Processo de ozonização de amendoim (Arachis hypogaea L.): cinética de decomposição, efeito fungicida e detoxificante de aflatoxinas e aspectos qualitativos

• Autor(a) principal: Alencar, Ernandes Rodrigues de
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/667
• topic: Ozônio; Detoxificação; Segurança alimentar; Qualidade; Ozone; Detoxification; Food safety; Quality; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA::ENGENHARIA DE PROCESSAMENTO DE PRODUTOS AGRICOLAS

The objective of this study was to evaluate decomposition kinetics of ozone gas, the effect of this gas as a fungicide agent and detoxificant against aflatoxins and possible quantitative alterations on peanuts and crude oil extracted from these nuts after undergoing the ozonation process. This study, performed in the Sector of Pre-processing and Storage of Agricultural Products pertaining to the Department of Agricultural Engineering and the Laboratory of Packaging of the Department of Food Technology, both of the Universidade Federal de Vicosa, was composed of three stages. In the fist stage, decomposition kinetics of ozone was evaluated using 1 kg peanut samples with moisture contents of 7.1 and 10.5% (w.b.), stored in 3 L glass recipients. The peanuts were ozonized at the concentration of 450 μg L-1, at temperatures of 25 and 35ºC and gas flows of 1.0 and 3.0 L min-1. Saturation time was determined and residual concentration of ozone was quantified by the iodometric method after passing the gas through the peanut mass until becoming constant. Decomposition kinetics of ozone was evaluated after saturation of the peanut mass with the gas. A residual concentration of ozone was obtained, followed by repose periods in which the gas reacted with the porous medium and was therefore decomposed. The first order kinetic model was adjusted to the data for residual ozone concentration in function of time, after linearization. From the values of the decomposition rate it was possible to obtain a half-life for ozone in peanuts. In the second stage, peanuts with moisture contents of approximately 9.0% (w.b.) were exposed to ozone gas for evaluation of its effect as a fungicide and detoxifying ability on aflatoxins. In the ozonation process, concentrations of 13 and 21 mg L-1, temperature of 25 ºC, gas flow rate of 1.0 L min-1 and ozonation periods of 0, 24, 48, 72 and 96 h were used. The effect of ozone gas on the count of total fungi and the potentially aflatoxigenic species Aspergillus flavus and A. parasiticus was evaluated by the dilution technique, and in internal infection of peanuts by these microorganisms, by the direct plating technique. It was observed on the microscopic level that morphological alterations occurred in the fungi due to exposure to ozone gas. To evaluate detoxification effectiveness of ozone gas, in each combination of gas concentration and exposure period, the concentrations of total aflatoxins and aflatoxin B1 in the peanuts were quantified by high performance liquid chromatography. In the third stage, quality of the ozonized peanuts and crude extracted oil was evaluated. Peanuts with moisture contents of 8.0% (w.b.) were used, and the ozonation process utilized ozone gas concentrations of 0, 13 and 21 mg L-1, flow rate of 1.0 L min-1 and exposure periods of 0, 24, 48, 72 and 96 h. For treatment of the control, peanuts were exposed to oxygen gas. Evaluation of peanut quality consisted of analysis for moisture content, electrical conductivity of the solution containing the peanuts, lipid concentration and peanut color. The qualitative parameters of the crude oil extracted from the peanuts analyzed were the concentration of free fatty acids, peroxide index and iodine index. For the peanuts with moisture contents of 7.1% (w.b.), at the temperatures of 25 and 35°C and flow rates of 1.0 and 3.0 L min-1, the values obtained for ozone gas saturation time remained between 173 and 192 min, with a saturation concentration of approximately 260 μg L-1. For the peanuts with moisture contents of 10.5% (w.b.), a greater concentration of residual ozone gas was obtained at the temperature of 25°C, equal to 190 μg L-1. The greatest value obtained of half-life was equal to 7.7 min, for the peanuts ozonized at 25ºC, while for those with moisture content of 10.5%, at the temperature of 35ºC, halflife was 3.2 min. Ozone was efficient for the control of potentially aflatoxigenic fungi in peanuts, with reduction greater than three log cycles at the concentration of 21 mg L-1 and exposure period of 96 h. In general, there was no alteration in quality of the peanuts or crude oil extracted due to exposure to ozone. It was concluded that from the obtained results that the decomposition process of ozone gas in peanuts, the determining factor is temperature. A 10ºC temperature increase of the peanuts implicated a decrease of at least 43% on the half-live of the gas. Ozone is an important alternative for peanuts when referring to food safety since it is efficient in the control of potentially aflatoxigenic fungi and can actuate in the reduction of aflatoxin levels of the product. The ozonation process, at a concentration of up to 21 mg L-1 and for up to 96 h does not affect quality of peanuts and crude oil extracted from peanuts.