Optimization of Storage Conditions of Cowpea (Vigna unguiculata L. Walp) Bagged Pics Containing Biopesticide (Lippia multiflora) Leaves by Factorial Design in Cote d’Ivoire

Abstract

This study aims to optimize storage conditions of two cowpea varieties grains in PICS bags containing leaves of Lippia multiflora. It was to assess, through a full factorial design, the effect of three factors (variety, biopesticide dose, storage duration) on the merchantability (moisture, water activity, mass loss, damages) and contamination levels of ochratoxin A (OTA), aflatoxin B1 (AFB1) and total aflatoxins (AFT) of cowpea grains during 8 months. The grains were collected from producers of the Loh-Djiboua region (5°50 'North 5°22' West). After the hulling, the grains have not undergone any treatment were sent to the laboratory for storage. The lots treated with leaves Lippia multiflora recorded lower values than those of control groups whatever the parameter studied. Indeed, the damages of grains are 7.60±0.16% and 39.66±1.77% respectively for the treated and control groups. Concerning mycotoxins, treated groups have concentrations of 4.01±0.06 µg/kg and 1.14±0.01 µg/kg respectively for OTA and AFB1. As against untreated groups have concentrations of 22.50±0.87 µg/kg and 8.41±0.48 µg/kg respectively for OTA and AFB1. These results reflect an action of leaves on insect activity and toxigenic molds. The results of full factorial design indicate that action of leaves of Lippia multiflora is independent the cowpea variety conserved. Furthermore, the mathematical model derived from this plan allows a prediction of values of parameters studied with Pearson coefficients (R2) equal to 0.99. Thus, the treatment with leaves Lippia multiflora of stock of cowpea has a positive impact on conservation of merchant and health quality of grains with a persistence up to 8 months. This inexpensive and easy to use treatment should be vulgarized among farmers.