Читать книгу Dry Beans and Pulses Production, Processing, and Nutrition - Группа авторов - Страница 75

Following harvest, beans are delivered to the elevator where samples are taken from each load to check for quality, color, and foreign material. All edible dry beans have a thin seed coat layer that is easily damaged in handling or drying. The bean moisture content is among the most important considerations following harvest (Rodiño et al. 2011; Bradford et al. 2018). Unless specific handling equipment is available, most farm operators should not consider moving beans to market if the moisture content is below 15% or above 18% (Maddex 1978). Most beans are harvested with combines, which results in direct mechanical damage to the beans in part due to impact loading. Mechanical damage can result from bean impact velocity, moisture content, temperature, and the size of bean.

It is essential to minimize seed coat checking and splitting during all stages of physical handling of dry beans (Aguilera and Rivera 1990). Bean seed coat damage is cumulative during each stage of handling from harvest to final distribution and preparation. Damage is most readily associated with mechanical dropping and shattering during conveyor transfers. Augers and poorly designed bucket lifts are particularly detrimental and result in high checked seed coats due to shearing action and fractional abuse to the seed. Conveyor belts that result in stationary aggregated beans during conveyance are superior to system designs in which “individual beans are dynamic” resulting in bean‐to‐bean and bean‐to‐conveyor abrasion.

Bean dropping has a profound influence on seed coat damage (Shahbazi et al. 2011). Emptying of combine bins into wagons or trucks and truck unloading during elevator receipt can result in severe bean impact. The filling of bins and silos or dumping into free‐standing piles are areas where significant seed coat damage may occur. It is recommended that minimum drop distances be maintained. It is recommended to establish a continuous flow from truck to bean pile rather having beans striking floors or grates when pit dumping. The length of drop into the bin is critical to control seed coat damage. Bean ladders are used to reduce the “free fall of beans” when they are filled into the storage facility. Construction of bean ladders within bins and silos enables beans to descend by sliding on a spiral ramp to levels ranging from the floor to any subsequent elevation within the storage structure.

Conveyor belts are used to move beans in and out of storage to reduce damage that may occur with auger conveyors. Although belt conveyors are more expensive than general grain handling augers, the reduction in damage typically makes the investment worthwhile. Belt conveyors for under‐bin‐flow unloading or for replacement of augers in dryers are custom‐made items. Belt conveyors are usually larger in size than auger conveyors thus require additional space (Uebersax and Siddiq 2012).