Abstract
To date, meat microbiology research has relied on culture-dependent methods. Amplicon sequencing technology provides a deeper look into the microbial community. This study set out to evaluate the bacterial community of fresh beef longissimus lumborum steaks exposed to retail packaging and display conditions. Four packaging treatments were assigned after fabrication 7 d postmortem: high-oxygen modified atmosphere packaging, overwrapped packages within a carbon monoxide tri-gas flushed motherbag, vacuum rollstock pouches, and traditional overwrap. After a 14-d dark storage, carbon monoxide motherbag overwrapped packages were removed from the motherbag, and packages were distributed to a retail lighting condition for 72 h of retail display: fluorescent, light emitting diode, or darkness. Aerobic plate count and psychrotrophic bacteria were enumerated, in addition to 16S ribosomal RNA sequencing of DNA for microbial profile investigation. Sampling occurred at fabrication (7 d), end of dark storage (20 d), and end of retail display (23 d). The V3–V4 regions of the 16S bacterial ribosomal RNA gene were sequenced using the Illumina MiSeq platform (Illumina, San Diego, CA). Counts for aerobic plate count bacteria differed by packaging (P = 0.039) but not lighting (P > 0.05). Firmicutes and Proteobacteria were the dominate phyla identified but were not affected by packaging or lighting (P > 0.05). Traditional overwrapped packages displayed in darkness and fluorescence had a higher abundance of Carnobacterium compared with those displayed under light emitting diode (P = 0.05). Dark-stored samples had more Pseudomonas compared with fluorescent display, regardless of packaging type (P = 0.03). While packaging and lighting conditions had a minimal impact on the community composition, these data positively contribute to a baseline establishing bacterial community profiles of fresh beef steaks subjected to retail display. This foundation suggests that further work is needed to understand whether shifts are more likely to occur during extended shelf life or in other retail beef display conditions.
Highlights
The study of microorganisms in fresh meat has predominantly focused on screening for pathogens or monitoring of prominent spoilage organisms to maintain shelf life
No lighting by packaging type interaction existed for aerobic plate counts (APC) or psychrotrophic plate counts (PPC) (P > 0.05) at the end of retail display
These enumeration data are consistent with results from similar studies of ground beef patties and beef tenderloin steaks exposed to retail display conditions (Brooks et al, 2008; Hoyle et al, 2009; Mansur et al, 2019)
Summary
The study of microorganisms in fresh meat has predominantly focused on screening for pathogens or monitoring of prominent spoilage organisms to maintain shelf life. Pathogens and prominent spoilage organisms are important, they do not make up the entirety of the fresh meat microbial community. While culture-based methods are standard in the meat industry, these methods overestimate bacterial species that are culturable and may miss the opportunity to represent those with no successful culturing methods (Dowd et al, 2008; Jarvis et al, 2018). These other members of the community have potential to influence behavior of the more prominent spoilage or pathogenic organisms. Using DNA extractions to amplify and study the 16s ribosomal RNA (rRNA)
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