Master of Science / Food Science Institute / Randall Phebus / Shiga toxin-producing E. coli (STEC) are frequently associated with foodborne illness outbreaks, especially attributable to beef. Intervention methods, such as water washes and organic acid application, are widely implemented across the beef industry to combat this risk. This research evaluates the efficacy of intervention methods applied to chilled beef subprimal pieces and pre-rigor beef carcasses to reduce STEC contamination. Beef strip loins were inoculated (ca. 5 log CFU/cm²) with a 7-serotype STEC cocktail and sprayed with increasing concentrations of peracetic acid (200-1800 ppm; ambient temperature), lactic acid (3-10%; 55°C), or a water control before being vacuum-packaged and stored for 24 h at 4°C. Meat surface excision samples and color readings (L*, a*, and b*) were obtained from each subprimal at three sampling points: post-inoculation, 5 min post chemical spray, and post-24 h vacuum packaged chilling. Peracetic acid spray and lactic acid spray reduced STEC populations by 0.5 -1.3 log CFU/cm² and 0.2 – 0.7 log CFU/cm², respectively, across the incremental concentration increases. All concentrations of peracetic acid and lactic acid concentrations ≥3.5% reduced (P ≤ 0.05) STEC populations compared to their respective control. Application of higher concentrations of lactic acid (7-10%) decreased (P ≤ 0.05) L* and b* values compared to the control, indicating that quality attributes of the subprimals were negatively effected. Carcass intervention methods were evaluated using a three-stage commercial carcass washing cabinet (Chad Equipment). Four pre-rigor carcass sides were inoculated by electrostatically spraying with a 7-serogroup STEC cocktail (ca. 6.5 log CFU/100 cm²). Three treatments were applied, in order, to each side: ambient water wash, hot water wash (82-92°C at the nozzle head), and antimicrobial mist. Meat surface excision samples were taken from the bottom, middle, and top section of each carcass side at five sampling points: 30 min post-inoculation, post-ambient water wash, post-hot water wash, post-antimicrobial spray, and after 18 h spray chilling. The combination of the high-volume ambient water wash stage and subsequent hot water wash stage reduced STEC populations on sides by 3.5, 4.7, and 4.8 log CFU/100 cm² at the bottom, middle, and top of the carcass, respectively. Due to STEC populations declining to very low or undetectable levels after the hot water stage, minimal additional STEC reductions were observed after chemical spray application and chilling. Sequential antimicrobial treatments applied using a three-stage Chad carcass wash cabinet and a subsequent chill step reduced STEC populations on pre-rigor beef carcasses by 4.5 – 5.3 log CFU/100 cm².

Beef subprimals (n = 356), representing USDA Low Choice and Select grades, were obtained from a major beef processor. Selected subprimals represented the normal weight variation and standard packer fat trim levels associated with commodity boxed beef. The subprimals selected included beef rib, blade meat; beef rib, ribeye roll, lip-on, bone-in; beef rib, ribeye roll (0x0); beef rib, ribeye, lip-on (2x2) (5.08 cm x 5.08 cm); beef rib, ribeye, lip-on modified (1x1) (2.54 cm x 2.54 cm); beef rib, ribeye (IM, individual muscle); beef rib, ribeye cap (IM); beef chuck, outside shoulder clod, trimmed; beef chuck, outside shoulder clod, top blade roast; beef chuck, square cut, pectoral meat (IM); beef chuck, chuck roll; beef plate, inside skirt (IM); beef round, top (inside) untrimmed; beef round, outside round (flat); beef round, eye of round (IM); beef loin, strip loin, bone in; beef loin, strip loin, boneless; beef loin, top sirloin butt, boneless, 2-piece; beef loin, bottom sirloin butt, flap boneless (IM); beef loin, bottom sirloin butt, ball tip, boneless; beef loin, bottom sirloin butt, tri-tip, boneless (IM); and beef chuck, outside shoulder, clod M. teres major. Subprimals were fabricated into bone-in or boneless retail or foodservice cuts and associated components by trained retail meat cutters. After each retail cutting test, trained technicians recorded weights of all cuts, lean trim, fat trim, and bone. All retail cuts were trimmed to an eighth of an inch (0.32 cm), unless otherwise specified. Time (s) was recorded for each-cutting test and in two major phases: opening (retrieval of the subprimal from vacuum-packaged bag) and cutting (removal of all external and seam fat, connective tissue, and separation of individual muscles, as well as producing tray ready retail cuts). In general, Select subprimals had higher saleable yields than Choice subprimals. Select subprimals had less trimmable fat than Choice subprimals, and differences in retail yields appeared to follow these factors. Few significant differences were observed for processing times between USDA quality grade groups. These data will serve as an update to the CARDS (Computer Assisted Retail Decision Support) software program.