Determination of the hygroscopic equilibrium and isosteric heat of aji chili pepper

Ednilton T Andrade,José H Da S Taveira,Flávio M Borém,Vitor G Figueira,Luciana P Teixeira

doi:10.1590/1807-1929/agriambi.v21n12p865-871

Abstract

ABSTRACT This study focuses on the determination of the hygroscopic equilibrium and isosteric heat of the aji chili pepper (Capsicum baccatum) under different controlled temperature and relative air humidity conditions. In addition, the objective was to adjust the model among the existing literature models that best represent the isothermal sorption behavior, as well as propose a new model to represent this phenomenon. Having obtained the mathematical models and experimental data, the best model and parameters that represent the hygroscopicity and the isosteric heat satisfactorily was determined. The temperatures used were 30, 55, and 70 °C, with water activity levels from 0.11 to 0.84. The model that best fit the data had a R2 value of 0.97. The integral isosteric heat of sorption for ‘Dedo-de-Moça’ chili pepper within a moisture content from 0.07 to 0.55 (dry basis) ranged from 3641.66 to 2614.38 kJ kg-1.

Highlights

Peppers have been used since the American continent was discovered
The relationship between the moisture content of a certain product and the relative humidity at equilibrium at a given temperature can be expressed by mathematical equations, socalled sorption isotherms or hygroscopic equilibrium curves (Goneli et al, 2014)
The hygroscopic behavior of diverse agricultural products has been studied by various researchers using various mathematical models, such as Chung–Pfost, Copace, modified GAB, modified Halsey, Henderson, modified Henderson, Oswin, Sabbah, and Sigma–Copace (Brooker et al, 1974; Hubinger et al, 2009; Ferreira et al, 2011; Silva & Rodovalho, 2012; Teixeira et al, 2012; Costa et al, 2013; Santos et al, 2015; Goneli et al, 2016)

Summary

Introduction

Peppers have been used since the American continent was discovered. The pepper is an important fruit, used in cooking, in allopathic and natural medicine, and even as a means of defense (Reifschneider & Ribeiro, 2008). Drying is a fundamental part in the conservation of the desirable qualities of plant products harvested with high moisture contents (Goneli et al, 2014). The relationship between the moisture content of a certain product and the relative humidity at equilibrium at a given temperature can be expressed by mathematical equations, socalled sorption isotherms or hygroscopic equilibrium curves (Goneli et al, 2014). The hygroscopic behavior of diverse agricultural products has been studied by various researchers using various mathematical models, such as Chung–Pfost, Copace, modified GAB, modified Halsey, Henderson, modified Henderson, Oswin, Sabbah, and Sigma–Copace (Brooker et al, 1974; Hubinger et al, 2009; Ferreira et al, 2011; Silva & Rodovalho, 2012; Teixeira et al, 2012; Costa et al, 2013; Santos et al, 2015; Goneli et al, 2016). To develop isotherms that represent this equilibrium relationship, empirical mathematical models are used

Objectives

Methods

Results