Evaluation of a Novel Antimicrobial Solution (AMS) with Retail Marinades on Fresh Beef
Type of Degreedissertation
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Pathogenic bacteria represent a public health concern when present on meat and result in recall of product from the market. Marination of meat and antimicrobial solutions are two technologies which reduce and prevent the growth of pathogenic bacteria. A novel antimicrobial solution has been developed by researchers at the USDA Agriculture Research Service, utilizing GRAS ingredients, and has shown favorable inhibition against pathogenic bacteria when evaluated on fruit rinds and vegetable stem scars. To date, this novel antimicrobial solution has not been evaluated on meat. The objective was to evaluate, in phases, the efficacy of this novel antimicrobial solution against pathogenic bacteria of concern on beef. Phase one was conducted in two parts. First, the survivability of pathogenic bacteria grown on different mediums was evaluated. One strain each of pathogenic Escherichia coli and Listeria monocytogenes were grown in tryptic soy broth (TSB) tubes and on plate count agar (PCA) plates. The cells were harvested and used to inoculate the surface of meat samples. The survivability of cells from the two growth mediums were compared and were found to be similar. Cultures grown on plates were more costly, requiring additional time and resources for growth and harvest. This, in addition to the similar survivability, was the basis for using broth grown cultures in future phases. In the second part of phase one the efficacy of the antimicrobial solution (AMS) against pathogenic bacteria was evaluated. The AMS was prepared and diluted to high, medium, and low concentrations using distilled water as the diluent and the control. Meat samples were inoculated with a cocktail of either pathogenic Escherichia coli O157:H7, non-O157:H7 E. coli (STECs), Salmonella spp., or Listeria monocytogenes, treated with the assigned treatment (antimicrobial concentration), and stored. The high, medium, and low concentration of the AMS inhibited the growth of pathogenic bacteria inoculated on the surface of fresh beef top round steaks. The inhibitory capacity of the AMS increased with increasing concentration. The medium concentration was selected for further research because it was the lowest concentration which consistently inhibited the growth of pathogenic bacteria. Phase two evaluated the efficacy of three retail marinades available against pathogenic bacteria. Marinades were chosen based on early 2014 market and food trends and included: 1) balsamic and roasted onion, 2) lemon pepper, and 3) classic steakhouse. Distilled water was used as the control. Meat samples were inoculated as previously described, treated with the assigned marinade, and stored. All three marinades inhibited the growth of pathogenic bacteria. The lemon pepper marinade was slightly more inhibitory than the balsamic and roasted onion and the classic steakhouse marinades which had similar inhibition of growth. Phase three evaluated the efficacy of the lemon pepper and classic steakhouse marinades combined with the medium concentration of the AMS. The AMS was prepared and diluted to the medium concentration using the marinade as the diluent. Distilled water was used as the control. Meat samples were inoculated as previously described, treated with the assigned AMS + marinade solution, and stored. Both the lemon pepper marinade solution and classic steakhouse marinade solution were more inhibitory of the growth of pathogenic bacteria than water. The lemon pepper marinade solution and the classic steakhouse marinade solution did not differ in the inhibition of growth of pathogenic bacteria. The combination of the marinade + AMS (marinade solution) was more inhibitory against pathogenic bacteria than water or marinade alone. Phase four evaluated the sensory and objective color of beef top round steaks marinated in water, water+ antimicrobial solution, lemon pepper marinade solution, and classic steakhouse marinade solution for 0, 6, 24, and 48 hours. Steaks were marinated in the assigned treatment for the assigned time before measuring color. Steaks were then grilled and labeled for the sensory panel. Steaks marinated in water+ solution, lemon pepper marinade solution, and classic steakhouse marinade solution received higher ratings for initial juiciness, sustained juiciness, initial tenderness, sustained tenderness, and flavor intensity compared to steaks marinated in water alone. Steaks marinated in lemon pepper marinade solution received slightly higher ratings than the other marinades. Color was altered with marination. Steaks marinated in water were the lightest in color, followed by lemon pepper marinade solution, water+ solution, and classic steakhouse marinade solution. Steaks marinated in water+ solution were the most red in color followed by classic steakhouse marinade solution, lemon pepper marinade solution, and water. Steaks marinated in the classic steakhouse marinade solution were more yellow in color than the other marinades. This research demonstrates the antimicrobial effects of this novel antimicrobial solution (AMS), determined an optimal concentration for application (medium), and demonstrates great potential for the meat industry in phase one. Phase two demonstrates that marination of meat has the potential to improve meat safety by inhibiting the growth of pathogenic bacteria. Phase three demonstrates the inhibitory effect of the combination of retail marinades and the AMS against pathogenic bacteria on beef. It also demonstrates that the combined marinade and AMS is more inhibitory against pathogenic bacteria than water or the marinade alone. Finally, phase four demonstrates that marination of steaks in solution with the AMS improves juiciness, tenderness, and flavor compared to marination in water alone. It also demonstrates that the AMS should be used in combination with a flavorful marinade to minimize the development of off flavors. This research, as a whole, serves as a basis for additional research of antimicrobial solutions as an ingredient in marinades to enhance meat safety, tenderness, juiciness, and flavor.