Three methods of measuring coffee roast degree were compared using titratable acidity as an indicator of roast-dependent flavor change. The first roast degree method was based on prediction of the cracks with online near infrared spectroscopy and partial least squares regression, the second was based on changes in online near infrared absorbance, and the third was the common L* value from the CIELAB color space in the visible spectrum. Roasting trials utilized arabica coffee from eight origins in an air roaster, and results demonstrated the superiority of an online near infrared sensor for real-time roast degree measurement. A second dataset with constant temperature roasts showed how acidity can be controlled by changing both the roasting temperature and roast degree, finding the linear effects of roast time and roast degree on acidity.

中文翻译：

---

在线测定咖啡烘焙度以控制酸度

使用可滴定酸度作为烘焙相关风味变化的指标，比较了三种测量咖啡烘焙度的方法。第一种烘焙度方法基于在线近红外光谱和偏最小二乘回归预测裂纹，第二种基于在线近红外吸光度的变化，第三种是来自 CIELAB 颜色空间的常见 L* 值可见光谱。烘焙试验在空气烘焙机中使用来自八个产地的阿拉比卡咖啡，结果证明了在线近红外传感器在实时测量烘焙度方面的优越性。恒温烘焙的第二个数据集显示了如何通过改变烘焙温度和烘焙度来控制酸度，发现烘焙时间和烘焙度对酸度的线性影响。