# Conching chocolate: A prototypical transition from frictionally jammed solid to flowable suspension with maximal solid content

## TL;DR

This paper investigates how mechanical energy and surfactant addition during chocolate conching can transition a jammed solid into a flowable suspension, increasing the maximum solid content achievable.

## Contribution

It demonstrates how energy input and staged surfactant addition shift the jamming point, enhancing flowability in powder-liquid dispersions.

## Key findings

- Mechanical energy input increases flowability.
- Staged surfactant addition shifts jamming volume fraction.
- Enhanced maximum solid content in chocolate suspension.

## Abstract

The mixing of a powder of 10-50{\mu}m primary particles into a liquid to form a dispersion with the highest possible solid content is a common industrial operation. Building on recent advances in the rheology of such 'granular dispersions', we study a paradigmatic example of such powder incorporation: the conching of chocolate, in which a homogeneous, flowing suspension is prepared from an inhomogeneous mixture of particulates, triglyceride oil and dispersants. Studying the rheology of a simplified formulation, we find that the input of mechanical energy and staged addition of surfactants combine to effect a considerable shift in the jamming volume fraction of the system, thus increasing the maximum flowable solid content. We discuss the possible microscopic origins of this shift, and suggest that chocolate conching exemplifies a ubiquitous class of powder-liquid mixing.