Department of Agri-food Industry, Food and Nutrition (LAN), Luiz de Queiroz College of Agriculture (ESALQ), University of São Paulo (USP), Piracicaba, SP, Brazil.
Ultrason Sonochem. 2019 Apr;52:176-183. doi: 10.1016/j.ultsonch.2018.11.015. Epub 2018 Nov 15.
This work aimed to demonstrate the internal and external structural changes in potato cylinders caused by different times of ultrasound pretreatment. In addition, the structural changes were associated with the viscoelasticity and mass transfer. For which, potato cylinders were immersed in distilled water and pretreated with and without ultrasound (ultrasonic bath of 91 W/L and 25 kHz) up to 120 min. Then, the microstructure was evaluated by stereoscopic observation as a direct method, and by viscoelasticity and mass transfer evaluation (pigment diffusion and drying) as indirect methods. Both external and internal structure of the material were evaluated. As results, it was demonstrated the formation of microchannels inside the potato tissue as well as the surface erosion caused by ultrasound, especially after 60 min of pretreatment. Further, it was observed that the product viscoelasticity is affected by the ultrasound pretreatment reducing the elasticity. In addition, the mass transfer on the cylinders was improved by ultrasound pretreatment. The pigment transfer was enhanced, demonstrating the acoustic erosion at the sample border. Furthermore, the drying process was accelerated by ultrasound, demonstrating the reduction of the internal resistance to water transfer. Finally, it was observed that high structural changes on the potato cylinders can bring some disadvantages such as changes on the color and severe shrinkage. This work concluded that the structural changes caused by ultrasound can be evidenced directly and indirectly. Furthermore, different structural changes took place, on both inside and outside of the vegetable sample. However, despite ultrasound improves further process, especially those that involve mass transfer, the parameters time and ultrasonic power must be optimized to obtain desirable results without reducing the product quality.
本工作旨在展示不同超声预处理时间引起的土豆圆柱体内外结构变化。此外，结构变化与粘弹性和传质有关。为此，将土豆圆柱浸入蒸馏水中，并在有无超声（91 W/L 和 25 kHz 的超声浴）的条件下预处理长达 120 分钟。然后，通过立体观察作为直接方法，以及通过粘弹性和传质评估（色素扩散和干燥）作为间接方法来评估微观结构。评估了材料的内外结构。结果表明，在土豆组织内部形成了微通道，并且超声会导致表面侵蚀，尤其是在预处理 60 分钟后。此外，观察到产品粘弹性受到超声预处理的影响，降低了弹性。此外，超声预处理提高了圆柱体上的传质。色素转移增强，表明样品边界处存在声侵蚀。此外，超声加速了干燥过程，表明内部水传递阻力降低。最后，观察到土豆圆柱的高结构变化可能带来一些缺点，例如颜色变化和严重收缩。本工作得出结论，超声引起的结构变化可以直接和间接地证明。此外，在蔬菜样品的内外都发生了不同的结构变化。然而，尽管超声可以进一步改善某些过程，特别是那些涉及传质的过程，但必须优化时间和超声功率等参数，以在不降低产品质量的情况下获得理想的结果。
