Effect of combined zinc oxide nanoparticles using citric acid and microwave heating on the quality of animal fat

The processing method of animal fat as a non-negligible food resource has attracted attention. ZnO nanoparticles (ZnONPs) are a widely studied inorganic antimicrobial agent. In this paper, citric acid modified ZnO nanoparticles (CA-ZnO) were prepared using citric acid for surface modification of ZnO nanoparticles. The surface modification reduced the agglomeration of ZnONPs in the water, and the particle size of CA-ZnO particles was reduced by about 4 times compared to the ZnONPs after dispersion in the water. CA-ZnO also showed a good inhibitory effect against Bacillus cereus, Escherichia coli, and Staphylococcus aureus at the concentration of 0.05 g/kg. Microwave heating combined with CA-ZnO (MCCZ) had a good bactericidal effect and disrupted the integrity of bacterial cell membrane leading to leakage of cell materials and altering the secondary structure of bacterial proteins such as the reduction of α-helix. Using this method for sterilization of animal fats (a mix of same amount of chicken oil and lard), the sterilization rate of animal fats reached 99.97% after 90 s of MCCZ treatment. And MCCZ resulted in less flavor change and quality deterioration compared to traditional high temperature treatment. Therefore, MCCZ could be used as a new method to preserve the product quality of mixed chicken oil and lard.