Quality control of sugarcane juice

Importance of the Topic

Sugarcane is a key agricultural commodity used for sugar, alcohol, yeast and other bioproducts. Monitoring juice quality parameters such as Brix, Pol, purity, reducing sugars and total recoverable sugars is essential for process optimization, product consistency and economic value. Traditional chemical methods require sample preparation and reagents, limiting throughput and increasing turnaround time.

Objectives and Study Overview

This study aimed to develop and validate a rapid, reagent-free near-infrared spectroscopy (NIRS) method for simultaneous quantification of multiple quality control (QC) parameters in sugarcane juice. A calibration model was built using 100 juice samples to predict:

• Brix (°Brix)
• Pol (%)
• Juice purity (%)
• Reducing sugars (%)
• Total recoverable sugars (kg t⁻¹)

Methodology and Instrumentation Used

Samples were measured in transmission mode on a Metrohm DS2500 Liquid Analyzer covering 400 – 2500 nm. A 1 mm pathlength flow cell was integrated with a peristaltic pump for continuous sample delivery. Vision Air Complete software managed spectral acquisition and calibration development. Reference values were obtained by standard laboratory techniques: refractometry for Brix, calculated Pol, ion chromatography for reducing sugars, polarimetry for sucrose reading and derived calculations for total recoverable sugars.

Main Results and Discussion

The NIRS models exhibited strong correlations between predicted and reference values:

• Brix: R² = 0.99, validation error ≈ 0.14 °Brix
• Pol: R² = 0.98, validation error ≈ 0.14 %
• Sucrose reading: R² = 0.99, validation error ≈ 0.50 %
• Total recoverable sugars: R² = 0.95, validation error ≈ 1.9 %
• Purity: R² = 0.82, validation error ≈ 0.56 %
• Reducing sugars: R² = 0.65, validation error ≈ 0.025 %

High R² values for Brix, Pol and sucrose reading demonstrate excellent predictive performance. Purity and reducing sugars showed moderate accuracy but can still support routine screening. All analyses were completed in under one minute without any chemical reagents or sample pretreatment.

Benefits and Practical Applications

The NIRS method offers multiple advantages:

• Simultaneous multi-parameter analysis
• Rapid throughput (<1 minute per sample)
• No chemical reagents or sample preparation required
• Robust operation suitable for laboratory and production environments
• High reproducibility and ease of use with integrated software

Future Trends and Potential Applications

Advances in NIRS calibration transfer, inline process monitoring and machine-learning algorithms will further enhance accuracy and applicability. Potential developments include:

• Automated online monitoring in juice processing lines
• Extension to other agricultural products and by-products
• Integration with quality management systems for real-time feedback
• Improved detection of minor constituents and spoilage indicators

Conclusion

This study demonstrates that a Metrohm DS2500 NIRS system can accurately and rapidly predict key quality parameters in sugarcane juice. The method provides a practical, cost-effective alternative to conventional laboratory assays, enabling high-throughput quality control without reagents or sample preparation.

Instrumentation Used

• Metrohm DS2500 Liquid Analyzer (400–2500 nm)
• 1 mm pathlength flow cell with peristaltic pump
• Vision Air Complete software for data acquisition and model development