The postharvest of the giant bean, called "pajuro" (Erytrhina edulis) in Peru has rarely been described; however, it is of great economic importance. Traditionally, this bean is consumed in two stages of maturity (green and ripe). After harvest, and depending on environmental conditions, these legumes are dehydrated to be stored for long periods of time. The present work was developed with the objective of evaluating the change in shape and color by image analysis. The changes are due to dehydration and are accentuated during storage, which was at room temperature in the city of Jaén (Peru). The images were collected at a distance of 10 centimeters between the smartphone and the plane with a Huawei P30 lite smartphone with a 24 MP front camera. The angle between the direction of the photo with the plane was 90°. Image processing was performed with ImageJ software (ImageJ-win64 software, USA). The specific parameters were the change in projected diameter and changes in "integrated density". Postharvest changes evidenced rapid dehydration manifested by drastic weight losses (>95%), while the projected area decreases by about 40%. The sample darkened, which was reflected especially in the reduction of the integrated density (~21, near zero is totally dark) and the "G" parameter, which implies that the samples reflect less and less green color and absorb less and less of the complementary color. Based on the results we can further study image analysis techniques for fast and low-cost quality control.