Irradiation disinfestation of stored cocoa beans

The relationship between effective dosages to induce mortality and sterility in several important storage beetles was investigated. To induce 100% mortality, doses ranging from 0.05 to 0.1 kGy require 4-7 weeks, 0.2-1.0 kGy need 1.5-3 weeks and 2.0 kGy require 1 week for Tribolium castaneum, Oryzaephilus surinamensis and Lasioderma serricorne, respectively. Only at 5.0 kGy did instant mortality occur in the insects tested. Total prevention of F1 progeny was achieved at the lowest dosage (0.05 kGy) for T. castaneum and O. surinamensis; for L. serricorne, the sterility level achieved was 92-99% for doses ranging from 0.05 to 1.0 kGy. Semi-pilot scale tests (12 months) were carried out to evaluate the efficacy of gamma irradiation to control insects (artificially infested L. serricorne and T. castaneum) and moulds in cocoa beans packed in either jute or laminated polypropylene or unlaminated polypropylene bags. Good control against insect infestations was achieved for the whole duration of storage. Laminated polypropylene afforded the best protection against insect reinfestation. Other than a change in moisture content, no changes in the physicochemical properties were observed in the flavour or in the total protein, soluble protein, amino acid and free fatty acid contents. 15 refs, 10 tabs