Document Type

Thesis - University Access Only

Award Date

2007

Degree Name

Master of Science (MS)

Department / School

Animal Science

Abstract

Three experiments (exp 1, exp 2, and exp 3) were conducted in order to determine: 1) the effect of pH-enhancement of beef bottom round (bicepsfemoris, BF)subprimals (USDA Select, n = 12) on the growth of E.coli O157:H7, 2) the effect ofpHenhancement of BF steaks (n = 120) on the growth of E. coli O157:H7, and 3) the effect of pH-enhancement of chicken breasts (n = 60) on the destruction of Salmonella spp. Meat products designated for pH-enhancement were injected with an alkaline solution. In exp 1, beef subprimals were cut into thirds, inoculated with E. coli O 157 :H7 and designated to three sampling days: baseline, pH-enhanced day 0 (PHE0), or pHenhanced day 2 (PHE2). On appropriate sampling days external and internal samples were analyzed. Externally, PHE0 had lower counts than baseline and PHE2. Treatmentgroup had no affect on internal samples. In exp 2, beef subprimals were used as either non-injected control or pH-enhanced. Steaks were cut from each subprimal, inoculated with E.coli O157:H7 and assigned to anaerobic or aerobic storage days. The pH ofpHenhanced was higher than control. There was a significant treatment by day interaction for the anaerobic steaks with pH-enhanced showing lower counts on days O and 2 and control showing lower counts on days 14, 28, and 56. There was a significant treatment by day interaction on days 0 and 2 for the aerobic steaks with pH-enhanced having lower counts. In exp 3, chicken breasts were assigned to five treatments: baseline, pHenhanced day 0 (PHE0), pH-enhanced day 2 (PHE2), injected without solution day 0 (IWOS0), or injected without solution day 2 (IWOS2). Breasts were then inoculated with Salmonella spp. Baseline breasts were inoculated, but not enhanced. The IWOS breasts were processed through the injector with no solution to determine the extent of the needles penetrating the surface of the meat and the forcing the bacteria to the interior of the breast. On appropriate sampling days both external and internal samples were analyzed from the pH-enhanced and baseline breasts, while only internal samples were obtained from the IWOS breasts. Externally, pH-enhanced had lower Salmonella spp. counts than baseline. Treatment group had no effect on internal samples. In conclusion, pH-enhancement reduced the amount of inoculated E.coli O157:H? and Salmonella spp. on beef subprimals and chicken breasts.

Library of Congress Subject Headings

Meat -- Microbiology

Meat -- Quality

Foodborne diseases -- Prevention

Bacterial growth

Escherichia coli O157:H7

Salmonella

Format

application/pdf

Number of Pages

57

Publisher

South Dakota State University

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