Antimicrobial activity and mechanism of protocatechualdehyde against Alicyclobacillus spp. And its effect on apple juice physicochemical properties

Abstract

The contamination of apple juice by Alicyclobacillus spp. can cause enormous economic losses to juice enterprises. Protocatechualdehyde (PCA), as a natural polyphenolic compound, exhibits broad-spectrum antibacterial effects. This study investigated the antibacterial activity and mechanisms of PCA on Alicyclobacillus acidoterrestris DSM-3923, Alicyclobacillus acidiphilus DSM-14558, Alicyclobacillus acidocaldarius SD-4, and Alicyclobacillus contaminans YL-5. The results showed that PCA exhibited strong antibacterial activity against DSM-3923, DSM-14558, SD-4, and YL-5, with MIC values of 0.156, 0.625, 0.626, and 0.625 mg/mL, respectively. The antibacterial activity of PCA was better than that of common preservatives sodium benzoate or potassium sorbate at the same concentration, which showed PCA still has good antibacterial activity at the allowed additive amount. PCA caused lipid peroxidation on the cell membrane, intracellular oxidative stress response, and a decrease in intracellular adenosine triphosphate levels, hindering further growth and reproduction of cells. Moreover, the antibacterial mechanism of PCA against Alicyclobacillus spp. mainly altered the permeability of the cell membrane and destroyed its integrity, leading to leakage of intracellular electrolytes, protein, lactate dehydrogenase, and reactive oxygen species, which resulted in cell death. Furthermore, PCA also exhibited good antibacterial effects on Alicyclobacillus spp. in apple juice without affecting the physicochemical quality of the juice. Therefore, PCA provides a reference for the selection of alternative preservatives for juice enterprises.