# Pressure Drop Process as a Pretreatment for Enhancing Rehydration of Adzuki Beans (Vigna angularis)

## TL;DR

A nonthermal pressure drop process improves adzuki bean soaking efficiency without significant heat, potentially replacing traditional heat treatments.

## Contribution

Development of a nonthermal pressure drop processor and its application to enhance adzuki bean rehydration.

## Key findings

- PDA and PDB pretreatments improved soaking efficiency more than heat treatments at 60 °C and 100 °C.
- Repeated PDB application increased moisture absorption without thermal influence.
- Pressure drop treatments caused structural changes like cracks and wrinkling in adzuki beans.

## Abstract

Pressure drop processes, such as dissolved inorganic carbon and gun-puffing, have shown utility in the food industry, but their reliance on heat remains a limiting factor. This study involved the development of a processor capable of performing nonthermal pressure drop treatment, which minimizes thermal changes in food. In addition, its effects on the structure and soaking efficiency of adzuki beans were analyzed. Two improved pressure drop processes were tested: PDA, which applied 1 kgf/cm2 of pressure before release, and PDB, which applied a higher pressure and gradually decreased it in steps of 1 kgf/cm2. Both the PDA and PDB pretreatments enhanced soaking more effectively than heat treatments at 60 °C and 100 °C, whereas no significant effect was observed at 25 °C, indicating a minimal heat requirement for moisture and gas release. Notably, repeated PDB application (more than 40 times) further increased the moisture absorption without thermal influence. Scanning electron microscopy revealed that the PDA, PDB, and heat treatments caused cracks in the hilum region and increased surface wrinkling and mesh structure deformation. These findings demonstrate the potential of pressure drop treatment to improve soaking efficiency through structural modification, supporting its use as an effective nonthermal pretreatment method.