Química (Mag.)

Permanent URI for this collectionhttp://98.81.228.127/handle/20.500.12404/770

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    Nuclear magnetic resonance and high performance liquid chromatography chemical analysis of peruvian roasted coffee beans
    (Pontificia Universidad Católica del Perú, 2020-03-10) Leyva Zegarra, Vanessa Elsie; Maruenda Castillo, Helena
    Coffee is the most traded agricultural commodity in the world. Currently, Peru is considered the third principal producer of Coffea arabica in South America, and the sixth worldwide, accounting for 6 % of the global production. However, most of the coffee (~ 99 %) is exported as green beans due, in part, to the fact that the local quality control of the roasting process is not yet optimal. Hence, it is crucial to develop a more standardized process for the quality control of roasted coffee beans that will allow local Peruvian coffee farmers to introduce to the market a more valuable product. In the thesis presented here, work associated with the project FINCyT-PIPEI-PUCPCENFROCAFE- 2012 on the quantitation of the main compounds developed during the roasting process was embraced using NMR and HPLC-DAD methodologies. Attention was focused on the secondary metabolites that, from a flavor-aroma perspective, are of interest: caffeine, 5- caffeoylquinic acid, trigonelline, 1-methylpyridinium ion and nicotinic acid, and 5- hydroxymethylfurfural as a marker of deterioration. One- and two-dimensional NMR techniques allowed the simultaneous identification of eleven compounds known to be associated with the flavor and aroma of coffee. The NMR quantitation of five compounds was performed using ERETIC2 and Standard Calibration Curves and the results were validated by a new HPLC methodology, which constitutes the only validated methodology currently available for the simultaneous quantitation of these five compounds. The percentage difference among this three methods was within acceptable values (1 – 20%) for most of the compounds. It was demonstrated that these numbers were sample dependent. In addition, PCA analyses of quantitative data (NMR and HPLC-DAD) allowed the discrimination of coffee samples acording to the degree of roasting, as well as to their origin (instant coffee, speciality coffees from different regions in Peru). Hence, these preliminary results indicate that NMR and HPLC can be used as quality control tools to optimize the roasting conditions of Peruvian specialty coffee. Recommendations are included in this work to improve further the error percentages between the NMR and HPLC data that in some cases (for 5-caffeoylquinic acid and nicotinic acid) were high.
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    Adsorción de cadmio y plomo en efluentes acuosos mediante borra de café peruano
    (Pontificia Universidad Católica del Perú, 2018-02-05) Angeles Villón, Luis Rosas; Gamboa Fuentes, Naida Rosa
    La borra de café tiene un alto potencial de aplicación en la descontaminación de aguas para consumo humano en zonas rurales. Este alto potencial se fundamenta, entre otras razones, por su capacidad de adsorción, estabilidad en el tiempo y bajo costo para su obtención. Se utilizó café verde de la especie Coffea arabica proveniente de Quillabamba/Cusco y Villa Rica/Pasco. Cada uno fue tostado en grado oscuro y claro, y sometidos a dos grados de molienda: medio (0,707 < d (mm) < 1,68) y fino (0,420 < d (mm) < 0,707). Se preparó café americano con el café molido medio y café expreso con el molido fino. Se ha determinado que el pH óptimo para la adsorción de Cd(II) y Pb(II) en soluciones acuosas separadas de concentración máxima 10 ppm es 6,5 y 4,0 respectivamente, y el tiempo óptimo de residencia para alcanzar el equilibrio es 10 y 2 horas respectivamente. La adsorción del Cd(II) con borra de café del tipo tostado oscuro y molido medio se ajusta al modelo isotérmico de Freundlich para el café de Villa Rica/Pasco y al modelo isotérmico de Langmuir para el café de Quillabamba/Cusco. Sin embargo, la adsorción del Pb(II) con borras de café del tipo tostado oscuro y molido medio de Quillabamba/Cusco o Villa Rica/Pasco solo se aproximan al modelo isotérmico de Freundlich. La borra de café del tipo tostado oscuro y molido medio de Villa Rica/Pasco fue 27% más eficiente que la de Quillabamba/Cusco, siendo su adsorción máxima de 43,3 y 33,9 mg de Cd por gramo de borra, respectivamente. En cuanto al Pb(II), es 68,3 y 67,6 mg de Pb, por gramo de borra, ambas de una eficiencia comparable.