Modeling the effects of sucuk production technique on Listeria monocytogenes, aerobic bacteria and lactic acid bacteria during ripening and storage Osman Erkmen Department of Food Engineering, University of Gaziantep, Faculty of Engineering, 27310 Gaziantep, Turkey 1. Introduction Traditional sucuks (Turkish dry-fermented sausages) are well- known and very popular meat products in Turkey. Nowadays, sucuks are produced throughout the year at butcher shops and by manufacturing companies from sheep and/or beef meat, beef fat or tail fat, salt, sugar, nitrite/nitrate, garlic and various spices such as black pepper, red pepper, cumin, cinnamon, allspice, clove (Bozkurt and Erkmen, 2003; Aksu and Kaya, 2004). Sucuk dough is stuffed into natural cattle small intestine cases which are then hung to ripening in dry in air at 18–22 8C for 15 days and stored at 4 8C. Like all fermented sausages, sucuks have a long storage life due to the added salt, the antimicrobial compounds such as additives (nitrite, nitrate), low pH and water activity (Bozkurt and Erkmen, 2003; Soyer et al., 2005). Listeria monocytogenes, the causal agent of listeriosis, is a Gram-positive, rod-shaped and psychrotrophic pathogen which is widely distributed in the natural environment and consequently present in various animal products and in vegetables (Johnson et al., 1990; Erkmen, 2007). L. monocyto- genes can contaminate meat and meat products during slaughter, processing and production, can persist and grow at low and high pH values, at low water activity and at refrigeration temperatures, and may cause serious food safety problems for consumers (Johnson et al., 1990; Tyopponen et al., 2003; Colak et al., 2007; Thevenot et al., 2005). L. monocytogenes is known to survive at the commercial dry food and bioproducts processing 86 (2008) 220–226 article info Article history: Received 30 May 2007 Accepted 24 July 2007 Keywords: Sucuk Listeria monocytogenes Modified-Gompertz model Logistic model Production techniques abstract The modeling of sucuk (Turkish dry-fermented sausage) production techniques on the survival of Listeria monocytogenes, aerobic bacteria (AB), lactic acid bacteria (LAB), and yeasts and molds (YM) during ripening and storage periods were studied. Effect of L. monocytogenes initially contaminated level (low, medium and high contaminated levels) with sucuk dough was also studied. Survival data were analyzed by non-linear regression of modified-Gom- pertz and logistic equations to generate ‘‘best fit’’. L. monocytogenes was immediately reduced during ripening period (during 15 days) in sucuks produced from both controlled and traditional methods. The reduction in the number of L. monocytogenes was also continued during storage periods (15 days). There was no survival of L. monocytogenes after 25 days (10 days storage) in sucuks contaminated with low level of L. monocytogenes ripened in both methods. AB, LAB and MY were also reduced during ripening and storage periods. Para- meters of non-linear modified-Gompertz and logistic models of L. monocytogenes, AB, LAB and YM in sucuks ripened in controlled and traditional methods were matched in a satisfactory way during ripening and storage periods. Both the modified-Gompertz and logistic models showed good fit to all the survival curves as assessed using the root mean square error (RMSE) and the correlation coefficient (R 2 ) between the experimental and predicted values but the modified-Gompertz model best fit (R 2  0.98) than the logistic model (R 2  0.96). As a consequence, the model provides parameters for different production methods in modified-Gompertz model against microorganisms. # 2007 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. E-mail address: erkmen@gantep.edu.tr. available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/fbp 0960-3085/$ – see front matter # 2007 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.fbp.2007.10.002