Quality control of sugarcane juice

Significance of the Topic

Near-infrared spectroscopy (NIRS) offers a rapid, reagent-free approach to quality control of sugarcane juice, a key feedstock for sugar, alcohol and bioethanol production. Traditional methods for determining °Brix, Pol, purity, reducing sugars and total recoverable sugars require sample treatment and multiple instruments, limiting throughput. Implementing NIRS enables simultaneous, multi-parameter analysis in under one minute, supporting real-time decision making and cost reduction in industrial QC workflows.

Study Objectives and Overview

This study aimed to develop and validate predictive calibration models for five critical quality parameters in sugarcane juice using a Metrohm DS2500 Liquid Analyzer. A dataset of 100 juice samples with reference lab values for °Brix, Pol, juice purity, reducing sugars and total recoverable sugars was used to train and test the NIRS models, demonstrating feasibility for routine process control.

Methodology and Instrumentation

• Instrument: Metrohm NIRS DS2500 Liquid Analyzer covering 400–2500 nm in transmission mode
• Sampling: 100 sugarcane juice specimens collected across varying maturity and processing conditions
• Optical setup: 1 mm pathlength flow cell fed by peristaltic pump for continuous sample introduction
• Software: Vision Air Complete for spectral acquisition, preprocessing and model development

Main Results and Discussion

• °Brix prediction: R2 = 0.9875, standard error of validation (SEV) = 0.138 °Brix
• Pol (% sucrose): R2 = 0.9833, SEV = 0.1388 %
• Juice purity (Pol/Brix): R2 = 0.8194, SEV = 0.564 %
• Reducing sugars: R2 = 0.6497, SEV = 0.0249 %
• Sucrose reading (polarimetry equivalent): R2 = 0.9911, SEV = 0.497 %
• Total recoverable sugars (calculated from Pol and reducing sugars): R2 = 0.9463, SEV = 1.9074 %

High correlation and low prediction errors for °Brix, Pol and sucrose validate the robustness of NIRS for major constituents. Lower performance for purity and reducing sugars reflects sample heterogeneity and reference method complexity but remains acceptable for rapid QC screening.

Benefits and Practical Applications

• Sub-minute analysis without chemicals or sample preparation
• Simultaneous multi-parameter output reduces instrument footprint
• Enhanced operational efficiency for mills and refineries through inline or at-line monitoring
• Reduced labor and consumable costs

Future Trends and Applications

Advances in portable NIRS sensors and machine learning algorithms will further improve model accuracy and enable decentralized QC at field or factory sites. Integration with process analytics networks and automated sampling robots can support continuous real-time control of extraction and fermentation processes. Multi-spectral data fusion and cloud-based calibration updates will facilitate adaptive models resilient to seasonal and varietal variations.

Conclusion

The Metrohm DS2500 Liquid Analyzer combined with Vision Air software successfully quantifies key quality parameters in sugarcane juice within one minute. This approach provides a reliable, high-throughput alternative to conventional lab methods, enabling faster decision making and improved process control in sugar and bioethanol production.

Reference

• Metrohm Application Note AN-NIR-110