Survival and development of stored product insects' eggs in baby food exposed to low oxygen


Abstract: Food industry has been increasingly using modified atmospheres for the protection of the packaged commodities from potential insect contamination in the product. This is especially so for foods which are sensitive to insect contamination like baby foods where packaging is carried out under nitrogen (N2). Canned packages were sealed and treated using N2 to achieve an initial concentration of 1% oxygen (O2). This concentration was shown to increase to 2.5% due to desorption of O2 from the commodity. The increase in customer complaints on presence of stored product insects in baby food formula led the manufacturer to the questions (1) whether adult insects can lay eggs in milk powder formula after its packaging at 1% O2; and (2) whether the eggs can develop at such low oxygen concentration. To answer those questions two sets of trials were made; (a) testing the egg stage of Lasioderma serricorne, Plodia interpunctella and Oryzaephilus surinamensis exposed to 2.5% and 6% O2 on baby food, containing mainly milk powder, that had equilibrium relative humidity of 46.6%, and (b) testing the survival of the adults of same insects and their ability to lay eggs at 2.5% and 6% O2. For the test purpose, adults of L. serricorne, P. interpunctella and O. surinamensis were reared at ambient air at 29 ± 1 °C and 65% ± 5 RH. Results show that eggs of the tested three species continued to develop after they were exposed to 6% O2. However, larvae could not survive the same oxygen concentration and no pupae neither adult’s stage were observed in the treated media. In an atmosphere containing 2.5% O2, eggs of L. serricorne and P. interpunctella failed to develop, but only O. surinamensis eggs hatched. The ability of adults of P. interpunctella to lay eggs was much higher than L. serricorne, in the same atmosphere. Whereas, adults of O. surinamensis failed to lay eggs in both O2 concentrations tested.

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