In order to increase the water migration rate during unripe banana drying process, two pre-treatments were applied. Experiments were performed as following: 20 min of ultrasound (US) + air-drying at 50 °C; 20 min of US + 60 min of pulsed-vacuum (PV) + air-drying at 50 °C; 25 min of US + air-drying at 60 °C and 25 min of US + 60 min of PV + air-drying at 60 °C. Experimental data were adjusted to five models and the Midilli model resulted to fit best experimental data with r² > 0.999, RMSE < 0.0119 and χ² < 0.00012. Increasing in water effective diffusivity, at the two falling rate periods, were observed due to the application of US, whereas the combined technique of US + PV did not improve the water migration, at both air-drying temperatures. The results revealed drying time savings of (28 and 18) % at (50 and 60) °C, respectively.

Industrial relevance

In this work, ultrasound and ultrasound-pulsed vacuum pre-treatments prior to air-drying were applied as an alternative to produce unripe banana flour (UBF). This study indicates that the drying kinetics increased due to the application of ultrasound, preserving the resistant starch content of the final product. Hence, this technology diminishes the drying time and consequently reduces the energy costs, in comparison with to the conventional process. Therefore, the UBF rich in resistant starch content can be considered a functional ingredient that promotes dietary intake of unavailable carbohydrates, which may reduce the risks of non-communicable diseases.

中文翻译：

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超声和脉冲真空对风干的综合作用以获得未成熟的香蕉粉

为了提高未成熟香蕉干燥过程中的水分迁移速率，进行了两次预处理。实验进行如下：超声（US）20分钟+在50°C空气干燥；20分钟US + 60分钟脉冲真空（PV）+在50°C空气干燥；25分钟US + 60°C风干和25分钟US + 60分钟PV + 60°C风干。实验数据进行了调整至五个模型和Midilli模型导致与拟合最佳实验数据- [R ²  > 0.999，RMSE <0.0119和χ ² <0.00012。由于使用了US，在两个下降速率时期，水的有效扩散率增加了，而在两种风干温度下，US + PV的组合技术都没有改善水的迁移。结果表明在（50和60）°C下干燥时间分别节省了（28和18）％。

行业相关性

在这项工作中，采用风干之前的超声和超声脉冲真空预处理作为替代方法来生产未成熟的香蕉粉（UBF）。这项研究表明，由于施加了超声波，干燥动力学得到了增强，从而保留了最终产品的抗性淀粉含量。因此，与常规方法相比，该技术减少了干燥时间并因此降低了能源成本。因此，富含抗性淀粉含量的UBF可以被认为是一种功能成分，可以促进饮食中摄入不可用的碳水化合物，从而可以减少非传染性疾病的风险。