Prediction of pelleting outcomes based on moisture versus strain hysteresis during the loading of individual pea seeds

• The strain hysteresis was proposed for predicting some outcomes of pelleting.
• The energy loss during cyclic loading shows a strong relevance to the pellet processing.
• The control of plasticity of a pelleted material is crucial for the pelleting optimisation.
• An empirical model for the estimation of pelleting effects was introduced.

The pelleting of pea is related to some of the mechanical features of the seeds. Varying in moisture, intact seeds were assigned to unconfined loading–unloading with the help of a universal testing machine. Elastic and permanent strain energy and associated deformations were evaluated on the basis of load–displacement curves. In parallel, samples of pea at the same moisture levels were pelleted. The pelleting energy usage and pellet quality features, that is strength, durability, and bulk density, were tested for correlations with strain hysteresis data. Seed moisture and energy loss during the loading of a single seed showed a strong relevance to the processing and pellet properties. An observed increase in the proportion of non-recoverable strain energy, from 15.5 to 176.1 mJ, resulted in a significant decrease in all analysed pelleting features. The specific energy consumption decreased from 296.5 to 240.1 kJ kg−1. Bulk density and pellet strength SI decreased from 773.6 to 652.7 kg m−3 and 16.61 to 13.60 kN m−1, respectively. An empirical model was introduced for the estimation of pelleting effects as a function of seed plasticity. It was based on a hyperbolic formula, which proved to be accurate for the prediction of energy requirements for pelleting and the properties of pellets.