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Low-Pressure Ozone Injection System: Relationship Between Reaction Kinetics and Physical Properties of Grains.

BACKGROUND
Ozonation of grains in a closed system at low pressure is a strategy with the potential for treating packaged products. Scientific investigations are fundamental to characterize the reaction kinetics of ozone in this type of injection system. That way, it will be possible to design chambers and determine the ozone concentrations suitable for commercial-scale applications. Therefore, the objective of this study was to characterize the low-pressure ozone injection system in relation to the physical properties of the grains and determine possible changes in their quality. Five-kilogram samples of common beans, cowpea beans, corn, popcorn kernels, paddy rice, and polished rice were exposed to ozone in a 70-liter hypobaric chamber. Initially, the internal pressure of the chamber was reduced to 500 hPa. Then, ozone was injected at a concentration of 32.10 g m-3 at a volumetric flow rate of 1 L min-1 until reaching a pressure of 1000 hPa. To relate the decomposition of ozone with the evaluated grains, different physical properties were determined, in addition to quality analyses.


RESULTS
In this study, it was possible to observe that ozone gas half-life outside and inside the package depended on the grain type. Ozone decomposition was the fastest in polished rice and the slowest in common beans. The half-life in the different grains ranged from 17.8 to 52.9 and 16.4 to 52.9 min, outside and inside the package, respectively. Considering the physical properties, specific surface (Ss), surface area (SA), and sphericity (φ) exhibited a significant correlation with the decomposition rate constant (k) of ozone. However, the variables volume (V), permeability (K), porosity (ε), and specific mass (ρ) showed no correlation with k.


CONCLUSION
Grain physical properties influence the reaction kinetics of ozone gas during the low-pressure injection process. Ozone gas injection at low pressures does not alter the quality attributes of the grains under study. This article is protected by copyright. All rights reserved.