Sugar in Tea
Sugar content in processed black tea is an underutilised but increasingly important quality parameter. Natural sugars remaining after oxidation influence liquor sweetness and mouthfeel, and are particularly relevant for specialty, herbal-blend, and health-positioned tea products. Export buyers with clean-label requirements are beginning to request compositional data alongside standard auction grades. Our NIR model enables rapid total sugar quantification without laboratory infrastructure.
Findings
What We've Established
NIR Sensitivity to Carbohydrate Content
Carbohydrate C–H and O–H stretching overtones in the 7,000–8,500 cm⁻¹ region provide measurable signal variation correlating with total soluble sugar content across black tea powder matrices. These bands are distinguishable from moisture and polyphenol contributions using the full multivariate spectral model.
Validation Against Phenol-Sulfuric Acid Reference
Reference values were generated by the phenol-sulfuric acid colorimetric method, recognised as the standard for total carbohydrate quantification in tea matrices. Model calibration achieved R² above 0.91 with acceptable RMSECV for the sugar concentration range found in commercially graded Sri Lankan black tea.
Methodology
Technical Approach
Samples were drawn from the same authenticated factory-grade lot collection used for the TPP calibration dataset, supplemented with samples from estates with documented variation in manufacturing temperature profiles - a variable known to affect residual sugar content. PLS-R with SNV preprocessing was applied consistently with the other tea parameter models.
Status
Where We Stand
The sugar model is validated and ready for deployment. It is being bundled with the moisture and TPP models as part of a combined quality scan report, reducing per-test overhead for factory clients running multiple parameters simultaneously.
Roadmap
Next Steps
Package into the combined multi-parameter scan report
Evaluate applicability to green tea and white tea matrices
Explore correlation between NIR-predicted sugar and sensory sweetness ratings from professional tasters
Explore More
Related Projects
Moisture Content - Green Tea
Real-time MC measurement for green tea. Model trained on TRI-standard data and independently validated in December 2025.
View project Model ReadyTotal Polyphenols (TPP)
Total polyphenol profiling for black tea - the leading proxy for antioxidant quality and a primary auction pricing signal.
View project Lite Model ReadyCaffeine Content
Rapid caffeine screening for black tea blends - lite model delivered, enabling blend certification and label compliance workflows.
View projectR&D Partnerships
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.