{"id":30637,"date":"2020-06-19T09:51:07","date_gmt":"2020-06-19T07:51:07","guid":{"rendered":"https:\/\/7grshop.kotuko.rocks\/coffee-roasting\/"},"modified":"2025-10-23T16:00:48","modified_gmt":"2025-10-23T14:00:48","slug":"coffee-roasting","status":"publish","type":"post","link":"https:\/\/www.7gr.it\/en\/coffee-roasting\/","title":{"rendered":"Coffee Roasting"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"30637\" class=\"elementor elementor-30637 elementor-3820\" data-elementor-post-type=\"post\">\n\t\t\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-643df506 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"643df506\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-2a1d2b12\" data-id=\"2a1d2b12\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-69a523b8 elementor-widget elementor-widget-text-editor\" data-id=\"69a523b8\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_76 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Indice<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-69f5ea3ddf917\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #000000;color:#000000\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #000000;color:#000000\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-69f5ea3ddf917\"  aria-label=\"Toggle\" \/><nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Coffee_Roasting\" >Coffee Roasting<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Coffee_Roasting_the_Raw_Material\" >Coffee Roasting: the Raw Material<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#What_is_Coffee_Roasting\" >What is Coffee Roasting<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#The_Joule_and_Temperature\" >The Joule and Temperature<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Conduction_Convection_and_Radiation\" >Conduction, Convection, and Radiation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Endothermic_and_Exothermic_Reactions\" >Endothermic and Exothermic Reactions<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Physical_Changes_in_Beans_During_Coffee_Roasting\" >Physical Changes in Beans During Coffee Roasting<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Effect_of_Roasting_on_Coffees_Chemical_Composition\" >Effect of Roasting on Coffee&#8217;s Chemical Composition<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Non-volatile_Component_after_Coffee_Roasting\" >Non-volatile Component after Coffee Roasting<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Coffee_Roasting_Alkaloids\" >Coffee Roasting: Alkaloids<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Macromolecules_Proteins_and_Polysaccharides\" >Macromolecules: Proteins and Polysaccharides<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Coffee_Roasting_Humic_Acids_and_Melanoidins\" >Coffee Roasting: Humic Acids and Melanoidins<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Carboxylic_and_Chlorogenic_Acids\" >Carboxylic and Chlorogenic Acids<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Phenolic_Compounds\" >Phenolic Compounds<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Coffee_Roasting_and_Lipids\" >Coffee Roasting and Lipids<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Minerals\" >Minerals<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Volatile_Component_after_Roasting\" >Volatile Component after Roasting<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Reactions_During_the_Roasting_Process\" >Reactions During the Roasting Process<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#Coffee_Roasting_and_Acrylamide\" >Coffee Roasting and Acrylamide<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/#BIBLIOGRAPHY\" >BIBLIOGRAPHY:<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"Coffee_Roasting\"><\/span>Coffee Roasting<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>Coffee roasting is a traditional process that, despite its great importance, is still designed and managed on an empirical basis, through trial and error.<\/p>\n\n<p>A less empirical and more scientific vision regarding coffee roasting comes from understanding the raw material and the compounds it contains.<\/p>\n\n<p>The following text aims to investigate in a simple way the main chemical compounds present in roasted coffee and the main physical modifications that occur during roasting, with particular focus on the chemical reactions that lead to the formation of different compounds, in general terms and without making distinctions between coffee species for now, in order to lead to future reading of more specific and targeted insights.<\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"Coffee_Roasting_the_Raw_Material\"><\/span>Coffee Roasting: the Raw Material<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>When discussing coffee roasting, the first fundamental role is played by the selection of green coffee beans.<\/p>\n\n<p>They already contain some of the chemical substances that will bring the perceptible characteristics to the coffee beverage&#8217;s taste, and partly the precursors that will lead to the formation of chemical substances that will evolve during coffee roasting.<\/p>\n\n<p>The expert roaster knows that the raw material must be guided towards the development of its components that undergo changes and that these cannot be created from nothing. Consequently, excellent green coffee can produce either excellent or terrible roasted coffee, but poor raw beans cannot be turned into good ones. <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-3822\" title=\"green coffee roasting\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/torrefazione-del-caff%C3%A8-green-coffee.jpg\" alt=\"Green Coffee Roasting\" width=\"750\" height=\"500\"><\/figure>\n<\/div>\n\n<h2><span class=\"ez-toc-section\" id=\"What_is_Coffee_Roasting\"><\/span>What is Coffee Roasting<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>Coffee roasting is an intense thermal process through which heat is transferred to coffee beans, initially green, through direct or indirect heating, leading to both physical and chemical changes in the beans.<\/p>\n\n<p>Roasting is essential to bring coffee beans to have the chemical and physical characteristics necessary to be ground and to produce, through extraction, the coffee beverage.<\/p>\n\n<p>The tastes, flavors, aromas, and all potentially perceptible characteristics in the cup from the raw material depend on the coffee roasting process.<\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"The_Joule_and_Temperature\"><\/span>The Joule and Temperature<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>It&#8217;s impossible to talk about heating without becoming familiar with the unit of measurement for heat.<\/p>\n\n<p>Since heat is one of the various forms that energy can take, it is measured in the International System in Joules (J).<\/p>\n\n<p>Heat is a form of energy directly connected to the thermal agitation of particles that make up a body. In short, the more the particles that make up a body move, the hotter this body becomes. <\/p>\n\n<p>Since it is difficult to indicate exactly how much thermal energy is contained in a body, it was necessary to create another physical quantity: temperature.<\/p>\n\n<p>Temperature defines a body&#8217;s ability to exchange thermal energy (heat) with the outside (or other bodies); in other words, temperature can be considered as an indication of the average state of movement of particles present in a body.<\/p>\n\n<p>To measure temperature in the simplest way, a thermometer is used. When a thermometer is placed near a hot body, the particles of the hot body (in motion) transmit this energy to the particles of the liquid present in the thermometer, which then begin to move until reaching a state of thermal equilibrium with the body they were put in contact with. <\/p>\n\n<p>The greater the energy transmitted, the greater the movement of the particles that make up the thermometer&#8217;s liquid. At a macroscopic level, this increase in movement is detected with an increase in the body&#8217;s volume, which is then measured with an appropriate scale. <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" width=\"625\" height=\"500\" class=\"wp-image-3823\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/termometro.jpg\" alt=\"\" srcset=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/termometro.jpg 625w, https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/termometro-320x256.jpg 320w\" sizes=\"(max-width: 625px) 100vw, 625px\" \/><\/figure>\n<\/div>\n\n<p>Inside the roaster, temperature is measured using one or more thermocouples.<\/p>\n\n<p>Each thermocouple consists of two different metal wires (the conductors) joined at one end at a point called the hot junction and separately connected at the other end to a point called the cold junction, forming a circuit.<\/p>\n\n<p>The hot junction is the point where the temperature to be measured is applied, while the other end (cold junction) is connected to a body whose temperature is known.<\/p>\n\n<p>The temperature difference between the two junctions creates what is called the Seebeck effect, meaning two different metals, when heated, can generate current within the circuit due to a potential difference, which can be used to measure (derive) the temperature of the measured body through the use of a voltmeter.<\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"Conduction_Convection_and_Radiation\"><\/span>Conduction, Convection, and Radiation<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>During coffee roasting, heat transfer occurs from the surrounding system to the coffee beans.<\/p>\n\n<p>As we have seen, bodies can transfer heat between them. There are three modes of heat transmission: <\/p>\n\n<p>\u2022 conduction;<\/p>\n\n<p>\u2022 convection;<\/p>\n\n<p>\u2022 radiation.<\/p>\n\n<p>Conduction is the method by which heat is transmitted in solid objects and objects in contact with each other. Through this mechanism, the atoms of the hotter body (excited) transmit their vibrations to the atoms of the cold body they are in contact with, which in turn transmit this vibration to nearby atoms, thus transmitting heat. <\/p>\n\n<p>This is the case of the roaster&#8217;s hot drum which, when in contact with coffee beans, transfers heat to them through conduction. Within the coffee beans themselves, heat is transmitted from outer particles to inner ones through conduction. It should be noted that the atoms within the object don&#8217;t move freely but &#8220;vibrate in place.&#8221;  <\/p>\n\n<p>Thermal convection occurs when at least one of the two bodies exchanging heat is a fluid (such as air). This fluid must be in relative motion to the other body with which it exchanges heat. This movement can be given naturally by &#8220;convective motions&#8221; or forcibly (for example through the use of a fan). The modes of heat transmission are similar to those of conduction, but at a macroscopic level, there is also the motion of the fluid that carries such energy.   <\/p>\n\n<p>During roasting, hot air flows over the coffee bean transmitting heat to its surface through convection (with excited particles moving toward the bean&#8217;s surface with subsequent transmission of such energy), from the bean&#8217;s surface to the inside of the bean itself (at least regarding solid materials) heat is then transmitted by conduction.<\/p>\n\n<p>Regarding radiation, it should be remembered that any body emits electromagnetic radiation; When energy is emitted from the hot body in the form of electromagnetic radiation and hits a second body, part is absorbed and part reflected. Only the absorbed component of radiant energy leads to actual heating of the body and thus heat transmission by &#8220;radiation.&#8221; <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" class=\"alignnone wp-image-3824\" title=\"coffee roasting machine\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/torrefazione-del-caff%C3%A8-uscita-dal-tamburo.jpg\" alt=\"coffee roasting machine\" width=\"751\" height=\"501\"><\/figure>\n<\/div>\n\n<h2><span class=\"ez-toc-section\" id=\"Endothermic_and_Exothermic_Reactions\"><\/span>Endothermic and Exothermic Reactions<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>During coffee roasting, chemical reactions occur inside the bean. A chemical reaction that develops heat while occurring is called &#8220;exothermic&#8221; (releases energy), while a chemical reaction that absorbs heat from the outside during its occurrence is called &#8220;endothermic&#8221; (requires energy). <\/p>\n\n<p>An &#8220;exothermic&#8221; reaction may still need heat to be activated and then develop a greater amount of heat than that needed for activation.<\/p>\n\n<p>It&#8217;s often mistakenly thought that exothermic reactions in the bean begin after the first crack (the moment during roasting when the coffee bean crackles with a characteristic sound similar to that of popcorn).<\/p>\n\n<p>In coffee heating, calorimetric curves show an endothermic peak above 100\u00b0C (aqueous phase transition) and at higher temperatures, an exothermic trend. These exothermic reactions begin at about 140\u00b0C for green coffee beans. These exothermic phenomena are mainly attributed to reactions occurring at the level of carbohydrates contained in the beans<sup><sup>46<\/sup><\/sup>.  <\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"Physical_Changes_in_Beans_During_Coffee_Roasting\"><\/span>Physical Changes in Beans During Coffee Roasting<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>During roasting, coffee beans undergo physical changes that briefly affect volume, mass, relative density, and coloration.<\/p>\n\n<p>Regarding volume, it increases approximately 40-65% depending on factors such as roasting time and temperature<sup><sup>45<\/sup><\/sup>.<\/p>\n\n<p>The mass lost concerns water evaporation, loss of organic matter, degradation, and evaporation of substances. According to Oosterveld et al., weight losses of 11%, 15%, and 22% represent light, medium, and dark roasted coffee beans respectively<sup>45<\/sup>. <\/p>\n\n<p>The coloration of coffee beans varies with the varying intensity of roasting (time\/temperature) involved.<\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3825\" title=\"coffee roasting beans\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/roasting-coffee.jpg\" alt=\"beans\" width=\"667\" height=\"500\" srcset=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/roasting-coffee.jpg 667w, https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/roasting-coffee-320x240.jpg 320w\" sizes=\"(max-width: 667px) 100vw, 667px\" \/><\/figure>\n<\/div>\n\n<h2><span class=\"ez-toc-section\" id=\"Effect_of_Roasting_on_Coffees_Chemical_Composition\"><\/span>Effect of Roasting on Coffee&#8217;s Chemical Composition<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>Coffee beans, besides water and minerals, contain a large quantity of substances whose concentrations can vary depending on the type of coffee.<\/p>\n\n<p>In general, the main components of coffee beans are carbohydrates, but other substances containing nitrogen, both protein and non-protein, lipids, organic acids, volatile substances, oils, and phenolic substances are also present.<\/p>\n\n<p>The reactions that take place during roasting still present knowledge gaps today due to the difficulty of reproducing results in laboratories of all reactions that take place inside the coffee bean. What is certain, and several studies demonstrate this, is that roasting modifies the initial chemical composition of coffee beans. <\/p>\n\n<p>Obviously, a &#8220;dark&#8221; roast leads to a much more significant variation in chemical composition compared to a &#8220;light&#8221; roast. Initially, the roasting process leads to the formation of carbon dioxide and water. <\/p>\n\n<p>Carbon dioxide is quantitatively the most important volatile component that originates during roasting, but it doesn&#8217;t contribute to coffee aroma. This originates from pyrolysis reactions and from the Strecker degradation reaction.<sup>1<\/sup> Subsequently, there is degradation of carbohydrates, proteins, and chlorogenic acids, with a relative increase in organic acids, while trigonelline and caffeine levels remain roughly unchanged.<sup>2<\/sup> <\/p>\n\n<p>Whatever the degree of roasting, a roasted coffee bean will always have a volatile component, meaning a set of chemical compounds that tend to evaporate, and a non-volatile one.<\/p>\n\n<p>Roasting plays a fundamental role for a coffee producer as it allows obtaining a non-volatile component, responsible for coffee aroma, which would otherwise exist only partially.<\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"Non-volatile_Component_after_Coffee_Roasting\"><\/span>Non-volatile Component after Coffee Roasting<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>From a chemical point of view, the non-volatile component of a roasted coffee bean essentially consists of:<sup>3<\/sup><\/p>\n\n<ol type=\"1\">\n<li>Alkaloids such as caffeine and trigonelline, which give coffee robustness and body;<\/li>\n<li>Macromolecules such as proteins and polysaccharides, like cellulose and hemicellulose, which play a fundamental role in retaining all the volatile components after roasting;<\/li>\n<li>Humic acids and melanoidins, derived from the reaction between amino acids and monosaccharides during roasting and which give the classic dark color to the bean;<\/li>\n<li>Carboxylic acids responsible for harshness;<\/li>\n<li>Chlorogenic acids, mainly cinnamic, caffeic, and ferulic;<\/li>\n<li>Lipids (terpenes, triglycerides, sterols) that confer a certain viscosity;<\/li>\n<li>Minerals such as potassium, manganese, iron, and copper, which play an important role during the reactions that occur in roasting.<\/li>\n<\/ol>\n\n<p>Many of the listed chemical species have evaporation temperatures that are reached and exceeded during the roasting process. Therefore, many substances should leave the roasted bean, which however doesn&#8217;t happen probably due to the conformation of the micropores inside the coffee beans. <\/p>\n\n<p>The internal micropore structure of coffee beans hasn&#8217;t been completely revealed yet, a &#8220;plasmodesma&#8221; structure or a more chaotic three-dimensional permeable structure of polysaccharides is suspected. In this latter case, the permeable network of polysaccharides would prevent bean degassing and oil surfacing<sup>47<\/sup>. <\/p>\n\n<p>An increase in polysaccharide degradation at higher temperatures could be the cause of the wider cell wall micropores found in high-temperature roasted coffee samples that cause increased degassing and oil migration to the surface<sup>47<\/sup>.<\/p>\n\n<p>Indeed, the ability to retain gases formed during roasting represents one of the most remarkable properties of coffee beans. Based on total CO2 content and bean porosity, maximum internal pressures (depending on the scientific research consulted) of 4.4 atm and 7.9 atm have been reported in coffee beans<sup>48<\/sup>. <\/p>\n\n<p>It is known that the increase in internal pressure in coffee beans leads, obviously, to an increase in the temperature necessary for the evaporation of many chemical substances.<\/p>\n\n<p>But what happens when the internal pressure in the coffee bean becomes too high? First of all, it must be remembered that during roasting, water evaporates from the coffee bean. When its content falls below 2 &#8211; 1.5%, it causes a change in the bean&#8217;s consistency from plastic and viscous to brittle and easily breakable<sup>4<\/sup>.  <\/p>\n\n<p>The increase in internal pressure caused by gases and the increase in bean brittleness lead to the formation of internal and external cracks in the bean and to the famous phenomenon of &#8220;cracking.&#8221;<\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"Coffee_Roasting_Alkaloids\"><\/span>Coffee Roasting: Alkaloids<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>It&#8217;s not simple to briefly define an alkaloid. Alkaloids can be defined as cyclic molecules, meaning closed on themselves, containing at least one nitrogen atom and of plant origin. <\/p>\n\n<p>They are highly reactive substances and have been the subject of pharmacological study since the 1940s. Some alkaloids like those belonging to the <em>taxane<\/em> class, have been used in chemotherapy due to their excellent antitumor properties; their chemical structure has represented the starting point for many researchers in the development of other antitumor drugs like <em>docetaxel<\/em>.<sup>5<\/sup> <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"653\" height=\"345\" class=\"wp-image-3826\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/docetaxel.jpg\" alt=\"\" srcset=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/docetaxel.jpg 653w, https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/docetaxel-320x169.jpg 320w\" sizes=\"(max-width: 653px) 100vw, 653px\" \/>\n<figcaption>Docetaxel<\/figcaption>\n<\/figure>\n<\/div>\n\n<p><em>Caffeine<\/em> and <em>trigonelline<\/em> belong to the alkaloid family and are part of those non-volatile chemical compounds contained in a coffee bean.<\/p>\n\n<p>Caffeine (1,3,7-trimethylxanthine) was isolated from coffee beans by chemist <em>Friedlieb Ferdinand Runge<\/em> in 1819. Most studies concern its physiological effects on humans that influence various systems: urinary, nervous, circulatory, etc. Regarding its role within the bean, it is hypothesized to act as a deterrent for parasites and pathogens. <\/p>\n\n<p>Its concentration within a green bean can vary between 0.9 and 2.5%. Although coffee roasting causes a total reduction in caffeine content of up to 30%, in darker roasted coffees a higher caffeine content is often detectable<sup>44<\/sup>. <\/p>\n\n<p>This happens because during the coffee roasting process, in addition to caffeine, the beans lose weight due to the evaporation of water and other compounds. For this reason, the percentage of caffeine appears increased in dark roasted coffees compared to light roasted coffees even though in reality the total level has decreased. <\/p>\n\n<p>Data has shown that roasting temperature, rather than time, has a greater influence on the final caffeine content<sup>44<\/sup>.<\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" class=\"wp-image-3827\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/Torrefazione-del-caff%C3%A8-caffeina.jpg\" alt=\"\">\n<figcaption>Caffeine<\/figcaption>\n<\/figure>\n<\/div>\n\n<p>Another alkaloid present in coffee is trigonelline (about 0.6%), derived from the methylation of nicotinic acid. Several studies show that this alkaloid has antitumor properties, while there are no studies clarifying its physiological function within the bean. <\/p>\n\n<p>It plays an important role in the roasting process as it leads to the formation of pyridines, acids, and pyrroles. In fact, a variable amount of trigonelline, between 50\u201380%, is degraded during roasting (the degraded amount depends on the roast level).<sup>7<\/sup> <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" class=\"wp-image-3828\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/Torrefazione-del-caff%C3%A8-trigonellina.jpg\" alt=\"\">\n<figcaption>Possible degradation of trigonelline during coffee roasting<\/figcaption>\n<\/figure>\n<\/div>\n\n<h2><span class=\"ez-toc-section\" id=\"Macromolecules_Proteins_and_Polysaccharides\"><\/span>Macromolecules: Proteins and Polysaccharides<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>Green coffee has a protein content that can vary between 10% and 15%, of which roughly 1% consists of free amino acids that disappear during roasting, where they are precursors for volatile compounds such as furans, pyridines, pyrazines, and pyrroles.<sup>8<\/sup><\/p>\n\n<p>A large portion of the dry weight of a coffee bean, however, is due to polysaccharides (around 50%), mainly cellulose and arabinogalactans, which make up 25% of a bean\u2019s cell wall.<sup>9<\/sup><\/p>\n\n<p>Due to thermal degradation, during roasting there can be a loss of carbohydrates between 10% and 40%, where polysaccharides release monosaccharides that then take part in Maillard reactions with the bean\u2019s proteins.<sup>10<\/sup><\/p>\n\n<p>In addition to polysaccharides, a substantial portion of the carbohydrates in coffee beans is sucrose, but very little remains after roasting. It undergoes a degradation process, called hydrolysis, which converts it into glucose and fructose. <\/p>\n\n<p>Glucose and fructose can be converted into aliphatic acids or take part in Maillard reactions with proteins and amino acids. By the end of a \u201cdark\u201d roast, 96\u201398% of sucrose is degraded. <\/p>\n\n<p>The acid content of coffee increases with darker roasting because more sucrose is degraded.<sup>11<\/sup><\/p>\n\n<p>The formation of lactic, formic, and acetic acid is described by <em>Lobry-de Bruyn-van Eckenstein<\/em>, who explain how glucose and fructose, resulting from sucrose hydrolysis, lead to molecules (1,2-enediol and 2,3-enediol) that then evolve into acids. The acids formed during roasting, however, do not have a significant effect on the coffee\u2019s final pH. <\/p>\n\n<p>This effect would seem to contradict what has been said so far (higher acid concentration = lower pH = more acidic coffee). In reality, the salts present in coffee buffer this effect. However, the coffee\u2019s final taste will depend greatly on the quantity and type of acids present in the finished beverage.   <sup>12<\/sup><\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"Coffee_Roasting_Humic_Acids_and_Melanoidins\"><\/span>Coffee Roasting: Humic Acids and Melanoidins<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>Humic acids are natural chemical compounds formed by the microbial action of bacteria on organic matter (plant or animal) or by complex reactions between amino acids and carbohydrates.<\/p>\n\n<p>We are not speaking of a single acid but rather a complex mixture of acids whose composition changes depending on the organic matter from which it is generated.<sup>13<\/sup><\/p>\n\n<p>Melanoidins, on the other hand, are complex dark-colored substances and are responsible for the brown color of roasted coffee. They are generated during roasting and belong to that category of molecules that boast antioxidant power both on the food and on the body\u2019s cells that absorb them.<sup>14<\/sup> <\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"Carboxylic_and_Chlorogenic_Acids\"><\/span>Carboxylic and Chlorogenic Acids<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>Carboxylic acids are a class of molecules easily identifiable by the presence of a COOH sequence of atoms.<\/p>\n\n<p>Carboxylic acids make up part of the non-volatile component of coffee beans after roasting, generated by the complex reactions that occur during roasting.<\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3829\" title=\"coffee roasting carboxylic\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/struttura-acido-carbossilico.jpg\" alt=\"\" width=\"145\" height=\"116\">\n<figcaption>General structure of a carboxylic acid<\/figcaption>\n<\/figure>\n<\/div>\n\n<p>It is not easy to state precisely which class of substances they originate from (proteins, lipids, or polysaccharides), since a carboxylic acid can be released quite readily\u2014thanks to the high roasting temperatures\u2014from any macromolecule present in a coffee bean.<\/p>\n\n<p>However, it has been shown that most of the acids released during roasting originate from sucrose. The most abundant acids found at the end of the roasting process are lactic, formic, acetic, citric, and malic acids, all water-soluble and therefore influential on the coffee\u2019s final taste. <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"237\" height=\"129\" class=\"wp-image-3830\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/struttura-acido-malico.jpg\" alt=\"\">\n<figcaption>Structure of malic acid<\/figcaption>\n<\/figure>\n<\/div>\n\n<p>Carboxylic acids can form hydrogen bonds that cause the molecules to remain linked together in a sort of network, preventing them from evaporating. This, in addition to pore structure, explains why these substances remain trapped despite the high temperatures reached during roasting.<sup>15<\/sup> <\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"Phenolic_Compounds\"><\/span>Phenolic Compounds<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>Among the compounds that play a key role in coffee are phenolic compounds. These include <em>chlorogenic acids<\/em> and <em>polyphenols<\/em>, such as <em>tannins<\/em>. <\/p>\n\n<p><em>Chlorogenic acids<\/em> are derivatives of quinic acid whose concentration in the bean increases during growth and then drops sharply upon maturation. They amount to about 10% of the green Arabica bean weight and 4% for Robusta.<sup>16<\/sup> <\/p>\n\n<p>During roasting the concentration of <em>chlorogenic acids<\/em> decreases and they degrade into <em>melanoidins<\/em> and other low-molecular-weight compounds, such as certain <em>phenolic acids<\/em>, but a significant amount remains trapped within the bean itself. They appear to have good antioxidant properties and thus play an important protective role against free radicals, which are responsible for aging. <\/p>\n\n<p>The term <em>chlorogenic acid<\/em> is often used, but it actually refers only to the product obtained by combining <em>caffeic acid<\/em> with <em>quinic acid<\/em>.<sup>17<\/sup><\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3831\" title=\"coffee roasting chlorogenic acid\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/Acido-clorogenico.jpg\" alt=\"\" width=\"455\" height=\"242\" srcset=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/Acido-clorogenico.jpg 455w, https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/Acido-clorogenico-320x170.jpg 320w\" sizes=\"(max-width: 455px) 100vw, 455px\" \/>\n<figcaption>Chlorogenic Acid<\/figcaption>\n<\/figure>\n<\/div>\n\n<p> <em>Polyphenols<\/em> are a widely studied class of molecules thanks to their antioxidant properties and are reported to have positive effects both at the cardiovascular level and against tumor growth.<sup>18<\/sup><\/p>\n\n<p><em>Tannins<\/em> (such as <em>tannic acid<\/em>) are water-soluble polyphenolic compounds that can be divided into two categories: <em>condensed tannins<\/em> (also called <em>flavanols<\/em>) and <em>hydrolyzable tannins<\/em>.<\/p>\n\n<p>Unlike condensed tannins, <em>hydrolyzable tannins<\/em> are easily degraded by acids and enzymes, leading to the formation of sugars and phenolic acids such as <em>gallic acid<\/em>.<sup>19<\/sup><\/p>\n\n<p>The content of <em>tannins<\/em> in the final roasted coffee depends essentially, as with <em>trigonelline<\/em> and other substances, on the temperature reached during roasting. Concentrations range from about 51.60 milligrams to 3.10 mg per 10 grams of coffee, moving from a green coffee to a \u201cdark\u201d roast coffee.<sup>20<\/sup> <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"696\" height=\"434\" class=\"wp-image-3832\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/acido-tannico.jpg\" alt=\"\" srcset=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/acido-tannico.jpg 696w, https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/acido-tannico-320x200.jpg 320w\" sizes=\"(max-width: 696px) 100vw, 696px\" \/><\/figure>\n<\/div>\n\n<h2><span class=\"ez-toc-section\" id=\"Coffee_Roasting_and_Lipids\"><\/span>Coffee Roasting and Lipids<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>Another important component of coffee beans is lipids. The lipid fraction consists mainly of triacylglycerols (about 75%), fatty acids (1%), sterols, tocopherols, and diterpenes.<sup>21<\/sup> <\/p>\n\n<p>Of particular interest are <em>cafestol<\/em> and <em>kahweol<\/em>, since they have been shown to have a protective effect against the onset of certain types of tumors in humans, although their function within the bean is still unknown.<sup>22<\/sup> The degradation of these two molecules during roasting is still under study.<\/p>\n\n<p>16-O-methylcafestol is another substance of interest because, besides not being produced by Arabica beans but only by the Robusta variety, it does not degrade during roasting, which makes it useful for detecting: \u201cHow much Robusta is in Arabica blends?\u201d.<sup>23<\/sup><\/p>\n\n<p>The fatty acid fraction consists mainly of unsaturated fatty acids (oleic, linoleic, and linolenic acids), which are important for preserving coffee freshness.<sup>24<\/sup><\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" class=\"wp-image-3833\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/Torrefazione-del-caff%C3%A8-lipidi.jpg\" alt=\"\">\n<figcaption>16-O-methylcafestol<\/figcaption>\n<\/figure>\n<\/div>\n\n<h2><span class=\"ez-toc-section\" id=\"Minerals\"><\/span>Minerals<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>Potassium accounts for 40% of all minerals present in a green coffee bean (about 1\u20132 grams per 100 grams of green coffee), while the remaining portion consists mainly of magnesium, calcium, manganese, iron, and copper.<\/p>\n\n<p>The mineral composition of a bean, however, depends greatly on the soil in which the plant producing the fruit is grown. There are few studies on their involvement in the reactions that occur during roasting, but it is hypothesized that they may act as catalysts, i.e., they increase the rate of a reaction.<sup>25<\/sup> <\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"Volatile_Component_after_Roasting\"><\/span>Volatile Component after Roasting<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>The volatile component of a coffee bean at the end of roasting is even more complex than the non-volatile part. From the plant to the bean, several hundred volatile chemical substances have been identified in coffee, many with still-unknown functions, yet fully representing the complexity of plant chemistry. <\/p>\n\n<p>A green coffee bean contains roughly 300 volatile compounds, many of which are degraded during roasting; others remain stable; others are transformed. Roasting itself is the key step for a good final coffee. <\/p>\n\n<p>The roasting process increases the concentration of volatile compounds, reaching nearly a thousand species present in a bean and, through their combination, giving rise to coffee\u2019s characteristic aroma. Volatile chemicals can be classified into:<sup>26<\/sup> <\/p>\n\n<ul>\n<li>Thiols, thiophenes, and thiazoles;<\/li>\n<li>Pyrazines, pyridines, and pyrroles;<\/li>\n<li>Furans;<\/li>\n<li>Aldehydes and ketones;<\/li>\n<li>Phenols.<\/li>\n<\/ul>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"145\" height=\"218\" class=\"wp-image-3834\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/limonene.jpg\" alt=\"\">\n<figcaption>Limonene<\/figcaption>\n<\/figure>\n<\/div>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"258\" height=\"170\" class=\"wp-image-3835\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/damascenone.jpg\" alt=\"\">\n<figcaption><br><strong>\u03b2<\/strong>-damascenone<\/figcaption>\n<\/figure>\n<\/div>\n\n<p>Gas chromatographic olfactometric analyses, such as AEDA (aroma dilution extraction analysis), have enabled the identification of certain key molecules responsible for coffee aroma, arising from reactions that occur during roasting.<\/p>\n\n<p>Among these are: 3-mercapto-3-methylbutyl formate, 2-furfurylthiol, \u03b2-damascenone, guaiacol, 4-vinylguaiacol, 4-ethylguaiacol, and 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone. Some of coffee\u2019s main positive notes (citrusy and fruity) are due to a class of compounds called monoterpenes (linalool, limonene, geraniol, etc.), which are released during roasting from polysaccharide chains.<sup>27<\/sup> <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3836\" title=\"coffee roasting table\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/torrefazione-del-caff%C3%A8-tabella.jpg\" alt=\"coffee roasting table\" width=\"536\" height=\"510\">\n<figcaption>Odorant molecules<\/figcaption>\n<\/figure>\n<\/div>\n\n<p>During roasting, carbon dioxide develops\u2014a volatile but odorless component. Quantitatively, it is the most abundant volatile component and is produced by pyrolysis reactions and by the <em>Strecker<\/em> degradation reaction (so named because the German chemist <em>Adolph Strecker<\/em> was the first to discover it in 1862). <\/p>\n\n<p>The amount of carbon dioxide that develops certainly depends on the degree of roast and can exceed 10 milliliters per gram of roasted coffee. It has been shown that 45% of the carbon dioxide formed is released from the roasted bean within the first 5 minutes after roasting.  <sup>29<\/sup><\/p>\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"wp-image-3837\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/torrefazione-del-caff%C3%A8-volatili.jpg\" alt=\"\">\n<figcaption>Odorant molecules<\/figcaption>\n<\/figure>\n\n<h2><span class=\"ez-toc-section\" id=\"Reactions_During_the_Roasting_Process\"><\/span>Reactions During the Roasting Process<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p>The reactions involved during roasting are extremely complex because they involve a large number of substances. Nevertheless, they are essential to coffee aroma. Among them are:<sup>30<\/sup>  <\/p>\n\n<ul>\n<li>Maillard reaction: reaction between nitrogen-containing compounds (proteins, peptides, and amino acids) and carbohydrates on one side, and acidic compounds and phenols on the other, to form aminoaldoses and aminoketones through condensation;<\/li>\n<li>Strecker degradation: reaction between an amino acid and a carbonyl compound to form aminoketones that condense to form aromatic heterocyclic compounds or react with formaldehyde to yield oxazolones;<\/li>\n<li>Formation of sulfur-containing compounds starting from amino acids and intermediates of the Maillard reaction;<\/li>\n<li>Trigonelline degradation with formation of pyridines, pyrazines, and pyrroles;<\/li>\n<li>Chlorogenic acid degradation with formation of phenols;<\/li>\n<li>Pigment degradation, especially carotenoids;<\/li>\n<li>Lipid degradation, especially diterpenes.<\/li>\n<\/ul>\n\n<p>As noted, roasting is a crucial process for a coffee producer because it allows the chemical composition of a green coffee bean to be modified, enhancing its aroma and taste.<\/p>\n\n<p>During roasting, the temperature inside the coffee bean exceeds 180 degrees Celsius. At this temperature, several reactions occur, including the Maillard reaction, which generates melanoidins\u2014and more\u2014that make up 29% of the weight of a roasted coffee bean.<sup>31<\/sup> <\/p>\n\n<p>The reaction is named after the French chemist <em>Louis Camille Maillard<\/em>, who was among the first to study it. When we speak of the Maillard reaction, we do not refer to a single reaction but to a set of very complex reactions that occur between sugars and proteins. <\/p>\n\n<p>For these reactions to occur, high temperatures are needed, typically reached when food is cooked. After cooking, the food appears brownish and reaches our nose with an aroma reminiscent of freshly baked bread.<sup>32<\/sup> <\/p>\n\n<p>All this indicates that the Maillard reaction has occurred. Reactant concentration, acidity, temperature, and cooking time are parameters that influence the reaction. Schematically, the reaction can be divided into three stages:<sup> 33<\/sup>  <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3838\" title=\"coffee roasting maillard\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/reazione-di-maillard.jpg\" alt=\"coffee roasting maillard\" width=\"782\" height=\"717\" srcset=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/reazione-di-maillard.jpg 782w, https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/reazione-di-maillard-320x293.jpg 320w, https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/reazione-di-maillard-768x704.jpg 768w\" sizes=\"(max-width: 782px) 100vw, 782px\" \/>\n<figcaption>Maillard reaction<\/figcaption>\n<\/figure>\n<\/div>\n\n<ul type=\"1\">\n<li>Reaction between a sugar and an amino acid found at the end of a protein chain. The reaction leads to the formation of a molecule belonging to the <em>glycosamine<\/em> family. These molecules are highly unstable and, through a series of reactions called <em>isomerization<\/em>, evolve into more stable compounds called <em>ketosamines<\/em> or <em>Amadori<\/em> compounds (named after the Italian chemist Mario Amadori, among the first to study them). This key step in the Maillard reaction is strongly influenced by acidity and does not produce odorant or colored molecules but only <em>ketosamines<\/em>, intermediate compounds that will subsequently transform in the second phase of the reaction.  <\/li>\n<\/ul>\n\n<ul>\n<li>The second phase of the reaction is even more complex than the first, as multiple simultaneous reactions can occur, leading to a set of new substances. First, the <em>ketosamines<\/em> formed in the first phase can be destroyed through dehydration (a reaction followed by the loss of water) or cleavage, leading to the formation of carboxylic acids and aldehydes such as <em>glyceraldehyde<\/em> and <em>pyruvic aldehyde<\/em>. In addition to destruction, <em>Amadori<\/em> compounds can transform into new compounds called <em>alpha-dicarbonyls<\/em>. The <em>alpha-dicarbonyl<\/em> compounds can, in turn, cyclize, cleave, or react with free amino acids forming carbon dioxide (the <em>Strecker<\/em> degradation). From this second, complex phase, molecules responsible for roasted coffee\u2019s aroma are obtained, such as furans, pyrazines, pyridines, pyrroles, etc.   <sup>  34<\/sup><\/li>\n<\/ul>\n\n<ul>\n<li>The third phase consists in the formation of substances that will give the classic dark brown color to the roasted coffee bean, namely brown proteins and melanoidins. Melanoidins are formed via polymerization reactions between furans and\/or pyrroles but also via polycondensations between aldehydes and ketones.<sup> 35<\/sup> This last phase, however, is very delicate because if the temperature of the roasting process is too high, <em>acrylamide<\/em> can be generated.<sup>36<\/sup> <\/li>\n<\/ul>\n\n<h2><span class=\"ez-toc-section\" id=\"Coffee_Roasting_and_Acrylamide\"><\/span>Coffee Roasting and Acrylamide<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<p><em>Acrylamide<\/em> is a low molecular weight compound, highly soluble in water, that is formed from the reaction of the amino acid <em>asparagine<\/em> with sugars, normally present in some foods, starting from temperatures above 120 degrees Celsius.<sup> 37<\/sup><\/p>\n\n<p>Why is it therefore easier to find higher quantities of acrylamide in light roasted coffee compared to dark roasted coffee? It should be known that, although acrylamide is formed at high temperatures, at higher temperatures it is largely removed; the higher the temperature reached in the bean, the less acrylamide we will find at the end of the process. <\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3839\" title=\"coffee roasting acrylamide\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/torrefazione-del-caff%C3%A8-e-acrilammide-960x525.jpg\" alt=\"coffee roasting acrylamide\" width=\"960\" height=\"525\">\n<figcaption>Acrylamide formation<\/figcaption>\n<\/figure>\n<\/div>\n\n<p>Studies show how <em>acrylamide<\/em> can increase the risk of developing cancer and, being present in many foods for daily use, this concern affects all consumers regardless of age group.<\/p>\n\n<p>REGULATION (EU) 2017\/2158 of the Commission of November 20, 2017, establishes mitigation measures and reference levels for the reduction of acrylamide presence in foods.<\/p>\n\n<p>The control of <em>acrylamide<\/em> levels in the coffee market starts from the cultivation of coffee plants up to the final product. The reference level of acrylamide, that is the maximum possible quantity, is 400 \u03bcg per kilogram of roasted coffee and 850 \u03bcg per kilogram of instant coffee. <sup>  38<\/sup><\/p>\n\n<p>It is not uncommon to find intermediate products in the roasted coffee bean, that is, products that have not completely degraded during the reaction, such as <em>5-hydroxymethylfurfural<\/em> often called more simply by the abbreviation <em>HMF<\/em>.<sup> 39<\/sup><\/p>\n\n<p>This is generated during roasting from the hydrolysis reaction of fructose that originates from sucrose (a reaction that is also currently used to produce it on an industrial scale) or from glucose.<sup>  40<\/sup><\/p>\n\n<p><em>HMF has<\/em> recently been recognized as a very versatile molecule for the production of various chemical products (fungicidal agents, pharmaceuticals and plastics). Currently there are many scientific studies regarding this compound as it could be used to replace some substances that are currently derived from petroleum. <sup>  41<\/sup><\/p>\n\n<p>If for a chemist <em>HMF<\/em> represents an interesting molecule, for a coffee consumer it would not be good to find it in high concentrations in their cup. Numerous studies demonstrate how <em>HMF<\/em> is a cytotoxic molecule, irritating to the eyes, skin and respiratory mucous membranes. <\/p>\n\n<p>Recent studies conducted on rats demonstrate how it is also capable of promoting the onset of tumors in the gastrointestinal tract.<sup> 42<\/sup> Therefore its levels in the roasted coffee bean must be periodically controlled even though the high temperatures of the process provide for the degradation of the molecule into aldehydes and ketones.<\/p>\n\n<p>Consequently there is no real danger of finding significant quantities of <em>HMF<\/em> in the final coffee that could compromise our daily desire for this beverage.<sup> 43<\/sup><\/p>\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"635\" height=\"1040\" class=\"wp-image-3840\" src=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/idrossimetilfurfurale.jpg\" alt=\"\" srcset=\"https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/idrossimetilfurfurale.jpg 635w, https:\/\/www.7gr.it\/wp-content\/uploads\/2020\/06\/idrossimetilfurfurale-293x480.jpg 293w\" sizes=\"(max-width: 635px) 100vw, 635px\" \/>\n<figcaption>HMF formation<\/figcaption>\n<\/figure>\n<\/div>\n\n<p>Do you want to have more information about coffee roasting through our courses or our products? <a href=\"https:\/\/www.7gr.it\/en\/contacts\/\">Contact us<\/a>!<\/p>\n\n<h2><span class=\"ez-toc-section\" id=\"BIBLIOGRAPHY\"><\/span>BIBLIOGRAPHY:<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n<ol>\n<li><a href=\"https:\/\/pubs.acs.org\/doi\/abs\/10.1021\/jf60015a004\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Dehydrated Foods, Chemistry of Browing Reactions in Model Systems, Hodge J. E., J. Ag. Food Chem., 1953, 1, 928-943.<\/a><\/li>\n<li>Coffee, Clarke R. J, Macrae R., Technology, vol 2, Elsevier: London, 1987.<\/li>\n<li><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1002\/ffj.1325\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Coffee Flavour: An overview, Buffo A. R., Cardelli-Freire C., Flavour Frag. J., 2004, 19, 99-104. <\/a><\/li>\n<li>Change of physical properties of coffee beans during rostaing, Marija J. R. et al. Technologica, 2012, 43, 21-31. <\/li>\n<li>Taxanes for the treatment of Metastatic Breast Cancer, Gradishar W. J., Breast Cancer, 2012, 6, 159-171; Docetaxel, Cortes J. E., Pazdur R., Journal of Clinical Oncology, 1995, 13, 2643-2655.<\/li>\n<li>Caffeine Effects on the Brain and Behavior: A metabolic Approach, Nehling A., ACS Sym. Series, 2000, 754, 46-53; The clinical toxicology of caffeine: A Review and case study, Willson C., Toxicol Rep., 2018, 5, 1140-1152.<\/li>\n<li>Anti-invasive activity of niacin and trigonellina against cancer cells, Hirakawa N., Okauchi R., Miura Y., Yagasaki K., Biosci. Biotechnol. Biochem, 2005, 69, 653\u2013658.  <\/li>\n<li>Water soluble protein and nonprotein components of Brazilian green coffee beans, Amorim H. V., Josephson R. V., J. Food. Sci., 1975, 40, 1179-1184.<\/li>\n<li><a href=\"https:\/\/europepmc.org\/article\/med\/11844494\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Polysaccharides of green Arabica and Robusta coffee beans, Fischer M., Reimann S., Trovato V., Redgwell R. J., Carbohydrate Research, 2001, 330, 93-101; Coffee beanarabinogalactans: acidic polymers covalently linked to protein, Redgwell R.J., Curti D., Fischer M., Nicolas P., Fay L. B., Carbohydrate Research, 2002, 337, 239-253.<\/a><\/li>\n<li>Effect of roasting on degradation and structural features of polysaccharides in Arabica coffee beans, Redgwell R. J, Trovato V., Curti D., Fischer M., Carbohydrate Research, 2002, 337, 421-431.<\/li>\n<li>Construction and characterization of a Coffea canephora BAC library to study the organization of sucrose biosynthesis genes, Leroy T. et al, Theor Appl Gene., 2005, 111, 1032-1041.<\/li>\n<li>Formation of aliphatic acids by carbohydrate degradation during roasting of coffee, Ginz M., Balzer H. H., Bradbury A. G. W., Maier H. G.,Eur. Food. Res. Technol., 2000, 211, 404-410.<\/li>\n<li>Humic Substances Formed during the composting of Organic Matter, Inbar Y., Chen Y., Hadar Y., Soil Science Society of American Journal, 1990, 5, 1316-1323.<\/li>\n<li><a href=\"https:\/\/www.researchgate.net\/publication\/277438513_Biological_Properties_of_Melanoidins_A_Review\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Biological Properties of Melanoidins: A Review, Langner E., International Journal of Food Prop., 2014, 17, 344-353.<\/a><\/li>\n<li>Infrared Spectra of the Hydrogen-Bonded Carboxylic Acids, Witkowski A., The Journal of Chemical Physics, 1967, 47, 3645-3648.<\/li>\n<li>Chlorogenic acids and other cinnamates. nature, occurrence and dietary burden., Clifford M. N., Journ Sci Food Agric, 1999, 79, 362-372; Phenolic compounds in coffee., Farah A., Marino D. C, Braz. J. Plant Physiol., 2006, 18, 23-36.<\/li>\n<li>Coffee drinking influences plasma antioxidant capacity in humans, Natella F., Nardini M., Giannetti I., Dattilo C., Scaccini C., J Agric Food Chem, 2002, 50, 6211-6216; Bioactive constituents in caffeinated and decaffeinated coffee and their effect on the risk of depression-A comparative constituent analysis., Hall S., Yuen J. W., Grant G. D., Beverages, 2018, 4, 79-83; In vitro and in vivo antioxidant properties of chlorogenic acid and caffeic acid, Iseki K.,International Journal of Pharmaceutics, 2011, 403, 136-138.<\/li>\n<li><a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/16823097\/\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">The roles of polyphenols in cancer prevention, Lee K. W., Lee K. J., BioFactors, 2006, 26, 105-121; Polyphenols: antioxidants and beyond, Scalbert A., Johnson I. T., Saltmarsh M., The American Journal of Clin. Nutr., 2005, 81, 215-217.<\/a><\/li>\n<li>Vegetable tannins, their composition and effects on decomposition of some organic compounds, Lewis J. A., Starkey R. L., Soil Science, 1968, 106, 241-247.<\/li>\n<li>Effect of roasting conditions on several chemical constituents of Vietnam Robusta Coffee, Le Linh T., Van Cuong T., Food Technology, 2014, 38, 43-56.<\/li>\n<li>Contents of tocopherols in coffee beans,coffee infusions and instant coffee, Ogawa, A., Kamiya, C., Iida, Y., Nippon Shokuhin Kogyo Gakkaishi, 1989, 36, 490-494.<\/li>\n<li>Cafestol and kahweol, two coffee specific diterpenes with anticarcinogenic activity, Cavin C., Holzhauser D., Scharf G. et al, Food Chem Toxicol, 2002, 40, 1155-1163.<\/li>\n<li>16-O-methylcafestol \u2013 a quality indicator for coffee, Speer K., Tewis R., Montag A., Proc. 14th ASIC Colloquium, 1991, 237-244. <\/li>\n<li>Lipid classes, fatty acid composition and triacylglycerol molecular species in crude coffee beans harvested in Brazil, Nikolova-Damyanova B., Velikova R., Jham G. N., Food Res. Int., 1998, 31, 479\u2013486.<\/li>\n<li><a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/21185010\/\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Inhibitory properties of Coffea canephora extract against oral bacteria and its effect on demineralisation of deciduous teeth., Antonio A. G., Iorio N. L. P., Pierro V. S. S., Candreva M. S., Farah A., dos Santos K. R. N., Maia L. C., Arch. Oral Biol., 2011, 56, 556\u2013564.<\/a><\/li>\n<li>Volatile sulfur compounds in food flavors, Shankaranarayana M. L., Raghvan B., Abraham K. O., Natarajan C. P., CRC Crit. Rev. Food Technol., 1974, 4, 395-435; Pyrazines in foods: an update, Maga J. A., CRC Crit. Rev. Food Sci. Nutr., 1982, 16, 1-48; Precursors of sulphur containing flavour compounds, Schutte L., CRC Crit. Rev. Food Technol., 1974, 4, 457-506; Biochemistry of Plant Volatiles., Dudareva N., Pichersky E., Gershenzon J., Plant Physiol, 2004, 135, 1893-1902.<\/li>\n<li>Unique biosynthesis of sesquarterpenes (C35 terpenes), Stato T., Biosci Biotechnol Biochem, 2013, 77, 1155-1159.<\/li>\n<li>Caffeine, Gene A. S., Health Research and Studies Center and Sphera Foundation Los Altos, California, 1998, CRC Press.<\/li>\n<li><a href=\"https:\/\/europepmc.org\/article\/agr\/ind605432067\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Effect of Roasting Conditions on Carbon Dioxide Degassing Behavior in Coffee, Wang X., Lim L., Food Research Intern., 2014, 61, 144-151.<\/a><\/li>\n<li>Reineccius GA. In Proceedings of the 16th ASIC Meeting, 1995, Kyoto; 249\u2013257; Determination of potent odourants in roasted coffee by stable isotope dilution assay, Semmelroch P, Laskawy G, Blank L, Grosch W., Flavour and Fragr., J., 1995, 10, 1-7.<\/li>\n<li>Coffee, tea, cocoa, Belitz H.-D., Grosch W., Schieberle P., Food Chemistry, 2009, 938-970.<\/li>\n<li>Functional properties of melanoidins: In vitro antioxidant, antimicrobial and antihypertensive activities, Morales F. J., Food Res Int., 2007, 40, 995-1002; A comparison study between antioxidant and mutagenic properties of cysteine glucose-derived Maillard reaction products and neoformed products from heated cysteine and hydroxymethylfurfural, Nicolas J., Food Chem., 2009, 114, 132-138;<\/li>\n<li>Infrared heating in food processing: an overview, Krishnamurthy K., Khurana H. K., Jun S., Irudayaraj J., Demirci A., Compr. Rev. Food Sci. Food Saf., 2008, 7, 1-13.<\/li>\n<li><a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/16386869\/\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Formation of flavour compounds in the Maillard reaction, Van Boekel M., Biotechnol Adv, 2006, 24, 230-233.<\/a><\/li>\n<li>Pentoses and hexoses as sources of new melanoidine-like Maillard polymers, Tressl R., Wondrak G. T., Garbe L.-A., Kruger R.-P., Rewicki D., Journal of Agricultural and Food Chemistry, 1998, 46, 1765-1776.<\/li>\n<li>Food Processing and Maillard Reaction Products: Effect on Human Health and Nutrition, Tamanna N., Mahmood N., Inter. Journal of Food Sci., 2015, 1-6; Analysis of acrylamide, a carcinogen formed in heated foodstuffs, Areke E., Rydberg P., Karlsson P., Eriksson S., J. Agric. Food Chem., 2002, 50, 4998-5006.<\/li>\n<li>Acrylamide: a cooking carcinogen?, Tareke E., Rydberg P., Karlsson P., Eriksson, Tornqvist M., Chemical Research in Toxicology, 2000, 13, 517-522.<\/li>\n<li><a href=\"https:\/\/eur-lex.europa.eu\/legal-content\/IT\/TXT\/?uri=CELEX%3A32017R2158\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Official Gazette, REGULATION (EU) 2017\/2158 of the Commission of November 20, 2017.<\/a><\/li>\n<li>Biomass into chemicals: Conversion of sugar to furan derivatives by catalytic process, Tong X., Ma Y., Li Y., Appl. Catal., 2010, 385, 1-13.<\/li>\n<li>Catalytic transformations of cellulose and its derived carbohydrates into 5-hydroxymethylfurfural, levulinic acid, and lactic acid, Deng W., Zhang Q., Wang Y., Sci. China Chem., 2015, 58, 29-46; Isotope labeling studies on the formation of 5-(hydroxymethyl)-2-furaldehyde (HMF) from sucrose by pyrolysis-GC\/MS, Perez-Locas C., Yaylayan V. A., Journal of Agriculture and Food Chemistry, 2008, 56, 6717-6723.<\/li>\n<li>5-hydroxymethylfurfural (HMF) as a building block platform: Biologic properties, synthesis and synthetic applications, Rosatella A. A., Simeonov S. P., Frade R. F. M., Afonso C. A. M., Green Chem., 2011, 13, 754-793.<\/li>\n<li>A review of 5-hydroxymethylfurfural (HMF) in parenteral solutions, Ulbricht R. J., Northup S. J., Thomas J. A., Fundamental and Applied Toxicology, 1984, 4, 843-853; 5-Hydroxymethylfurfural and 5-sulfooxymethylfurfural increase adenoma and flat ACF number in the intestine of Min\/\u00fe mice, Svendsen C., Hus\u00f8y T., Glatt H., Paulsen J. E., Alexander J., Anticancer Research, 2006, 29, 1921-1926; Acrylamide and 5-hydroxymethylfurfural (HMF): A review on metabolism, toxicity, occurrence in food and mitigation strategies, Capuano E., Fogliano V., Food Science and Technology, 2011, 44, 793-810.<\/li>\n<li>Effect of brewing process and sugar content on 5-hydroxymethylfurfural and related substances from Turkish coffee, Mortasa M., Gulb O., Yazicia F., Dervisoglua M., Intern. Journal of Food Properties, 2017, 20, 1866-1875. <\/li>\n<li><a href=\"https:\/\/www.intechopen.com\/books\/the-question-of-caffeine\/how-much-caffeine-in-coffee-cup-effects-of-processing-operations-extraction-methods-and-variables\" target=\"_blank\" rel=\"noopener noreferrer nofollow\">Severini C., Derossi A., Ricci I., Fiore A., Caporizzi, R. (2017). How Much Caffeine in Coffee Cup? Effects of Processing Operations, Extraction Methods and Variables. 10.5772\/intechopen.69002.   <\/a><\/li>\n<li>M. Jokanovi\u0107 et al. (2012). Changes of physical properties of coffee beans during roasting. Acta Periodica Technologica.  <\/li>\n<li>A. Raemy and P. Lambelet (1982). A calorimetric study of self-heating in coffee and chicory. J. Fd Technol.  <\/li>\n<li>S. Schenker et al. (2000). Pore Structure of Coffee Beans Affected by Roasting Conditions. J. of food science.  <\/li>\n<li>S. Smrke et al. (2017). Time-Resolved Gravimetric Method To Assess Degassing of Roasted Co\ufb00ee. Journal of Agricultural and Food Chemistry.  <\/li>\n<\/ol>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Coffee Roasting Coffee roasting is a traditional process that, despite its great importance, is still designed and managed on an empirical basis, through trial and error. A less empirical and more scientific vision regarding coffee roasting comes from understanding the raw material and the compounds it contains. The following text aims to investigate in a &#8230; <a title=\"Coffee Roasting\" class=\"read-more\" href=\"https:\/\/www.7gr.it\/en\/coffee-roasting\/\" aria-label=\"Read more about Coffee Roasting\">Read more<\/a><\/p>\n","protected":false},"author":2,"featured_media":31704,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[763],"tags":[],"class_list":["post-30637","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-coffee-roasting"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.5 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Coffee Roasting - 7Gr. 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