RESUMEN
A novel dynamic approach is described to profile volatile organic compound (VOC) and semi-VOC (SVOC) emission during coffee roasting aimed at analysing components present in the roasting plume, and to monitor their evolution during the process. Two sorbents - coconut shell charcoal (CSC) and styrene-divinylbenzene resin (XAD-2) - were evaluated while collecting substances in four sequential time intervals (0-3, 3-6, 6-9 and 9-12â¯min). Extracted VOCs (<200â¯Da) and SVOCs were analysed by gas chromatography (GC), and comprehensive two-dimensional gas chromatography (GCâ¯×â¯GC) with flame ionisation (FID) and time-of-flight mass spectrometry (TOFMS) detection. Results showed CSC extraction presented poor recovery of VOCs and SVOCs released during roasting. However, XAD-2 was able to collect both groups, including SVOCs of >400â¯Da. GCâ¯×â¯GC resolved many co-eluting compounds observed in 1D GC and allowed chemical group type cluster analysis, revealing that many non-polar VOCs are observed within the 0-3â¯min interval, and that the release of polar and higher molar mass SVOCs were mostly found within the 3-6â¯min interval. These group-type cluster analyses offer a broad spectrum chemical profile of the released substances. It may also reveal detailed insights into the roast process evolution over time.
Asunto(s)
Café/química , Semillas/química , Compuestos Orgánicos Volátiles/análisis , Brasil , Ácidos Grasos/análisis , Ionización de Llama , Cromatografía de Gases y Espectrometría de Masas/métodos , Espectrometría de Masas , Extractos Vegetales/química , Esteroles/química , Factores de TiempoRESUMEN
Cafestol and kahweol (C&K), two coffee diterpene alcohols with structural similarity which exhibit anticarcinogenic effects, were isolated from green coffee Arabica beans, followed by their lipase-catalysed esterification and purification by preparative high-performance liquid chromatography (HPLC). The isolation and enzymatic synthesis parameters of C&K esters were studied, with the latter optimised by a Central Composite Design; both procedures were monitored by gas chromatography. Scale up and improved isolation conditions resulted in 1.29â¯g of C&K, with 98% purity from 300â¯g of green Arabica beans. The highest C&K ester yields were observed using an alcohol:fatty acid molar ratio of 1:5, 73.3â¯mgâ¯mL-1 of CAL-B enzyme, 70⯰C and 240â¯rpm for 3â¯days in toluene, leading to 85-88% conversion among a variety of tested C&K esters, including n-C14:0-C20:0, C18:1, C18:2 and C18:3.