Viability of Escherichia coli O157:H7 in Fermented Semidry Low-Temperature-Cooked Beef Summer Sausage

Abstract

The population of inoculated Escherichia coli O157:H7 was monitored during the manufacture and storage of a semidry beef summer sausage processed by fermentation and cooking at a low temperature by heating to an internal temperature of 130°F (54°C). The all-beef batter (11% fat and nonmeat ingredients) was inoculated with the commercial starter culture Pediococcus acidilactici HP (≥8.6 log CFU/g of batter) and a five-strain mixture of E. coli O157:H7 (≥7 log CFU/g) and then hand stuffed into 2.5-inch (64-mm) diameter fibrous casings. The sausages were fermented at an initial temperature of 85°F (29°C) to a final temperature of 105°F (41°C) over ca. 13 h at 80% relative humidity (RH) to pH 4.6 or pH 5.0. After fermentation to pH 4.6, the internal temperature of the chubs was raised to 130°F (54°C) instantaneous over 3.6 h at 60% RH. After fermentation to pH 5.0, the internal temperature of the chubs was raised to 130°F (54°C) over 3.6 h at 60% RH and the chubs were maintained under these conditions for 0, 30, or 60 min. he chubs were cold water showered for 15 min and then chilled at 39°F (4°C) for 6 h before being vacuum packaged and stored at 39°F (4°C) or 77°F (25°C) for 7 days. Regardless of the target pH, fermentation alone resulted in only a 1.39-log CFU/g decrease in pathogen numbers. However, fermentation to pH 4.6 and heating to an internal temperature of 130°F (54°C) instantaneous reduced counts of E. coli O157:H7 by ≥7.0 log units to below detection levels (<10 CFU/g). Pathogen numbers remained below levels detectable by direct plating, but viable E. coli O157:H7 cells were recovered by enrichment of samples during sausage storage at either refrigeration or abuse temperatures. In contrast, fermentation to pH 5.0 and heating to an internal temperature of 130°F (54°C) instantaneous resulted in a 3.2-log-unit decrease in counts of E. coli O157:H7. No appreciable reductions in pathogen numbers were observed thereafter following storage at either 39°F (4°C) or 77°F (25°C) for 7 days. Fermentation to pH 5.0 and heating to an internal temperature of 130°F (54°C) instantaneous followed by holding for 30 or 60 min resulted in about a 5- or 7-log reduction, respectively, in pathogen numbers. For chubs held for 30 min at 130°F (54°C), pathogen numbers decreased to 2.02 and <1.0 log CFU/g at 39°F (4°C) and 77°F (25°C), respectively, after 7 days; viable cells were only observed by enrichment after storage at 77°F (25°C). For chubs held for 60 min at 130°F (54°C), pathogen numbers remained below levels detectable by direct plating, but viable cells were recoverable by enrichment after 7 days at both storage temperatures. These data will be useful guidelines to manufacturers for developing processing conditions to further ensure the safety of this category of fermented sausages relative to food-borne pathogens such as serotype O157:H7 strains of E. coli.

Health and Safety Considerations of Fermented Sausages

“…Including a storage step at ambient temperatures in addition to the production process itself may not be enough to achieve the 5-log reduction required in some countries. Heat treatments may be effective to reduce the numbers of pathogens in sausages, also taking into account the fact that E. coli O157:H7 show reduced tolerance to heat in low pH meat products compared to higher pH meat products [269][270][271]. Total reductions of >5 log were obtained for several combinations of products and storage/mild heat treatment regimes.…”

Survival of Escherichia coli in foods

“…Use of 'mild' heating temperatures, e.g. 54 DC, for relatively short periods of time (30 min) has also been suggested as an effective process step to ensure the safety of fermented meats (Calicioglu et al 1997).…”

Survival of Escherichia coli 0157:H7 in Feta cheese during storage

“…and several deaths 5 have been also reported. Most of these outbreaks were caused from products, such as beef meat 6 and dairy products of cows milk origin 7 , as well as from other foods such as mayonnaise 8 9 , apple cider 10 n and other acid foods such as salami 12 and yogurt 13 . Since first foodborne outbreaks were derived from products of cows origin (meat products and raw milk), the cattle were considered to be the main reservoir of the pathogen.…”

“…This pathogenic microorganism causes haemorrhagic colitis with complications, such as hemolytic uremic syndrome mainly to young people and thrombocytopenic purpura mainly to adults 12 . The hemolytic uremic syndrome can lead to renal deficiency that can cause death to 5-8% of patients 3 .…”

“…), ακό μη και με θανατηφόρα αποτελέσματα 5 . Πολλές από αυτές προέρχονται από προϊόντα, όπως βόειο κρέας 6 και γαλα κτοκομικά προϊόντα με βάση το αγελαδινό γάλα 7 , αλλά και από άλλα τρόφιμα όπως μαγιονέζα 89 και χυμός μήλου 10 n ή άλλα όξινα τρόφιμα όπως σαλάμι 12 και γιαούρτι 13 . Επειδή οι πρώτες τροφολοιμώξεις απο τψΕχοΙί 0157:Η7 προέρ χονταν απο απαστερίωτο αγελαδινό γάλα και κρεατο-σκευάσματα απο βόειο κρέας, τα βοοειδή θεωρήθηκαν ότι ήταν η κΰρια πηγή του μικροοργανισμού.…”