Analysis of Heat and Moisture Transfer and Fungi-Induced Hot Spots in Maize Bulk with Different Broken Kernel Contents

Kernel breakage and fungi-induced hot spots can easily lead to potential safety hazards in maize storage. The objective of this study was to focus on the formation and development of hot spots in maize bulk with two different broken kernels contents (BKCs), i.e., 4.26% (BKC4.26) and 6.14% (BKC6.14), and a moisture content of 16.3% under the same storage conditions. A multifunctional simulation system was developed to simulate the heat and moisture transfer process in stored grain bulk, and a new method was proposed to evaluate the effect of local hot spots on the storage safety of maize bulk with different BKCs. The results showed that there are differences in fungal respiration rates in the maize bulk with two different BKCs, and the temperature impact range caused by hot spots under the same storage conditions was different. The maximum temperature caused by fungal growth in BKC4.26 and BKC6.14 was 37.47 °C and 38.81 °C, and the proportion of high-temperature areas caused was 64.2% and 62.3%. The relative humidity at local hot spots continued to decrease, reaching 64.8% and 71.7% when stored for 1800 h in BKC4.26 and BKC6.14. The CO2 concentration at hot spots in BKC6.14 was higher than that of BKC4.26, while the O2 concentration was lower than BKC4.26. Dry matter loss (DML) at the hot spots in BKC6.14 was higher than that in BKC4.26. A nonlinear model was developed to predict temperature changes of fungi-induced hot spots in maize bulk considering the storage time, temperature, relative humidity, and CO2 concentration at the hot spots, and the model fit the experimental data reasonably well.