Postmortem Invasion of Muscle Food by a Proteolytic Bacterium

Abstract

Serratia marcescens was used to study the process of bacterial invasion of intact and cornminuted meats (fresh and frozen-thawed) as well as the bacterium's ability to hydrolyze reconstituted collagen. Fresh intact pork was more susceptible to invasion when the inoculated surface was vertical to the inoculum. In cornminuted beef and pork, invasion was more extensive in meat that had undergone at least one freeze-thaw cycle. The addition of sodium tripolyphosphate (up to 0.5% , w/w) to cornminuted beef and pork results in a reduction in the depth of penetration (up to 16% and 84%, respectively). Cooked (63°C and 77°C) intact beef samples were more susceptible to bacterial invasion than uncooked beef. Meat cooked to an end-point temperature of 77°C exhibited less resistance to bacterial invasion than samples cooked to an end-point temperature of 63°C. Fiber orientation in cooked beef samples played a significant role in the final depth of penetration. Bacterial invasion in cooked beef was more pronounced in samples where the inoculated surface was vertical to the inoculum. Results indicated that bacterial invasion is not a function of the collagenolytic acitivity present in bacterial proteases. The invasive process or mechanism is strongly influence by the hydration of the meat proteins and the availability of pores or canals, which are created during cooking or as a result of freezing and thawing of meats.

Kinetics of migration of colloidal particles in meat muscles in the absence and presence of a proteolytic enzyme to simulate non-motile bacteria penetration

“…Such surface contaminations may increase after slaughtering because biological mechanisms preventing contaminations have ceased to function, and protective coverings have been removed (Elmossalami & Wassef, 1971). Some later studies though demonstrated that microorganisms appeared to be able to penetrate muscle tissue, and authors attributed this to a wide range of different mechanisms (Anderson, Marshall, & Dickson, 1991;Elmossalami & Wassef, 1971;Gill, Leet, & Penney, 1984;Gill & Penney, 1977;Gill & Penney, 1982;Gill, Uttaro, Badoni, & Zawadski, 2008;Gupta & Nagamohini, 1992;Sikes & Maxcy, 1980;Thomas, O'Rourke, & McMeekin, 1987;Warsow, Orta-Ramirez, Marks, Ryser, & Booren, 2008).…”

Freezing skeletal muscle tissue does not affect its decomposition in soil: Evidence from temporal changes in tissue mass, microbial activity and soil chemistry based on excised samples

“…The results are thought to be a consequence of increased interstitial cavity sizes between cells caused by the formation of ice crystal artifacts [8]. By comparison another study found no increased bacterial invasion after freezing [9].…”

“…Bacterial invasion after a freeze-thaw cycle has also been investigated, freezing led to more extensive bacterial proliferation in SMT in comparison to fresh SMT samples [8]. The results are thought to be a consequence of increased interstitial cavity sizes between cells caused by the formation of ice crystal artifacts [8].…”

“…The experiment had three treatments: control with no skeletal muscle tissue, microcosms containing frozen skeletal muscle tissue and those containing refrigerated tissue. The microcosms were destructively harvested at sequential periods of 2, 4, 6,8,12,16,23,30 and 37 days after interment of skeletal muscle tissue. These harvests were replicated 6 times for each treatment.…”

“…During freezing the withdrawal of water from cells leads to a decrease in diffusion and material Forensic Science International 183 (2009) [6][7][8][9][10][11][12][13] The study of decaying organisms and death assemblages is referred to as forensic taphonomy, or more simply the study of graves. This field is dominated by the fields of entomology, anthropology and archaeology.…”