Drying characteristics and water desorption isotherm of Ulva spp. using different drying methods

Abstract

Green algae belonging to the genera Ulva (Chlorophyta) are common seaweeds distributed worldwi de. They possess an interesting nutritional composition making their commercial exploitation attractive to produce functional food ingredients. However, to obtain a product suitable for industrial processing it is necessary to control the preservation and drying conditions. The aim of this work was to establish the effect of different drying methods on drying characteristic, desorption Isotherms and color of green seaweeds genus Ulva from Region of Coquimbo, Chile. Four different drying conditions were used: freeze-drying for 390 min; sun content was determined by a gravimetric technique. The surface color of the samples were measured using a HunterLab colorimeter and the CIE L*, a* and b* colour scale. Drying results showed that different drying methods had significant effects on the drying characteristics and kinetics. The CD had the best drying characteristics with the shortest drying time and the fastest drying rate. Monolayer moisture content evaluated by the BET model corresponded to the moisture content at which local minimum integral entropy value was observed for sorption processes. Brightness parameter (L*) of the product increased its value independent of the applied drying method, where FD stood out due to its increase, whereas the chromatic coordinates ( a* and b*) showed a different pattern, these values decreased in all treatments compared to the control sample (p <0.05). This work provides an important information about the drying characteristics by application of different drying methods to the Chilean edible green seaweed, Ulva spp. Keywords: Ulva spp., drying methods, water desorption isotherm, surface color