Controlled atmosphere storage of brown cowpea under nitrogen

Laboratory studies were conducted to investigate the efficacy of the long-term controlled atmosphere storage of brown cowpeas under nitrogen in Kano, Nigeria, where hot dry weather prevails, typical for a semi-arid zone. The 30-month storage trial consisted of the application of nitrogen in an experimental 0.65 m3 mini-silo containing half a tonne of the commodity. The storage in nitrogen completely suppressed insect infestation, and grain quality was maintained during the period. There was a significant difference (P < 0.05) in the population of insects in the cowpea stored under nitrogen, and the control. The initial insect population of 15 adults of C. maculatus, and one adult of T. castenium per kg of cowpea died after 12 months of storage under nitrogen. They however, increased in the control to 1288, and 54 adults per kg respectively before their eventual death. Free fatty acid contents increased from 2.60% to 6.51% under nitrogen, but increased rapidly to 58.60% in the control cowpea. This was attributed to the action of insect activities, mould infection and water activities in the control cowpeas. Viability dropped slightly from 89.75% to 72.84% in nitrogen, but dropped rapidly to 0.00% in the control. The palatability of cowpea did not change adversely in nitrogen, whereas it became very poor in the air-stored commodity. The germinability of cowpea seeds stored in the inert atmosphere silos was maintained above 85% after 12 months of storage, which shows that the technology is effective for seeds storage