Ozone as fungicide in rice grains

Abstract

The fungistatic activity, especially during storage, can lead to rapid deterioration in the nutritional quality of grains, and reduce their use and disposal in industrial process due to contamination with toxins (aflatoxins and others). Among the technologies identified as promising in controlling these microorganisms, there is ozonation. The objective of this study was to determine the concentration and the saturation time of ozone gas in rice grains and set the effective ozonation disinfection time in filamentous fungi and yeast. Rice grains (14.3% w.b.) were inoculated with Penicillium spp. and Aspergillus spp. and, subsequently, ozonized at the concentration of 10.13 mg [L.sup.-1], under continuous flow of 1.0 L [min.sup.-1], in five periods of exposure (12, 24, 36, 48 and 60 h). Ozone gas concentration and saturation time in rice grains were 5.00 mg [L.sup.-1] and 13.97 min, respectively. There was a reduction of 3.8 log cycles (100%) in the count of yeasts and complete inhibition of fungal from the genera Aspergillus and Penicillium in ozonized grains.

A atividade fungiostatica pode, principalmente durante o armazenamento, levar a rapida deterioracao na qualidade nutricional dos graos e reduzir seu aproveitamento e inutilizacao em processo industrial pela contaminacao com toxinas (aflatoxinas entre outras). Dentre as tecnologias apontadas como promissoras no controle desses microrganismos se destaca a ozonizacao. Objetivou-se, com este estudo, determinar a concentracao e o tempo de saturacao do gas ozonio em graos de arroz e definir o tempo de ozonizacao eficaz na desinfeccao de fungos e leveduras. Graos de arroz (14,3% b.u.) foram inoculados com Penicillium spp. e Aspergillus spp. e posteriormente sua ozonizacao foi realizada na concentracao de 10,13 mg [L.sup.-1], em fluxo continuo de 1,0 L [min.sup.-1], em cinco periodos de exposicao (12, 24, 36, 48 e 60 h). A concentracao e o tempo de saturacao do gas ozonio nos graos de arroz foram de 5 mg [L.sup.-1] e 13,97 min, respectivamente. Observou-se reducao em 3,8 ciclos log (100%) na contagem de leveduras e completa inibicao para os fungos dos generos Aspergillus e Penicillium nos graos ozonizados.