A systemic approach of qualitative changes in the stored wheat ecosystem: prediction of deterioration risks in unsafe storage conditions in relation to relative humidity, infestation by Sitophilus oryzae (L.), and variety influence

A multidimensional laboratory trial was carried out to identify how key overall quality traits of different common wheat varieties change during storage, to understand their interactions in the process of deterioration, and finally to reveal underlying trends of critical storage conditions that may endanger grain quality. A large set of qualitative criteria were followed on grain batches of three wheat varieties with various qualities for food processing, which were stored for 160 d at 22-23°C, under two different relative humidities (r.h.), and with or without infestation by the rice weevil Sitophilus oryzae. All variables involved in quality components assessment were recorded at 42-d periods. From the Pearson’s product moment correlation matrix, it was observed that the quality traits that correlated significantly to biotic variables (insect and fungal species dynamics) were: moisture content, hL mass, seed viability, and fat acidity of extracted flour. The interactions between biotic deteriorative factors and qualitative trait changes revealed through principal component analysis (PCA) were significant between four factors explaining the major part of qualitative criteria variance: storage duration; moisture content; hidden infestation density; fungal contamination level. The rate of increase of insect population was significantly different among varieties. PCA revealed that the significant difference in qualitative deterioration pattern among the three varieties was not related to their hardness, but to a different r.h. affinity. The germination rate was the qualitative criteria the more early declining during storage. The technological properties of extracted flour from each variety were significantly affected only when insect density exceeded 1000 insects per kg, a situation only observed in hot-spots. This work highlighted the trends of variation in quality traits of wheat varieties when stored under critical conditions. It can be used in IPM approaches to predict the susceptibility of a wheat variety to insect and fungi damage during storage. Keywords: Common wheat, Variety, Qualitative change, Insect pest, Fungal spoilage, Multivariate analysi