Effect of ultrasound treatment on physicochemical parameters and drying time in nopal cladodes Opuntia spp. (e-Latin Food 2020)
Nopal (Opuntia spp.) is a cactus consumed as a vegetable that has been recognized as a functional food, since it contains bioactive compounds such as organic acids, fiber, mucilage, pigments, minerals, and antioxidants. The new technologies in the food industry have shown that the application of power ultrasound, can promote mass transfer mechanisms when used as pre-treatment to improve the food drying. The objective of this work was to evaluate the effect of ultrasonic treatment on color, microstructure and bioactive compounds content for subsequent dehydration and determination of drying time of nopal cladodes. Full factorial experimental design with a central point was performed, considering the amplitude (20, 48 and 76%) and the sonication time (10, 15 and 20 min) as factors. The application of power ultrasound treatment on nopal cladodes, affects the microstructure, deforming and distanced the cells, mainly at 76% amplitude for 15 min. The content of bioactive compounds such as total polyphenols and chlorophyll increased from 11.7 until 18 mg EGA/g d.b. and from 30.9 until 93.6 mg/g d.b., respectively by treating the nopal cladodes with ultrasound. After the ultrasound treatment, the hot-air drying process causes color changes from green to red/brown and decreases between 9-41% of the polyphenols concentration; however, ultrasound managed to reduce drying time by up to 26%.
Key Words: ultrasound, hot air-drying, nopal cladodes, bioactive compounds, microstructure.