Ohmic Heating Destruction Kinetics of Clostridium sporogenes PA 3679 Spores in Low-Acid Foods: Case Study of Concentrated Maple Sap

Abstract Food such as concentrated maple sap is prone to microbial contamination during collection, handling and transport, requiring effective processing to ensure safety. Conventional thermal treatments can compromise nutritional quality, sensory and physicochemical properties. Ohmic heating (OH) offers a promising alternative green process with valuable benefits while preserving food quality, reducing energy consumption and greenhouse gas emissions. This study evaluates Clostridium sporogenes PA 3679 destruction rates as a surrogate for low-acid (pH 7.9) concentrated maple sap (10, 20 and 28.5°Brix) at different temperature (95–121 °C) under direct OH at a voltage gradient (V g ) of 90 (V/cm). A nonlinear microbial death rate was observed with a sharp spore inactivation during come-up time (CUT) due to high applied V g , followed by a tailed lag during holding time at a lower V g . This profile likely caused a change in spore protein structure that resulted in a change of spore inactivation rate due to the synergistic effect of the thermal and electrical field. The survival data were fitted to various primary kinetic models (Weibull, log-linear model, Gompertz and sigmoid). The Weibull model provided the best fit (δ: 0.010–0.446; β: 0.238–0.408; adj-R 2 : 0.891–0.934), yielding equivalent D-values ranging from 0.21 to 3.3 min across different temperatures (95 to 121 °C) and media tested. Imaging using transmission electron microscopy and scanning electron microscopy revealed distinct structural destruction changes of C. sporogenes spores under rapid CUT as a result of electrical-thermal shock during OH. These findings offer a scientific basis for designing safe pasteurization or sterilization processes for food products such as concentrated maple sap, fruit juices and milk using a green emerging technology such as OH.