Study of the impacts of electro-activated solutions of calcium lactate, calcium ascorbate and their equimolar mixture combined with moderate heat treatments on the spores of Bacillus cereus ATCC 14579 under model conditions and in fresh salmon

Abstract

Widespread in very diverse environments, the spores of Bacillus cereus are highly resistant to hostile conditions and can contaminate a huge variety of food products, posing a potential health hazard to consumers. Given this significant risk, the objective of this research work was to study the impacts of electro-activated solutions (EAS) made with calcium ascorbate, calcium lactate, and their equimolar mixture on Bacillus cereus ATCC 14579 spores in model conditions and food matrix, the fresh Atlantic salmon. The model conditions consisted of a direct application of the EAS to the spores, which avoided any interference with factors external to those of the solutions. Salmon was chosen as a food model because it is a product sensitive to bacterial spoilage and can be eaten raw. To achieve this, the solutions were prepared by electro-activation using an electric current with an intensity of 750 mA for 30 min, resulting in mean pH values of 1.94 ± 0.15–2.16 ± 0.01 and titratable acidity of 0.102 ± 0.001–0.109 ± 0.001 mol/L, depending on the type of solution. These conditions were chosen because of their excellent antibacterial efficacy previously demonstrated against vegetative cells of B. cereus. The results showed high sporicidal activities of the EAS against B. cereus with a 7 to 9 log reduction, using an initial spore population of 109 CFU/mL, depending on the conditions evaluated, namely: in direct contact (2–30 min), in salmon used as a food matrix (2–7 min), and in combination with moderate heat treatments from 60 to 90 °C (0.5–2 min). In addition, it was observed that the sporicidal capacity of the EAS increased with temperature and the contact time. Otherwise, analysis of the color and lipids of the salmon have not shown any major impacts of the use of EAS as a rinsing solution for this highly perishable food. Furthermore, micrographs taken by scanning and transmission electron microscopy revealed the destructive effects of the EAS used in the vital structures/components of the spores. In general, this study has demonstrated that the electro-activation technology is effective in producing EAS capable of destroying/inactivating B. cereus spores and that they can be used for the improvement of food safety and preservation.