研究目的
To monitor the evolution of the spectral pattern of extra virgin olive oil (EVOO) samples exposed to indirect light at room temperature using fluorescence spectroscopic techniques, and to develop fast inspection procedures for assessing oxidation status.
研究成果
The 3D FF spectra reveal detailed excitation-emission regions related to oxidation processes. Simultaneous excitation below 400 nm in RA experiments provides a fast procedure to monitor oxidation, showing evolution in chlorophyll and oxidation by-products signals. Hyperspectral imaging allows precise sorting of olives for homogeneous oil classification.
研究不足
The study is preliminary, and further modelling with official EVOO samples is needed. The RA prototype may have limitations in capturing all fluorophores, and the hyperspectral imaging requires validation for broader applications.
1：Experimental Design and Method Selection:
The study used front-face (FF) and right-angle (RA) fluorescence spectroscopy to monitor EVOO samples. Three-dimensional fluorescence spectra were analyzed with excitation wavelengths from 230 to 646 nm and emission from 250 to 698.5 nm. Principal component analysis (PCA) and partial least-square regression (PLSR) were employed for data analysis.
2：5 nm. Principal component analysis (PCA) and partial least-square regression (PLSR) were employed for data analysis. Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Three sets of samples were used: Set 1 included EVOO and olive oil samples from producers and retail markets; Set 2 included EVOO samples exposed to indirect light for 5 months; Set 3 included olive fruit samples sorted by maturity stage. Data were acquired using spectrofluorometers and hyperspectral imaging systems.
3：List of Experimental Equipment and Materials:
Spectrofluorometer (LS45; Perkin-Elmer), photonic multichannel spectrometer (Hamamatsu), UV-VIS light source (L10290, Hamamatsu), quartz cuvettes (10×10×45 mm), optical filters, hyperspectral vision system with CCD camera (Andor Luca) and spectrograph (Headwall Photonics Hyperspec? VNIR), halogen lamps, and barium sulfate white reference.
4：Experimental Procedures and Operational Workflow:
Samples were measured without prior preparation. For FF, spectra were measured with specific slit widths and wavelength steps. For RA, a prototype was used with simultaneous excitation below 400 nm and emission above 400 nm. Hyperspectral images were acquired with push-broom scanning, and spectra were pre-processed using standard normal variate and Savitsky Golay techniques.
5：Data Analysis Methods:
Coefficient of variation (CV) was computed for signal intensity. Univariate analysis involved R2 computation between signal intensity and K270 values. Multivariate analysis used PLSR with evaluation through R2c and SEPc.
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spectrofluorometer
LS45
Perkin-Elmer
Used to measure 3D front-face fluorescence spectra with excitation and emission monochromators.
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UV-VIS light source
L10290
Hamamatsu
Provides light for excitation in right-angle experiments, using a deuterium lamp.
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CCD camera
Luca
Andor
Part of the hyperspectral vision system for acquiring images in push-broom mode.
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spectrograph
Hyperspec? VNIR
Headwall Photonics
Used in the hyperspectral imaging system to capture spectral data from 400 to 1000 nm.
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photonic multichannel spectrometer
Hamamatsu
Used to obtain right-angle fluorescence spectra with detection wavelengths from 196.9 to 958.8 nm.
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quartz cuvette
10×10×45 mm
Holds oil samples for fluorescence measurements without prior preparation.
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optical filter
Coupled to the right-angle setup to constrain excitation wavelengths below 400 nm and emission wavelengths above 400 nm.
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halogen lamp
Provides illumination for the hyperspectral imaging system.
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barium sulfate white reference
Used as a reference for computing relative reflectance in hyperspectral image processing.
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