Effect of infestation with Callosobruchus maculatus on the GC/MS chemical constituents and minerals of cowpea seeds

Abstract

• The effect of cooking and insect infestation on cowpea seeds was studied. • We found volatiles characteristic of raw, infested and infested cooked beans. • GC-MS is used to determine these volatiles characteristic. • These volatile compounds can be used to detect infested cowpea. • Mineral content was also modified by infestation and cooking. Poor storage of cowpea seeds causes the infestation of store pests, and consequently, the quality of the seeds decreases in quantity and quality. Therefore, continuous detection of the infestation has become necessary. Cowpea is one of the most economically essential legumes in different world areas. Cowpea is severely damaged in the store by the cowpea storage pest, Callosobruchus maculatus (Fab.), and early detection of insect infestation is essential for implementing timely and effective pest management decisions to protect them. The effect of insect infestation with Callosobruchus maculatus on the chemical composition of cowpea seeds ( Vigna unguiculata ) and mineral content was studied. The volatile compounds were analyzed and identified by gas chromatography-mass spectrometry (GC–MS) for the raw (non-infested), cooked, infested, and cooked cowpea seeds and the adult insect of C. maculatus . GC–MS analysis results showed that six volatile compounds were identified from raw cowpea seeds and only three from cooked ones. (9,12- Octadecadienoic acid, methyl ester) was identified in cooked seeds but not detected in raw seeds. Eight volatile compounds were detected only in infested seeds with C. maculatus alone, and these compounds can be used for detecting C. maculatus in cowpea seeds. Two specific compounds, such as Stigmasterol, and Beta-Sitosterol, were detected in infested cooked cowpea seeds. In cowpea seeds, infestation caused a reduction in the concentration of Aluminum (Al) and Iron (Fe), while Manganese (Mn) increased either after or before the cooking. Without infestation, the cooking process alone decreased Al, Fe, and Mn concentrations.