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Abstract Cold plasma sterilization is an emerging non-thermal technology that is receiving great attention in the food processing area. Plasma is a neutral ionized gas composed of reactive gas species that inactivate bacteria or spores in a variety of food materials without compromising the main physico-chemical characteristics of the food. Survival curves of Bacillus subtilis spores were obtained after spore strip samples containing an initial spore population of 1.5–2.5 × 106 cfu/strip were subjected to plasma treatment. The shape of the survival curves was clearly not linear indicating that spores exhibited a spectrum of inactivation resistances to the plasma treatment. A Weibull model was used to describe these curves. In order to capture the effects of the typical variability in the concentration of the inactivating reactive gas species during plasma processing, time-varying concentrations were incorporated in the calculating approach. The result was an ordinary differential equation (ODE) that was numerically solved using MATLAB. This approach was successfully applied to describe the survival of B. subtilis spores during plasma processing as well as data obtained from the literature for B. atrophaeus. Ozone was assumed the lethal reactive gas species responsible for spore inactivation. Industrial relevance Modeling plasma processing is of great interest because it may provide an accurate estimation of time and conditions required for a complete plasma-based sterilization process. Highlights • Experimental survival curves of Bacillus spores after plasma treatment are non-linear. • The concentration of reactive gas species during plasma treatment are not constant in the process. • Inactivation is better described by taking into account the change of the reactive gas with time. • Inherent varying concentrations of the inactivating gas species in the process are considered in the calculations. [ABSTRACT FROM AUTHOR]

Fat, oil and grease (FOG) blockages in sewer systems are a substantial problem in the United States. It has been estimated that over 50% of sewer overflows are a result of FOG blockages. In this work, a thorough laboratory study was undertaken to examine key variables that contribute to FOG deposit formation under controlled conditions. Physical and chemical properties and their interactions were evaluated and conditions that generated deposits that mimicked field FOG deposits were identified. It was found that 96 of the of 128 reaction conditions tested in the laboratory formed FOG deposits with similar physical and chemical characteristics as field FOG deposits. It was also found that FOG deposits can be created through fatty acid crystallization and not just saponification. Furthermore FOG deposits were found to be more complex than previously documented and contain free fatty acids, fatty acid metal salts, triacylglycerol's, diacylglycerol's and, monoacylglycerol's. Lastly it was found that FOG deposits that only contained saturated fatty acids were on average 2.1 times higher yield strength than deposits that contained unsaturated fatty acids. [ABSTRACT FROM AUTHOR]