Destructive and non-destructive mechanical characterisation of chocolate with different levels of porosity under various modes of deformation

Abstract

Chocolate exhibits a complex material response under the varying mechanical loads present during oral processing. Mechanical properties such as Young’s modulus and fracture stress are linked to sensorial attributes such as hardness. Apart from this link with hardness perception, these mechanical properties are important input parameters towards developing a computational model to simulate the first bite. This study aims to determine the mechanical properties of chocolate with different levels of micro-aeration, 0–15%, under varying modes of deformation. Therefore, destructive mechanical experiments under tension, compression, and flexure loading are conducted to calculate the Young’s modulus, yield, and fracture stress of chocolate. The values of Young’s modulus are also confirmed by independent ultrasonic mechanical experiments. The results showed that differences up to 35% were observed amongst the Young’s modulus of chocolate for different mechanical experiments. This maximum difference was found to drop with increasing porosity and a negligible difference in the Young’s modulus measurements amongst the different mechanical experiments is observed for the 15% micro-aerated chocolate. This phenomenon is caused by micro-pores obstructing the microscopic inelastic movement occurring from the early stages of the material’s deformation. This work provides a deeper understanding of the mechanical behaviour of chocolate under different loading scenarios, which are relevant to the multiaxial loading during mastication, and the role of micro-aeration on the mechanical response of chocolate. This will further assist the food industry’s understanding of the design of chocolate products with controlled and/or improved sensory perception.