# Texture Phenotypes of Fiber-Enriched Extruded Snacks Revealed by Mechanical–Acoustic Analysis, Tribology, and Sensory Mapping

## TL;DR

This study explores how adding soybean residue to snacks changes their texture, using mechanical, acoustic, and sensory methods to better understand and improve their texture for consumers.

## Contribution

The study introduces a new framework combining mechanical, acoustic, and sensory data to characterize texture in fiber-enriched extruded snacks.

## Key findings

- Higher okara content leads to less crisp and louder snacks with smoother force profiles and lower acoustic amplitudes.
- Okara-rich snacks are perceived as harder and grittier, with reduced crunchiness and sound intensity.
- Tribology shows okara snacks require higher lubrication to transition from boundary to mixed lubrication during mastication.

## Abstract

Texture perception in extruded snacks is commonly evaluated using force-based measurements, although crispness-related oral sensations arise from fracture, sound emission, and lubrication during mastication. This study developed a mechanistically grounded framework for texture characterization of fiber-enriched extruded snacks by integrating instrumental and sensory analyses within an oral-processing context. Extruded snack samples containing soybean residue (okara; 0%, 29%, and 40%) and commercial benchmarks were evaluated using synchronized mechanical–acoustic testing (five-blade Allo-Kramer shear and three-point bending tests), oral tribology, and sensory evaluation combining intensity rating and ranking. Increasing okara content shifted fracture behavior from brittle, sound-emitting failure toward damped, progressive deformation with approximately 3–5-fold lower acoustic envelope amplitudes and smoother force–time profiles. These changes corresponded to lower perceived Crunchiness and Sound Intensity, reflecting diminished crispness-related perception, and higher Hardness and Grittiness/Coarseness attributes (increases of ~25–45%). Oral tribology revealed cohesive, poorly lubricated boli for okara-rich snacks, requiring higher entrainment parameters (Uη0 ≈ 1.0 × 105–3.5 × 105) to transition from boundary to mixed lubrication compared with commercial benchmarks (Uη0 ≈ 7.0 × 104–2.0 × 105). Convergent multivariate analyses established instrumentally defined texture phenotypes that translate mechanical–acoustic and tribological signatures into sensory-interpretable texture categories, providing a practical framework for discriminating and optimizing nutritionally enhanced extruded snack products.