Study of adsorption isotherms of green coconut pulp

Abstract

Brazil is considered one of the largest producers and consumers of tropical fruits. Green coconut (Cocos nucifera L.) stands out not only for its production and consumption, but also for the high amount of waste produced by coconut water industry and in natura consumption. Therefore, there is a need for utilization of this by-product. This study aims to study the adsorption isotherms of green coconut pulp and determine its isosteric heat of sorption. The adsorption isotherms at temperatures of 30, 40, 50, 60, and 70 °C were analyzed, and they exhibit type III behavior, typical of sugar rich foods. The experimental results of equilibrium moisture content were correlated by models present in the literature. The Guggenheim, Anderson and De Boer (GAB) model proved particularly good overall agreement with the experimental data. The heat of sorption determined from the adsorption isotherms increased with the decrease in moisture content. The heat of sorption is considered as indicative of intermolecular attractive forces between the sorption sites and water vapor, which is an important factor to predict the shelf life of dried products.

Water sorption kinetics of damaged beans: GAB model

“…Since the monolayer moisture content indicates the amount of water strongly bound to specific regions in the food, this is a value that must be achieved to ensure stability of the foods (Lavoyer et al, 2013). In products with moisture content lower than the monolayer moisture content, lower deterioration is expected, because the water is strongly bound to the food and does not participate in reactions (Dalgiç et al, 2012).…”

Modelling the effect of temperature on the water sorption isotherms of chitosan films

“…Moisture adsorption isotherms of chitosan films obtained as a function of temperature are shown in Figure 1, the curves are considered type III isotherms according to the classification of Brunauer (Lavoyer et al, 2013). The moisture adsorbed by chitosan films increased when subjected to high levels of a w and decreased with the increase of temperature at a given a w value.…”

“…The parameters are the moisture content in the monolayer (x m ) and the energy involved in the process of water adsorption (c). x m is the amount of water which is adsorbed strongly at specific binding sites on the surface of the material and can also be set as a measure of the availability of active sites of a material for the adsorption of water molecules (Figura & Teixeira, 2007;Lavoyer et al, 2013;Quirijns et al, 2005). In the chitosan-based films, BET model fitted appropriately the range from 0 to 0.75 a w .…”

“…The modified GAB model gave a better fit than the original model for the experimental data obtained from the moisture adsorption isotherms in the range from 0.10 to 0.90 a w (Table 3). As the parameters of the GAB equation are based on the physical phenomena involved in water adsorption by hydrophilic materials, it is considered the most suitable model to describe experimental data (Bratasz et al, 2012;Figura & Teixeira, 2007;Furmaniak et al, 2007;Lavoyer et al, 2013;Medeiros et al, 2006;Souza et al, 2015;Timmermann et al, 2001;Zhang & Han, 2008).…”

Hygroscopic trend of lyophilized ‘mangaba’ pulp powder

“…This type of curve is common in foods that have significant levels of soluble compounds, such as sugars (Lavoyer et al, 2013), although most of the foods show type II curve (sigmoid). A type III curve was also found by Oliveira et al (2014a) in atomized 'macauba' (Acrocomia aculeata (Jacq.)…”