Centro de Investigación Avanzada en Agroingeniería, Universidad Privada del Norte (UPN), Peru.
Centro de Investigación Avanzada en Agroingeniería, Universidad Privada del Norte (UPN), Peru.
Food Res Int. 2024 Feb;178:114007. doi: 10.1016/j.foodres.2024.114007. Epub 2024 Jan 11.
The objective of this study was to evaluate, during the drying of spent coffee grounds, the application of pretreatments with ethanol and the application of ultrasound assisting the refractive window (RW) drying, and to compare with convective drying by hot air (AC). The effect on the kinetics parameters of the Fick and Page models were evaluated, as well as on the content of total phenolics and antioxidant capacity. For AC drying, samples of spent ground coffee were prepared in the form of fixed rectangular beds 0.7 cm high, which were placed on polyester sheets and pretreated up to 10 times sprayed with ethanol, then dried by AC at 80 °C and 0.8 m/s. For RW drying, the samples prepared in the same way as for AC were used. For this case, the application of ethanol as pretreatment and the use of ultrasound during process were tested. As results, regardless of the conditions applied, drying by RW was up to 50 % faster, evidenced in the highest values of effective diffusivity (from the Fick model) and the kinetic parameter (from the Page model). Regarding the treatments applied and their effect on the drying kinetics, any treatment had a significant effect on AC drying. On the contrary, the strategies applied in RW drying had significant effects, both the application of pretreatment with ethanol as well as the application of ultrasound assisting the process accelerated the drying kinetics. However, the treatment with ethanol and RW drying was the one that best preserved the phenolic compounds and the antioxidant capacity in the samples. Therefore, these strategies could be a good option to improve RW drying by accelerating the process and preserving the bioactive compounds in the spent coffee grounds for subsequent utilization.
本研究的目的是在干燥废咖啡渣的过程中，评估乙醇预处理和超声辅助折射窗（RW）干燥的应用，并与热空气（AC）对流干燥进行比较。评估了菲克（Fick）和佩杰（Page）模型的动力学参数以及总酚含量和抗氧化能力的变化。对于 AC 干燥，将废咖啡渣样品制备成固定的矩形床，高 0.7 厘米，放置在聚酯片上，预处理 10 次，每次用乙醇喷洒，然后在 80°C 和 0.8 m/s 的条件下进行 AC 干燥。对于 RW 干燥，使用与 AC 相同的方法制备样品。在这种情况下，测试了乙醇预处理的应用和过程中超声的使用。结果表明，无论应用何种条件，RW 干燥的速度都快了 50%，这表现在有效扩散系数（从菲克模型）和动力学参数（从佩杰模型）的最高值上。关于所应用的处理及其对干燥动力学的影响，任何处理对 AC 干燥都有显著影响。相反，RW 干燥中应用的策略有显著影响，乙醇预处理的应用和超声辅助过程都加速了干燥动力学。然而，乙醇处理和 RW 干燥是保留样品中酚类化合物和抗氧化能力最好的处理方法。因此，这些策略可以是改进 RW 干燥的一种很好的选择，既可以加速干燥过程，又可以在废咖啡渣中保留生物活性化合物，以供后续利用。
