# The Effect of Pretreatments and Infrared Drying on the Quality of White Radish Slices

## TL;DR

This study explores how different pretreatments affect the quality of dried white radish slices, finding that osmotic dehydration and spice coatings preserve structure and nutrients best.

## Contribution

The study introduces a comparative analysis of various pretreatments for infrared drying of white radish, highlighting osmotic dehydration and spice coatings as novel effective methods.

## Key findings

- Osmotic dehydration with inulin minimized shrinkage, color change, and preserved phenolic content and antioxidant activity.
- Spice-coated samples showed low hardness, vivid color, and high porosity, with paprika-coated samples reaching 57.5% porosity.
- Blanching, ultrasound, and PEF caused greater structural changes and increased hygroscopicity in dried white radish slices.

## Abstract

White radish is a nutritious root vegetable that provides dietary fiber, essential vitamins and minerals, and a range of bioactive compounds. This study aimed to determine how steam and microwave blanching, pulsed electric field, ultrasound, osmotic dehydration with inulin or trehalose, and coating with spices such as turmeric or sweet paprika influence the characteristics of convective infrared dried white radish slices. To assess the effect of each pretreatment, moisture content, water activity, shrinkage, density, texture, color parameters, structural characteristics (SEM and µ-CT), vapor adsorption, thermal changes, and antioxidant properties were analyzed. Osmotic dehydration with inulin most effectively limited shrinkage and color change, stabilized the microstructure, and resulted in the highest relative phenolic content and antioxidant activity (TPC, DPPH). Spice-coated samples showed low shrinkage, low hardness and breaking work, and vivid color. Furthermore, µ-CT microstructure analysis showed that these samples had the highest porosity, with those with paprika reaching 57.5%. In contrast, blanching, ultrasound, and PEF led to greater structural changes and increased hygroscopicity. Multivariate analyses confirmed the significant influence of the type of pre-treatment on the quality characteristics of the dried material. Osmotic dehydration and spice coating proved to be the most effective methods for obtaining structurally stable and visually attractive dried white radish slices with attractive bioactive compounds.