Numerical study of rusk checking during storage

Abstract

Checking is a recurring problem in the dry cereal products industry which involves hydromechanical and thermomechanical phenomena. This study focuses on the hydromechanical problem at constant temperature. The objective is to develop a model giving access to stress and the resulting strain fields in a rusk undergoing moisture equilibration during a 7‐day storage period in closed packaging to understand how checking occurs. A model was developed and implemented with Comsol Multiphysics. The effect of cells and the shape of the rusk on the stress field is investigated. Set‐ups were designed to determine the model parameters. Simulations showed that the rusks undergo shrinkage caused by moisture equilibration. Stresses reached maximal values around the cells of the matrix. The stress field varied significantly with the shape of the rusk. Practical Applications Checking in dry cereal products is a recurrent problem that has not yet been solved for many products, as it depends on the formulation of the latter and the processes used. Rusks, in particular, are subject to this phenomenon. This work provides elements for understanding the checking mechanism. It provides guidance to manufacturers on how to modify their processes to reduce the proportion of rusks that crack during storage.