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A simple method based on surface-enhanced Raman scattering (SERS) was developed for the rapid determination of alternariol (AOH) in pear fruits using an easily prepared silver-nanoparticle (AgNP) substrate. The AgNP substrate was modified by pyridine to circumvent the weak affinity of the AOH molecules to the silver surface and to improve the sensitivity of detection. Quantitative analysis was performed in AOH solutions at concentrations ranging from 3.16 to 316.0 μg/L, and the limit of detection was 1.30 μg/L. The novel method was also applied to the detection of AOH residues in pear fruits purchased from the market and in pear fruits that were artificially inoculated with Alternaria alternata. AOH was not found in any of the fresh fruit, whereas it resided in the rotten and inoculated fruits. Finally, the SERS method was cross validated against HPLC. It was revealed that the SERS method has great potential utility in the rapid detection of AOH in pear fruits and other agricultural products.

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The major sugars in fruits, including glucose, fructose, and sucrose, play a critical role in fruit quality control and maturity evaluation. Many novel methods and techniques such as enzymatic and nonenzymatic biosensors, nuclear magnetic resonance, and near-infrared spectroscopy have been developed to provide the rapid estimation of sugar inversion under different storage conditions. This review provides a description of recent advancements in these technologies for the determination of sugar contents in fruits. The prospects of emerging spectroscopic technologies such as Raman spectroscopy, hyperspectral imaging, and terahertz imaging, for assessing sugars in intact fruits are discussed. The challenges for further developments of these methods and technologies to meet the increasing demand for rapid and on-line quality control are also presented.

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