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Chemistry - Agricultural Science |
Alvarado, Luis; Molina-Rojas, Erick; Gonzalez, Jose; Irizarry, Efrain; Rivera, Melany; Toro, Miguel. Natural Sciences Department, UPR-Aguadilla.
Analysis of volatile aroma compounds in a home brewed ale beer by means of solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS)
Beer is a very popular beverage made of the fermentation of malted cereal grains (mostly barley, but also wheat, rice and maize). The malted grains release the enzymes and sugars, the yeast will later ferment to obtain low alcohol content and the characteristic flavor of beer. More than seventy styles of beer are available to satisfy the taste of millions of people around the world. In the United States, for example, 880 breweries produced more than 200 millions of barrels of beer in 1995. As an average, each American adult consumed 32 gallons of beer that year. Each style of beer derives its unique characteristics of aroma and flavor from its ingredients and subtle differences in the elaboration process. Nowadays it turns out essential to evaluate the quality of the ingredients used to brew the beer. As the malted grains and other adjuncts used to elaborate beer could vary in their nature and composition, almost every brewery has at least one expert called Master Brewer who is responsible of evaluating the process as much as the final product. Nevertheless, the use of the technology has been improving and the Brewing Process is now not a matter of artisan companies, but fully equipment ones with the state-of-the-art technology. In order to evaluate the quality of beers on a simple, fast, reproducible and cost-efficient way we have conducted an investigation with the main goal to stablish a routine analysis of the beer, correlating aroma of volatile compounds with ingredients and the elaboration process used. The use of Solid-Phase Microextraction (SPME) coupling with Gas Chromatography-Mass Spectrometry (GC-MS) to analyze the aroma composition of foods and beverage has grown enormously during the last years and we have adapted pretty well those techniques to the analysis of the aroma of a Homebrewed Ale draft beer. The resuls are very promising since different types of compounds have been detected, such as terpenes, ketones, aldehydes, and mainly low molecular esters. These compounds vary its composition through time, and monitoring them we could be able to predict the best time to consume the beer and also correlate the aroma profile with the flavor of the beer.
González Santiago, Miguel, Universidad Interamericana, Recinto de Arecibo, Dept. de Ciencias y Tecnología.
Estudio Molecular y Cálculo de Propiedades Termodinámicas de Ácido Hipofluoroso
El estudio teórico de moléculas poliatómicas es un campo de actualidad, gracias a los avances de la mecánica cuántica y las capacidades de las computadoras personales. Es de interés, el estudio molecular y el cálculo de propiedades termodinámicas de un ácido oxidante por su capacidad desinfectante en un ambiente real. Este trabajo presenta algunos resultados de simulación computacional, a través de distintos métodos semi-empíricos y Ab initio , de la estructura, propiedades moleculares y propiedades termodinámicas de HOF.
Además, se desarrolla un análisis del enlace H-O a través del cálculo de su curva de energía potencial. Simulaciones de este tipo de curvas se pueden obtener a partir del programa computacional de Gaussian 98 utilizando diversos métodos y cuyos resultados permiten encontrar mediante un ajuste de mínimos cuadrados una serie de parámetros, tales como la energía de disociación de enlace, constantes de fuerza y longitud de enlace en el equilibrio.
La investigación presentada en este trabajo se desarrolló gracias a los fondos aportados por el proyecto MSEIP en Química, “Integration of Chemistry and Biology through Molecular Modeling ” y el apoyo de la Universidad Interamericana de Puerto Rico.