A Review of Grain Kernel Damage: Mechanisms, Modeling, and Testing Procedures

Abstract

HighlightsPublished literature on grain kernel damage during handling is reviewed.Types and sources of grain kernel damage are discussed.Factors affecting the level of grain kernel damage are outlined.Models to predict grain kernel damage and corresponding test devices are summarized.Abstract. Grain kernel damage during harvest and handling continues to be a challenge in grain postharvest operations. This damage causes physical and physiological changes to grain, which reduces the grain quality and leads to significant yield loss. During harvesting and handling, grain kernels are subject to complex loading conditions consisting of a combination of impact, shear, and compression forces. The main damage mechanisms include impact, which causes external and internal cracks or even fragmentation of the kernel; attrition, which generates fine material; jamming, which deforms and breaks kernels due to high compressive forces; and fatigue, which produces broken kernels and fine material via repeatedly applied loads. Grain kernel damage accumulates as the grain moves through harvesting and handling operations. Harvesting is the major cause of cracks and breakage, while conveying after drying produces fine material. This article provides a comprehensive review of the types of grain kernel damage, sources of grain kernel damage, factors affecting damage, predictive damage models, and the experimental methods used to assess the damage. This review shows that although there is considerable empirical data focused on kernel damage, there is a lack of generalizable mechanics-based predictive models. Mechanics-based models are desirable because they would be useful for providing guidance on designing and operating grain handling processes to minimize kernel damage and thus improve grain quality. In addition, several damage models developed for non-grain particulate materials based on fracture mechanics are reviewed. With some modifications and detailed property analysis, there is potential for adapting the models developed for inorganic materials to predict grain kernel damage. Keywords: Grain kernel damage, Grain harvesting and handling, Breakage susceptibility, Grain damage prediction.