Biocontrol of insect-pests bruchid in postharvest storage of Vigna unguiculata grains: Process modeling, optimization, and characterization

Abstract

The modeling and optimization of postharvest preservation of Vigna unguiculata (cowpea) grain using hot aqueous extract of Syzygium aromaticum L. bulb (clove), and Myristica fragrans H. (nutmeg) fruit by employing three-level factorial-response surface methodology (3LF-RSM) was studied. Clove and nutmeg seeds were processed into flour and their active compounds were extracted by the infusion technique; and then lyophilized. The obtained extracts were used to control bruchid in stored cowpea. Infrared active functional groups in the extracts were identified using standard procedures. The optimal quantity of each extract (23.03 ml/kg grains) and a period of 1.95 days were established with the corresponding mortality rate of range 93.89%–99.20% for males and 96.82–99.90% for female bruchids in V. unguiculata. Functional groups evaluation showed the presence of –OH (from phenol), N–H (amide), C꞊O (amide, and ketone), C–O (ether), C–Cl (aryl-chloride), and C–I (aryl-iodide) in the extracts whereas, treated cowpea grains had –OH (phenol, carboxylic acid), N–H (amide and amine), CN (nitrile), CC (alkaynal), C꞊O (carboxylic acid, ester, amide, and ketone), C–F (aryl-fluoride), C–O (ester, and phenol)), C–Cl (aryl-chloride), and C–I (aryl-iodide). The functional groups in the extracts were concentrated in the fingerprint region. Aryl-halides of chlorine and iodine and ether were identified in the extracts as the active functional groups responsible for the pesticide attributes. The treated grains had an amylose range of 28.92–29.49% and good pasting properties which could make it find application as a thickener in food formulation and allied processes; it has low gel breakdown and low retrogradation tendency.