Modeling mass transfer during osmotic dehydration of different vegetable structures under vacuum conditions

João Renato De Jesus Junqueira,Ronaldo Elias De Mello Junior,Jefferson Luiz Gomes Corrêa,Kamilla Soares De Mendonça,Amanda Umbelina Souza

doi:10.1590/fst.02420

Abstract

Abstract Osmotic dehydration (OD) is a method to partially reduce moisture of food, aiming to improve the shelf life and the stability of the products. The mass transfer that occurs during this process can be enhanced with the application of reduced pressure in the first minutes of the osmotic dehydration (pulsed vacuum osmotic dehydration - PVOD). The present work aimed to study the vacuum effect on the kinetics of osmotic dehydration of vegetables (carrot, eggplant and beetroot) in terms of water loss, solids gain and water activity, in ternary solution. Moreover, mathematical modeling of experimental data obtained from the osmotic processes, was employed for correlating the mass transfer of the food product under the different conditions. An intensification of mass transfer was observed for carrot and eggplant in the vacuum treatments. This was related to their porous structure. The present work demonstrated a lack of fit of Fick’s second law for describing the dehydration kinetics of the eggplant.

Highlights

The dehydration of food is an usual technique to extend the shelf life and the stability of perishable products
Due to the osmotic pressure gradient, two mass transfer fluxes are generated, the water present in the tissues migrates to the osmotic solution, and the solutes of the osmotic solution are incorporated to the food matrix (Luchese et al, 2015; Ramya & Jain, 2017)
The mass transfer rates can be intensified if in the beginning of the process a reduced pressure is applied, in the operation known as pulsed vacuum osmotic dehydration (PVOD)

Summary

Introduction

The dehydration of food is an usual technique to extend the shelf life and the stability of perishable products. Due to the osmotic pressure gradient, two mass transfer fluxes are generated, the water present in the tissues migrates to the osmotic solution (dehydration), and the solutes of the osmotic solution are incorporated to the food matrix (impregnation) (Luchese et al, 2015; Ramya & Jain, 2017). The mass transfer rates can be intensified if in the beginning of the process a reduced pressure is applied, in the operation known as pulsed vacuum osmotic dehydration (PVOD). Mass transfer through porous structure is related to the higher fluxes of water removal and solids incorporation during the osmotic dehydration. This is observed due to the larger internal surface area. During the PVOD, this effective surface for mass transfer is extended due to the expulsion of the occluded fluids on account of the pressure gradient created (Fito, 1994; Junqueira et al, 2018; Şahin & Öztürk, 2016)

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