Sugarcane (Saccharum spp.) is a very important crop for the global economy. It is often used as a raw material for the production of sugar, alcohol, yeast, and more. Brix (°Brix), Pol (%), juice purity (%), reducing sugars (%), and total recoverable sugars (Kg t^-1) are some of the many quality control (QC) parameters that must be analyzed in sugarcane juice.

Numerous methods based on several analytical techniques are available for sugarcane juice quality control. These methods can be quite time-consuming since sample treatment is a prerequisite. A quicker alternative to these other methods is near-infrared spectroscopy (NIRS). NIRS allows the simultaneous determination of several QC constituents, without chemicals or sample preparation, in less than one minute.

Sugarcane juice was analyzed by NIRS, and a total of 100 spectra were collected to create a prediction model for quantification of several QC parameters. All samples were measured with a Metrohm NIRS DS2500 Liquid Analyzer (400–2500 nm) in transmission mode with a DS2500 Holder Flow Cell (Figure 1). A flow cell with 1 mm pathlength was used in this study. This flow cell was filled via peristaltic pump. The Vision Air Complete software package from Metrohm was used for all data acquisition and prediction model development.

The obtained Vis-NIR spectra (Figure 2) were used to create a prediction model for quantification of Brix (°Brix), Pol (%), juice purity (%), reducing sugars (%), and total recoverable sugars (Kg t^-1). The quality of the prediction model was evaluated using correlation diagrams which display a very high correlation between the Vis-NIR prediction and the reference values. The respective figures of merit (FOM) display the expected precision of a prediction during routine analysis (Figures 3–8).

This Application Note demonstrates the feasibility to determine Brix, Pol, juice purity, reducing sugars, and total recoverable sugars in sugarcane juice with NIR spectroscopy. Vis-NIR spectroscopy enables a fast and highly accurate alternative to other standard methods (Table 2). No sample preparation is required, and results are delivered in less than a minute.