Assessment of the microbiological safety and quality of marinades collected over a 12-month period from specialty retailers near Raleigh, North Carolina

Authors: Jung, Yang Jin; RUPERT, CHRISTOPHER - North Carolina State University; CHAPMAN, BENJAMIN - North Carolina State University; Porto-Fett, Anna; Luchansky, John

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2017
Publication Date: 3/1/2018
Citation: Jung, Y.N., Rupert, C., Chapman, B., Porto Fett, A.C., Luchansky, J.B. 2018. Assessment of the microbiological safety and quality of marinades collected over a 12-month period from specialty retailers near Raleigh, North Carolina. Journal of Food Protection. 81:490-496.

Interpretive Summary: Marination is performed by soaking, massaging, injecting, and/or tumbling raw meat in a solution typically containing some fat, acids, seasonings, salt, and possibly some sugar. The process and associated ingredients make meat more tender, flavorful, and juicy. Since raw and undercooked beef may contain Shiga toxin-producing Escherichia coli (STEC), marinated beef also may pose a potential risk of foodborne illness caused by STEC if the meat is not properly handled, prepared, and/or stored. However, no previous studies have reported recovery of STEC from marinade or marinated beef. Thus, we evaluated the levels and types of microorganisms, including STEC, in marinades collected from four specialty retail shops (stores A-D) in the vicinity of Raleigh, North Carolina. Stores A and B simply immersed raw beef cuts in marinade, while stores C and D used a vacuum tumbler for marinating. Although tumbling the meat in a marinade solution while under a vacuum allows for increased penetration of the marinade into the meat, at the same time, microorganisms in the marinade may also be transferred into the deeper tissues of the meat via this process. Our results showed that none of the 115 marinade samples (58 fresh and 57 spent marinades) tested positive for STEC; however, used/spent marinades, particularly those collected from stores C and D, contained appreciable levels of select types of bacteria that may subsequently be transferred to the inside of the meat. Thus, workers at the retail level should continue to recognize the possibility that marinades may harbor bacteria both on the surface and within the deeper tissues of the meat. To minimize risk, proprietors should continue to properly prepare, handle, and store marinade and avoid re-using marinades if possible, as well as ensure that all equipment, including a vacuum tumbler, are properly and frequently cleaned to prevent cross-contamination of meat with harmful microorganisms.

Technical Abstract: We assessed the microbiological quality and safety of marinades used by specialty retailers in the vicinity of Raleigh, North Carolina. Over a 12-month period, a total of 115 marinade samples (58 fresh marinades and 57 spent marinades) were collected from four specialty retailers (stores A-D) and screened for total aerobic mesophilic plate count (M-APC), total psychrotrophic aerobic plate count (P-APC), and total Enterobacteriaceae aerobic plate count (E-APC). These same marinade samples were also screened for the presence of the seven regulated serogroups of Shiga toxin-producing Escherichia coli (STEC). In addition, an informal survey was conducted to address retailers’ practices used for marinating beef. Regarding the survey, stores A and B used immersion as a method to marinade raw beef cuts and prepared the marinade solution on-site, whereas stores C and D used vacuum tumbling and purchased the marinade from an outside vendor. On average, marinade temperatures at the stores ranged from 1.8 to 6.6degreeC, and beef cuts were marinated from a few minutes to up to 3 days. Regarding microbiological quality, regardless of the process used to marinade meat, levels of M-APC and P-APC in fresh marinades ranged from 3.4 to 4.5 and 1.4 to 1.8 log CFU/ml, whereas Enterobacteriaceae were not detected in any fresh marinades even after enrichment. However, levels of M-APC, P-APC, E-APC in spent marinades collected from stores C and D (ca. 3.6 to 7.1 log CFU/ml) were significantly higher ( P < 0.05) when compared to levels these same types of bacteria in spent marinades from stores A and B (ca. less than or equal to 0.7 to 4.9 log CFU/ml). None of the 115 marinade samples tested positive for STEC using the BAX® system real-time PCR. These findings confirm that retailers must continue efforts to mitigate the potential risk of microbial cross-contamination of marinade by not repeatedly re-using spent marinade, by keeping marinade solutions and meat at less than or equal to 4 degree C, and by properly and frequently sanitizing the equipment and environment.