Assessment of chocolate with Raman spectroscopy

Importance of Topic

Quality control of chocolate is essential for food safety, product consistency and brand reputation. Raman spectroscopy delivers a molecular “fingerprint” of samples, enabling non-destructive, rapid assessment of composition and crystallinity. As global chocolate consumption and market value continue to rise, manufacturers require robust analytical tools to monitor raw materials and end products.

Study Objectives and Overview

This study aimed to demonstrate how Raman spectroscopy can distinguish chocolate types, quantify cocoa and sugar content, detect thermal damage and support real-time quality control. Various commercial chocolates (white, milk, 70%, 85% and 100% cocoa) were analyzed to establish optimal measurement conditions and build predictive models for key quality attributes.

Methodology and Sampling Protocol

Raman spectra were acquired from solid chocolate bars using a fiber-optic probe in a fixed holder. Laser power (5–15%) and integration times (>60 s) were adjusted to maximize signal while preventing melting. Samples were positioned at a calibrated focal distance to ensure reproducibility. Key spectral regions (1060–1100 cm⁻¹, 1200–1600 cm⁻¹) were selected for chemometric analysis.

Used Instrumentation

• i-Raman NxG 1064 laboratory Raman spectrometer (1064 nm excitation)
• Fiber-optic sampling probe with distance regulator
• SpecSuite software for data acquisition and PLS model building

Results and Discussion

Laser power optimization revealed that dark (100%) chocolate melted at lower powers (≈10%) due to higher absorption, whereas lighter chocolates tolerated up to 15% without visible damage. Subtle shifts in crystallinity were observed in white chocolate above 10% power, highlighting the importance of careful power control.

Sugar-related bands (e.g., 848 cm⁻¹, 1460 cm⁻¹) were prominent in white, milk and 70% chocolates, whereas high-cocoa samples only exhibited a weak sugar feature at 1460 cm⁻¹. Cocoa solids displayed characteristic peaks at ~1300 cm⁻¹ and 1420–1480 cm⁻¹. Partial Least Squares (PLS) models built on these regions achieved high predictive accuracy for both cocoa content (low standard error) and sugar concentration, confirming Raman’s suitability for quantitative QC.

Benefits and Practical Applications

• Non-destructive, rapid measurements directly on solid samples
• Minimal sample preparation and real-time feedback in production
• High specificity for cocoa solids, fat and sugar quantification
• Capability to detect thermal alterations and crystallinity changes

Future Trends and Potential Applications

• Integration of 785 nm excitation for lower-power, fluorescence-rejected measurements
• Expansion of calibration datasets to cover wider chocolate varieties and processing conditions
• Inline or at-line process monitoring with fiber-optic probes
• Combination with other vibrational techniques and machine-learning algorithms for comprehensive product profiling

Conclusion

Raman spectroscopy, coupled with chemometric modeling, provides a reliable, nondestructive QC method for measuring cocoa and sugar content and monitoring thermal effects in chocolate. The approach supports rapid decision-making in manufacturing and can be scaled for routine in-process analysis.

Reference

1. marknteladvisors. Chocolate Market Size, Share, Analysis and Industry Trend to 2030.
2. Esmonde-White K.; Lewis M.; Lewis I. R. Direct Measurement of Chocolate Components Using Dispersive Raman Spectroscopy at 1000 nm Excitation. Appl Spectrosc. 2023, 77(3):320–326. https://doi.org/10.1177/0003702822114794
3. Lindt Shop Intl. Chocolates, Truffles, and Delicious Gifts. https://www.chocolate.lindt.com/ (accessed 2025-08-17).