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Soy protein and carboxymethylcellulose films and its application as edible coating on intermittent drying of papaya

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Author(s):
Maria Mariana Garcia de Oliveira
Total Authors: 1
Document type: Master's Dissertation
Press: São José do Rio Preto. 2019-09-27.
Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências Letras e Ciências Exatas. São José do Rio Preto
Defense date:
Advisor: Maria Aparecida Mauro; Keila de Souza Silva
Abstract

This study aimed to investigate the development of protein and polysaccharide-based edible coatings and its application in intermittent drying of papaya pieces, in order to minimize nutritional losses and energy consuming. Soy protein (SPI) based films with different concentrations (0.125; 0.25; 0.375 and 0.5%) of carboxymethylcellulose (CMC) were prepared at pH 11 and at biopolymers coacervation pH (pHc). The intensity of proteinpolysaccharide interaction, the pH effects, ionic strength and SPI/CMC ratio on the net charge of these biopolymers were investigated by measuring the zeta potential of filmogenic solutions. The films were characterized regarding their morphology, mechanical, structural and optical properties and water vapor (WVP) and oxygen (OP2) permeabilities. The films strength has improved with increasing polysaccharide addition, however, films at pHc lost their elasticity, becoming more brittle and morphologically more heterogeneous than at pH 11, besides presenting a great increase of opacity. The WVP of films didn’t show expressive changes with CMC addition and/or pH change, but they presented increased solubility at pH 11. On the other hand, the oxygen permeability of films at pH 11 decreased with the CMC incorporation in film matrix, being the formulation composed by 0.375% CMC the less permeable to the gas and, therefore, selected to be applied as a pretreatment in papaya (Carica papaya L.) drying, as edible coating, with the goal to delay oxidative reaction during hot air drying. For this, papaya pieces, with or without coating, were dried until to achieve a water content of 6.67 ± 0.45% (w.b.) by continuous or intermittent convective drying. The drying trials with application of thermal intermittence were conducted in two stages. The first one at elevated temperatures of 80 and 95 °C lasting 40 and 15 minutes, respectively, and, the second stage, at lower temperature of 60 °C. The continuous drying was conducted at the same temperature as the second stage of intermittent drying (60 °C). The effects of coating and different drying operations (with and without intermittence) were evaluated by changes in physical and nutritional characteristics of the final product and by the energy consumption calculated through an energy balance. Coating improved the lycopene retention in continuous and intermittent drying. On the other hand, the thermal intermittence caused higher lycopene degradation than continuous drying, regardless the presence of the coating. The fresh papaya characteristic color was preserved throughout the dehydration process and intensified with the intermittence and the coating. Besides that, the thermal intermittence reduced the total drying time and provided an energy saving of approximately 17%. (AU)