RESIDUE OF ETHANOL IN PINEAPPLE DRIED USING ETHANOL AND ULTRASOUND AS PRE-TREATMENTS

Ethanol and ultrasound have been used to improve drying of food products. However, the residue of ethanol in the final product is frequently neglected. The present work evaluated the drying process of pineapple using ethanol in pre-treatments with (ET+US) and without (ET) ultrasound, focusing on describe the residual ethanol in the final product. Short cylinders were immersed in ethanol at 25 ºC by 7.5-30 minutes, in a regular or an ultrasonic bath (25 kHz, 14.90 W/L). Posteriorly, the samples were dried in an oven with forced air circulation at 50 °C and 1±0.1 m/s. Page model was fitted to the drying data. The residue of ethanol was determined in the dried products by headspace-gas chromatography/mass spectrometry. A calibrating curve was obtained by adding known aliquots of HPLC grade ethanol (up to 4% v/w) in the control treatment (in natura pineapple dried). All the pre-treatments accelerated the drying process. The rate parameter of Page increased with ET+US pre-treatment time. The pre-treatments ET and ET+US longer than 7.5 min presented residue of ethanol between 1 and 4%. However, the treatment ET+US during 7.5 min resulted in lower concentration of ethanol than the control. Therefore, ethanol pre-treatment can be used to accelerate pineapple drying without leaving residues, by combining ultrasound and process conditions.