Abstract Edible coatings are recently gaining attention for potential applications in bakery products to extend the shelf-life and incorporate functional characteristics, like probiotics, antimicrobial or an antioxidant compound, for which drying of the coating is an essential step. The aim of this work was to utilize near infrared (NIR) spectroscopy as a tool to rapidly monitor and develop predictive model for the drying of edible coating on bread (mini-burger buns) surfaces. The buns coated with edible coating were dried at two different temperature regimes, at 25 °C and 60 °C for one layer of coating and one temperature regime at 60 °C for two layers of coating. NIR spectra were collected and moisture content was determined at different drying times. The spectral data were pre-treated and subjected to Principal component analysis (PCA) for discrimination of drying times and subsequently to Partial least squares (PLS) regression for moisture prediction for given temperature, time and surface. Results show that NIR spectroscopy was able to reflect the drying process and discriminate between the various surfaces of bread and times of drying, primarily by the differences in water and protein absorption bands (1940 nm, 1500 nm, 2050 nm). Also, the subsequent PLS regression of the spectral data was found to describe satisfactorily the drying behaviour and the optimal drying moment with RMSE values ≤ 3% for the calibration and cross validation data sets. The procedure proposed could be used for faster quantification of moisture during drying process.

中文翻译：

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用近红外光谱评价面包可食用涂层的干燥

摘要 食用涂料最近因在烘焙产品中的潜在应用而受到关注，以延长保质期并结合功能特性，如益生菌、抗菌剂或抗氧化化合物，因此涂层的干燥是必不可少的步骤。这项工作的目的是利用近红外 (NIR) 光谱作为一种工具来快速监测和开发面包（迷你汉堡包）表面可食用涂层干燥的预测模型。涂有可食用涂层的面包在两种不同的温度范围内干燥，一层涂层在 25 °C 和 60 °C 下干燥，而一种温度范围在 60 °C 下进行两层涂层。收集 NIR 光谱并测定不同干燥时间的水分含量。对光谱数据进行预处理并进行主成分分析 (PCA) 以区分干燥时间，随后进行偏最小二乘 (PLS) 回归以预测给定温度、时间和表面的水分。结果表明，近红外光谱能够反映干燥过程并区分面包的不同表面和干燥时间，主要是通过水和蛋白质吸收带（1940 nm、1500 nm、2050 nm）的差异。此外，发现光谱数据的后续 PLS 回归令人满意地描述了干燥行为和最佳干燥时刻，对于校准和交叉验证数据集，RMSE 值 ≤ 3%。建议的程序可用于在干燥过程中更快地量化水分。