Use of the Triple-Layer Hermetic Bag against the Maize Weevil, Sitophilus Zeamais (Mots) in Three Varieties of Maize

Maize ranks with wheat and rice as one of the world’s chief grain crops. However, the safety of this important food crop is threatened by pests such as insects, rodents and moulds which results from inappropriate storage methods. Insect pest infestation accounts for about 20-50% of all food crop losses. This study was carried under ambient laboratory conditions of 32± 2oC and 72-88% r.h to determine the effectiveness of the triple-layer hermetic bag in controlling the maize weevil Sitophilus zeamais (Mot) on three varieties of maize (Obatampa, Abrodenkye and Kamangkpong). Five (5) kilograms of each variety with three replicates were infested with 50 S. zeamais and stored for three (3) months in three different types of bags (hermetic, Polypropylene and Jute). Destructive sampling was done monthly to determine the moisture content, viability of each variety and weight loss after storage. Percentage damage of grain due to S. zeamais was assessed on the different types of storage bags. The results show that the high yielding Obatampa was more susceptible to S. zeamais than the two local varieties; Abrodenkye and Kamangkpong. Damage, weight loss and germination rates were significantly (p  higher in the polypropylene and jute bags than the hermetic bags. These were also dependent on the length of storage. The triple-layer hermetic bags were effective against S. zeamais and could be used for storage of maize. Keywords: Maize weevil, Sitophilus zeamais; Triple-layer hermetic bag; Polypropylene; Jute

Evaluation of the impact of nitrous oxide use on quality and shelf life of packaged fresh-cut 'iceberg' lettuce and wild rocket

Shelf life of fresh-cut salad is limited by deterioration of quality characteristics during storage. The objective of this study was to assess the potential of the use of non conventional nitrous oxide gas in maintaining the quality of fresh-cut 'Iceberg' lettuce (Lactuca sativa L.) and Wild rocket (Diplotaxis tenuifolia) under modified atmosphere packaging (MAP) in comparison to nitrogen gas. Leaves of rocket and cut 'Iceberg' lettuce were washed, dried and packaged fresh in two different non-micro perforated plastic film bags (polypropylene +polyamide, PP+PA and polypropylene + polyethylene terephthalate, PP+PET). The headspace of each pair of two plastic films was filled and sealed with three gas mix treatment compositions: (97 % N2O + 3 % O2), (50 % N2O + 47 % N2 + 3 % O2) and (97 % N2 + 3 % O2) for "Iceberg lettuce" and two gas mix treatments: (95% N2O + 5 % O2) and (95 % N2 + 5 % O2) for rocket leaves. Lettuce and rocket leaves were stored over a period of 9 days and 12 days respectively at 5 oC. Results showed that the two plastic films maintained the nitrous oxide concentration within the bags, with some slight differences in O2 and CO2 concentrations. No significant differences (p0.05) were observed in texture, colour, and sensory quality (off-odor, off-flavor, texture and overall acceptability). All treatments delayed microbial growth (mesophiles, yeast and mould, psychrophiles and enterobacteria) and compared to control in air, reduced weight losses in both rocket and lettuce. MAP treatments maintained very good quality and freshness of 'Iceberg' lettuce for 4 days. Slight increase in off-odor and off-flavor observed during storage were below the moderately acceptable limit even after 9 days. As for rocket, although quality characteristics of the leaves were lessening over the storage period, treatment with nitrogen gas in PP+PA bags seemed to maintain them slightly better than treatment with nitrous oxide gas. The results suggested that nitrous oxide gas does not improve quality compared nitrogen modified atmosphere storage