures, around 110 ° C with a similar principle, even if the relationship between water and powders varies, and a coffee that is sometimes excessively aggressive.
The espresso machine works much faster. Water at 93 ° C is pushed by pressure through very fine powders, used in very high quantities, three or four times those typical of a moka. The extraction time is short, about 30 seconds, and the concentration of extracted materials is very high with the formation of a cream, a dispersion of gas in the liquid, which traps many of the substances present in the coffee, allowing a gradual release in the mouth, with a real explosion of taste.
The aroma and taste of coffee are due to a mixture of at least 500 different compounds: caffeine and phenols are responsible for the bitter taste and astringency of the drink, while the other substances present are responsible for the myriad of different characteristics of the different mixtures and of the different methods of preparation. Adding milk or cream to coffee reduces its astringency – milk proteins bind tannins – but it also binds many of the molecules responsible for taste, significantly reducing its impact.
The typical espresso cup has a caffeine content that is between 30 and 80 mg, while the typical cup of coffee, much more abundant, can reach around 90-160 mg. The dose of caffeine considered safe for an adult is about 300 mg / day, although it is recommended to keep around 200 mg, amount present in three cups of espresso. Remember that caffeine is not only present in coffee but also in tea, chocolate and in carbonated drinks and energy drinks: it is not so difficult to get an overdose of stimulants.
We close the review taking into consideration decaffeinated coffee and instant coffee. Decaffeinated is obtained by eliminating caffeine with two different methods: one involves the use of solvents – dichloromethane and ethyl acetate – while the other uses only water and carbon filters. The caffeine content can be reduced by up to 2-3% of the initial content.
The instant coffee is obtained with successive infusions, at temperatures of 100 and then 170 ° C. The obtained solution is dehydrated or lyophilized, until a powder is obtained which is then agglomerated into larger particles, the form in which the coffee is commercialized. The drink is prepared simply by adding hot water to taste. The taste is not that of espresso, but the speed of preparation makes it a very popular product.
Superfluous that you speak of the thousand and more ways in which coffee is served: it would seem that the creative energies of the human race have concentrated in the conception of the most imaginative methods of preparation. Whether you like it short or long, glass or cream, Irish, Scottish, Arabic or American, remember that coffee is a long-standing beverage, the world market leader, full of substances with marked effects on our body: seize the sides positive, avoiding problems that may come from excessive consumption.