Romenique da Silva de Freitas

Effects of ozone fumigation treatment on the removal of residual difenoconazole from strawberries and on their quality

The effect of ozone fumigation on the reduction of difenoconazole residue on strawberries was studied. Strawberries were immersed in 1.0 L of aqueous solution containing 400 μL of the commercial product (250 g L−1 of difenoconazole) for 1 min. Then, they were dried and exposed to ozone gas (O3) at concentrations of 0.3, 0.6 and 0.8 mg L−1 for 1 h. The ozone fumigation treatments reduced the difenoconazole residue on strawberries to concentrations below 0.5 mg kg−1, which corresponds to a 95% reduction. The strawberries treated with ozone and the control group, which was not treated with ozone, were stored at 4°C for 10 days. Some characteristics of the fruit were monitored throughout this period. Among these, pH, weight loss and total color difference did not change significantly (P > 0.05). The fumigation with ozone significantly affected the soluble solids, titratable acidity and ascorbic acid content (vitamin C) of the strawberries preventing a sharp reduction of these parameters during storage.

Quality of beans stored under hermetic conditions

Este trabalho teve por objetivo avaliar a qualidade de feijao (Phaseolus vulgaris L.), armazenado com diferentes teores de agua, sob condicoes hermeticas. Feijao com teores de agua de 12,3%, 15,7% e 17,8% foram acondicionados em silos tipo bolsa (3 kg), garrafas pet (1,5 L) e recipientes de vidro (3 L), cobertos com organza (controle) e armazenados a temperatura de 25 oC e umidade relativa de 70±5%, por 120 dias. Avaliaram-se o teor de agua, a massa especifica aparente, a condutividade eletrica, a porcentagem de germinacao, o tempo de coccao e a classificacao do feijao, a cada 30 dias. A excecao da condutividade eletrica e do tempo de coccao, as demais caracteristicas foram mantidas por 120 dias no material armazenado com teores de agua de 12,3% e 15,7%, em condicoes hermeticas. No produto armazenado com 17,8%, ocorreu aumento no teor de agua, condutividade eletrica e tempo de coccao, e reducao na massa especifica aparente e na germinacao. No controle, independentemente do teor de agua, o material apresentou acentuada perda de qualidade ao longo do armazenamento. Concluiu-se que e possivel armazenar feijao com teores de agua de 12,3% e 15,7%, com qualidade, por ate 120 dias, em condicoes hermeticas.

Desenvolvimento do método de extração sólido-líquido com partição em baixa temperatura para determinação de inseticidas em grãos de milho ozonizados

The objective of this study was to optimize and validate a solid-liquid extraction method with low-temperature partitioning (SLE/LTP) for the analysis of pesticides. This method was coupled with gas chromatography (GC/ECD) and used to evaluate the degradation of bifenthrin and pirimiphos-methyl in maize grains on exposure to ozone. The optimized SLE/LTP-GC/ECD method is simple, effective and consumes low quantities of the solvent. It can be routinely used for the determination of bifenthrin and pirimiphos-methyl in maize samples. The use of this method of analysis determined that the levels of the insecticides in maize grains were reduced on exposure of the grains to the ozone gas. The observed reduction in the levels of insecticide was directly proportional to the increase in the concentration of the ozone gas.

Bioactivity of diatomaceous earth to Sitophilus zeamais (Coleoptera: Curculionidae) in different application conditions

The objective of this study was to evaluate the insecticidal activity of diatomaceous earth (DE) at different ambient temperatures on adult Sitophilus zeamais and progeny, using different doses and exposure periods. The experiments were performed in Petri dishes containing 40 g of the whole corn kernel, treated with DE at doses of 0, 0.25, 0.5 and 1.0 kg Mg-1. Each dish was infested with 25 S. zeamais adults and kept at climatic chambers under temperatures of 20, 25, 30, 35 and 40 oC. The insect mortality was recorded after six and 15 days from the beginning of the bioassays. The grains evaluated at 15 days were separated from insects and kept in the dishes for another 75 days under the same temperature conditions. After this period the effect of ambient temperature and of diatomaceous earth doses on the emergence of S. zeamais in the F1 generation was evaluated. It was found that the mortality of S. zeamais increased with the higher dose and temperature during the exposure period of six and 15 days. The number of insects emerged reduced with increasing temperature in these two exposure periods. The increase of temperature and exposure period favored the efficacy of DE in lower doses for control of S. zeamais.