Analysis of the heat and mass transfer during coffee batch roasting

Hernández, J.A.; Heyd, B.; Irles, Claudine; Valdovinos, B.; Trystram, Gilles

doi:10.1016/j.jfoodeng.2005.12.041

Cited by 68 publications

(58 citation statements)

References 7 publications

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“…Moisture cannot be reduced below a humidity limit, because the grain obtained will be burned and all the quality attributes are lost. Changes in moisture content are used as a quality tool to determine the combined features of flavor and aroma after roasting [20]; therefore, the moisture content is a variable used as a control and optimization variable because it defines the end point of roasting [4]. The particular case of cocoa beans roasting process aimed to reach a final moisture content of 2 g 100 g −1 [1].…”

Section: Changes In Moisture Content and As An Effect Of Roasting Timmentioning

confidence: 99%

“…During roasting, some compounds increase in concentration, the volatile fraction decreases, and new compounds are formed. Moisture loss and chemical reactions suffered by the beans in the roasting process affect the color, volume, mass, shape, bead pop, pH, density, and especially volatile compounds and flavor [4,5]. Moreover, with the growing interest in the content of antioxidants in food and its relation to health, several products, including cocoa derivatives, have been investigated to determine their antioxidant properties and how the conditioning processes affect the content and antioxidant capacity thereof [6,7].…”

Section: Introductionmentioning

confidence: 99%

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Physicochemical Changes of Cocoa Beans during Roasting Process

García-Alamilla

Lagunes-Gálvez

Barajas-Fernández

et al. 2017

Journal of Food Quality

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During cocoa beans roasting, there are physicochemical changes that develop the chocolate quality attributes. Roasting systems have a particular influence on the development of these characteristics, and the effects of operation variables for each system must be evaluated. The objective of this study was to evaluate the effect of roasting time and temperature in a rotatory system on cocoa beans physicochemical parameters of quality as moisture, water activity, pH, total acidity, color ( * , * , * ), total phenolic content (TPC), and DPPH radical capacity. Cocoa beans were roasted as a function with a central rotatable design with 2 2 + 5 central points and 4 axial points (−1.414, −1, 0, +1, and +1,414) and a response surface methodology was applied. Temperature and time levels were 110-170 ∘ C and 5-65 minutes, respectively. The effect of the variables was nonlinear and modeled with a second-order response polynomial. Roasting time and temperature presented a significative effect ( < 0.05) on the response variables except for both TPC and DPPH radical capacity in aqueous extract.

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Section: Changes In Moisture Content and As An Effect Of Roasting Timmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Physicochemical Changes of Cocoa Beans during Roasting Process

García-Alamilla

Lagunes-Gálvez

Barajas-Fernández

et al. 2017

Journal of Food Quality

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“…Development of the heat and mass transfer model follows the models proposed by [6] and [14]. MATLAB® Simulink was used for the simulation of the equations below.…”

Section: B Heat and Mass Transfer Modellingmentioning

confidence: 99%

“…One reason that emphasises the importance of moistures content in coffee parchment is that too high or too low moisture content will result in coffee not reaching its optimum cupping quality [5]. The second phase is roasting wherein pyrolysis causing chemical changes such as oxidation and reduction results at a starting temperature of 190ºC [6]. About ten known models (with one succession and improvement on the other) has been developed, proposed, analysed and evaluated to investigate and predict the effect of temperature on the coffee bean roasting profile with regard to the heat and mass transfer during roasting of green coffee bean.…”

Section: Introductionmentioning

confidence: 99%

“…The model also accounts for exothermic reactions with the assumption that there is a proportional relationship between heat generation rate and production reaction rate [8]. With the shortcoming of the physical model mentioned above, reference [6] evaluated and analysed a dynamic model that predicts temperature of the bean and the moisture content during roasting and therefore pointed out that the bean temperature profile against time can be a roast-degree indicator; a phenomenon that [7] did not observe.…”

Section: Introductionmentioning

confidence: 99%

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Validation and Improvement of Heat and Mass Transfer Model in Predicting the Coffee Roasting Profile

2016

International Conference on Advances in Science, Engineering, Technology and Natural Resources (ICASETNR-16) Nov. 24-25, 2016 P

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Abstract-Evolution of a cup of coffee consist of 24 steps, with roasting as one of the most important steps since it establishes the organoleptic properties of coffee. The coffee roasting process is an exothermic reaction, characterised by a change in colour, aroma, expansion and crack of the green coffee beans. In this study, heat transfer parameters that play a role in the coffee roasting process and roasting profile were investigated. Ten models were developed and published up to date to predict the coffee bean roasting profile, and all of the investigations on this topic use heat and mass transfer parameters as constants given by reference [7]. The aim of this study is to evaluate the heat transfer parameters; air to bean heat transfer coefficient, specific heat capacity of the bean and thermal conductivity of the bean, and validate an improved model that predicts the roasting profile. The roasting profiles were investigated with four different roasting temperatures, i.e. 170 ºC, 190ºC, 210ºC and 230ºC. MATLAB® Simulink was used to simulate Schwartzberg"s model to estimate the coffee roasting profile. The effect of heat transfer parameters on the roasting profile was investigated and the roasting profile predicted by the model was validated with experimental data. The model was then improved by varying the specific heat capacity of the bean, thermal conductivity of the bean and heat transfer coefficient. It was found that the effect of thermal conductivity of the bean on the roasting profile is very small and therefore negligible. Increasing the specific heat of the bean or decreasing the heat transfer coefficient decreases the mean squared error between predicted roasting profile and experimental roasting profile.

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Influence of roasting conditions on fatty acids and oxidative changes of Robusta coffee oil

Budryn

Nebesny

Żyżelewicz

et al. 2012

Euro J Lipid Sci & Tech

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The aim of this study was to determine the influence of roasting conditions, including elevated humidity of air used in the process, on the properties of coffee oil. Beans of Robusta coffee were roasted in a laboratory convective roaster with a possibility of changing the temperature, humidity, and velocity of roasting air. Roasting temperatures from 190 to 2168C, air humidity from 0.07 to 1%, and air velocity of 0.5 and 1 m/s were used. Parameters analyzed in roasted beans were: oil content, fatty acids composition, including trans fatty acids using the GC/FID method and indicators of oxidation level, namely peroxide value and content of conjugated dienes and trienes. Also a thermal profile of oil with the use of the DSC method and finally the bean aroma were evaluated. For maintaining the maximal amount of PUFA, the most favorable roasting conditions were, either, roasting at relatively high temperature and short time, or roasting at low temperatures. Using moderately high temperature resulted in the highest oxidative changes, but on the other hand, the aroma of received beans presented the best sensory properties. For the best nutritional properties, the best roasting conditions were: temperature 2108C and 1% humidity content in roasting air at 1 m/s flow velocity. In such conditions roasted beans obtained a very high quality aroma, and the roasting time was relatively short.Practical applications: This research concerns the quality of oil obtained from roasted coffee beans. The composition of coffee oil changes slightly during roasting, but nevertheless it might be a source of peroxides and trans fatty acids in human diet. In industrial processing coffee oil is extracted from the remains left over from instant coffee production, and it is a popular agent for aromatizing food products. Thus, in this kind of processing, roasting conditions that limit the unfavorable changes of coffee oil should be used.

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Analysis of the heat and mass transfer during coffee batch roasting

Cited by 68 publications

References 7 publications

Physicochemical Changes of Cocoa Beans during Roasting Process

Physicochemical Changes of Cocoa Beans during Roasting Process

Validation and Improvement of Heat and Mass Transfer Model in Predicting the Coffee Roasting Profile

Influence of roasting conditions on fatty acids and oxidative changes of Robusta coffee oil

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