Integration of nanofiltration and spray drying processes for enhancing the purity of powdered fructans from Agave salmiana juice

A combination of nanofiltration (NF) and spray drying was selected for this study to remove low molecular weight sugars and consequently to avoid the use of carrier agents and to increase the purity of fructans from Agave salmiana juice. NF experiments were performed in a stirred-cell unit using hydrophilic cellulose membrane with MWCO of 1000 Da, operated in concentration and diafiltration mode with volume reduction factor (VRF) = 2.7, 4 and volume dilution factor (VDF) = 1, 2.7 and 4, respectively. Retentates were collected and dried in a mini spray drier B-290 at inlet temperatures between 160 and 180 degrees C. A rotatable central composite design with five center points was used and powder yield (PY), moisture content (MC), purity value (PV) and glass transition temperature (Tg) of powders were measured as dependent variables. Response surface plots (p < 0.05) showed that the highest PY value and fructans with the highest purity were obtained when NF was combined with a VDF of 4 and spray drying at 170 degrees C. For MC, the inlet temperature and dilution factor were the most important factors. No significant effect of the experimental factors was observed on Tg, and an average value of 131.4 +/- 43 degrees C was found for anhydrous Agave salmiana fructans with a PV that ranged from 87.3 to 99.2%. (C) 2017 Elsevier B.V. All rights reserved.