Modeling the growth and volatile metabolite production of spoilage-causing Brochothrix thermosphacta on solid meat substrates under modified atmospheres

Abstract

Spoilage microorganisms including Brochothrix thermosphacta are associated with various volatile organic compounds (VOCs) and off-odors in meat. Modified atmosphere packaging (MAP) limits microbial growth and affects metabolic activities. However, the exact impact of gas compositions on B. thermosphacta still remains unclear, especially regarding the direct relationship between its growth and VOC accumulation. This study thus aimed to investigate and model these behaviors by growing B. thermosphacta on solid pork simulation media under different packaging atmospheres. Five $O_2$/${\mathrm{CO}}_2$/$N_2$ ratios (v/v%: air, 0/0/100, 60/40/0, 5/40/55, 0/40/60) were examined to study the synergy of MAP gases on the aerobic/anaerobic metabolism of B. thermosphacta. The quantities of VOCs (${\mathrm{ppb}}_v$) were fitted against respective bacterial numbers (log CFU/g) of different individual samples assessed at regular storage intervals. Results suggest that VOCs including acetoin, ethanol, benzaldehyde, and 3-methyl-1-butanol are the major metabolites of B. thermosphacta. Under air, the observable increase of multiple VOCs started at 5.9–6.6 log CFU/g and was closely correlated with microbial growth. In contrast, 100 % $N_2$ caused low acetoin levels and high ethanol emission because of shifting to an anaerobic metabolism. Under high-${\mathrm{CO}}_2$ atmospheres, concentrations of most VOCs were reduced, likely linked to limited microbial counts. Through this study, predictive modeling offers novel insights into the impact of the atmosphere on bacterial growth and VOC production. This helps to fully understand microbial spoilage and contributes to the development of suitable meat storage strategies.