Total Polyphenols (TPP)
Total polyphenol content (TPP) is the most commercially significant quality parameter for black tea at the Colombo auction. High TPP correlates with stronger antioxidant activity, more intense liquor colour, and consistently commands higher lot prices. Our NIR model delivers TPP estimates within seconds from a dry tea powder scan - replacing multi-hour wet chemistry workflows that are impractical at auction or factory pace.
Findings
What We've Established
Spectral Correlation with Polyphenol Concentration
The aromatic ring system of polyphenolic compounds - catechins, theaflavins, and thearubigins - produces characteristic near-infrared absorption patterns. Combined second-overtone C–H and O–H band interactions provide a discriminative spectral window for TPP quantification across the 4,000–10,000 cm⁻¹ region.
Calibration Against Folin-Ciocalteu Reference
Reference TPP values were generated using the standard Folin-Ciocalteu colorimetric assay on a curated set of black tea samples spanning 35+ Ceylon tea grades sourced from multiple factories. Cross-validation R² exceeded 0.93 on the calibration set, with RMSECV within acceptable limits for grade-level differentiation.
Grade Differentiation Capability
The model reliably separates high-grade and standard-grade auction lots by TPP band with accuracy sufficient for practical price guidance - the primary use case identified in early client validation sessions.
Methodology
Technical Approach
Black tea powder samples were prepared from authenticated factory-grade lots and scanned using a benchtop NIR spectrometer in diffuse reflectance mode. Spectral preprocessing included multiplicative scatter correction (MSC) and mean centring. PLS-R was applied with optimal latent variables selected via cross-validation. Reference TPP was measured by an accredited external laboratory using the Folin-Ciocalteu method to ISO 14502-1. A held-out validation set from a separate factory harvest was used for final model assessment.
Status
Where We Stand
The TPP model is complete and validated. We are currently coordinating integration with factory quality management workflows and preparing a summary report for review by industry quality bodies. The model is available for pilot deployment with existing clients who are already using the moisture detection system.
Roadmap
Next Steps
Complete review with industry quality management stakeholders
Integrate TPP output into the multi-parameter scan report alongside moisture and sugar
Evaluate cross-factory model transferability without recalibration
Begin planning for the next-level polyphenol fractionation models: Catechins, TF, TR
Explore More
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Interested in This Research?
If you have relevant data, domain expertise, or a measurement problem in this area, we're open to research collaboration and data-sharing agreements.