研究目的
To detect fungal decay in postharvest strawberries based on water-soluble sugar analysis using near-infrared hyperspectral imaging, with goals to investigate sugar variation during decay, explore NIR-HSI feasibility for sugar determination, extract key wavelengths, and provide a strategy for decay stage detection.
研究成果
The research demonstrates that NIR-HSI combined with sugar analysis effectively detects and monitors fungal decay in strawberries. Key findings include acceptable prediction performance for TWSS content (RPD of 2.603) and high classification accuracy for decay stages (up to 95.4%). This non-destructive approach offers a rapid strategy for quality control in postharvest management, with potential for online detection systems. Future work should explore automation and applicability to other fruits and decay types.
研究不足
The study is limited to one strawberry variety ('Hongyan') and specific storage conditions, which may not generalize to other varieties or environments. The NIR-HSI system requires calibration and processing time, potentially limiting real-time application speed. The method focuses on fungal decay caused by Botrytis cinerea and may not apply to other pathogens. Sample size and external validation could be expanded for broader applicability.
1:Experimental Design and Method Selection:
The study used reflectance near-infrared hyperspectral imaging (NIR-HSI) in the 1000–2500 nm range to non-destructively detect fungal decay in strawberries. It involved analyzing sugar constituents (fructose, glucose, sucrose, TWSS) via HPLC as a reference method. Key wavelengths were selected using the successive projection algorithm (SPA), and support vector machine (SVM) regression was employed for prediction models.
2:Sample Selection and Data Sources:
Strawberries (Fragaria × ananassa Duch. 'Hongyan' variety) were harvested at commercial maturity from a local orchard in Nanjing, China. Samples were inoculated with Botrytis cinerea spores for the infected group, with a control group using sterile saline. Samples were stored at 20°C and 85% relative humidity, with data collected at various time points over 120 hours.
3:List of Experimental Equipment and Materials:
Equipment included an NIR-HSI system (Xeva-T2SL-9928 camera, Xenics Ltd.), HPLC system (Shimadzu LC-20A), halogen lamps, transport unit (IRCP0076, Isuzu), computer (Dell Vostro-3667), and software (SPSS
4:0, MATLAB 2014, PLS Toolbox 5). Materials included strawberries, Botrytis cinerea spores, trichloroacetic acid, ultrapure water, acetonitrile, sugar standards (fructose, glucose, sucrose), and PTFE for white reference. Experimental Procedures and Operational Workflow:
Samples were prepared by inoculation and storage. Hyperspectral images were captured using the NIR-HSI system with calibration using dark and white references. Sugar content was measured destructively via HPLC after sample freezing and extraction. Spectral data were pre-processed with standard normal variate correction (SNV). Key wavelengths were selected using SPA, and SVM models were built for prediction and classification of decay stages.
5:Data Analysis Methods:
Statistical analysis used ANOVA with LSD in SPSS. SVM regression models were evaluated using correlation coefficients (R2), root mean square errors (RMSE), and relative percentage of deviation (RPD). Classification accuracy for decay stages was assessed based on key wavelengths.
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Near-Infrared Spectral Camera
Xeva-T2SL-9928
Xenics Ltd.
Used to capture hyperspectral images in the near-infrared range for non-destructive analysis of strawberry samples.
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HPLC System
LC-20A
Shimadzu
Used for reference measurement of sugar constituents (fructose, glucose, sucrose) in strawberry samples via high-performance liquid chromatography.
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Imaging Spectrometer
N25E
Specim Ltd.
Part of the NIR-HSI system for spectral imaging, used to analyze the distribution of chemical constituents.
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Lens
031505
Specim Ltd.
Used in the NIR-HSI system for focusing and capturing images.
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Transport Unit
IRCP0076
Isuzu
Motorized stage for moving samples during hyperspectral imaging to enable line scanning.
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Computer
Vostro-3667
Dell
Used for data storage and processing of hyperspectral images and analytical models.
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Software
SPSS 18.0
IBM Corporation
Used for statistical analysis, including ANOVA and LSD tests.
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Software
MATLAB 2014
The MathWorks Inc.
Used for data processing, implementation of SPA and SVM algorithms.
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Software
PLS Toolbox 7.5
Eigenvector Research, Inc.
Used for building and evaluating SVM regression models.
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Halogen Lamp
Light source for the NIR-HSI system to illuminate samples during imaging.
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Digital Vernier Caliper
Used to measure the thickness of sample slices for sugar analysis.
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Hemocytometer
Used to measure the concentration of Botrytis cinerea spore solution.
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Centrifuge
Used to separate supernatant during sugar extraction.
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Filter
0.45-μm membrane filter
Used to filter samples before HPLC analysis to remove particulates.
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Evaporative Light-Scattering Detector
ELSD
Used in HPLC for detection of sugar compounds that do not absorb UV radiation effectively.
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