Almond analysis with near-infrared (NIR) spectroscopy

Importance of the Topic

Near-infrared spectroscopy (NIRS) enables rapid, non-destructive evaluation of critical almond quality parameters such as moisture, protein, and fat content. Traditional analytical methods require extensive sample preparation and costly reagents, limiting throughput in industrial and research laboratories.

Objectives and Study Overview

• Develop robust NIR calibration models for moisture, protein, and fat in whole and ground almonds.
• Assess model performance by comparing NIR predictions with AOAC reference methods.

Methodology and Instrumentation

A total of 120 almond samples (60 whole and 60 ground) were analyzed using a Metrohm NIR Analyzer in reflection mode over 1000–2250 nm. Samples were measured with a rotating large-cup accessory and spectral averaging to minimize inhomogeneity. Metrohm software facilitated spectral acquisition and chemometric model development.

Main Results and Discussion

• Protein (whole): R²=0.997, SEC=0.23 %, SECV=0.28 %
• Moisture (whole): R²=0.998, SEC=0.22 %, SECV=0.25 %
• Fat (whole): R²=0.917, SEC=1.56 %, SECV=1.84 %
• Protein (ground): R²=0.999, SEC=0.10 %, SECV=0.14 %
• Moisture (ground): R²=0.999, SEC=0.09 %, SECV=0.15 %
• Fat (ground): R²=0.914, SEC=1.62 %, SECV=1.67 %

The high correlation and low error values indicate reliable simultaneous quantification of multiple constituents, with slightly lower precision observed for fat content.

Benefits and Practical Applications

• Simultaneous determination of moisture, protein, and fat without reagents.
• Minimal sample preparation and fast analysis time (seconds per sample).
• Cost-effective solution for routine quality control in processing and packaging.

Future Trends and Applications

Advances in miniaturized NIR instrumentation and machine-learning algorithms are expected to enhance sensitivity and enable real-time on-line monitoring. Expansion of calibration libraries can adapt this approach to other nut varieties and complex food matrices.

Conclusion

NIR spectroscopy represents a rapid, accurate, and economical alternative to conventional methods for almond quality assessment, supporting efficient processing and stringent quality assurance.

References

• Duduzile Buthelezi, N. M.; Tesfay, S. Z.; Ncama, K.; et al. Destructive and Non-Destructive Techniques Used for Quality Evaluation of Nuts: A Review. Scientia Horticulturae. 2019;247:138–146.