Department of Food Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
J Agric Food Chem. 2012 May 30;60(21):5446-53. doi: 10.1021/jf300348e. Epub 2012 May 16.
In this study, Brazilian coffee beans processed to different stages of roast at 210, 220, 230, and 240 °C were analyzed for pH value, titratable acidity, moisture content, and color lightness. Fourier transform infrared (FTIR) spectroscopy, in conjunction with principal component analysis, was conducted to study the effects of process time and temperature on the IR-active components of the acetyl acetate extract of the roasted coffee. The results showed that high-temperature-short-time resulted in higher moisture content, higher pH value, and higher titratable acidity when the beans were roasted beyond the start-of-second-crack stage, as compare to low-temperature-long-time process (LTLT). The LTLT process also resulted in greater IR absorbance for aldehydes, ketones, aliphatic acids, aromatic acids, and caffeine carbonyl bands on the FTIR spectra. Clusters for principal component score plots were well separated, indicating that the changes IR-active components in the coffee extracts, due to the different roasting treatments, can be discriminated by the FTIR technique. On the basis of the loading plots of principal components, changes of IR-active compounds in the coffee extract at various stages of roasting were discussed.
本研究对在 210、220、230 和 240°C 下不同烘焙阶段的巴西咖啡豆进行了 pH 值、可滴定酸度、水分含量和颜色亮度分析。采用傅里叶变换红外（FTIR）光谱结合主成分分析，研究了加工时间和温度对乙酰乙酸提取物中红外活性成分的影响。结果表明，高温短时间处理会导致咖啡豆在第二爆点开始后烘焙的水分含量、pH 值和可滴定酸度升高，而低温长时间处理（LTLT）则会导致 FTIR 光谱中醛、酮、脂肪酸、芳香酸和咖啡因羰基带的 IR 吸收率增加。主成分得分图的聚类很好地分离，表明由于不同的烘焙处理，FTIR 技术可以区分咖啡提取物中红外活性成分的变化。基于主成分的加载图，讨论了咖啡提取物在不同烘焙阶段中 IR 活性化合物的变化。
