Читать книгу Dry Beans and Pulses Production, Processing, and Nutrition онлайн

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Dry beans must be aerated and monitored for temperature to reduce the accumulation of localized moisture during storage. High moisture beans (> 18%) will result in mold growth, which will lead to storage shelf‐life reduction and quality loss. Moisture migration and localized accumulation usually begins soon after harvest (typically initiated in the fall and continuing into the early stages of the winter season). As is typical in all stored grains, convection currents form within the grain mass as cooler weather causes air at bin walls to cool and settle, and warmer air to rise within the grain mass (Roberston and Frazier 1978). Condensation occurs when this warm air comes in contact with the cold grain and spoilage results. Convection air currents move within stored grain when declines in external temperatures chill the internal surfaces of the bin. Air near the bin walls is cooled and settles, causing the warmer air in the center of the bin to rise. When the warmer moist air from the center of the bin comes in contact with the cold grain at the surface, it is chilled, and moisture condenses on the upper bean layers. This moisture is absorbed by the beans in the surface layer, causing an increase in moisture content and resulting in mold growth, crusting, and spoilage. It is important that the bean mass is uniform and does not enable air current channelling. The scalping operation (pre‐cleaning) is essential to remove plant material, splits and fines that will likely cause disruption of airflow and inefficient and ineffective bean aeration. To provide uniform cooling and drying, duct systems located at the base of the bins are used (Uebersax and Siddiq 2012).