Otimização da desidratação osmótica de fatias de Yacon assistida por ultrassom

Abstract

The present work was designed aiming to study, the behavior of yacon slices during osmotic dehydration (OD) processes using polyols, with and without the use of ultrasound. The analysis of the OD kinetic curves of yacon slices using xylitol, maltitol, erythritol, isomalt and sorbitol showed that the use of sorbitol or xylitol provided an intermediate solid gain (SG), higher water loss (WL), diffusivities effective and reduced water activity (aw) on samples. An osmotic dehydration assisted by ultrasound (ODAU) experiment was led according to a central composite design (CCD). A full factorial 2² was conducted with 4 axial points and 5 central points, for each osmotic agent analysed (sorbitol and xylitol). The investigated factors were the ultrasound application time (tus) (0 to 40 minutes) and the osmotic concentration (C.S.) (20 to 60 °B). The analysis of variance showed that the C.S. and tus presented significant effect on increasing WL, SG and reducing fructan retention (FruR) and water activity (aw), for both osmotic agents. The models showed good adjustment. The tus had an important effect on the degradation of fructans. The desirability function applied on results provided acceptable and excellent desirability points for both, the treatments with sorbitol (0 min; 60 °B) and xylitol (2,67 min; 60 °B). The C.S. and tus effect analysis on parameters: moisture content (Mdb), total soluble solids content (TSS), proportional volume (V/V0), color parameters (L*, a* and b*), total color variation (ΔE), stress at rupture (σHF), strain at rupture (εHF) and deformability modulus (Ed) demonstrated a significant effect on all response variables analysed, at least on one of osmotic agents employed. The analysis of variance showed that the models generated fitted well to the datas, except for the response of Ed with sorbitol. The optimized conditions with the aid of desirability function were, for treatments with sorbitol; 31,33 min of application of ultrasound and 22,23 °B, and for xylitol treatments; 29,33 min of application of ultrasound and 27,33 °B. The predicted values analysis of the response variable in the optimized conditions of both processes optimization showed that sorbitol provided more adequate responses to ODAU of yacon slices.