Читать книгу Dry Beans and Pulses Production, Processing, and Nutrition - Группа авторов - Страница 78

Dry beans are commonly stored in a wide variety of structures constructed as wood cribs, concrete silos, or steel bins. These vary based on the availability of existing infrastructure and general market conditions. Concrete silos have been noted for their capacity, structural strength, and general mass. These facilities resist rapid temperature change, which impacts the internal temperature of both the beans and the interspatial air. Storage facilities, particularly in northern latitudes, are exposed to the heat of the southern sun, and such surface heating will cause differential temperature changes within the stored beans and result in moisture migration and localized regions of high moisture spoilage. Concrete has been demonstrated to resist this temperature gradient better than other materials (Roberston and Frazier 1978; Maraveas 2020).

Economical flat‐storage, in which beans are piled on a reinforced concrete floor, has gained popularity due to the availability of free‐span pole building construction, rapid and flexible filling with adequate control of seed coat checking and splitting, and a high capacity to cost benefit ratio. It is noted that this technique requires beans of stable moisture content, and full knowledge of the angle of repose (which is the naturally self‐aligning angle that the bean pile assumes). Exceeding this angle will result in lateral pressure and cause cascading avalanches that can readily damage or destroy the side walls of the facility (Uebersax and Siddiq 2012).

Steel bins are arguably the most common and are available in different sizes (height and diameter). These are used in both elevator and on‐farm systems. Steel bins are relatively simple and can be easily installed on site. They are positioned on a poured support footing, and side walls are made by bolting curved sections of corrugated steel into place to form a circular bin structure. Successive tiers are added to the designated height, and a steel roof cap is bolted in place. These bins are equipped with mechanical aeration systems and belt conveyors that deliver beans into and out of bins. All of these facilities are equipped with bean ladders (generally, a spiral chute or alternating plates in a zig‐zag formation) that allow the beans to descend into the silo or bin with minimum damage (Roberston and Frazier 1978).

Dry beans may be stored in pallet‐sized tote boxes constructed of either wood, cardboard, or polypropylene sacks each containing up to one ton of product. These systems provide direct and flexible handling (using a forklift truck) of small lots without excessive bean movement, thus reducing seed coat checking. It is common for beans with highly differentiated quality standards, such as dark and light kidneys, cranberry, and the limited quantities of specialty beans such as yellow eyes, soldier bean and heritage varieties to be handled on‐farm and in local elevator facilities using individual tote storage and handling. Totes may be carefully off‐loaded to bagging systems or shipped directly to the end users (Roberston and Frazier 1978; Uebersax and Siddiq 2012).