Roasters Guild Class: Advanced Level Craft Roasting Class J16 This advanced level class will focus on the chemistry of roasting. The lecture portion of the class will address the physical changes to the coffee bean during roasting and the primary chemical effects of heat application over time. Instruments and measurements used in analyzing a roast will also be reviewed. The roasting exercise part of this class will feature measured experiments used to demonstrate the ideas presented in the lecture. The class will conclude with cuppingCupping is a method of tasting coffee by steeping grounds in separate cups for discrete amounts of ground coffee, to reveal good flavors and defects to their fullest.... ...more, where participants will see how the information and experiments presented come together into the experience of the final product. This is a Roasters’ Guild Journeyman Level accredited class. Class J16 Today is the very first advanced roasting class the Roasters Guild has offered. This class contains approximately 65% lecture and 35% hands on roasting and cupping: Saturday May 3, 2008 9:00 am – 12:00 pm (3 hrs) CLASS AGENDA: Opening introductions of Instructors and Station Leads Lecture: Visible physical changes to the coffee bean during roasting happening in a simultaneous and concurrent manner · Color changes (bean absorbs heat and slowly changes from a green color to a yellowish/ then yellow / then light brown / then brown and if the roast continues the bean will become dark brown and the oils may become exposed.) · Growth of the bean during roasting: water moisture, bound and free, will evaporate fracturing the bean structure cell and releasing enormous amounts of energy. The bean will almost double in size, while at the same time loose non bound moisture. Shrink can be recognized to be between 15% and 25% depending on the roast level. · ChaffChaff is paper-like skin that comes off the coffee in the roasting process. Chaff from roasting is part of the innermost skin (the silverskin) of the coffee fruit... ...more (silver skin) flaking off the bean (before the first crackFirst crack in one of two distinct heat-induced pyrolytic reactions in coffee. It is distinguished by a cracking or popping sound in the coffee, and occurs between 390... ...more) · Release of bound oils onto bean exterior. All coffee has natural oils which will come to the surface at one point or another after the coffee was roasted. The release of the oils can be accelerated if the coffee was roasted dark and even more so if roasted faster. On a light roast the oils are still driven to the surface of the bean but they take longer as the structure of the bean cell was not as fractured during the roast process. · ScorchingPatches of discolored burn marks on the coffee bean, due to a high-heat roast environment or other roast error.: Scorching refers to a roast error that can be... ...more (photo) · TippingTipping refers to a roast error that can be discerned by inspecting the roasted coffee, where the ends of the elongated bean appear burnt. It can easily be... ...more (photo) · FacingFacing can mean turning toward, standing up to, being brave. But in coffee roasting though, it means scorching a roast.: Facing refers to scorch marks found on the... ...more (photo) · Review Visuals and Other Green CoffeeGreen coffee refers to the processed seed of the coffee tree fruit. Coffee is a flowering shrub that produces fruit. The seeds of the fruit are processed, roasted,... ...more Changes handout Lecture: Non visible physical and sugar development changes during roasting · Moisture loss (shrinkage, discuss) · CaramelizationA reaction involving sugars that occurs during coffee roasting. A caramelized sugar is less sweet, but has greater complexity of flavor and aroma. Caramelization is slower than Maillard... ...more: Green coffee has a certain amount of carbohydrates in them. During the roast process these carbohydrates caramelize into sugars and remain in the coffee giving it a certain residual sweetnessSweetness is an important positive quality in fine coffees, and is one of five basic tastes: Sour, Sweet, Salty, Bitter, Savory (Umami). In coffee, sweetness is a highly... ...more. Further caramelization can volatilize the sugars completely becoming the residual coffee with a more pronounced bitterBitterness is one of 5 basic tastes: Sour, Sweet, Salty, Bitter and Umami (savory flavors). There are many types of bitterness, hence not one avenue to tracking down... ...more taste. · Sugar Browning and MaillardAn important reaction in coffee roasting that results in the browning of the green coffee seed.: The Maillard reaction is a chemical reaction between an amino acid and... ...more Reaction (review ppt and handout explaining Sugar browning, Maillard Reactionand chemical changes through roasting) · Chemical changes during roasting (review chemical changes handout) · Fats · Sugars (Caramelization) · AcidsMany acids contribute to coffee flavor: acetic, malic, citric, quinic, tartaric, phosphoric, etc.: Many acids contribute to coffee flavor; malic, citric, quinic, tartaric, phosphoric, etc. See Acidity or... ...more: Two primary types of acids in coffee, some are created during the roast (citric, malic), others are natural to coffee and came from the phosphate of the earth where the coffee was planted (phosphoric). · Other pertinent compounds: There are many compounds in coffee. Some of these are created during the roasting process while others are dissipated during the roasting process. Roasting session: Two roasts to the same roast level, but roasting at two radically different profiles: One roast done to offer positive character and one offering negative characters. · Roast #1 protocol: Allow the green coffee to absorb the heat from the drum and allow the coffee temperature to raise steadily through the entire roast, offering steady development, evaporation of non bound moistures and optimum sugar development. · Roast #2 protocol: Leave on high heat well past first crackAn audible popping sound heard during roasting. In coffee, one refers to "first crack" and "second crack," which come from two different classes of chemical reactions.: An audible... ...more. Pull roast whenthe coffee reaches the same color as Roast #1. The idea is to create tipping, scorching and facing if possible. · High Resolution Photo Presentation: Review photos and explain different roast methods for the differing bean cell photos: Cupping session: Each attendee should have a minimum of 2 cups of each of the two roasts done in their group. Focal points: · AromaAroma refers to sensations perceived by the olfactory bulb and conveyed to the brain; whether through the nose or "retro-nasally": The aromatics of a coffee greatly influence its... ...more differences · Taste differences o BodyAssociated with and sensed by mouthfeel, body is sense of weight and thickness of the brew, caused by the percentage of soluble solids in the cup, including all... ...more o AcidityAcidity is a positive flavor attribute in coffee, also referred to as brightness or liveliness. It adds a brilliance to the cup, whereas low acid coffees can seem... ...more o Flavor Question and Answer period 1 Green Coffee To Roasted Coffee Visual & Others Green Coffee Changes Advanced Roasting Class J16 Bean Color – Green(nish) > Whitish > Yellow. It darkens to brown when temperature increases. Bean Surface – Bean surface starts “stretching”. Eventual oils “sweat” to the surface. Color Difference Within the bean – Highest color difference for the fastest roasts specially on the light roasts. Bean Structure – Release of huge amounts of Co2. Bean becomes porous. Brittleness – increases with the degree of roastDegree of Roast simply means the roast level of a coffee, how dark it has been roasted.: Degree of Roast simply means the roast level of a coffee,... ...more. DensityThe density of a coffee bean is often taken as a sign of quality, as a more dense bean will roast more with a better dynamic. The density... ...more – Changes from 600-830 grams/litter to 300 to 460 grams/litter. Moisture – Liberation of free and chemical bound water. OrganicGrown without the use of artificial fertilizers, herbicides, etc.: Organic coffee has been grown according to organic farming techniques, typically without the use of artificial fertilizers. Some farms... ...more losses – Mostly chlorogenic acids + carbohydrates + trigonellineTrigonelline is a bittering compound that is reduced as the roast gets progressively darker. Trigonelline is 100% soluble in water and therefore will end up in the cup.... ...more + amino acids. Aroma – Maximum generation at low roast. At medium roast loss is higher than generation. P.H. – 4.9 low roast to 5.4 dark roast. (sources: Maier; Clarke; Viani; Illy; Petrarco) Enzymatic Browning Unlike coffee roastingThe application of heat to green coffee seeds (beans) to create palatable material for brewing a great cup!: Coffee roasting is a chemical process induced by heat, by... ...more which require high temperatures to initiate, enzymatic browning reactions occur spontaneously and at room temperatures. However, like all reactions occurring in nature, a source of energy is required for initial activation. In the case of coffee, the activation energy is provided by the heat created by roasters, but in enzymatic reactions – their reaction requires the presence of a specific catalyst, or enzyme. Simply put, an enzyme is a unique protein that accelerates specific reactions. There are literally thousands of enzymes in biological systems and without them life would come to a grinding halt. Just like a Russian KGB agent carries a pill of lethal cyanide with him (in the event of capture by enemies), the appleAn acid that adds to favorable perceptions of cup quality; malic acid often adds apple-like acidity, and perhaps other taste aspects recalling apples. Malic acid is yet another... ...more senses that when cut, it’s been attacked and immediately jumps into self-defense mode – how? By creating the very same brown polymers we discussed. According to researchers, the brown polymer created during enzymatic browning is highly toxic to bacteria. It’s Mother Nature’s way of protecting the plant from bacterial infection during its latter, more vulnerable stages of ripening. Though the benefits of enzymatic browning remain limited to only a handful of products such as raisins, plums, figs, cacao, the reaction is for the most part, a detriment and serious quality concern. Because of its spontaneous nature, enzymatic browning represents a significant economic loss within the fruits and vegetables industry. It’s been estimated that at least 50% of all fruits and vegetables goods are damaged due to bruising/tearing during transport to market. As such, scientists have developed relatively simple ways of inactivating enzymes and mitigating browning loses. Blanching, or essentially steaming, is useful as the heat deactivates PPO and prevents browning. Unfortunately not all products can be subject to this and the method is usually limited for products such as shrimp. Another method involves the addition of an acid, usually ascorbic acid, to the pre-oxidized product. Many che fs for example, add a bit of lime juice to fresh guacamole during preparationPreparation refers to the dry-milling steps of preparing coffee for export: hulling, grading, classifying, sorting.: Preparation refers to the dry-milling steps of preparing coffee for export: hulling, grading,... ...more. Turns out that the decrease in pH prevent the phenolsA compound in coffee that at high levels contributes to negative flavors, but can have positive aspects as well: Phenols are a set of organic compounds, relatively stable,... ...more from oxidizing and thus prevent, or at least delay, enzymatic browning. Fortunately, enzymatic reactions do not play a significant role in flavor development for coffee as compared to products such as tea and cacao (ie.chocolate). Well discuss some of the more complexThe co-presence of many aroma and flavor attributes, with multiple layers. A general impression of a coffee, similar to judgments such as "balanced" or "structured" ...more chemical reactions taking place during roasting in the next set of browning reactions – non-enzymatic browning. OK – I understand enzymatic browning, but at this point I need to know more about how it related coffee!!! how it effects appearance, taste, aroma, shelf life, etc… Non-Enzymatic Browning Unlike the enzymatic browning reactions discussed earlier, these next set of reactions are quite different, but encompass the bulk of the chemical changes occurring during roasting. Caramelization Caramelization is perhaps the easier of the two non-enzymatic browning reactions to describe. Simply put, caramelization is the oxidation or the thermal decomposition of sugars into color and flavors. Although any sugar can be used, sucroseSucrose is important to the taste of sweetness in light roast coffees, as it is completely converted or destroyed in darker roasts.: Sucrose is largely destroyed by the... ...more, or commonly known as table sugar, is typically used in several cooking applications. As sucrose is heated to 160C it slowly begins to melt, losing water molecules in the process and becoming a viscous semi-transparent liquid. As heating reaches 200C, the compounds in the molten sugar begin to rearrange, forming brown colored caramel-like compounds and imparting its characteristic burntBurnt flavors in coffee are the result of over-roasting, fast roasting, or roasting in a high-heat environment. This often occurs when the initial roaster temperature when the green... ...more/caramel aroma. But this isn’t your grandpas caramelCaramel is a desirable form of sweetness found in the flavor and aroma of coffee, and is an extension of roast taste. Extremely light or dark coffees will... ...more! For the caramel created in this process is unlike the caramel candy we’ve all grown to love as kids. This caramel is a bitter/burnt gooey compound with little to no sweetness, occasionally used in the toppings such as custard desserts. The caramel we know, is created by mixing sugar, milk and other flavorings, but is produced in much the same manner. Depending on the heating conditions, manufacturers can shift the byproducts of caramelization to either maximize the formation of aromatic compounds, or colored caramel-like compounds. In the latter condition, sugar is heated in the presence of ammonia to produce high concentrations of brown colored compounds, typically used by the cola industry for coloring. But in addition to creating aroma and color, caramelization creates a broad range of compounds including organic acids in the process. We can clearly see this, for example, in the making of peanut brittle. In the latter stages of commercial brittle making, caramelized sugar is allowed to cool and thicken, at which time baking soda and other flavorings are usually added. The baking soda then reacts with the organic acids produced during caramelization, neutralizing them and to form carbon dioxide gas. The gas then acts as a leaving agent, creating tunnels in the product and producing the characteristic “swiss chesse” texture so commonly found in candy brittle. In coffee, the carbon dioxide created due to the decomposition of sucrose, increases cell pressure within the bean, rupturing it, and ultimately producing the audible “pop” we hear during first crack. Up to 90% of the initial sucrose is decomposed during roasting to produce a wide range of byproducts, some of which include organic acids such as formic and acetic acidAcetic acid can lead to vinegar-like flavors in over-mature coffees, or bitterness in high quantities. But in moderate amounts it adds a positive winey note to the cup.... ...more. Studies have shown that acetic acid concentrations in model studies can increase up to twenty times its initial concentration, namely in the early part of roasting, then quickly evaporating in latter stages – due to its volatility. But acetic acid is also unique in that is a relatively weak acid, having effect on coffee quality and acidity. Its no surprise then, that with ArabicaArabica refers to Coffea Arabica, the taxonomic species name of the genus responsible for around 75% of the worlds commercial coffee crop.: Arabica refers to Coffea Arabica, the... ...more containing almost twice the concentration of sucrose as robustaAteng is a common name for Catimor coffees widely planted in Sumatra and other Indonesia isles.: Ateng, with several subtypes, is a common name for Catimor coffees widely... ...more, we usually see a greater intensityWe have a simple scale to rate intensity in our coffee reviews, from Mild to Bold. Low intensity does not mean low quality!: We have a simple scale... ...more of aroma and perceived acidity in the cup. Again, food description are great and much needed to uderstand the science, but we need more coffee information. Does coffee go through a caramelization? or just Maillard? 1 Maillard Reaction = Formation of volatile aromas & color pigmentation. Roasting changes amino acids, peptides and proteins which react with reducing sugars to form glysocosylamines / aminoaldoses / aminoketones thru condensation, after reacting with other hydroxyl groups, which form aromas and color pigmentation. Maillard reaction was discovered 80 years ago but not all its pathways have been identified. Here’s a schematic of the “Maillard development”: AMINO ACIDS PEPTIDES PROTEINES ? ? ROAST AND REACT WITH REDUCING SUGARS ? ? GLYCOSYLAMIDES ? ? RAPIDLY REARANGMENTS (AMADORI & HEYNS REARANGMENTS) ? ? AMINOALDOSES & OR AMINOKETONES ? ? REACTION WITH OTHER HYDROXY GROUPS ? ? VOLATILE AROMAS AND COLOR PIGMENTATION “STRECKER DEGRADATIONAn important roast reaction related to the Maillard reaction. The Strecker Degradation is an interaction of amino acids with a carbonyl compound in an environment with water, creating... ...more” Roasting makes specific amino acids with an a-dicarbonyl form an aminoketone Condense or Reaction with formaldehyde Pyrazines & Nitrogen Oxazoles Heterocyclic Compounds Pyrazines and Oxazoles are two main classes present in coffee aroma 1 Green Coffee To Roasted Coffee Chemical Changes (% Dry Weight) Green Roasted CaffeineAn alkaloidal compound that has a physiological effect on humans, and a bittering taste. It is found throughout the coffee plant but is more concentrated in the seed... ...more 1.2 1.1 Comments: Very small change thru the roast due to caffeine stability. Trigonelline 1.0 1.0 Comments: It shows some decrease thru the roasting forming aromatic compounds. Amino Acids 0.5 0.0 Comments: Decomposes with release of Carbon Dioxide and forms volatile aromas. Proteins 9.8 7.5 Comments: Are partially transformed in melanoidins. Chlorogenic AcidChlorogenic acids (CGAs) are important to coffee flavor, contributing to flavor when in the proper balance and level. They are a group of phenolic acids esterified to quinic... ...more 6.5 2.5 Comments: Changes gradually forming volatile aromas & melanoidins (Co2 release). Loss is proportional to degree of roast & inversely proportional to speed of roast. Carbohydrates Sucrose 8.0 0.0 Comments: Changes completely forming volatile aromas and caramel. Carbohydrates Reducing Sugars 0.1 0.3 Comments: see sucrose comments. Carbohydrates Polysaccharides 49.8 38.0 Comments: Carbohydrates change gradually transforming in polysaccharides (not a lot of decomposition) Lipids 16.2 17.0 Comments: Roasting causes migration of the lipids to the bean surface. Caramelization & Condensation 0.0 25.4 Comments: Transformation thru heat of sugars into flavor & color. Volatile Aromatics Traces 0.1 Comments: Mechanism of volatile aroma formation v. complex and not attributed to a single aroma compound. Water 8-14 0-5 Comments: Moisture in bean and chemically bound do evaporate during the roast.
