Impact of olive leaf extract coating chitosan on Bacillus cereus and its toxins in refrigerated beef burger

Abstract

This study aimed to examine the impact of olive leaf extract (OL-E) and olive leaf extract coating chitosan (OL-Ch) on Bacillus cereus and its toxin genes, as well as, the sensory qualities of refrigerated beef burgers. The primary phenolic components of olive leaf extract were oleeuropein and protocatechuic acid, identified by HPLC-DAD analysis. The concentrations of OL-E and OL-Ch that were in vitro effective against B. cereus were 62.5 mg/mL and 125 mg/mL, respectively. In burgers treated with OL-E and OL-Ch, viable B. cereus dramatically decreased (p < 0.05) over time during cold storage. The count decreased to 2 log CFU/g in the OL-E group and 1.3 log CFU/g in the OL-Ch group after thirteen days of preservation. The entFM gene expression levels on day thirteen were 0.09 in the OL-Ch group and 0.2 in the OL-E group. Conversely, the cytK gene expression levels in the OL-E and OL-Ch groups were 0.09 and 0.15, respectively. Both supplements could control physicochemical characteristics (pH, volatile basic nitrogen (TVBN), and thiobarbituric acid (TBA)) to be 6.12±1.55, 16.1±2.98, and 0.869±0.28, respectively, in the OL-E group during a storage period. Moreover, they were 5.79, 14.3±2.79, and 0.816±0.31 in the OL-Ch group. They also did not appear to affect the average sensory score of burgers. Thus OL-E and OL-Ch could be used as natural food additives to prevent B. cereus contamination in the meat industry.