The effect of calcination conditions on the size and killing activity of CaO nanoparticles towards L. plantarum was studied in this paper. The results showed that CaO nanoparticles with a diameter of 20 nm could be obtained under the investigated conditions. The lethal effect of CaO nanoparticles after incubation of 6 or 24 h increased with increasing calcination time. Using CaO-SA, CaO-SB, and CaO-SC after a 24-h exposure, 2.25, 3.37, and 5.97 log L. plantarum were killed, respectively, at a concentration of 100 ppm. The current results show that the use of CaO nanoparticles as antibacterial agents has significant potential in food-relevant industries.

The antibacterial activity of MgO nanoparticles prepared by a sonication method was evaluated in this paper. The effect of calcination conditions on the size and antibacterial activity of MgO nanoparticles was investigated. MgO nanoparticles were characterized for purity (TGA), crystallinity and crystal size (XRD), particle size and morphology (TEM) and surface area (BET). Results showed that the smallest size of 6 nm could be obtained. The lethal effects of nanocrystalline MgO were evaluated on Lactobacillus plantarum. At a concentration of 100 ppm, the killing effect of MgO was close to 1 log reduction for L. plantarum after 24 h exposure. At 1000 ppm and 24 h exposure, the killing effect of MgO was more than a 2.8 log reduction. With the increase of calcination time, the lethal effect of MgO nanoparticles increased after 6 h or 24 h exposure at 100 ppm or 1000 ppm. 2.86 log and 2.89 log were killed at 1000 ppm after 24 h exposure using the sample MgO, sonication, A, and the sample MgO, sonication, B, respectively. When the sample MgO, sonication, C, was used, the lethal quantity of L. plantarum was increased to a 3.36 log reduction.