Osmotic dehydration/impregnation kinetics of Padron pepper (Capsicum annuum L. Longum) with sodium chloride solutions:: Process modelling and colour analysis

Experimental determinations were carried out to evaluate the dehydration/impregnation mass transfer rates that take place during osmotic processing of Padron peppers (Capsicum annuum L. var. Longum) with sodium chloride solutions. Several sodium chloride concentrations (from 17 to 26.5% w/w) and temperatures (from 25 to 45 degrees C) and contact times (up to 8h) were selected as variables. Solids gain, weight reduction, water loss, normalised moisture content and normalised solids content were calculated at each experimental condition. These data allowed the calculation of water and salt mass transfer coefficients for modelling the corresponding kinetics. Additionally, pepper colour changes during osmotic contact at different experimental conditions were determined. In all cases, solids gain, weight reduction and water loss increased with temperature and salt concentration. Water loss values are low and water loss/salt gain ratio is also low (as it is usual when sodium chloride solutions are employed as osmotic media). In this way, osmotic process can be basically considered as an impregnation process. In all experimental conditions the colour changes were only significant at the highest temperature assayed and also depended on osmotic concentration.