Evaluation and modelling the mechanical damage to cowpea seeds under impact loading

Abstract

Mechanical damage of seeds due to harvest, handling and other process is an important factor that affects the quality and quantity of seeds. Mechanical damage to the cowpea seeds with moisture contents of 9.65 to 25% (wet basis) at four impact velocities from 7.5 to 15 m/s, was evaluated using an impact damage assessment device. The results showed that impact velocity, moisture content, and the interaction effects of these two variables significantly influenced the percentage physical damage in cowpea seeds (P<0.01). Increasing the impact velocity from 7.5 to 15 m/s caused a significant (P<0.05) increase in the mean values of damage from 4.42 to 33.58%. The mean values of physical damage decreased significantly (P<0.05) by a factor of 2.77 (from 29.56 to 10.64%), with increase in the moisture content from 9.65 to 20%. However, by a higher increase in the moisture from 20 to 25%, the mean value of damage showed a non-significant increasing trend. There was an optimum moisture level of about 20%, at which seed damage was minimised. An empirical model composed of seed moisture content and velocity of impact was developed for accurately description of the percentage physical damage to cowpea seeds. It was found that the model provided satisfactory results over the whole set of values for the dependent variable.