A Case Study of Turbulent Free Jet Flows Issuing from Rectangular Slots on Process Performances and Quality of Hot-Air-Dried Apple

Virginie Boy,Jean-Louis Lanoisellé,Yves Lemée,Marina Giblaine,Sahar Mlayah

doi:10.3390/pr9111900

Abstract

This study deals with the improvement in drying process performances and the quality of the final product for industrial equipment in the food industry. Designers need to optimize the design parameters of devices to create synergies between the greater energy efficiency of the process and high-quality dried products. Air impingement drying was carried out on apple cylinders at 323 K and with air velocities ranging between 30 and 60 m s−1. The studied drying process presents a particular setup of jets as they are multiple rectangular slot jets issued from triangular nozzles. The effect of four design jet parameters (slot width, nozzle-to-surface height, nozzle-to-nozzle spacing, and airflow) on the drying process performances and the quality of the final product was analyzed and optimized using response surface methodology (RSM). A minimal influence of design jet parameters on the process performances was shown, while an important impact was observed on the quality of dried apple. The slot width and the nozzle-to-nozzle spacing had a significant effect on the textural and functional properties. Predictive models were established and good agreements were found between predictive and observed values. Sorption isotherms were properly modeled by the Guggenheim–Anderson–de Boer (GAB) model.

Highlights

IntroductionThe high temperature and long drying time needed in conventional hot-air dryers negatively impact the organoleptic (color and texture), functional (rehydration), and nutritional qualities of food products [1,2,3,4]
This research has focused on studying the impact of design jet parameters on the drying process performances and the quality attributes of apples using response surface methodology (RSM)
A greater significant influence of the examined parameters was shown through the quality of the product compared with the drying process performances

Summary

Introduction

The high temperature and long drying time needed in conventional hot-air dryers negatively impact the organoleptic (color and texture), functional (rehydration), and nutritional qualities of food products [1,2,3,4]. Among the different drying methods available, the drying process that uses impinging jets seems to be promising for food thermal treatment [5]. During the air impingement drying process, the air reaches the surface of the product at high velocities which reduces the air layer that is directly in contact with the product (boundary layer), increases heat and mass transfers, diminishes the drying time, and increases the global quality of the product [6,7]. Air impingement drying has become popular over the past 25 years in the food industry and has been applied to vegetables and fruits (seedless grapes, Hami melon flakes, apricots, carrots, line peppers), herbs (American ginseng, yam), foods (tortilla chips, potato chips, fish cakes, fish particles, shrimp), seeds, and soy residue or okara [8]

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