Raman and NIR spectroscopy: A discussion of calibration robustness for food quality measurements through two case studies

Sammendrag

Background: Fast and nondestructive spectroscopic measurements of food quality are of great interest to
the food industry due to their huge potential in decision support and optimization of processes and food
value chains. Choosing the type of spectroscopic technique to invest in is not always straight-forward. In this
work, we discuss the robustness aspect of Raman and NIR spectroscopy as a relevant factor to consider. We
hypothesize that Raman spectroscopy has an advantage in calibration development and maintenance due to
the higher degree of chemical details in the spectra, lower degree of band overlap and lower sensitivity to
water.
Results: Robustness was discussed through two case studies, assessing (1) the transferability of intact
strawberry sugar calibrations between seasons and (2) the transferability of fat models between different meat
grinding degrees. The work indicates that Raman spectroscopy has an inherent chemometric advantage for
robustness. This was particularly pronounced in the strawberry case, where Raman models of around half the
complexity (number of PLSR components) of NIR-based models reached similar performances and provided
more interpretable regression vectors. The meat case demonstrated that the robustness of the techniques may
depend on the sensitivity to different sample textures and heterogeneity. A Raman probe with a spot size of
3 mm diameter suffered from higher prediction errors than a probe with 6 mm diameter spot size. We also
demonstrated an additional challenge of increasing fluorescence with longer meat storage time for Raman
spectroscopy. Still, a Raman system with 6 mm spot size outperformed a reflection geometry NIR system with
approximate illumination spot of 1 cm.
Significance: Few studies that compare Raman and NIR spectroscopy within food applications, focus on the
differences regarding robustness. This work shows that the cost of developing and maintaining a calibration
industrially should be considered to a higher extent and be part of the evaluation on final cost and
implementation ease, when deciding between Raman and NIR spectroscopy or what type of sampling optic to
invest in. The findings should motivate critical comparisons of the two techniques prior to long-term sensing
implementation.

Les publikasjonen her:

DOI : doi.org/10.1016/j.aca.2025.344...
NVA : hdl.handle.net/11250/3222689