Navegando por Autor "Gutiérrez-Guzmán, Nelson"

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ATR-FTIR for characterizing and differentiating dried and ground coffee cherry pulp of different varieties (Coffea arabica L.)
(Associação Brasileira de Engenharia Agrícola, 2021) Barrios-Rodríguez, Yeison; Collazos-Escobar, Gentil A.; Gutiérrez-Guzmán, Nelson
This study aimed to evaluate the performance of the infrared spectrum in the range of 4000−650 cm−1 for characterizing and differentiating dried and ground coffee cherry pulp of different varieties. The spectral data were subjected to first and second derivative treatments to perform the statistical analyses. Three varieties of coffee pulp were previously characterized for color, water activity, moisture, chlorogenic acids, and caffeine. The results of principal component analysis (PCA) showed that Fourier transform infrared (FTIR) spectroscopy is a viable technique for characterizing and differentiating dried and ground coffee cherry pulp among different varieties, showing the best differentiation with treatment of data from the first derivative, which was mainly associated with the caffeine content and chlorogenic acids. This study is the first investigation of FTIR spectroscopy with attenuated total reflectance for characterizing dried and ground coffee cherry pulp from coffee varieties grown in Colombia.
ATR-FTIR for discrimination of espresso and americano coffee pods
(Editora UFLA, 2018-10) Monje, Andrés Felipe Bahamon; Parrado, Lina Ximena; Gutiérrez-Guzmán, Nelson
Roasted and ground coffee for encapsulation in single-serve capsules compatible with keurig® and coffee powder obtained from Nespresso® commercial capsules were analyzed for pH value, titratable acidity, moisture content, water activity and color (lightness); a data matrix that contains the physicochemical properties and the absorbance measurements using a baseline of 1600 to 1800 cm–1 by FTIR-ATR technique, was evaluated through the combined methods of principal component analysis (PCA) and cluster analysis in order to discriminate between the types of capsules. In the PCA biplot two distinct groups can be identified and in the cluster analysis two groups are that correspond to the two types of capsules. The results reveal that FTIR-ATR based methods seem to be a promising alternative for the discrimination of coffee samples for the pods industry or for the type of consumption.
Effect of roast degree, preparation method, and variety in the sensory and chemical characteristics of coffee (coffea arabica): a mid-infrared spectrum analysis
(Editora UFLA, 2021) Barrios-Rodríguez, Yeison Fernando; Córdoba, Gisela-Andrea; Bahamón-Monje, Andrés Felipe; Gutiérrez-Guzmán, Nelson
In coffee beverages, there are several factors that affect the final compounds and generate sensory variations. This study evaluated the effect of five preparation methods, three roast degrees, and three different varieties (coffea arabica) on the physicochemical compounds of coffee (coffea arabica) be fore and after preparation by using information obtained from the mid-infrared spectrum. The effect on some sensory attributes was assessed by means of a panel of 54 habitual coffee consumers. Spectrum data were processed using hierarchical clustering and principal component analysis (PCA), while a mixed general linear model was applied for sensory analysis. The results showed that each factor behaves independently, showing a significant effect (p < 0.05) on a greater number of attributes. The preparation method and the roast degree are attributed to the changes generated in the chemical character istics of coffee during these processes. Through the analysis of the infrared spectrum (IR) by hierarchical cluster, it was found that, before the preparation of the coffee drinks, the samples are grouped by roast degree, regardless of the type of variety. Spectrum analysis by PCA after brewing indicated that there is a greater effect of the roast degree and variety of coffee (coffea arabica) on the chemical markers of the IR spectra. Finally, wavelengths 1,800, 1,740, 1,650, 1,550, 1,480, 1,150, and 710 cm-1, which had a greater contribution in the PCA and allowed the evaluated samples to be grouped differently, are those related to non-volatile compounds such as caffeine, chlorogenic acids, and trigonelline, which provide sensory characteristics to the final drink.
Modeling dynamic adsorption isotherms and thermodynamic properties of specialty ground roasted-coffee (Coffea arabica L.)
(Editora UFLA, 2019-01) Collazos-Escobar, Gentil Andres; Gutiérrez-Guzmán, Nelson; Váquiro-Herrera, Henry A.
Specialty coffee is highly differentiated product because of its sensorial attributes: aroma, body and brand reputation. In specialized markets, these products are highly valued, and sometimes up to six times their commercial value is paid. Thus, it is essential to preserve their freshness. Sorption isotherms are necessary for determining and studying water sorption changes in specialty coffee during storage. This study aimed to determine the adsorption isotherms of specialty ground roasted-coffee at temperatures of 25 °C, 30 °C and 40 °C and water activities between 0.1 and 0.8 using the dynamic dewpoint method (DDI). The experiment sorption data were modeled using 12 different equations with non-linear regression to represent the dependence of the equilibrium moisture content with both water activity and temperature. In addition, the thermodynamic properties were determined with the experiment adsorption data. The results showed that type III isotherms were obtained according to the Brunauer classification, and the Weibull equation satisfactorily modeled the effect of the temperature on the hygroscopic equilibrium in the specialty ground roasted-coffee. The results of thermodynamic analysis showed that the net isosteric heat of adsorption and Gibbs free energy decreased as the equilibrium moisture content increased, indicating the amount of energy released, a strong bond energy between water molecules in the product components and spontaneity in the adsorption process. The entropy of the adsorption increased with the moisture content, leading to product stability conditions during storage; it was possible to conclude that to guarantee the stability of high quality, ground, roasted coffee should store in environments where the water activity does not exceed 0.5 at temperatures between 25 °C and 40 °C. The results were similar to those reported for the roasted and ground coffee of others cultivars.
Moisture dynamic sorption isotherms and thermodynamic properties of parchment specialty coffee (Coffea arabica L.)
(Editora UFLA, 2020) Collazos-Escobar, Gentil Andres; Gutiérrez-Guzmán, Nelson; Váquiro-Herrera, Henry Alexander; Amorocho-Cruz, Claudia Milena
Sorption isotherms represent an efficient and valuable tool for predicting the equilibrium moisture content of foods under different humidities and temperatures; thus, they are useful for determining shelf-life and safe storage conditions. The aims of this study were to determine the sorption isotherms of parchment specialty coffee at water activity values of 0.1−0.8 and temperatures of 25, 30, and 40 °C using the dynamic dew point method. The experimental sorption data were modeled using 12 different equations to represent the dependence of equilibrium moisture content on water activity and temperature. Thermodynamic properties were also obtained from the experimental data. The results showed a type II sigmoid shape according to Brunauer-Emmett-Teller (BET) classification, and the double log polynomial (DLP) equation successfully modeled the effects of temperature on the sorption isotherms, obtaining a good fit (R2 adj = 0.99 and RMSE = 0.1 % dry basis). The dynamic dewpoint isotherm (DDI) method was advantageous for modelling due to its high availability of experimental data. Thermodynamic analyses showed that the net isosteric heat of sorption, Gibbs free energy, and sorption entropy decreased as equilibrium moisture content increased, and the compensation theory provided evidence that the sorption process was controlled by enthalpy (Tβ > Thm).
A novel tasting platform for sensory analysis of specialty coffee
(Editora UFLA, 2018-07) Gutiérrez-Guzmán, Nelson; Cortés-Cabezas, Albeiro; Chambers IV, Edgar
Although there are many good tools to evaluate coffee, such as rigorous cupping protocols, all of them require improvements in order to benefit scientific research. One aspect to highlight is that coffee is a very important product worldwide and has been and is being investigated for its complexity. All research and any improvement in crop or processing ends-up being verified in the coffee cup quality, which is accomplished through the cupping procedures. However, sufficient tools have not been designed in order to manage the cupping procedures, in accordance with the technological level we have available now. Basically, sheets of paper are used to manage the cupping scores, which hinder the subsequent analysis process, making hard to know what happens inside coffee beans with greater precision and thoroughness. Another worrying aspect is that each region, at each country uses a different format with different flavor references to carry out the scoring, which has generated problems of unity of criteria on the analysis and this is not good to the coffee business. This paper presents the design of a web platform to make information storage and results processing of cupping procedures of specialty coffees easier. The main objective is to achieve better managing of the cupping model for the sensory analysis using a digital environment, allowing greater agility in the treatment of results and a more organized management of the information of the specialty coffees.
Numerical approach for prediction of airflow behavior in coffee bean monolayers during dryng process
(Associação Brasileira de Engenharia Agrícola, 2022-05-02) Bustos-Vanegas, Jaime Daniel; Aragón, Larissa; Gutiérrez-Guzmán, Nelson; Córdoba, Nancy
The homogeneity and efficiency of moisture removal from coffee beans depend on the airflow patterns inside the drying chambers used for drying. This study aimed to implement a porous medium model to simulate the airflow through mesh trays containing parchment and ripe fruit coffee ( Coffea arabica L.) using computational fluid dynamics (CFD). The geometry of the ripe fruit and parchment coffee beans was simplified as spherical and semi-ellipsoidal, respectively. The pressure drop in the normal direction to the monolayer was calculated as the average pressure of the normal planes located 1 mm before and after the bean layer for different air velocities. The viscous and inertial terms were adjusted by nonlinear regression for each case and incorporated into the Navier–Stokes equations as subdomains. The pressure drops calculated by the porous medium model and those calculated using the bean layers presented a good fit. The modeling of the trays as porous media can help reduce the computational resources required for CFD simulations while maintaining an acceptable accuracy.