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 (<em>Capsicum pubescens</em>) 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 (X<sub>w</sub>). The differential entropy (ΔS) was less at 15°C, making the adsorption process thermodynamically favorable at low temperatures.
Highlights
Rocoto pepper (Capsicum pubescens), is a fruit native to Bolivia and Perú, is grown in the highlands of Mexico to Argentina (León, 2000)
Because of its high average moisture content of 89.5% (García et al, 2009), it has been chosen for various unit operations to diversify its presentation and extend the shelf life, from processing in sauces, brines, heat treatments and frozen, fried or blanched and dehydrated (Loizzo et al, 2015; Martínez-Girón and Ordóñez-Santos, 2015)
The vegetal product was stored at 5°C and 90% Relative Humidity (RH)
Summary
Rocoto pepper (Capsicum pubescens), is a fruit native to Bolivia and Perú, is grown in the highlands of Mexico to Argentina (León, 2000). It is characterized by its flower purple and black seeds are morphologically medium-sized apple shaped and bright red (Yamamoto et al, 2013). Because of its high average moisture content of 89.5% (García et al, 2009), it has been chosen for various unit operations to diversify its presentation and extend the shelf life, from processing in sauces, brines, heat treatments and frozen, fried or blanched and dehydrated (Loizzo et al, 2015; Martínez-Girón and Ordóñez-Santos, 2015). Genus Capsicum has been processed by the freeze-drying where the final product presented a greater reconstitution properties with better features in color and with minimal loss of volatile components (Shofian et al, 2011; Toontom et al, 2012; Topuz et al, 2011)
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