Ozonation of Brazil Nuts in Aqueous Media at Different pH Levels: Ozone Decomposition, Aspergillus flavus Inactivation, and Effects on Nut Color and Crude Oil Lipid Profile

Abstract

ABSTRACT The present work aimed to evaluate the decomposition kinetics of ozone in aqueous media with Brazil nuts. It also intended to investigate the potential of ozonation for inactivating Aspergillus flavus, and to determine changes in nut color and crude oil lipid profile. To do so, an inlet ozone concentration of 13.0 mg L−1, at a flow rate of 1 L min−1 and 25°C, was adopted. For the ozonation process, distilled sterilized water at the pH levels of 8.1, 7.1, and 3.0 was used. The second-order kinetic model was fit to the residual ozone concentration data. To evaluate the effect of ozonation on A. flavus, the treatment was performed for 120 min at the different water pH levels aforementioned. The quality of Brazil nuts was appraised by analyzing their moisture content, as well as their color and the lipid profile of the crude oil. The sharpest decrease in the ozone concentration was noticed at pH 3.0, at which the ozone within the medium with Brazil nuts displayed a half-life of 16.14 min. At the pH levels 7.1 and 8.1, the half-life values were equal to 37.42 and 188.54 min, respectively. The A. flavus count reduced by 1.25 and 1.28 log cycles, when the water was ozonated at the pH levels of 7.1 and 3.0, respectively. Despite promoting some color alteration in the nuts, the ozonation did not change the fatty acid profile of the crude oil. In conclusion, the second-order kinetic model satisfactorily represented the ozone decomposition in aqueous media containing Brazil nuts. Moreover, as the pH reduces, there is an increase of the initial concentration of ozone dissolved in aqueous media in the presence of Brazil nuts and, consequently, a trend of reduction of the ozone half-life. The ozonation proved to be more efficient at controlling A. flavus in Brazil nuts when performed in an aqueous medium with an acid pH.