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News — The study, which compares four spectroscopy tools, aims to optimize spectral data processing, ensuring more accurate classification. This advancement promises significant implications for the agri-food industry, improving coffee quality control and traceability.

Vibrational spectroscopy has long been valued in the pharmaceutical and forensic sectors, and its application is expanding into agriculture, particularly for quality and origin verification of biological materials. Techniques such as near-infrared (NIR), mid-infrared (FTIR), Raman, and hyperspectral imaging (HSI) spectroscopy enable rapid, non-invasive analysis of food products.   However, variability in sample characteristics, such as particle size and density, can introduce noise in spectral data, hindering accuracy. To address these issues, preprocessing of spectral data is crucial for removing physical artifacts and enhancing model performance.

A published in  on 29 March 2024, is particularly valuable for the coffee industry, where verifying geographic origin is crucial for ensuring product authenticity and quality.

 The study compared four vibrational spectroscopy tools—dispersive near-infrared (DG-NIR), near-infrared hyperspectral imaging (HSI-NIR), attenuated total reflectance Fourier transform infrared (ATR-FTIR), and Raman spectroscopy—using different preprocessing techniques to classify coffee samples from Indonesia, Ethiopia, Brazil, and Rwanda.  This initial exploration aimed to identify the necessary preprocessing methods and detect potential outliers. The main challenges identified included three spectral data issues: offsets, slopes, and curvature, which affect signal accuracy. Offsets, typically caused by instrumental drift or inconsistent particle grinding, were not found in the data. However, slopes, particularly in the Raman spectra due to fluorescence interference, and curvature in DG-NIR and HSI-NIR, caused by light scattering, were observed. These nonlinearities, arising from varying sample surface characteristics, were mitigated through specific preprocessing techniques.

To address these challenges, the spectra underwent mean-centering before further analysis. No outliers were identified in any of the datasets, as confirmed by the high KNN distances and reduced Hotelling’s T2 and Q residuals tests, which were within the 95% confidence interval. The study highlights that preprocessing methods such as normalization, scatter corrections, and spectral derivations are essential to remove physical artifacts. Additionally, Matthew’s Correlation Coefficient (MCC) was used as a key decision parameter to address data imbalances, providing a more comprehensive assessment of model performance than accuracy or F1 scores. This allowed the identification of the best preprocessing treatments for each instrument, optimizing the classification of coffee origin across different countries.

According to the study's researcher, Dr. Joy Sim, "Our study introduces a systematic approach to selecting the best preprocessing method, addressing a critical challenge in vibrational spectroscopy. This work not only enhances classification accuracy but also provides a robust framework for future applications in food traceability."

This study paves the way for more sustainable and efficient methods of verifying the origin  of coffee and other biological materials, highlighting the potential of vibrational spectroscopy as a powerful tool for ensuring food safety and quality, with wide-ranging applications across agriculture and beyond.

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Funding information

We would like to acknowledge the University of Otago for the Doctoral Scholarship.

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Food is essential to life and relevant to human health. The rapidly increasing global population presents a major challenge to supply abundant, safe, and healthy food into the future. The open access journal (e-ISSN 2836-774X), published by Maximum Academic Press in association with China Agricultural University, Zhejiang University and Shenyang Agricultural University, publishes high-quality research results related to innovations and advances in food science and technology. The journal will strive to contribute to food sustainability in the present and future.