ABSTRACT
RESUMEN El objetivo de este estudio fue evaluar el efecto de las condiciones de secado y presecado en muestras de café pergamino, almacenadas durante 6 meses, en condiciones controladas de humedad relativa, 70% y temperatura, 25°C, determinando la Conductividad Eléctrica (CE), Lixiviación de Potasio (LK) y Acidez Grasa (AG), de granos secos de café. El proceso de secado consistió en procesos combinados a temperaturas 50 y 60°C, dos periodos de 4 y 8 horas en el presecado mecánico y, posteriormente, llevado a humedad comercial en patio solar y dos tratamientos testigos, conformados por el secado mecánico completo y el secado solar completo. Los resultados mostraron los siguientes valores: 6,35 - 16,34µSm cm-1/ g MS, para CE; 2,0 - 4,45ppm/gMS, para LK y 0,76 - 1,57mL KOH/ 100g MS, para AG, donde los análisis estadísticos mostraron que no hubo efecto del tipo de secado sobre las variables estudiadas; sin embargo, los mayores promedios acumulados en el tiempo de almacenamiento fueron observados para el secado mecánico completo. Los valores encontrados no indicaron daños de la estructura celular atribuidos según, el marco referencial, a secados con alta temperatura o prolongado almacenamiento. Las pruebas de Conductividad Eléctrica (CE) y Acidez Grasa (AG) mostraron sensibilidad al tiempo de almacenamiento, mientras que la prueba de Lixiviación de Potasio (LK), no se constituyó en un indicador del deterioro del grano, atribuible al estrés termomecánico o al tiempo de almacenamiento.
ABSTRACT The aim of this study was to evaluate the effect of drying and pre-drying conditions of samples of parchment coffee stored during 6 months under controlled conditions of relative humidity of 70% and temperature of 25°C quantifying the Electrical Conductivity (EC), Potassium Leaching (KL) and Fatty Acidity (FA) of the grain. The coffee drying consisted on combined processes using air temperatures of 50°C and 60°C and two periods of 4 and 8 hours in the mechanical pre-drying and subsequently taken to commercial moisture content under patio drying, and two control treatments consisting of complete mechanical drying and complete solar drying. The results of the tests showed the following values: 6.35 - 16.34 µSm cm-1 / g DM (EC), 2.0 - 4.45ppm / g DM (KL) and 0.76 - 1.57mL KOH / 100g MS (FA), where the statistical analysis shows that there is no effect of the drying type on the studied variables. However, the highest accumulated averages in the storage time were observed for the complete mechanical drying. The values did not show deterioration of the cellular structure attributed to the frame of reference of drying with high temperature or prolonged storage. The tests of Electrical Conductivity (EC) and Fatty Acidity (FA) shows sensitivity to the storage time while the Potassium Leaching (KL) test did not constitute an indicator of grain deterioration attributable to thermomechanical stress or storage time.
ABSTRACT
Background: Sugarcane is one of the world's largest crop. It grows in the tropical and subtropical regions, and its harvest provides 80% of the world's sugar. In Latin America unrefined cane sugar is widely available and much less expensive than refined sugar. Sugarcane is a crop of great interest in Colombia due to the economic impact on the rural population and its application as sweetener agent. The powder of sugarcane (Saccharum officinarum L.) is widely used as a raw material in a wide range of industries such as foods, pharmaceutical, cosmetic and chemical. Objectives: The aim of the research work was the evaluation of the adsorption thermodynamics of sugarcane powder obtained by spray drying technology. Methods: The adsorption isotherms of sugarcane powder were evaluated at temperatures of 4 ± 0.1, 20 ± 0.2 and 30 ± 0.3 °C and its thermodynamic properties such as Gibbs free energy (G), differential heat of adsorption (∆H) and differential entropy (∆S) were calculated as a function of moisture content. Experimental data of adsorption isotherms were fitted to the GAB (Guggenheim Andersen - de Boer), BET (Brunauer Emmett - Teller), Henderson, Caurie, Smith, Hasley, Peleg, and Oswin models. Results: The results showed a type-II sigmoidal behavior, with temperature having a statistically significant effect. The GAB equation showed a better fit to the experimental data modeling (0.11≤aw≤0.87) although all models showed validity and goodness of fit to the experimental data. The net isosteric heat increased to a maximum value (57 kJ mol-1) and then decreased with the increase in moisture content. Conclusions: The sugarcane powder with maltodextrin, obtained by spray drying got low adsorption thermodynamic stability, as it required very low energy to occur this phenomenon, being obtained the maximum net isosteric heat when moisture content of 4.7% (d.b). This value is within the range of the monolayer moisture content found in the GAB and BET models.