# Regulating Extruded Expanded Food Quality Through Extrusion Die Geometry and Processing Parameters

## TL;DR

This study explores how die geometry and processing parameters affect the quality of extruded expanded foods using CFD simulations and experiments.

## Contribution

The study introduces an integrated CFD and extrusion process approach to optimize die design and process parameters for food quality.

## Key findings

- An optimal die configuration of 14 nozzles with L/D = 1.25 minimized flow variance and ensured stable flow.
- Screw speed and moisture content significantly influenced water absorption and solubility indices.
- Moisture and temperature were key factors affecting bulk density and starch gelatinization.

## Abstract

Quality regulation of extruded expanded foods represents a critical technological challenge in this field. Current research has predominantly focused on the impact of extrusion processing parameters, largely overlooking the regulatory role of die structure. This study presents an integrated “CFD + Extrusion Process” methodology to systematically explore the effects of die design and process conditions on expanded product quality. Computational fluid dynamics (CFD) simulations evaluated the influence of nozzle number (12–15) and L/D ratio (1.25–2.5) on flow uniformity, the CFD results identified an optimal die configuration of 14 nozzles with L/D = 1.25, which minimized flow variance (velocity variance: 1.09 × 10−5 (m/s)2; viscosity variance: 2.777 (Pa·s)2) and established a stable flow foundation. Building on this, the RSM-based experiments revealed how process parameters specifically fine-tune quality attributes: screw speed and moisture content significantly (p < 0.05) affected Water Absorption Index (WAI) and Water Solubility Index (WSI), whereas moisture and temperature were the dominant factors (p < 0.05) governing bulk density and starch gelatinization. The findings of this study can provide a theoretical reference for the precise control of the quality of expanded food products.