Starters in the processing of meat products

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Baechu-kimchi is a traditional Korean dish of fermented vegetables, in which kimchi cabbage is the major ingredient. Seafood is added to baechu-kimchi in coastal areas, giving this dish regional diversity. However, little is known about how the addition of seafood affects the bacterial diversity of kimchi. Therefore, in this study, the bacterial diversity of five varieties of baechu-kimchi with seafood and one variety of baechu-kimchi without seafood was analyzed using culture-independent techniques. In 81.7% of all kimchi analyzed, the predominant species were members of the phylum Firmicutes and the lactic acid bacteria, Latilactobacillus sakei, Leuconostoc mesenteroides, Pediococcus inopinatus, and Weissella koreensis. These organisms were similar to those identified in baechu-kimchi without the addition of seafood, which was used as a control group, and bacterial community of previously reported kimchi. Therefore, the results of this study confirmed that the addition of seafood did not significantly affect the bacterial community in baechu-kimchi.

Usage of in situ exopolysaccharide-forming lactic acid bacteria in food production: Meat products-A new field of application?

In the meat industry, hydrocolloids and phosphates are used to improve the quality attributes of meat products. However, latest research results revealed that the usage of exopolysaccharide (EPS)-forming lactic acid bacteria (LAB), which are able to produce EPS in situ during processing could be an interesting alternative. The current review aims to give a better understanding of bacterial EPS production in food matrices with a special focus on meat products. This includes an introduction to microbial EPS production (homopolysaccharides as well as heteropolysaccharides) and an overview of parameters affecting EPS formation and yield depending on LAB used. This is followed by a summary of methods to detect and characterize EPS to facilitate a rational selection of starter cultures and fermentation conditions based on desired structure-function relationships in different food matrices. The mechanism of action of in situ generated EPS is then highlighted with an emphasis on different meat products. In the process, this review also highlights food additives currently used in meat production that could in the future be replaced by in situ EPS-forming LAB.

Effect of fermentation by various bacterial strains on quality of dried duck meat slice

The effects of fermentation on the sensory qualities, lipid oxidation, harmful substances, and microbial growth of dried duck meat slice (DDMS) were investigated. The results showed that the optimal fermentation was controlled at 22.18 °C for 49.15 h with the mixed inoculation (7.09 log CFU/g) of Lactobacillus acidophilus and Pediococcus pentosaceus (2:1). Under the optimal fermentation conditions, the fermented DDMS presented higher scores of color (9.0 ± 0.16), aroma (8.8 ± 0.35), and total (8.9 ± 0.24) with lower hardness (5316 ± 98.80 g), compared to control (8.6 ± 0.21, 8.3 ± 0.26, 8.4 ± 0.08, and 7016 ± 114.17 g, respectively). Meanwhile, the histamine content decreased, and the nitrite content was reduced by nearly 60% in fermented DDMS. The lipid oxidation and microbial growth (Escherichia coli, mold, and yeast) in DDMS were also inhibited by fermentation. It provides useful data for improving the quality and safety of meat products.

Effect of a Debaryomyces hansenii and Lactobacillus buchneri Starter Culture on Aspergillus westerdijkiae Ochratoxin A Production and Growth during the Manufacture of Short Seasoned Dry-Cured Ham

Recently, specific dry-cured hams have started to be produced in San Daniele and Parma areas. The ingredients are similar to protected denomination of origin (PDO) produced in San Daniele or Parma areas, and include pork leg, coming from pigs bred in the Italian peninsula, salt and spices. However, these specific new products cannot be marked as a PDO, either San Daniele or Parma dry cured ham, because they are seasoned for 6 months, and the mark PDO is given only to products seasoned over 13 months. Consequently, these products are called short-seasoned dry-cured ham (SSDCH) and are not branded PDO. During their seasoning period, particularly from the first drying until the end of the seasoning period, many molds, including Eurotium spp. and Penicillium spp., can grow on the surface and work together with other molds and tissue enzymes to produce a unique aroma. Both of these strains typically predominate over other molds. However, molds producing ochratoxins, such as Aspergillus ochraceus and Penicillium nordicum, can simultaneously grow and produce ochratoxin A (OTA). Consequently, these dry-cured hams may represent a potential health risk for consumers. Recently, Aspergillus westerdijkiae has been isolated from SSDCHs, which could represent a potential problem for consumers. Therefore, the aim of this study was to inhibit A. westerdijkiae using Debaryomyces hansenii or Lactobacillus buchneri or a mix of both microorganisms. Six D. hansenii and six L. buchneri strains were tested in vitro for their ability to inhibit A. westerdijkiae. The strains D. hansenii (DIAL)1 and L. buchneri (Lb)4 demonstrated the highest inhibitory activity and were selected for in situ tests. The strains were inoculated or co-inoculated on fresh pork legs for SSDCH production with OTA-producing A. westerdijkiae prior to the first drying and seasoning. At the end of seasoning (six months), OTA was not detected in the SSDCH treated with both microorganisms and their combination. Because both strains did not adversely affect the SSDCH odor or flavor, the combination of these strains are proposed for use as starters to inhibit OTA-producing A. westerdijkiae.

Interspecies assertiveness of Lactobacillus curvatus and Lactobacillus sakei in sausage fermentations

Lactobacillus (L.) curvatus and L. sakei contain strains, which are assertive in sausage fermentation. Previous work has demonstrated differences in assertiveness at strain level within one species, and revealed either exclusion of competitors by complementary partner strains or their inhibition by single strains. This work addresses interspecies differences in the assertiveness of L. curvatus and L. sakei. Strain sets of L. curvatus and L. sakei were employed as starters in a fermented sausage model and their abundancy upon fermentation was determined by strain-specific MALDI-TOF MS identification. Generally, single or groups of L. sakei strains outcompeted L. curvatus strains. In multiple growth tests employing mMRS and mMSM it could be shown that assertive L. sakei strains can be predicted along their μ max in mMSM. Still, L. curvatus TMW 1.624 could suppress all L. curvatus and most L. sakei strains in competitive settings. This could be referred to its expression of several bacteriocins, which are active against all of the L. curvatus strains. Strain specific differences could be demonstrated in the susceptibility of L. sakei to bacteriocins, and in oxidative stress tolerance, which is higher in co-existing L. sakei strains than in the bacteriocin producer. This suggests that tolerance to bacteriocins and oxidative stress represent additional determinants for assertiveness, above previously reported bacteriocin production versus metabolic complementarism of partner strains.

Application of isolated Lactobacillus sakei and Staphylococcus xylosus strains as a probiotic starter culture during the industrial manufacture of Tunisian dry-fermented sausages

For decades, lactic acid bacteria has been isolated and selected to be used as starter cultures in meat fermentation for standardization and management of quality of dry-fermented sausage which constitute a considerable challenge. The aim of this study was to evaluate the effect of Lactobacillus sakei strains, isolated from different origins, on qualities of dry-fermented sausages. These last, manufactured with different combinations of starter cultures (L. sakei + Staphylococcus xylosus), were ripened, using the same raw materials and conditions, for 45 days. Samples were collected during this period, and microbiological, physicochemical, fatty acid profile, and sensorial analyses determined. Lactic acid bacteria were the dominant flora during ripening. A desirable PUFA/SFA ratio, corresponding to 1:1.7 (0.6), was detected after 24 days of maturation in sausages inoculated by L. sakei BMG 95 and S. xylosus. Sensory analysis showed that fermented sausages manufactured with L. sakei and S. xylosus had a more desirable odor, flavor, and texture and consequently were preferred overall. In particular, sensory panellists preferred sausages produced with either L. sakei 23K or L. sakei BMG 95 when compared to fermented sausage produced with a commercial starter or no starter at all.

Effect of different strategies of Lactobacillus plantarum incorporation in chorizo sausages

BACKGROUND

Chorizo is a high-value Spanish-type dry fermented sausage, highly appreciated by consumers. In this kind of product, Lactobacillus plantarum plays an important role in the fermentation process and can also be considered as a probiotic. The impact of different strategies for incorporating probiotic L. plantarum into the physico-chemical, microbiological, and sensorial characteristics of chorizo sausages was studied. These strategies were: free cells (Cfc); alginate beads (Calg); water-in-oil emulsion (Cwo), and water-in-oil-in-water emulsion (Cwow). Proximate composition, weight loss, pH, a_w , color, and microbiological behavior were evaluated during the ripening (20 days) of chorizo.

RESULTS

The strategy of incorporating L. plantarum significantly affected the proximate composition, pH, and a_w of sausages. However, the traditional red color of chorizo was maintained for all formulations. The incorporation of probiotics as free cells or encapsulated in alginate beads resulted in higher counts of lactic acid bacteria and L. plantarum, lower counts of Enterobacteriaceae, and in acceptable sensory scores.

CONCLUSION

Overall, the quality of chorizo sausages was conditioned by the incorporation strategy, and the addition of probiotics in alginate beads (Calg) was the most effective strategy. © 2019 Society of Chemical Industry.

The life and times of yeasts in traditional food fermentations

Yeasts are eukaryotic microorganisms which have a long history in the biotechnology of food production, as they have been used since centuries in bread-making or in the production of alcoholic beverages such as wines or beers. Relative to this importance, a lot of research has been devoted to the study of yeasts involved in making these important products. The role of yeasts in other fermentations in association with other microorganisms - mainly lactic acid bacteria - has been relatively less studied, and often it is not clear if yeasts occurring in such fermentations are contaminants with no role in the fermentation, spoilage microorganisms or whether they actually serve a technological or functional purpose. Some knowledge is available for yeasts used as starter cultures in fermented raw sausages or in the production of acid curd cheeses. This review aimed to summarize the current knowledge on the taxonomy, the presence and potential functional or technological roles of yeasts in traditional fermented plant, dairy, fish and meat fermentations.

Physicochemical, sensory and microbiological characterization of Asturian Chorizo, a traditional fermented sausage manufactured in Northern Spain

Industrial standardization of fermented meat products requires starter culturesto avoid random variations in the initial microbiota of food matrix. This allows to homogenize production batches regarding sensory and physicochemical characteristics. Also, starters contribute to assure safety, as they compete with pathogens or spoilage species, facilitating pH reduction and secretion of inhibitors. Asturian Chorizo is a traditional fermented sausage from Northern Spain, still produced in a traditional way, without starters. This work describes its characterization at the sensory, physicochemical and microbiological levels. In contrast to other fermented sausages, Asturian Chorizo microbiota is represented mainly by Lactobacillus plantarum, with secondary contributions from Lb. sakei and Lb. futsai. This results may path the way towards development of specific starter cultures for this product, avoiding the loss of the original characteristics of the fermented product in a traditional way, as it would happen in the case of using industrial processes with conventional starters.

Monitoring of assertive Lactobacillus sakei and Lactobacillus curvatus strains using an industrial ring trial experiment

AIMS

In a previous study, we used a 5-day fermenting sausage model to characterize assertiveness of Lactobacillus curvatus and Lactobacillus sakei starter strains towards employ autochthonous contaminants. In this work, we probed those findings and their transferability to real sausage fermentation including the drying process in an industrial ring trial experiment.

METHODS AND RESULTS

Raw fermented sausages ('salami') were produced with three L. curvatus and four L. sakei strains as starter cultures in cooperation with three manufacturers from Germany. We monitored pH, water activity and microbiota dynamics at strain level over a total fermentation and ripening time of 21 days by MALDI-TOF-MS identification of isolates. The principal behaviour of the strains in real sausage fermentations was the same as that one observed in the 5-day model system delineating single strain assertiveness of a bacteriocin producer from co-dominance of strains.

CONCLUSIONS

The water activity decrease, which is concomitant with the sausage ripening process has only limited impact on the assertiveness and survival of the starter strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results of a 5-day model can provide insight in the assertiveness of a specific starter strain in sausage fermentation.

Phylogenomic Analysis of Lactobacillus curvatus Reveals Two Lineages Distinguished by Genes for Fermenting Plant-Derived Carbohydrates

Lactobacillus curvatus is a lactic acid bacterium encountered in many different types of fermented food (meat, seafood, vegetables, and cereals). Although this species plays an important role in the preservation of these foods, few attempts have been made to assess its genomic diversity. This study uses comparative analyses of 13 published genomes (complete or draft) to better understand the evolutionary processes acting on the genome of this species. Phylogenomic analysis, based on a coalescent model of evolution, revealed that the 6,742 sites of single nucleotide polymorphism within the L. curvatus core genome delineate two major groups, with lineage 1 represented by the newly sequenced strain FLEC03, and lineage 2 represented by the type-strain DSM20019. The two lineages could also be distinguished by the content of their accessory genome, which sheds light on a long-term evolutionary process of lineage-dependent genetic acquisition and the possibility of population structure. Interestingly, one clade from lineage 2 shared more accessory genes with strains of lineage 1 than with other strains of lineage 2, indicating recent convergence in carbohydrate catabolism. Both lineages had a wide repertoire of accessory genes involved in the fermentation of plant-derived carbohydrates that are released from polymers of α/β-glucans, α/β-fructans, and N-acetylglucosan. Other gene clusters were distributed among strains according to the type of food from which the strains were isolated. These results give new insight into the ecological niches in which L. curvatus may naturally thrive (such as silage or compost heaps) in addition to fermented food.

Why Are Weissella spp. Not Used as Commercial Starter Cultures for Food Fermentation?

Among other fermentation processes, lactic acid fermentation is a valuable process which enhances the safety, nutritional and sensory properties of food. The use of starters is recommended compared to spontaneous fermentation, from a safety point of view but also to ensure a better control of product functional and sensory properties. Starters are used for dairy products, sourdough, wine, meat, sauerkraut and homemade foods and beverages from dairy or vegetal origin. Among lactic acid bacteria, Lactobacillus, Lactococcus, Leuconostoc, Streptococcus and Pediococcus are the majors genera used as starters whereas Weissella is not. Weissella spp. are frequently isolated from spontaneous fermented foods and participate to the characteristics of the fermented product. They possess a large set of functional and technological properties, which can enhance safety, nutritional and sensory characteristics of food. Particularly, Weissella cibaria and Weissella confusa have been described as high producers of exo-polysaccharides, which exhibit texturizing properties. Numerous bacteriocins have been purified from Weissella hellenica strains and may be used as bio-preservative. Some Weissella strains are able to decarboxylate polymeric phenolic compounds resulting in a better bioavailability. Other Weissella strains showed resistance to low pH and bile salts and were isolated from healthy human feces, suggesting their potential as probiotics. Despite all these features, the use of Weissella spp. as commercial starters remained non-investigated. Potential biogenic amine production, antibiotic resistance pattern or infection hazard partly explains this neglecting. Besides, Weissella spp. are not recognized as GRAS (Generally Recognized As Safe). However, Weissella spp. are potential powerful starters for food fermentation as well as Lactococcus, Leuconostoc or Lactobacillus species.

Antifungal Microbial Agents for Food Biopreservation-A Review

Food spoilage is a major issue for the food industry, leading to food waste, substantial economic losses for manufacturers and consumers, and a negative impact on brand names. Among causes, fungal contamination can be encountered at various stages of the food chain (e.g., post-harvest, during processing or storage). Fungal development leads to food sensory defects varying from visual deterioration to noticeable odor, flavor, or texture changes but can also have negative health impacts via mycotoxin production by some molds. In order to avoid microbial spoilage and thus extend product shelf life, different treatments—including fungicides and chemical preservatives—are used. In parallel, public authorities encourage the food industry to limit the use of these chemical compounds and develop natural methods for food preservation. This is accompanied by a strong societal demand for ‘clean label’ food products, as consumers are looking for more natural, less severely processed and safer products. In this context, microbial agents corresponding to bioprotective cultures, fermentates, culture-free supernatant or purified molecules, exhibiting antifungal activities represent a growing interest as an alternative to chemical preservation. This review presents the main fungal spoilers encountered in food products, the antifungal microorganisms tested for food bioprotection, and their mechanisms of action. A focus is made in particular on the recent in situ studies and the constraints associated with the use of antifungal microbial agents for food biopreservation.

The Effect of Autochthonous Starter Culture, Sugars and Temperature on the Fermentation of Slavonian Kulen

In this study, the effect of an isolated and well-characterised autochthonous starter culture, glucose and maltodextrin (w=0.8%) and temperatures of 12 and 20 °C on fermentation and quality of Slavonian kulen produced using the traditional technology and recipe were investigated. Physicochemical and microbiological analyses were carried out after 20 days of fermentation. Upon the completion of the production process (90 days), a sensory analysis was carried out. Furthermore, pH value was continuously measured throughout the twenty-day fermentation period. The addition of an autochthonous starter culture and sugars and different fermentation temperatures significantly (p<0.05) affected the instrumental colour and texture parameters of the Slavonian kulen. The fermentation was most intense in the samples with added autochthonous starter culture and 0.8% glucose, and fermented at 20 °C. Microbiological analysis showed that samples with added autochthonous starter culture and fermented at higher temperature contained a higher number of lactic acid bacteria and coagulase-negative staphylococci and were safe. Sensory evaluation confirmed the outcomes of physicochemical and microbiological analyses and showed differences among samples fermented at two different temperatures and with added glucose or maltodextrin and an autochthonous starter culture.

Yeast inoculation as a strategy to improve the physico-chemical and sensory properties of reduced salt fermented sausages produced with entire male fat

Yeast inoculation of dry fermented sausages manufactured with entire male fat was evaluated as a strategy to improve sausage quality. Four different formulations with entire male/gilt back fat and inoculated/non-inoculated with Debaryomyces hansenii were manufactured. The use of entire male back fat produced the highest weight losses, hardness and chewiness in dry sausages. Consumers clearly distinguished samples according to drying time and D. hansenii inoculation while the use of entire/gilt back fat was not highly perceived. The presence of androstenone and skatole was close to their sensory thresholds. Androstenone was not degraded during the process but skatole was affected by yeast inoculation. D. hansenii growth on the surface regulated water release during ripening, reduced hardness and chewiness in entire male sausages and resulted with similar texture to gilt sausages. Yeast inoculation inhibited lipid oxidation providing fruity odours and less oxidized fatty sausages in the sensory analysis. The effectiveness of yeast to mask boar taint was demonstrated by sensory analysis.

Phenotypic and genotypic characterization of peptidoglycan hydrolases of Lactobacillus sakei

Lactobacillus sakei, a lactic acid bacterium naturally found in fresh meat and sea products, is considered to be one of the most important bacterial species involved in meat fermentation and bio-preservation. Several enzymes of Lb. sakei species contributing to microbial safeguarding and organoleptic properties of fermented-meat were studied. However, the specific autolytic mechanisms and associated enzymes involved in Lb. sakei are not well understood. The autolytic phenotype of 22 Lb. sakei strains isolated from Tunisian meat and seafood products was evaluated under starvation conditions, at pH 6.5 and 8.5, and in the presence of different carbon sources. A higher autolytic rate was observed when cells were grown in the presence of glucose and incubated at pH 6.5. Almost all strains showed high resistance to mutanolysin, indicating a minor role of muramidases in Lb. sakei cell lysis. Using Micrococcus lysodeikticus cells as a substrate in activity gels zymogram, peptidoglycan hydrolase (PGH) patterns for all strains was characterized by two lytic bands of ∼80 (B1) and ∼70 kDa (B2), except for strain BMG.167 which harbored two activity signals at a lower MW. Lytic activity was retained in high salt and in acid/basic conditions and was active toward cells of Lb. sakei, Listeria monocytogenes, Listeria ivanovii and Listeria innocua. Analysis of five putative PGH genes found in the Lb. sakei 23 K model strain genome, indicated that one gene, lsa1437, could encode a PGH (N-acetylmuramoyl-L-alanine amidase) containing B1 and B2 as isoforms. According to this hypothesis, strain BMG.167 showed an allelic version of lsa1437 gene deleted of one of the five LysM domains, leading to a reduction in the MW of lytic bands and the high autolytic rate of this strain. Characterization of autolytic phenotype of Lb. sakei should expand the knowledge of their role in fermentation processes where they represent the dominant species.

Effect of Addition of Allium hookeri on the Quality of Fermented Sausage with Meat from Sulfur Fed Pigs during Ripening

The effect of the addition of Allium hookeri on the quality of fermented sausage made with meat from sulfur fed pigs was examined, throughout a 60 d ripening period. There were two treatments in animal management: normal feed fed pigs, and sulfur fed pigs given 0.3% sulfur mixed normal feed. Fermented sausage manufactured with meat from normal feed fed pigs, and with meat from sulfur fed pigs, and 1% A. hookeri-containing fermented sausage processed with meat from sulfur fed pigs, were determined at 1 d, 15 d, 30 d, and 60 d. The meat qualities in fermented sausage were measured by DPPH radical scavenging activity (DPPH), ABTS(+) radical scavenging activity (ABTS(+)), total phenolic acids, and total flavonoid contents. Fermented sausage made from pigs that had been fed with 0.3% sulfur was protected from oxidation by reduced free radical, as shown by the significant increase in DPPH and ABTS(+) values, compared with fermented sausage made from normal feed fed pigs (p<0.05). A. hookeri-added fermented sausage with sulfur fed pork was shown to increase the values in DPPH, ABTS(+), total phenolic acid, and total flavonoid contents, by comparison with both the control sausage, and sausage with sulfur fed pork, at 60 d. These results suggest that A. hookeri in meat from sulfur fed pigs could be a source of natural addition, to increase quality in the food industry.

Antiviral Potential of Selected Starter Cultures, Bacteriocins and D,L-Lactic Acid

The antiviral potential of selected bacteria species [lactic acid bacteria (LAB) and micrococcaceae] was examined. By this, the effect of their cell-free supernatants as well as of certain species-related metabolites (sakacin A, nisin, and lactic acid) was investigated on different viruses after exposure at 24 °C for 3 days. Viruses were incubated with supernatants and metabolites in a dilution ratio of 1:10. Data for antiviral effects towards murine norovirus S99 (MNV), influenza A virus A/WSN/33 (H1N1), Newcastle disease virus Montana (NDV) and feline herpesvirus KS 285 (FHV) were generated in vitro simulating pH and temperature conditions according to raw sausage fermentations. Investigations showed no antiviral effect of sakacin A and nisin on MNV, H1N1, FHV and NDV. Furthermore, the antiviral potential of D,L-lactic acid was determined for MNV and H1N1. At raw sausage-related pH values (5.0-6.2) it could be shown that the virus titre for MNV and H1N1 was reduced by a maximum of 3.25 log and 2.5 log units, respectively. In addition, 29 culture supernatants of different bacteria species, mainly LAB and staphylococci, were tested for their antiviral activity against MNV. Only the cell-free supernatant of a Lb. curvatus strain showed a higher virus titre reduction of MNV by 1.25 log units compared to the control. Further studies on the characterisation of this cell-free supernatant were carried out, however, the antiviral substance could not be identified so far.

Characterization of the microbial flora from a traditional Greek fermented sausage

The microbial flora of naturally fermented sausages was studied. Lactic acid bacteria were the dominant species at the end of fermentation in all 3 batches (ca. 10(8) cfu g(-1)). Enterobacteria, Pseudomonas, yeasts and aerobic spore-formers decreased during fermentation and the ripening process and were below the detection limit in the end product. Enterococci exceeded 10(4)-10(5) cfu g(-1) during fermentation and remained constant at this level during ripening. Gram-positive, catalase-positive cocci exceeded 10(5) cfu g(-1), except for batch 1, during the first days of fermentation and then decreased until the end of ripening (10(2)-10(4) cfu g(-1)). No pathogenic staphylococci, sulfite reducing clostridia or Salmonella spp. were detected. Listeria spp. occurred in the first days of fermentation but were eliminated by the end of whole process in all batches. Identification showed that the majority of lactobacilli isolated from MRS agar strains were assigned to the species of Lactobacillus plantarum and Lb. plantarum/pentosus. All the isolated strains from the mannitol salt agar belonged to the genus of Staphylococcus. The predominant species were Staphylococcus saprophyticus, Staphylococcus xylosus and Staphylococcus simulans. The tests used to characterize the lactic acid bacteria and staphylococci as well as their distribution on the three batches were also discussed.

The effect of nitrite and starter culture on microbiological quality of "chorizo"-a Spanish dry cured sausage

The effect of nitrite and starter culture on the survival of Enterobacteriaceae, Micrococcaceae, Lactic acid bacteria and other microorganisms was evaluated during ripening of "chorizo", a Spanish dry sausage. Sodium nitrite 50 and 150 ppm and Lactobacillus sake CL35 added to the "chorizo" have a significant inhibitory effect on Enterobacteriaceae counts but did not on Micrococcaceae. The use of Lact. sake could be an adequate safety factor in this product.

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.

Quality traits of wild boar mould-ripened salami manufactured with different selections of meat and fat tissue, and with and without bacterial starter cultures

Quality traits of wild boar mould-ripened salami were assessed in eight batches produced from two different assortments of meat (hind leg vs. shoulder), fat tissue (backfat from domestic pigs vs. fat tissue from wild boar), and with and without addition of a commercial bacterial starter culture. Chemical composition of finished products (day 35) were in compliance with national food codex. Batches produced with a bacterial starter culture were generally preferred by taste panels, had significantly lower concentrations of TBARS (<1.5 mgmalondialdehyde/kg) and peroxide values (POVs) and lower concentrations of cadaverine (<50 mg/kg), histamine (<10 mg/kg) and putrescine (<60 mg/kg). TBARS and POVs were inversely related to sensory preference scores (r(2)=0.84 and 0.88). Batches produced from shoulder muscles contained significantly higher concentrations of cadaverine, histamine and putrescine. TBARS were highest in batches manufactured with fat tissue from wild boars. These findings should be considered when guides to good practice for the manufacture of game meat products are developed.

Erythromycin- and tetracycline-resistant lactobacilli in Italian fermented dry sausages

AIMS

To assess the frequency of erythromycin- and tetracycline-resistant lactobacilli in Italian fermented dry sausages.

METHODS AND RESULTS

We isolated lactobacilli colonies from 20 salami from the north of Italy (Piacenza province) using selective medium supplemented with erythromycin or tetracycline; we determined the minimum inhibitory concentration and searched for selected erythromycin and tetracycline resistance genes. A total of 312 lactobacilli colonies were genetically ascribed to 60 different strains belonging to seven Lactobacillus species. Lactobacillus sakei, Lactobacillus curvatus and Lactobacillus plantarum were the most frequently found species. Thirty strains (50%) were phenotypically resistant to erythromycin, 45 (75%) to tetracycline and 27 (45%) were resistant to both. The most frequently detected resistance genes were tet(M) and erm(B).

CONCLUSIONS

This study provides evidence of the presence of tetracycline- and, to a lesser extent, erythromycin-resistant lactobacilli in fermented dry sausages produced in northern Italy.

SIGNIFICANCE AND IMPACT OF THE STUDY

Although these antibiotic-resistant lactobacilli could serve as reservoir organisms, in our study, 16 of 20 salami could be considered safe in regard to possible antibiotic resistance gene transfer to pathogens, whereas 4 of 20 could represent a borderline situation.