Harvest Moisture to Maintain Dry Edible Bean Quality
April 15, 2002
Kenneth Hellevang, Agricultural & Biosystems Engineering Dept., North Dakota State University
Six farmer cooperators and Bob Henson at the Carrington Research and Extension Center collected samples of pinto beans harvested at various moisture contents and harvest dates during the fall of 2001. The beans were evaluated for mechanical damage using a standard screening and visual separation procedure. The bean color was determined using a colorimeter.
The amount of mechanical damage observed at various harvest moisture contents is shown in Figure 1. The amount of mechanical damage generally increased as harvest moisture content decreased. There are so many factors that affect the amount of mechanical damage, that the relationship to moisture content probably cannot be determined more accurately with this type of field study.
The amount of mechanical damage occurring to navy beans at selected moisture contents in a laboratory tester as reported by a Canadian researcher is shown in Table 1. This recent research indicates that the amount of damage to navy beans increases substantially at moisture contents below 15%.
The effect of harvest date on pinto bean color (whiteness or lightness) is shown in Figure 2. Pinto beans harvested in late September were darker than those harvested at the beginning of September. The decrease from an L-value of 56 to about 53 is a noticeable darkening. The effect of harvest date on bean color should be studied further.
No trend was observed in the effect of pinto bean harvest moisture content on the lightness of the beans, Figure 3.