RESUMEN
Free volatile compounds in six varieties of citrus juices were analyzed by solid-phase microextraction-gas chromatography-mass spectrometry. Bound fractions were isolated and extracted with methanol and Amberlite XAD-2 resin and then hydrolyzed by almond ß-glucosidase. A total of 43 free and 17 bound volatile compounds were identified in citrus. Free volatile contents in sweet orange were the most abundant, followed by those in grapefruits and mandarins. Among free volatiles, terpenes were the most abundant in citrus juice. Sensory analysis results showed that the flavor of the same citrus cultivars was similar, but the flavor of different cultivars varied. Among bound volatiles, benzenic compounds were the most abundant in these citrus juices. Bound volatiles also significantly differed among cultivars. In addition, only p-vinylguaiacol were detected in all of the samples.
Asunto(s)
Citrus/química , Frutas/química , Gusto , Compuestos Orgánicos Volátiles/análisis , Femenino , Cromatografía de Gases y Espectrometría de Masas , Humanos , Masculino , Metanol , Poliestirenos , Análisis de Componente Principal , Microextracción en Fase Sólida , Terpenos/análisisRESUMEN
The principle of step scan FTIR spectroscopy and the relationship between phase modulation and sample modulation were described in detail. Demodulation of the frequency domain detector signal was discussed and illustrated using double digital signal processing (DSP2) algorithm. In-phase and quadrature dynamic spectra of polyurethane with 5 Hz stretching under 100 Hz phase modulation as compared to the normal spectrum were presented. The spectral resolution of the overlapped features had greatly been enhanced.