Coffee roaster
A coffee roaster is a device for making potable coffee from green coffee by roasting the coffee beans . Coffee roasters are also used to make substitute coffee . Green coffee has many ingredients such as caffeine , fats , proteins , acids and sugar - they all affect the taste and aroma of the coffee. But it is only through controlled combustion in a multi-stage roasting process that chemical-physical reactions occur (e.g. the Maillard reaction ) through which the diverse aromas and characteristic taste of a coffee develop.
Working principle
For roasting, the roaster used must have a temperature that can be defined by the master roaster (typically 100 ° C to 260 ° C in the "traditional roasting process") or a set temperature curve. The energy supply from the roaster to the beans takes place through contact and convection or predominantly convection. During the roasting process, the coffee must be constantly circulated in order to ensure that the roasted food is heated evenly and the degree of roasting is even. The water originally still contained in the green coffee beans (between around 12 and 18 percent of the bean weight) evaporates, which is known as burn- in. During the roasting, controls of the color and other sensory criteria are often carried out, either manually using a sampler or automated. To stop the roasting process, the coffee must be cooled down quickly so that the beans do not roast or burn from the inside out. This takes place either in the air flow of a cooling sieve outside the roaster or in large industrial plants by adding water, also known as quenching . After the roasting process, the roasted coffee beans continue to gas out for several days ("post-gassing"). For this reason, when the roasted goods are packed immediately, it must be ensured that the outgassing can continue to take place with the aid of a degassing valve in the packaging without oxygen reaching the beans, which in turn causes the product to go rancid early . Various complex reactions, in particular the Maillard reaction , create the actual coffee aroma. So far, over 1000 aroma components have been identified in roasted coffee.
The roasting can be carried out batchwise or continuously. The roasting times are between one and a half and twenty minutes, with the time-saving industrial roasting process in an ultra-hot air stream at temperatures of up to 550 ° C. See also the Roasting section under Coffee .
Areas of application
Different devices are used for roasting for different applications:
- Sample roaster
A device for roasting small quantities of coffee in the laboratory or in rehearsal or tasting kitchens. These devices are used on plantations, in the green coffee trade and in production. With sample roasters, green coffee potentials and their properties can be determined, coffee qualities can be produced for tastings in small batches and mixtures can be tested. Sample roasters are also of great help in determining and creating roasting profiles (optimal temperature and roasting time) for larger systems and for ongoing quality control. There are devices with one and those with up to six roasting drums, so that several test roasts can run in parallel to save time.
- Shop or small roasters
Devices for the ongoing production of small quantities of coffee. Typical sizes are 1 kg to 25 kg. Drum roasters that are heated electrically or with gas are mostly used for this, with gas systems - using the example of gas stoves - facilitating temperature control. These devices can be used to produce small quantities of coffee on customer request, single-variety, unblended coffees or blends according to the ideas of a master roaster.
- Industrial roaster
Roasting plants for use in factories are devices on an industrial scale. The term industrial roaster is used to describe roasters in production processes that roast coffee. Different hot air processes are often used; these are more economical, faster and enable a continuous process. These are often integrated into production lines, which run through all process steps in a closed chain, from cleaning and mixing the green coffee beans to the ground, finished end product (vacuum packaging, pad, etc.).
- Home roaster
After simply roasting green coffee in the open frying pan , the coffee roaster was once a common kitchen appliance. The devices spread in the 18th and 19th centuries with the introduction of coffee, initially in wealthy homes and gradually also in the bourgeoisie and in the country. There were coffee roasters for use on the open fire of the farmhouses in the form of pots and as use in coal stoves. The pots were provided with a sliding or hinged lid. Another variant were drum roasters made of sheet iron . The devices were rotated in the embers until the desired color and typical aroma developed. For this purpose, the roasters for the open fire were stored on a tripod or fire trestle or hung on a special stand with a rotating mechanism.
In the 20th century, especially during or after wartime, private coffee roasting became popular again. There were several reasons for this; Roasted coffee beans were taxed very heavily until 1953 (most recently in Germany at 10 DM / kg) and were poorly available, so green coffee was often mixed with other substitute coffees in order to obtain a cheaper product. Or very different substitute coffees were drunk depending on availability.
Today, home roasters are only used by small parts of the population in the hobby area. Here, the reasons are to be found in certain preferences, such as the optimization of aroma, taste, acidity, body, crema or the selection of green coffee specialties. Also in Germany to save the currently levied coffee tax of 2.19 euros per kilogram of roasted coffee or to make sure that the coffee has been roasted in a gentle long-term process. In addition, many commercial roasters start their careers through home roasters. Roasting is carried out either in specially made devices, which are operated either with an electric heating element or with a gas fire.
Historical coffee roaster for use on the stove
Large-scale roasting plant
Small commercial drum roasting machine with hot air exhaust
Historic coffee roaster for home use
(probably early 20th century)
Global roaster to Röstzwecken ( weaving and museum Laichingen )
Sample roaster for three parallel roasts
Web links
literature
- Scott Rao: The Coffee Roasters Companion. , 2014. (Excerpt in English online)
- Claus Fricke: Roasting coffee at home. Publishing house Die Werkstatt, Göttingen 2011.
- Paul Ciupka: Coffee, Coffee Substitute and Coffee Additive . Otto Meissner Verlag, Bleckede Castle ad Elbe 1949.
- H. Garloff, H. Lange, R. Viani: Coffee. In: Rudolf Heiss (ed.): Food technology. 3. Edition. Springer-Verlag, Berlin / Heidelberg 1990, ISBN 3-540-51737-5 , pp. 358-370.
- Dieter Seyer: fire - stove - oven: lessons in Westphalian museums. Issue 17, Landschaftsverband Westfalen-Lippe, Münster (Westf.) 1985, ISBN 3-923432-19-4 .
- VDI 3892 : 2015-03 Emission reduction - Roasted coffee producing industry - Plants with a daily production of at least 0.5 tonnes of roasted coffee (Emission control - Roasted-coffee-producing industry - Plants with a minimum daily output of at least 0.5 tonnes) . Beuth Verlag, Berlin. ( Summary online )
Individual evidence
- ↑ German Roaster Guild. Retrieved March 25, 2019 .
- ↑ a b c d e f g h VDI 3892: 2015-03 Emission reduction - Roasted coffee producing industry - Plants with a daily production of at least 0.5 tons of roasted coffee (Emission control - Roasted-coffee-producing industry - Plants with a minimum daily output of at least 0.5 tonnes) . Beuth Verlag, Berlin ( online summary ), pp. 8–26.
- ↑ a b H. Garloff, H. Lange, R. Viani: Coffee. In: Rudolf Heiss (ed.): Food technology. 3. Edition. Springer-Verlag, Berlin / Heidelberg 1990, ISBN 3-540-51737-5 , pp. 358-370.
- ↑ a b Processing - Roasting. Retrieved September 17, 2014 .
- ↑ Steffen Schwarz, Martin Kienreich: FAQ Coffee - Questions, Answers, Quintessences. 2008, p. 59.
- ↑ Fascination with coffee. Editor of the German Coffee Association. Bucher Verlag, Munich 2012, p. 158.
- ↑ Reasons to roast coffee yourself. In: Roast Rebels. Retrieved March 25, 2019 .