The aim of the present work was to determine the efficacy of handheld portable Vis–NIR spectroscopy in rapid non-destructive moisture content monitoring during the solar drying of mangoes. Mango slices (1.5 cm thick) from five (5) commercial mango cultivars and two breeding selections were pre-treated by hot water blanching, dipping in distilled water (control); sodium metabisulphite and citric acid solutions. Vis–NIR absorbance spectra in the range of 474–1047 nm (191 spectra points) of the samples were recorded during solar drying at temperatures of 16.8–54.3 °C and relative humidity of 19.2–99.3%. A training set consisting of 168 spectra was utilized to develop models based on partial least squares regression. Chemometric analysis gave an optimum wavelength range model that could explain 95.2% of the variance in the moisture content with a detection limit of 5.39%. The optimum model was tested for prediction of the moisture content based on 72 spectra from similarly treated samples. The model could explain 91.6–98.7% of the variance in the moisture content of the test samples with detection limits ranging from 3.97–6.61% w/w. The research demonstrated that portable hand-held Vis–NIR spectroscopy was a robust and effective method for rapid non-destructive monitoring of moisture during solar drying of mangoes. Non-destructive hand-held portable Vis–NIR spectrophotometers can hence facilitate the production of high quality solar dried mangoes.

中文翻译：

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在芒果进行太阳能干燥过程中，使用手持式便携式Vis-NIR分光光度计快速进行无损水分监测（Mangifera indica L.）

本工作的目的是确定手持便携式Vis-NIR光谱在芒果太阳能干燥过程中快速无损水分监测中的功效。将五（5）个商品芒果品种和两个育种选择的芒果片（1.5厘米厚）通过热水烫煮，浸入蒸馏水（对照）进行预处理；焦亚硫酸钠和柠檬酸溶液。在16.8–54.3°C的温度和相对湿度19.2–99.3％的太阳干燥过程中，记录了样品在474–1047 nm（191个光谱点）范围内的Vis–NIR吸收光谱。利用由168个光谱组成的训练集来开发基于偏最小二乘回归的模型。化学计量分析给出了可以解释95的最佳波长范围模型。水分含量变化的2％，检出限为5.39％。测试了最佳模型，基于来自相似处理的样品的72个光谱预测了水分含量。该模型可以解释测试样品水分含量的91.6–98.7％的变化，检出限为3.97–6.61％w / w。研究表明，便携式手持式Vis-NIR光谱技术是一种用于芒果日光干燥期间快速无损监测水分的有效方法。因此，无损手持式便携式Vis-NIR分光光度计可以促进生产高品质的芒果干。测试样品水分含量变化的7％，检出限为3.97–6.61％w / w。研究表明，便携式手持式Vis-NIR光谱技术是一种用于芒果日光干燥期间快速无损监测水分的有效方法。因此，无损手持式便携式Vis-NIR分光光度计可以促进生产高品质的芒果干。测试样品水分含量变化的7％，检出限为3.97–6.61％w / w。研究表明，便携式手持式Vis-NIR光谱技术是一种用于芒果日光干燥期间快速无损监测水分的有效方法。因此，无损手持式便携式Vis-NIR分光光度计可以促进生产高品质的芒果干。