Thermodynamic Study of Adsorption Properties of Rocoto Pepper (Capsicum pubescens) Obtained by Freeze-Drying

Abstract

The aim of this study was to establish a study of the thermodynamic adsorption to rocoto pepper obtained by freeze-drying at temperatures of 15, 25 and 35°C, by the gravimetric method in the range of water activity between 0.131 and 0.847. Rocoto pepper (Capsicum pubescens) is a natural source of capsaicinoids which gives the level of pungency or hotness attractive gastronomy. Actually, dehydrated and powered food matrices are a good option to ensure stability and techno-functional properties for later uses and applications. A mathematical modeling of the respective isotherms was obtained using different models reported in the literature. The BET model (Brunauer-Emmett-Teller), GAB (Guggenheim-Anderson-de Boer), Herdenson, Smith, Oswin, Peleg and Caurie, based on the moisture content in equilibrium reached freezer-dried samples pepper. The statistical results indicated that the model GAB was the most appropriate to describe the respective sorption curves, whose behavior was completely sigmoidal type II. From these results, the net isosteric heat of adsorption was determined using the Clausius-Clapeyron, ranging from 52.5 to 46.6 (kJ/mol) a moisture content from 2 to 38% dry basis. Also, Gibb's energy (∆G<0) showed that the process will proceed spontaneously (exothermic process) which increased to higher moisture content (Xw). The differential entropy (&DeltaS) was less at 15°C, making the adsorption process thermodynamically favorable at low temperatures.