Ripening Of Fermented Sausages Research Articles

Reduction of biogenic amine concentration in fermented sausage by selected starter cultures

We determined the effects of selected starter cultures for the production and ripening of fermented sausages on their ability to reduce biogenic amines accumulation. Starter cultures used were: Group L: Lactobacillus plantarum; Group X: Staphylococcus xylosus; Group M: Lactobacillus plantarum together with Staphylococcus xylosus; and Group C: control group without added starter cultures. At the end of ripening period, those inoculated with S. xylosus had only a slight effect on reduction of tyramine (21%), histamine (25%) and cadaverine (22%) compared with the control group. Addition of S. xylosus plus L. plantarum effectively reduced tryptamine, phenylethylamine, putrescine, cadaverine, histamine and tyramine by nearly 100, 100, 86, 63, 82 and 43%, respectively. There were no statistically significant (P > 0.05) differences between batches M and L. Results indicated that L. plantarum used in this work had a strong effect on inhibiting the production of biogenic amines.

SLEDOVÁNÍ POČTU PROBIOTICKÝCH BAKTERIÁLNÍCH BUNĚK LACTOBACILLUS CASEI VE FERMENTOVANÝCH TEPELNĚ NEOPRACOVANÝCH SALÁMECH

Combination of microbiology cultivation methods and methods of molecular biology is the best way how to achieve correct qualitative and quantitative probiotic analysis. The aim of this study was mo­ni­to­ring of amounts of different starter bacteria supplemented with probiotic bacterial cells Lactobacillus casei (Chr. Hansen) during fermentation and ripening of fermented sausages. Two starter cultures, one consisted of Pediococcus pentosaceus and Staphylococcus xylosus, the second of Pediococcus pentosaceus and Staphylococcus carnosus, were used for the production of sausages. As a detection method of starter and probiotic cell counts, the cultivation on MRS –IM – sorbitol agar was used. Furthermore, the confirmation of L. casei was carried out using species specific PCR. The counts of probiotic L. casei in both probiotic sausages were 106/g and stayed at this level during the whole ripening period (100 days). The counts of starter bacteria were 107/g after the 7 days of fermentation and stayed at this level during the whole fermentation period. PCR from one bacterial colony confirmed the identity of L. casei in 80% of analysed colonies.

Effect of starter cultures on microbial ecosystem and biogenic amines in fermented sausage

The microbial ecology of fermented sausages inoculated with different starter cultures ( Pediococcus pentosaceus + Staphylococcus xylosus, batch A; Lactobacillus farciminis + Staphylococcus saprophyticus, batch B) was studied by culture-dependent and independent methods. The concentration of biogenic amines, pH and a w (water activity) were followed. The starter B can inhibit indigenous bacteria effectively judged by traditional microbiological method and PCR-DGGE fingerprint. There was no statistical difference in pH between batches A and B at 2 days when substantial amounts of BAs were produced, while the amounts of histamine, putrescine, cadaverine and tyramine in batch B was lower than in batch A significantly ( P < 0.001). As a result, the starter cultures which can complete, grow well and inhibit amine-positive bacteria play an important role in reducing the production of BAs during ripening of fermented sausage.

Protease and esterase activity of staphylococci

The aim of this work was to characterize protease and esterase activities of staphylococci in order to establish if they could contribute to the release of amino acids and short-chain fatty acids during ripening of fermented sausages. Eighteen Staphylococcus strains belonging to the species Staphylococcus xylosus (5), S. saprophyticus (3), S. equorum (4), S. carnosus (4) and S. simulans (2), previously isolated from different types of Southern Italian fermented sausages, were screened for proteinase, aminopeptidase and esterase activities. Most of the staphylococci strains lacked detectable levels of proteinase activity against casein-fluorescein isothiocynate. In the active strains, this activity was extracellular or cell-envelope associated. The studied staphylococci strains also showed low levels of aminopeptidase activities, which preferentially hydrolysed substrates containing l-methionine, l-leucine and l-phenylalanine as N-terminal residue. In contrast, all staphylococcal strains possessed significant activity against short-chain fatty acid esters. The maximum esterase activities were detected in whole-cell suspensions and cell-free extracts and to a lesser extent in the extracellular medium. The substrates preferentially hydrolysed were ρ-nitrophenyl (ρ-NP) butyrate and ρ-NP caprylate and, secondly, ρ-NP palmitate. The extracellular extracts of most of the strains were only active against ρ-NP butyrate except for those of S. equorum (SI3, SI4) and S. simulans (Ssm12, Ssm21), which also hydrolysed ρ-NP caprylate and ρ-NP palmitate. The cell-free extracts and whole cells were mainly active against ρ-NP butyrate and ρ-NP caprylate, showing activity levels from 1760 U/mg of proteins to 54 U/mg of proteins and from 12,200 U/mg of proteins to 133 U/mg of proteins respectively. These activities were especially high in the strains that belonged to S. xylosus and S. equorum species. The diversity of the studied metabolic properties and, especially, the esterase activities in different staphylococcal species and even strains of the same species emphasize the relevance of these in vitro characterization studies for a rational selection of new starter cultures.

Gene transfer of vancomycin and tetracycline resistances among Enterococcus faecalis during cheese and sausage fermentations

This study assessed the frequency of transfer of two mobile genetic elements coding for virulence determinants and antibiotic resistance factors, into food associated enterococci during fermentation processes. First, the transfer of the pheromone-inducible pCF10 plasmid, carrying tetracycline resistance and aggregation substance (AS) as virulence factor, between clinical and food strains of Enterococcus faecalis, was investigated in models of cheese and fermented sausage. The experiments demonstrated that even in the absence of selective tetracycline pressure, plasmid pCF10 was transferred from E. faecalis OG1rf cells to food strain E. faecalis BF3098c and that the plasmid subsequently persisted in these environments. Very high frequency of transfer was observed in sausage (10 −3/recipient) if compared to cheese (10 −6) and plate mating (10 −4). Transconjugants were subsequently verified by PCR. The second transmissible element was the plasmid harbouring the vancomycin resistance (VanA phenotype) from E. faecalis A256. The transfer of this antibiotic resistance to a food strain of E. faecalis was studied in vitro and in food models. Although the transfer of vancomycin resistance was achieved in all the environments, the highest conjugation frequencies were observed during the ripening of fermented sausages, reaching 10 −3 transconjugants/recipient cell. PCR confirmed the transfer of the VanA genotype into a food associated Enterococcus strain. This study showed that even in the absence of selective pressure, mobile genetic elements carrying antibiotic resistance and virulence determinants can be transferred at high frequency to food associated enterococci during cheese and sausage fermentation.

Evolution of microbial populations and biogenic amine production in dry sausages produced in Southern Italy.

To evaluate the occurrence and evolution of biogenic amines during ripening of fermented sausages and their relationship with physico-chemical and microbiological properties of the product. Salsiccia and Soppressata were obtained from artisanal and industrial plants in Basilicata and pH, aW, microbial counts and biogenic amine content were measured. A high variability in amine content was observed. 2-Phenylethylamine and histamine were rarely found, while the tyramine, putrescine and cadaverine content increased during ripening. No correlation was found between individual biogenic amine content, microbial counts or physico-chemical parameters. Starter cultures did not necessarily prevent the production of biogenic amines whose total contents were usually higher in Soppressata, a product with a larger diameter and aW compared with Salsiccia. Literature findings on biogenic amine content and the evolution of microbial populations were confirmed. Normal ranges for amine content in Salsiccia and Soppressata are reported.

Effectiveness of a Lactobacillus sakei Starter Culture in the Reduction of Biogenic Amine Accumulation as a Function of the Raw Material Quality

The effectiveness of an amine-negative starter culture (Lactobacillus sakei CTC494) in the reduction of biogenic amine production during the ripening of fermented sausages was examined. Four batches were manufactured in parallel:spontaneously fermented and starter-mediated sausages were manufactured from two lots of raw materials of different hygienic quality. Besides the biogenic amine contents, changes in the microbial counts, nitrogenous fractions, pH, and water content were measured at several sampling points during the ripening process. In sausages manufactured from good quality meat, the starter strain of L. sakei reduced and even inhibited biogenic amine accumulation during sausage fermentation, the end products showing extremely low biogenic amine contents (tyramine levels less than 15 mg/kg of dry matter and putrescine and cadaverine levels less than 5 mg/kg of dry matter). Nevertheless, starter-mediated sausages made from poorer-quality raw materials showed much higher amine contents (308, 223, and 36 mg/kg of dry matter of cadaverine, tyramine, and putrescine, respectively), which were only slightly lower than those of the spontaneously fermented sausages made from the same raw materials. The relatively high bacterial numbers of raw materials of poorer-hygienic quality diminished the beneficial effect of the starter strain. Therefore, the effectiveness of the starter was strongly dependent on the hygienic quality of the raw materials used.

Tyramine degradation by micrococci during ripening of fermented sausage

The ability of tyramine oxidase exhibiting strains of Micrococcus varians to degrade tyramine in vivo during sausage fermentation was investigated. Fermented sausage was produced with a tyramine forming strain of Lactobacillus curvatus which acquired a final tyramine concentration of 190ppm. The addition of either one of two strains of M. varians exhibiting a potential to oxidise tyramine decreased the amount of tyramine formed to 160 and 150ppm, respectively. No effect on growth of L. curvatus and pH development in the fermented sausage was observed when micrococci were present during a three weeks ripening period. Sausage fermentation was further carried out with a non-amine forming strain of L. sake and M. varians after addition of 100ppm tyramine to the raw material. The amount of tyramine in the end product was 60ppm, and during the first 10 days of ripening the decrease was faster on the outside of the sausage.

Use of Bacterial Cultures in the Ripening of Fermented Sausages

Pure bacterial cultures were used in the production of Argentina salami, the most popular cured meat product in the country. Three selected groups of two strains each of Lactobacillus plantarum and Micrococcus varians were used as a starter cultures, with two different sugar concentrations. Apart from the use of these starter cultures, the salami was manufactured under the same conditions normally used in industrial production. When 0.6% sucrose was used, the levels of L. plantarum and M. varians were 108 and 107 CFU/g, respectively, on the second day of ripening. Similar levels of lactic acid bacteria were found in non-inoculated sausages at 2 d post-preparation. Under these conditions, coliforms decreased significantly. The final pH of the inoculated and uninoculated sausage were 5.0 and 5.2, respectively, after 7 d of ripening. When 0.9% glucose plus 0.6% sucrose was added, the level of lactic acid bacteria was 109 CFU/g on the second day, a value that remained constant in the inoculated sausages to the end of the ripening period. Staphylococci showed a marked decrease in population, while coliforms disappeared on the second or third day. The final pH of 4.40 or 4.55 was reached within 4 d. The product obtained under these conditions had a firm texture, a good slicing surface and pleasant flavor and aroma. The use of starter cultures in cured dry Argentine-style sausage shortened the ripening period from 14 to 7 d.