Autores UPV
Óscar Rogríguez,
Santacatalina Bonet Juan Vicente,
Simal Florindo Susana,
García Pérez José Vicente,
ANTONIO FEMENÍA,
Rossello Matas Carmen
Abstract
The effect of drying air temperature and power ultrasound (US) application on the drying curves of apples
(var. Granny Smith) and on the quality (total polyphenol (TPC) and flavonoid (FC) contents, the antioxidant
activity (AA) and microstructure after drying) have been evaluated. Drying curves were studied at
air temperatures of 30 C, 50 C, and 70 C; without ultrasound (AIR) and using two levels of ultrasonic
power: 18.5 kW/m3 (AIR + US1) and 30.8 kW/m3 (AIR + US2), being the drying time significantly
(p < 0.05) reduced as these two operational variables increased. A diffusional model, taking into account
the influence of drying temperature and US power on both the diffusion and the external mass transfer
coefficients allowed the accurate simulation of the drying curves (MRE = 5.8 ± 2.1%). TPC and FC were
affected by drying temperature and US application. In AIR samples, the increase of drying temperature
led to lower losses of TPC, FC, and AA. The US application (AIR + US1 and AIR + US2) involved lower
TPC and FC losses in comparison to AIR samples only at 30 C. The use of US promoted notorious changes
in the microstructure (SEM observation) of apple samples, in comparison to the samples dried without US
at all the temperatures considered, due to the stress developed by ultrasonic waves
