Survival of Listeria innocua in dry fermented sausages and changes in the typical microbiota and volatile profile as affected by the concentration of nitrate and nitrite

The involvement of nitrate and nitrite in the formation of N-nitrosamines in foods is a matter of great concern. This situation has led to revise the real amount of nitrate and nitrite needed in meat products to exert proper technological and safety activities, and also to extensive research to find alternatives to their use. The present study addresses the possibility of reducing the ingoing amounts of these additives below the legal limits established by the current European regulations. Different concentrations of nitrate and nitrite were tested on Spanish salchichón-type dry fermented sausages concerning their role in the microbiota and volatile profile. Sausages were manufactured with the maximum ingoing amounts established by the EU regulations (150 ppm NaNO₃ and 150 ppm NaNO₂), a 25% reduction and a 50% reduction; control sausages with no nitrate/nitrite addition were also prepared. The mixtures were inoculated with 5 log cfu/g of Listeria innocua as a surrogate for Listeria monocytogenes. L. innocua numbers in the final product were approximately 1.5 log cfu/g lower in the batch with the maximum nitrate/nitrite concentration when compared to 25 and 50% reduced batches, and about 2 log cfu/g in comparison to the control sausages. The final numbers of catalase-positive cocci were 1 log cfu/g higher in the 50% nitrate/nitrite reduced batch and 2 log cfu/g higher in the control sausages, compared to products manufactured with the maximum nitrate/nitrite concentration. This increase was related to a higher amount of volatile compounds derived from carbohydrate fermentation and amino acid degradation. Sausages with no addition of nitrate/nitrite showed higher amount of volatiles from lipid oxidation. Enterobacteriaceae counts reached detectable values (1-2 log cfu/g) in both nitrate/nitrite reduced sausages and in the control batch, while these organisms were not detected in the batch with the maximum ingoing amount. Nitrate and nitrite exerted a significant effect on the typical microbiota of dry fermented sausages and effectively contributed to control Listeria. These considerations should be taken into account in view of a future restriction in the use of these curing additives.     

Effect of meat ingredients (sodium nitrite and erythorbate) and processing (vacuum storage and packaging atmosphere) on germination and outgrowth of Clostridium perfringens spores in ham during abusive cooling

The effect of nitrite and erythorbate on Clostridium perfringens spore germination and outgrowth in ham during abusive cooling (15 h) was evaluated. Ham was formulated with ground pork, NaNO₂ (0, 50, 100, 150 or 200 ppm) and sodium erythorbate (0 or 547 ppm). Ten grams of meat (stored at 5 °C for 3 or 24 h after preparation) were transferred to a vacuum bag and inoculated with a three-strain C. perfringens spore cocktail to obtain an inoculum of ca. 2.5 log spores/g. The bags were vacuum-sealed, and the meat was heat treated (75 °C, 20 min) and cooled within 15 h from 54.4 to 7.2 °C. Residual nitrite was determined before and after heat treatment using ion chromatography with colorimetric detection. Cooling of ham (control) stored for 3 and 24 h, resulted in C. perfringens population increases of 1.46 and 4.20 log CFU/g, respectively. For samples that contained low NaNO₂ concentrations and were stored for 3 h, C. perfringens populations of 5.22 and 2.83 log CFU/g were observed with or without sodium erythorbate, respectively. Residual nitrite was stable (p > 0.05) for both storage times. Meat processing ingredients (sodium nitrite and sodium erythorbate) and their concentrations, and storage time subsequent to preparation of meat (oxygen content) affect C. perfringens spore germination and outgrowth during abusive cooling of ham.     

Effect of freeze-dried leek powder (FDLP) and nitrite level on processing and quality characteristics of fermented sausages

Fermented sausages were produced with 0.84% and 1.68% freeze-dried leek powder (FDLP), providing 75 and 150 mg/kg NaNO₃, respectively, and three levels of added nitrite (0, 75, and 150 mg/kg NaNO₂). A control treatment was also produced with 150 mg/kg NaNO₂. Sausages with FDLP were darker and yellower (p < 0.05) than the control. Higher FDLP levels produced less red, yellower and darker sausages (p < 0.05). Lower FDLP levels resulted in higher (p < 0.05) sensory scores for external appearance, flavour and overall acceptability. No differences were found among the treatments with FDLP plus 75 or 150 ppm NaNO₂ in TBA value, lightness, redness (cross section), redness stability, yellowness, texture parameters and sensory firmness, flavour and overall acceptability. The use of 0.84% FDLP and 75 ppm NaNO₂ is considered more appropriate for the production of fermented sausages, as it results in a 50% reduction in added nitrite.     

Antimicrobial activity of 5-hydroxy-1,4-naphthoquinone isolated from Caesalpinia sappan toward intestinal bacteria

The methanol extract of Caesalpinia sappan heartwoods was tested for the growth effects toward five intestinal microorganisms. The biologically active constituent of the C. sappan extract was characterized as 5-hydroxy-1,4-naphthoquinone (C₁₀H₆O₃). The growth responses varied depending on the bacterial species and dose tested. In the test with Clostridium perfringens, 5-hydroxy-1,4-naphthoquinone produced the strong (+++) inhibition at 5 and 2 mg/disk and moderate (++) inhibition at 1, 0.5, and 0.25 mg/disk. Furthermore, this isolate revealed a weak (+) growth inhibition against Lactobacillus casei at 5 and 2 mg/disk. In comparison of naphthoquinone derivatives, 5-hydroxy-2-methyl-1,4-naphthoquinone had moderate growth inhibition against C. perfringens at 5 and 2 mg/disk, whereas 1,4-naphthoquinone at 5 mg/disk significantly inhibited the growth of all bacteria tested. 1,2-Naphthoquinone had growth inhibition against all bacteria tested at 1 mg/disk. The structure-activity relationship revealed that 5-hydroxy-1,4-naphthoquinone had selective growth inhibition against C. perfringens. These results indicate that hydroxyl functional group of naphthoquinone seems to be required for selective growth-inhibiting activity against C. perfringens. Accordingly, as naturally occurring antimicrobial agents, C. sappan heartwood-derived material could be useful as a preventive agent against diseases caused by C. perfringens.     

Antioxidant effects of Satureja montana L. essential oil on TBARS and color of mortadella-type sausages formulated with different levels of sodium nitrite

This study aimed to evaluate the effect of adding winter savory (Satureja montana L.) essential oil (EO) at concentrations of 7.80, 15.60 and 31.25 μl/g on color and lipid oxidation (TBARS) in mortadella-type sausages formulated with different sodium nitrite (NaNO₂) levels (0, 100 and 200 mg/kg) and stored at 25 °C for 30 days. The EO was extracted by hydrodistillation and analyzed by gas chromatography–mass spectrometry (GC–MS). Twenty-six chemical compounds were identified; the most prominent of which were thymol (28.99 g/100 g), p-cymene (12.00 g/100 g), linalool (11.00 g/100 g) and carvacrol (10.71 g/100 g). Among the nitrite levels tested, a concentration of 100 mg/kg of sodium nitrite appeared to be sufficient for the formation of the characteristic red color. The use of EO at concentrations exceeding 15.60 μl/g adversely affected the color of the product by reducing redness (a¹) (p ≤ 0.05) and increasing yellowness (b¹ h¹). The EO antioxidant activity was confirmed by β-carotene bleaching method and DPPH assay. Reduced values of thiobarbituric acid reactive substances (TBARS) (p ≤ 0.05) were observed in mortadellas formulated with the lowest concentrations of EO without added nitrite. This significant effect on lipid oxidation was also observed in samples containing EO and reduced amounts of sodium nitrite. The results suggest possible benefits from the combined use of EOs and minimal amounts of sodium nitrite in cured meat products.     

Fluorescent in situ hybridization in combination with filter cultivation (FISHFC) method for specific detection and enumeration of viable Clostridium perfringens

To reduce time for enumeration of viable Clostridium perfringens, fluorescence in situ hybridization in combination with filter cultivation (FISHFC) was employed. The method utilized a CLP-180 probe, based on the 16S rRNA region of C. perfringens, and FISHFC fluorescence microscopy to detect C. perfringens, but not organisms from other species. Optimal cultivation requirements for micro-colony formation were TSC medium, anaerobic conditions, 37 °C, and incubation for 6 h. Under these conditions, micro-colony diameters reached 100 μm, a size sufficient for hybridization. Enumeration of C. perfringens using the CLP-180-aided FISHFC method was realized in 9 h as compared to 3–5 days required by the conventional plate count method. Moreover, viable C. perfringens counts of food samples from the two methods were not significantly different.     

Effect of starter culture and fermentation temperature on water mobility and distribution in fermented sausages and correlation to microbial safety studied by nuclear magnetic resonance relaxometry

Water mobility and distribution in fermented sausages produced with differences in pH development as a result of the use of three different starter cultures (T-SPX, F-1, or F-SC-111) and two fermentation temperatures (24 °C, or 32 °C) were studied using low-field proton NMR relaxometry. Changes in the distribution and mobility of water in fermented sausages upon fermentation and drying were detectable by NMR T₂ relaxation, and the progress in the drying process could be followed as a shift towards faster relaxation times. In addition, the distribution of water in the sausages was significantly affected by the pH decline. The sausages were spiked with Listeria monocytogenes, Salmonella, and Escherichia coli VTEC, and partial least squares regressions revealed that 90% of the variation in reduction of Salmonella and VTEC could be explained by the NMR T₂ relaxation decay. Consequently, the study demonstrated that NMR relaxometry is a promising technique for elucidating process parameters and microbial safety in the production of fermented meat products.     

Reduction of verotoxigenic Escherichia coli by process and recipe optimisation in dry-fermented sausages

Outbreaks of verotoxigenic Escherichia coli (VTEC) linked to dry-fermented sausages (DFSs) have emphasized the need for DFS manufacturers to introduce measures to obtain enhanced safety and still maintain the sensory qualities of their products. To our knowledge no data have yet been reported on non-O157:H7 VTEC survival in DFS. Here, the importance of recipe and process variables on VTEC (O157:H7 and O103:H25) reductions in two types of DFS, morr and salami, was determined through three statistically designed experiments. Linear regression and ANOVA analyses showed that no single variable had a dominant effect on VTEC reductions. High levels of NaCl, NaNO₂, glucose (low pH) and fermentation temperature gave enhanced VTEC reduction, while high fat and large casing diameter (a_w) gave the opposite effect. Interaction effects were small. The process and recipe variables showed similar effects in morr and salami. In general, recipes combining high batter levels of salt (NaCl and NaNO₂) and glucose along with high fermentation temperature that gave DFS with low final pH and a_w, provided approximately 3 log₁₀ reductions compared to approximately 1.5 log₁₀ reductions obtained for standard recipe DFS. Storage at 4 °C for 2 months provided log₁₀ 0.33-0.95 additional VTEC reductions and were only marginally affected by recipe type. Sensory tests revealed only small differences between the various recipes of morr and salami. By optimisation of recipe and process parameters, it is possible to obtain increased microbial safety of DFS while maintaining the sensory qualities of the sausages.     

Strategy to inactivate Clostridium perfringens spores in meat products

The current study aimed to develop an inactivation strategy for Clostridium perfringens spores in meat through a combination of spore activation at low pressure (100–200 MPa, 7 min) and elevated temperature (80 °C, 10 min); spore germination at high temperatures (55, 60 or 65 °C); and inactivation of germinated spores with elevated temperatures (80 and 90 °C, 10 and 20 min) and high pressure (586 MPa, at 23 and 73 °C, 10 min). Low pressures (100–200 MPa) were insufficient to efficiently activate C. perfringens spores for germination. However, C. perfringens spores were efficiently activated with elevated temperature (80 °C, 10 min), and germinated at temperatures lethal for vegetative cells (≥55 °C) when incubated for 60 min with a mixture of l-asparagine and KCl (AK) in phosphate buffer (pH 7) and in poultry meat. Inactivation of spores (∼4 decimal reduction) in meat by elevated temperatures (80–90 °C for 20 min) required a long germination period (55 °C for 60 min). However, similar inactivation level was reached with shorter germination period (55 °C for 15 min) when spore contaminated-meat was treated with pressure-assisted thermal processing (568 MPa, 73 °C, 10 min). Therefore, the most efficient strategy to inactivate C. perfringens spores in poultry meat containing 50 mM AK consisted: (i) a primary heat treatment (80 °C, 10 min) to pasteurize and denature the meat proteins and to activate C. perfringens spores for germination; (ii) cooling of the product to 55 °C in about 20 min and further incubation at 55 °C for about 15 min for spore germination; and (iii) inactivation of germinated spores by pressure-assisted thermal processing (586 MPa at 73 °C for 10 min). Collectively, this study demonstrates the feasibility of an alternative and novel strategy to inactivate C. perfringens spores in meat products formulated with germinants specific for C. perfringens.     

Growth response and modelling of the effects of Zataria multiflora Boiss. essential oil, pH and temperature on Salmonella Typhimurium and Staphylococcus aureus

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0.0, 0.015, 0.03 and 0.06%), pH values (7.3 and 6.0) and storage temperatures (T: 15, 25 and 35 °C) on some growth kinetics, time-to-detection (TTD, time to the nearest visible detection) and log₁₀ probability percentage (log P%) of growth initiation of Salmonella Typhimurium and Staphylococcus aureus in Brain Heart Infusion broth were evaluated in a factorial design study. For the log P%, the effects of another variable, storage time (D, up to 43 days) was also assessed as an additional factor. The TTD and log P% of both organisms were significantly affected (P<0.01) by the values of EO, pH, T and D (just for log P%). The combinations of pH=7.3, and EO?0.015 could not obviously affect the growth kinetics of the organisms in this study. Whereas, strong inhibitory action was observed by increasing of EO concentration to 0.06% at the considered pH (7.3) and T (?35 °C). The growth of both organisms was completely inhibited at the combinations of EO=0.06%, pH=6.0 and up to 43 days of storage. Regression equations were derived relating TTDs to EO, pH and T and log P% of both organisms to EO, pH, T and D. From these models the values of predicted TTD and log P% of S. Typhimurium and St. aureus can be calculated by any combinations of EO, pH, T and D (for log P%) within the limits studied. However, between the two TTD and log P% models obtained for both organisms in this study, the TTD models of S. Typhimurium and St. aureus showed better prediction (R²=0.951 and 0.978, respectively) than the log P% models of them (R²=0.852 and 0.804, respectively).     

Effects of water extract of Urtica dioica L. and modified atmosphere packaging on the shelf life of ground beef

Effects of lyophilized Urtica dioica L. water extract (LUWE) and modified atmosphere packaging (MAP) on the quality and shelf life of ground beef were investigated. Ground beef was stored as aerobic control, MAP (80%O₂ + 20% CO₂), MAP + 250 ppm LUWE and MAP and 500 ppm LUWE at 2 ± 0.5 °C for 14 days. MAP and LUWE had significant effects on mesophilic, psychrotrophic and lactic acid bacteria and Pseudomonas counts. Depending on the level of LUWE, Pseudomonas and psychrotrophic counts decreased. Treatment with 500 ppm LUWE + MAP showed the lowest TBARS values compared to other groups during storage. 80% O₂-MAP increased TBARS values. Treatment had no significant effect on L* and b* values of the exterior of the ground beef, but had significant effects on the color of interior sections.     

Changes in biogenic amine levels during storage of Mexican-style soft and Spanish-style dry-ripened sausages with different aw values under modified atmosphere

Two raw sausages were prepared: a soft and a dry-ripened one, both by local traditional and industrial manufacturing practices. Sausages were packaged under a CO₂/N₂ atmosphere at different targeted activity water (a_w) values: 0.96 and 0.92 (soft sausages) and 0.88 and 0.82 (dry-ripened sausages). Sausages were then stored at 5 °C for 42 days or at 12 °C for 240 days (soft and a dry-ripened sausages, respectively). The time-related changes in dominant microbiota, pH and biogenic amine contents during storage were determined. Tyramine was the most abundant biogenic amine in all the sausages. Biogenic amine levels were higher in dry-ripened sausages than in soft sausages at packaging. However, during refrigerated storage soft sausages were fermented and the levels of biogenic amines increased (P < 0.05). At the end of storage, traditional soft sausages with 0.96 a_w presented comparable levels of biogenic amines to traditional dry-ripened sausages.     

Efficacy of chemically characterized Ocimum gratissimum L. essential oil as an antioxidant and a safe plant based antimicrobial against fungal and aflatoxin B1 contamination of spices

The paper reports the essential oil (EO) of Ocimum gratissimum as plant based preservative and recommends its application as a nontoxic antimicrobial and antiaflatoxigenic agent against fungal and aflatoxin contamination of spices as well their shelf life enhancer in view of its antioxidant activity. The EO exhibited antifungal activity against fungal isolates from some spices and showed better efficacy as fungitoxicant than prevalent fungicide Wettasul-80. The EO also completely checked the aflatoxin B₁ (AFB₁) synthesis by the toxigenic strains LHP-6 and LHP-10 of A. flavus isolated from Piper nigrum and Myristica fragrans respectively at 0.6 ??l/ml and 0.5 ??l/ml, respectively. In addition, EO showed antioxidant activity through DPPH free radical scavenging and ??-carotene-linoleic acid bleaching assay. Methyl cinnamate (48.29%) and ??-terpinene (26.08%) were recorded the major components of the oil through GC-MS analysis. The EO was found non-mammalian toxic showing high LD₅₀ (11622.67 ??l/kg) during oral toxicity on mice.     

Antimicrobial activity of leptospermone and its derivatives against human intestinal bacteria

The anaerobic growth inhibiting activity of the essential oil of Leptospermum scoparium seeds against intestinal bacteria was evaluated in vitro. The essential oil at 5.0 mg/disc strongly (+++) inhibited the growth of Clostridium difficile and Clostridium perfringens, but did not inhibit the growth of Bifidobacterium breve, Bifidobacterium longum, Escherichia coli, or Lactobacillus casei. Spectroscopic analyses revealed that the active component of the essential oil was leptospermone. Leptospermone strongly inhibited the growth of C. difficile and C. perfringens at 1.0 mg/disc and moderately inhibited their growth at 0.5 mg/disc. However, leptospermone did not inhibit the growth of B. breve, B. longum, and L. casei. When compared with the leptospermone derivatives, 1,2,3-cyclohexanetrione-1,3-dioxime exerted strong inhibition against C. perfringens and moderate inhibition against C. difficile at 0.5 mg/disc, whereas the other derivatives exerted weak or no growth inhibition against all bacteria tested. Taken together, these results indicate that cyclohexanetrione is required for triketone derivatives to inhibit the growth of C. difficile and C. perfringens. These findings indicate that L. scoparium seed-derived materials and 1,2,3-cyclohexanetrione-1,3-dioxime are naturally occurring antimicrobial agents that could be useful in the development of new agents for the specific control of C. difficile and C. perfringens.     

Application of high pressure processing to reduce verotoxigenic E. coli in two types of dry-fermented sausage

The effect of high pressure processing (HPP) on the survival of verotoxigenic Escherichia coli (VTEC) in two types of Norwegian type dry-fermented sausages was studied. Two different types of recipes for each sausage type were produced. The sausage batter was inoculated with 6.8 log₁₀ CFU/g of VTEC O103:H25. After fermentation, drying and maturation, slices of finished sausages were vacuum packed and subjected to two treatment regimes of HPP. One group was treated at 600 MPa for 10 min and another at three cycles of 600 MPa for 200 s per cycle. A generalized linear model split by recipe type showed that these two HPP treatments on standard recipe sausages reduced E. coli by 2.9 log₁₀ CFU/g and 3.3 log₁₀ CFU/g, respectively. In the recipe with higher levels of dextrose, sodium chloride and sodium nitrite E. coli reduction was 2.7 log₁₀ CFU/g in both treatments. The data show that HPP has a potential to make the sausages safer and also that the effect depends somewhat on recipe.     

Predictive model for growth of Clostridium perfringens during cooling of cooked uncured meat and poultry

Comparison of Clostridium perfringens spore germination and outgrowth in cooked uncured products during cooling for different meat species is presented. Cooked, uncured product was inoculated with C. perfringens spores and vacuum packaged. For the isothermal experiments, all samples were incubated in a water bath stabilized at selected temperatures between 10 and 51 °C and sampled periodically. For dynamic experiments, the samples were cooled from 54.4 to 27 °C and subsequently from 27 to 4 °C for different time periods, designated as x and y hours, respectively. The growth models used were based on a model developed by Baranyi and Roberts (1994. A dynamic approach to predicting bacterial growth in food. Int. J. Food Micro. 23, 277-294), which incorporates a constant, referred to as the physiological state constant, q₀. The value of this constant captures the cells’ history before the cooling begins. To estimate specific growth rates, data from isothermal experiments were used, from which a secondary model was developed, based on a form of Ratkowsky’s 4-parameter equation. The estimated growth kinetics associated with pork and chicken were similar, but growth appeared to be slightly greater in beef; for beef, the maximum specific growth rates estimated from the Ratkowsky curve was about 2.7 log₁₀ cfu/h, while for the other two species, chicken and pork, the estimate was about 2.2 log₁₀ cfu/h. Physiological state constants were estimated by minimizing the mean square error of predictions of the log₁₀ of the relative increase versus the corresponding observed quantities for the dynamic experiments: for beef the estimate was 0.007, while those for pork and chicken the estimates were about 0.014 and 0.011, respectively. For a hypothetical 1.5 h cooling from 54 °C to 27° and 5 h to 4 °C, corresponding to USDA-FSIS cooling compliance guidelines, the predicted growth (log₁₀ of the relative increase) for each species was: 1.29 for beef; 1.07 for chicken and 0.95 log₁₀ for pork. However, it was noticed that for pork in particular, the model using the derived q₀ had a tendency to over-predict relative growth when the observed amount of relative growth was small, and under-predict the relative growth when the observed amount of relative growth was large. To provide more fail-safe estimate, rather than using the derived value of q₀, a value of 0.04 is recommended for pork.     

Development of dry fermented sausages rich in docosahexaenoic acid with oil from the microalgae Schizochytrium sp.: Influence on nutritional properties,sensorial quality and oxidation stability

Significant enrichment of dry fermented sausages in n−3 polyunsaturated fatty acids (PUFA) was achieved by incorporating algae oil from Schizochytrium sp. into an emulsion that partially substituted pork backfat from the traditional formulation. Two different levels of substitution were initially tested, both including BHA and BHT as antioxidants: (15% and 25%). A triangular test showed that products with 25% substitution were not sensorially acceptable. Sausages with 15% substitution supplied 1.30 g/100 g product of docosahexaenoic acid (DHA), with an interesting n−6/n−3 ratio of 2.62. No signs of oxidation were detected at the end of the ripening process, with low values of TBARs (<0.2 mg/kg), peroxides (<2 meq O₂/kg fat) and volatile aldehydes. Storage of these sausages under vacuum during 30 days totally guaranteed their stability, whereas after 90 days certain degree of oxidation was detected, only by means of aldehydes analysis. Hexanal, nonanal and dienals increased, whereas no increment in TBARs or peroxides were observed. Aerobical storage of these sausages was not viable due to a high oxidation susceptibility of the new formulation, despite the use of antioxidants.     

Effect of sodium chloride, sodium nitrite and temperature on desorption isotherms of previously frozen beef

Moisture desorption isotherms of beef were determined in the relative humidity range of 23 to 90% at 5, 15 and 25 °C and at 2.5% NaCl and 2.5% NaCl + 150 ppm NaNO₂ content. Desorption isotherms were found to be typical type II sigmoid. The water content at equilibrium was higher in beef with NaCl and NaCl + NaNO₂ than control samples. Experimental data were fitted to various mathematical models and it was found that the Peleg model was best in describing the equilibrium moisture content relationship for beef samples over the entire range of temperatures. The net isosteric heat of sorption was estimated from equilibrium desorption data, using the Clausius-Clapeyron equation. Isosteric heats of desorption were found to increase with decreasing moisture content.     

Effect of reducing nitrate and nitrite added to dry fermented sausages on the survival of Salmonella Typhimurium

Salmonella is one of the pathogens that most frequently contaminate pork processing lines. Several hurdles can control this organism in dry fermented sausages, among them is nitrite. However, the traditional use of nitrate/nitrite in the meat industry is being questioned due to their involvement in nitrosamine formation. In this study, minced pork and sausages inoculated with Salmonella Typhimurium were prepared with 150 ppm NaNO₃ and 150 ppm NaNO₂ (maximum amounts allowed by EU), and with a reduction of 25% and 50%. The absence of nitrate/nitrite favored Salmonella growth, with 2–2.5 log cfu/g higher counts at the end of ripening, compared to nitrate/nitrite added batches. The 50% reduction showed the same inhibitory effect as the maximum amounts. Nitrate/nitrite represented an essential hurdle to control Salmonella even when pH and a_w were below the values considered as minimum for its growth. The effect of this reduction on other pathogens should be considered.     

Tyrosine- and histidine-decarboxylase positive lactic acid bacteria and enterococci in dry fermented sausages

Lactic acid bacteria (LAB) and enterococci were isolated immediately after stuffing (day 0), at the end of ripening (28th day) and at the end of storage (112th day) from dry fermented sausages produced by two different producers (K; R) in two diameters (4.5 and 7 cm) using either of two spice mixtures (P; H) and either of two starter cultures (Pediococcus pentosaceus, C; Lactobacillus curvatus + Staphylococcus carnosus, F), resulting in a total of 16 different combinations. Tyrosine-decarboxylase DNA sequence (tyrdc) was identified on average in 88% and 44% of enterococci and LAB isolates, respectively at the end of ripening, the corresponding figures regarding histidine-decarboxylase gene sequence (hisdc) was 71% and 16%, respectively. Lactobacillus plantarum, L. brevis and L. casei/paracasei, and Enterococcus faecium and Enterococcus faecalis were identified as tyramine/histamine producers in the sausages.