Validation of a manufacturing process for fermented, semidry Turkish soudjouk to control Escherichia coli O157 : H7

Two soudjouk batters were prepared from ground beef (20% fat) and nonmeat i ngredients and inoculated with a five-strain mixture of Escherichia coli O1 57:H7 to yield an initial inoculum. of 7.65 log(10) CFU/g. One batter conta ined a commercial-starter culture mixture (similar to8.0 log(10) CFU/g) and dextrose (1.5%), while the other batter relied upon a natural fermentation with no added carbohydrate. Following mixing, sausage batters were held at 4 degreesC for 24 h prior to stuffing into natural beef round casings. Stu ffed soudjouk sticks were fermented and dried at 24 degreesC with 90 to 95% relative humidity (RH) for 3 days and then at 22 degreesC with 80 to 85% R H until achieving a product moisture level of approximately 40%. After ferm entation and drying with an airflow of 1 to 1.5 m/s, the sticks were either not cooked or cooked to an instantaneous internal temperature of 54.4 degr eesC (130 degreesF) and held for 0, 30, or 60 min. The sticks were then vac uum packaged and stored at either 4 or 21 degreesC. For each of three trial s, three sticks for each treatment/batter were analyzed for numbers of E. c oli O157:H7 after inoculation, after fermentation, after cooking, and after storage for 7, 14, 21, and 28 days. Reductions in numbers of E. coli O157: H7 after fermentation and drying for sticks fermented by the starter cultur e (pH 4.6) and for sticks naturally fermented (pH 5.5) were 1.96 and 0.28 l og(10) CFU/g, respectively. However, cooking soudjouk sticks produced with a starter culture and holding at 54.4 degreesC for 0, 30, or 60 min reduced pathogen numbers from an initial level after fermentation and drying of 5. 69 log(10) CFU/ g to below a detectable level by either direct plating (<1. 0 log(10) CFU/g) or by enrichment. In contrast, cooking soudjouk sticks pro duced without an added starter culture decreased pathogen numbers from an i nitial level after fermentation and drying of 7.37 to 5.65 log(10) CFU/g (5 4.4'C, no hold), 5.04 log(10) CFU/g (54.4'C, 30 min hold), and 4.67 log(10) CFU/g (54.4'C, 60 min hold). In general, numbers of E. coli O157:H7 within both groups of soudjouk sticks decreased faster during storage at 21 degre esC compared to 4 degreesC. After 28 days of storage, total reductions in p athogen numbers in soudjouk sticks produced using a star-ter culture but th at were not subsequently cooked were 7.65 and 3.93 log(10) CFU/g at 21 and 4 degreesC, respectively. For naturally fermented soudjouk, total reduction s varied from 4.47 to 0.45 log(10) CFU/g, depending on the cooking time and storage temperature. These data provide guidelines for manufacturers of dr y sausage of ethnic origin, including soudjouk, to assess the safety of the ir processes for control of E. coli O157:H7.