Characteristics of lactobacilli isolated from dry fermented sausages

A study of the microflora of Spanish dry fermented sausages showed a similar pattern to that observed in other sausages during ripening. Lactic acid bacteria and organisms growing on Mannitol-salt-agar increased during the first five days, remaining at constant levels afterwards. From MRS agar, 368 strains were isolated and characterized. All Lactobacillus strains (343) could be separated into three groups according to their reactions in the API-50 L system. The biochemical characteristics of the Lactobacillus strains analyzed were those typical of isolates from sausages and other meat products. The extracellular and intracellular lipolytic activities of some strains of the three groups were also studied. It is concluded that lipolytic activity of lactobacilli is mainly directed against mono- and diglycerides and short-chain fatty acid triglycerides.     

Selected characteristics of micrococci isolated from Spanish dry fermented sausages

The flora development of two batches of Spanish dry sausages has been studied. Lactic acid bacteria and organisms growing on Mannitol—Salt agar increased during the first five days, remaining at constant levels afterwards. From Mannitol—Salt agar, 629 strains were isolated. The maximum recovery of Gram-positive, catalase-positive cocci was between 5 and 15 days of ripening and after 20 days no micrococci were detected. All isolates of nitrate reducing micrococci (42 strains) showed an acceptable growth at temperatures (19–25°C) and water activities (0.93–0.95) of the sausages during the fermentation step. From the quantitative determination of the nitrate reduction ability, six strains were selected as potential starters for industrial sausage production.     

A survey of antibiotic resistance in Micrococcaceae isolated from Italian dry fermented sausages

The transfer of bacteria that are resistant to antimicrobial agents or resistance genes from animals to humans via the food chain is increasingly a problem. Therefore, it is important to determine the species and the numbers of bacteria involved in this phenomenon. For this purpose, 148 strains of microstaphylococci were isolated from three types of Italian dry fermented sausages. Eight of 148 strains belonged to the genera Kocuria and Micrococcus. The remaining 140 strains belonged to 11 different species of the genus Staphylococcus. The species most frequently isolated was Staphylococcus xylosus, followed by Staphylococcus saprophyticus and Staphylococcus aureus. Antibiotic resistance levels differed among the species and depended on the strain origin. Microstaphylococci were generally susceptible to beta-lactams, but 12 strains were resistant to methicillin, 8 were resistant to oxacillin, and 9 were resistant to penicillin G. No resistance was observed for aminoglicosides and cephalosporines. Many strains were resistant to sulfonamide, colistin suphate, tetracyclin, and bacitracin. Two strains of S. aureus, four strains of S. xylosus, and one strain of Staphylococcus sciuri were able to grow in the presence of 8 microg of vancomycin per g, but all strains were susceptible to teicoplanin. Twenty-two microstaphylococci were resistant to at least five of the tested antibiotics. The multiresistant strain S. aureus 899 was unaffected by eight antibiotics, including vancomycin and methicillin, indicating that a more prudent use of antibiotics in animal husbandry and better hygienic conditions during production should be encouraged because they can play a major role in reducing the incidence of such multiresistant microorganisms and the possible spread of the genetic elements of their resistance.     

Proteolytic and lipolytic activities of mould strains isolated from Spanish dry fermented sausages

Proteolytic and lipolytic activities of ninePenicillium strain and oneMucor strain previously isolated from Spanish dry fermented sausages have been studied.P. camemberti STCC 2267 andAspergillus oryzae ATCC 9362 were also used. Myofibrillar and sarcoplasmic proteins as well as fat extracted from pork meat and -naphthyl acetate, -naphthyl caprilate and -naphthyl laurate were used as substrates. Mould strains were grown in an enrichment medium prepared at pH 5.5 and 7.0 and malt extract broth. Strains were incubated at 18°C and 22°C. Myofibrillar proteins and -naphthyl caprilate were the most hydrolysed substrates. The greater enzymatic activities were observed at a pH 7.0 and 22°C. However, five mould strains showed considerable enzymatic activities under conditions similar to those used for ripening dry fermented sausages. These strains can be assayed as potential starter cultures for industrial sausage production.     

Microbiological and sensory quality of dry fermented sausages containing alginate-microencapsulated Lactobacillus reuteri

The probiotic bacterium Lactobacillus reuteri was added to dry sausage batter, without or after being microencapsulated in alginate using either extrusion or emulsion technology. Pediococcus pentosaceus and Staphylococcus carnosus were added at 7 log cfu/g as starter cultures for fermentation. The sausage batter was stuffed in 55 mm fibrous casings and fermented, with smoking, at 相似文献   

Amino acid-decarboxylase activity of bacteria isolated from fermented pork sausages.

The occurrence of amino acid-decarboxylase activity in 92 strains of lactic acid bacteria, coagulase-negative staphylococci, and Enterobacteriaceae isolated from Spanish fermented pork sausages was investigated. The presence of biogenic amines in a decarboxylase synthetic broth was determined by ion-pair high performance liquid chromatography with o-phtalaldehyde post-column derivatization. Among the 66 lactic acid bacteria strains tested, 21 lactobacilli (in particular, Lactobacillus curvatus) and all 16 enterococci were amine producers. Tyramine was the main amine produced by these bacteria, although they also produced phenylethylamine, tryptamine, and/or the diamines putrescine and cadaverine. None of the lactic acid bacteria produced histamine. Coagulase-negative staphylococci were found to be negative amine-producers. Aromatic monoamines, apart from histamine, were not formed by Enterobacteriaceae. This family was responsible for cadaverine and putrescine production. The results obtained for biogenic amine production by bacteria in a synthetic medium suggest that amino acid-decarboxylase activity is strain dependent rather than being related to specific species.     

Accelerated ripening of dry fermented sausages

Research on accelerated ripening of dry fermented sausages started in the early 1990s. Fermented sausages manufacture is a very important part of meat industry in many countries and the acceleration of ripening would result in a reduction of the storage time and would increase the profit margin and the competitiveness of the end product. The different strategies that have been assayed with this purpose include ripening at elevated temperature, use of genetically modified starter bacteria, addition of enzymes and addition of slurry systems. Over the last decade, numerous studies have been carried out, especially on the addition of enzymes. The aim of this paper is to review and update the knowledge on this topic. The more recent approaches in this field, such as the use of microbial extracts, are also presented.     

Use of molecular tools to characterize Lactobacillus spp. isolated from Greek traditional fermented sausages

In this study, our purpose was to molecular characterize Lactobacillus strains isolated from naturally fermented sausages, produced in three different processing plants in continental Greece, in order to investigate the differences of strains coming from different producing areas. Three-hundred and thirty eight strains were isolated throughout the fermentation periods on MRS. They were identified by species-specific PCR and sequencing of partial 16S rRNA gene. The results obtained highlighted that the main populations involved in the fermentations studied belonged to the species Lactobacillus sakei, Lactobacillus plantarum and Lactobacillus curvatus. However, for each of the fermentations, the percentage of isolation for the three main species was different. Molecular characterization of these strains was performed by RAPD-PCR with primer M13 and cluster analysis was applied to define relations and degrees of similarities between strains. This analysis led to the understanding that some strains were plant-specific, whereas others shared a degree of homology independently of the provenience. This evidence is highlighting the capability of the strains to adapt to specific production condition, becoming the main responsible for the transformations, thereby influencing the final characteristics of the sausages.     

风干香肠中乳酸菌的分离鉴定及益生特性研究

由风干香肠中分离纯化得到的3株乳酸菌ORC2、QM7和QM8,均能产乳酸、革兰氏染色阳性、接触酶阴性。经系统发育分析,结合菌落形态、细胞形态、生化反应试验,确定菌株ORC2和QM7为肠膜明串珠菌,QM8为柠檬明串珠菌。乳酸菌ORC2、QM7和QM8均能降低培养基中的胆固醇,且对·OH、DPPH·和O-2·有一定的清除能力,其清除率都与细胞浓度呈正相关。在细胞浓度为5×108CFU/mL时,菌株ORC2对·OH的清除率最高,为65.36%;菌株QM8对DPPH·的清除率最高,为61.21%;而对O-2·的清除率最高的菌株为QM7,达到75.70%。菌株QM7在培养96 h能清除最多的胆固醇,清除率为51.2%。     

Proteolytic activity of Lactobacillus strains isolated from dryfermented sausages on muscle sarcoplasmic proteins

The proteolytic activity of seven strains of Lactobacillus from two species isolated from dry cured sausages was assayed using a soluble muscle extract as a source of proteins, at a temperature of 30 °C. The results indicated that the strains of Lactobacillus plantarum tested had the more active proteolytic system, showing the highest amino acid release in the medium after 72 hr of incubation (L. plantarum CRL 681) when the microorganism was in the stationary phase of growth. The strains of L. casei showed a continued hydrolytic activity with a lower amino acids concentration along the studied period. The SDS-PAGE profiles showed that the major changes in sarcoplasmic proteins were produced in the 13 kDa and 36-40 kDa molecular weights region.     

干发酵香肠中的生物胺

综述干发酵香肠中生物胺产生的条件,国外干发酵香肠中常见生物胺的种类及含量,与生物胺积累有关的微生物以及影响生物胺产生的理化因素,并提出了控制干发酵香肠中生物胺积累的措施。     

从自然发酵风干肠中分离出的葡萄球菌生产性能的研究

从自然发酵风干肠中分离出五株葡萄球菌,通过菌种的耐亚硝酸盐能力、耐酸能力、生长温度和最适生长温度、蛋白质及脂肪降解活性等实验,对其生产性能进行研究。结果表明,木糖葡萄球菌(Staphylococcu sxylosus,S2)能在0.015‰亚硝酸盐中生长;耐pH为3的酸性环境;不耐65℃的高温,烘烤后可被灭活;30～35℃内旺盛生长;具有降解蛋白质和脂肪的能力,符合作为肉制品发酵剂的要求。      

Molecular characterization of Lactobacillus species isolated from naturally fermented sausages produced in Greece,Hungary and Italy

The ecology of the lactic acid bacteria (LAB) in naturally fermented sausages produced in three European countries was investigated with the purpose of defining the geographic distribution of specific populations responsible for the fermentation and maturation of the sausages. Three-hundred and fifty eight strains belonging to the LAB group were isolated and identified by PCR-DGGE and sequencing. Three species were common to all three countries studied and were the most numerous. Lactobacillus curvatus, L. plantarum and L. sakei strains were subjected to RAPD-PCR followed by cluster analysis to obtain a genetic characterization. The distributions reflected in almost all cases the provenience of the strains, thereby distinguishing Italian, Greek and Hungarian LAB populations. The application of molecular methods for the identification and characterization of bacterial populations isolated from naturally fermented products allows a better understanding of the ecology. As a consequence measures can be taken to protect the biodiversity characterizing a specific system.     

Differentiation of Staphylococci from Iberian dry fermented sausages by protein fingerprinting

The Staphylococci populations in different types of Iberian dry fermented sausages from central-west Spain were identified. A simple electrophoretic method of whole-cell proteins and extracellular protein profiling was evaluated for speed of identification. This study was correlated with a 16S rRNA gene sequence analysis and biochemical identification by API Staph. A total of 81 isolates were identified by SDS-PAGE of the whole-cell proteins. These showed stable profiles in the range 99-14kDa that were clearly different for the different species, and were grouped into clusters together with the profiles of the eight reference strains. SDS-PAGE of the extracellular protein extracts provided additional characteristic banding patterns for the characterization of the Staphylococcus species present. The whole-cell SDS-PAGE showed that the predominant species was Staphylococcus saprophyticus (61.7%) followed by Staphylococcus aureus (19.7%). The identifications were confirmed by the 16S rRNA gene sequencing and by a BLAST search of the GenBank database. However, the API Staph biochemical identifications were frequently erroneous at the species level. In sum, SDS-PAGE analysis showed itself to be rapid and accurate in identifying the most commonly encountered Staphylococcus isolates in dry fermented sausages.     

Antioxidant activity of Lactobacillus plantarum strains isolated from traditional Chinese fermented foods

Eleven Lactobacillus plantarum strains isolated from traditional Chinese fermented foods were investigated for their in vitro scavenging activity against hydroxyl and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals, and their resistance to hydrogen peroxide. L. plantarum C88 at a dose of 10(10) CFU/ml showed the highest hydroxyl radical and DPPH scavenging activities, with inhibition rates of 44.31% and 53.05%, respectively. Resistance of intact cells to hydrogen peroxide was also found in all strains. L. plantarum C88 was the most resistant strain against hydrogen peroxide. When L. plantarum C88 was administered to senescent mice suffering oxidative stress induced by d-galactose, the serum superoxide dismutase activity, the glutathione peroxidase activity and the total antioxidant capacity in liver increased significantly, while the level of malondialdehyde in liver decreased significantly. L. plantarum C88 isolated from traditional Chinese fermented dairy tofu could be considered as a potential antioxidant to be applied in functional foods.     

从风干肠中分离出的三株乳酸菌发酵性能的研究

对从自然发酵风干肠中分离出的三株乳酸菌的发酵性能进行研究,主要包括菌种的耐盐性试验、耐亚硝酸盐试验、生长温度的测定、产酸速率的测定、蛋白质及脂肪降解活性试验、拮抗性试验。结果表明:分离乳酸菌1号菌的耐热性强,可能在烘烤后继续发挥产酸效力,因此不适合作为发酵剂使用;2号菌、3号菌则可在6%的食盐浓度下和0.15g/kg的亚硝酸钠下生长,在65℃以上完全不生长,产酸速度快,不分解蛋白质和脂肪,相互之间无拮抗作用,完全符合肉制品发酵剂的要求。     

自然发酵风干肠中葡萄球菌的筛选与鉴定

以自然发酵风干肠为研究对象,分析了风干肠中细菌总数、葡萄球菌和乳酸菌的变化情况,结果表明,发酵初期葡萄球菌受到乳酸菌的抑制,增长缓慢;发酵后期乳酸菌生长进入衰退期,葡萄球菌开始快速繁殖。通过对风干肠中葡萄球菌的分离筛选,共鉴定出5株符合生产要求的葡萄球菌,分别为模仿葡萄球菌(Staphylococcus simulans),木糖葡萄球菌(Staphylococcus xylosus),腐生葡萄球菌(Staphylococcus saprophyticus),表皮葡萄球菌(Staphylococcus epidermidis)和克氏葡萄球菌(Staphylococcus kloosii)。     

Characterization of Micrococcaceae isolated from dry fermented sausage

One hundred Micrococcaceae strains were isolated from two types of naturally fermented dry sausages at four different stages of the ripening process in order to select the most suitable strains according to their technological characteristics including antimicrobial activity against foodborne pathogens. Identification of the isolates revealed that 91% belonged to genus Staphylococcus, whereas 5% were identified as Kocuria varians, 2% asArthrobacter agilis and 2% as Dermacoccus nishinomiyaensis. The species most often isolated was S. saprophyticus (22%), followed by S. carnosus (20%) and S. xylosus (10%). The isolated strains of S. xylosus (10 isolates), S. carnosus (20 isolates) and K. varians (five isolates) were further characterized. A large majority of the above strains was able to grow in the presence of 10% and 15% NaCl, to reduce nitrates at 18°C and to hydrolyse casein. The majority of the strains of S. xylosus produced acetoin and 30% of them hydrolysed tributyrin. All S. xylosus strains and a large majority of S. carnosus and K. varians strains exhibited an anti-listerial activity against three Listeria monocytogenes strains.The enzymatic potential of the strains was evaluated using the API ZYM system. S. xylosus strains exhibited high β -galactosidase and esterase–lipase activities, whereas S. carnosus strains indicated strong cysteine aminopeptidase and acid phosphatase activities and K. varians indicated very weak activities of the enzymes tested. A rapid characterization of the above strains according to their enzymatic pattern could be achieved in order to follow the strains selected as starter cultures during sausage fermentation. The contribution of the selected strains to a possible inhibition ofL. monocytogenes in situ on fermented meats would be of considerable interest to enhance the hygienic quality of these products.     

New insertion sequence in Lactobacillus fructivorans strains isolated from spoiled sake

A genomic subtraction between Lactobacillus fructivorans ATCC 8288(T) and an alcoholophilic strain of L. fructivorans (ATCC 15435 strain H-1) was performed. Subtractive DNA fragments were identified to be parts of a 1468-bp insertion sequence, a few copies of which were present with in four alcoholophilic strains tested. The insertion sequence, which we named ISLfr1, seems to belong to the ISL3 family. For three alcoholophilic strains, primer walk sequencing revealed that ISLfr1 was inserted into the ORF, which showed homology to accC2 of Lactobacillus plantarum WCFS1. accC2 in one strain seemed to be nonfunctional because of deletion and frameshift mutations, although ISLfr1 was not found in this gene. Although accC2 encodes acetyl-CoA carboxylase, which is essential for lipid metabolism, L. fructivorans was found to have a homolog of accC2. Nonfunctional accC2 might be involved in producing the unusually long acyl chains observed only in alcoholophilic L. fructivorans. From a food engineering standpoint, it appears that the concomitant PCR amplification of ISLfr1 and rDNA is useful for the specific detection of alcoholophilic L. fructivorans.     

Biogenic amines in dry fermented sausages: a review

Biogenic amines are compounds commonly present in living organisms in which they are responsible for many essential functions. They can be naturally present in many foods such as fruits and vegetables, meat, fish, chocolate and milk, but they can also be produced in high amounts by microorganisms through the activity of amino acid decarboxylases. Excessive consumption of these amines can be of health concern because their not equilibrate assumption in human organism can generate different degrees of diseases determined by their action on nervous, gastric and intestinal systems and blood pressure. High microbial counts, which characterise fermented foods, often unavoidably lead to considerable accumulation of biogenic amines, especially tyramine, 2-phenylethylamine, tryptamine, cadaverine, putrescine and histamine. However, great fluctuations of amine content are reported in the same type of product. These differences depend on many variables: the quali-quantitative composition of microbial microflora, the chemico-physical variables, the hygienic procedure adopted during production, and the availability of precursors. Dry fermented sausages are worldwide diffused fermented meat products that can be a source of biogenic amines. Even in the absence of specific rules and regulations regarding the presence of these compounds in sausages and other fermented products, an increasing attention is given to biogenic amines, especially in relation to the higher number of consumers with enhanced sensitivity to biogenic amines determined by the inhibition of the action of amino oxidases, the enzymes involved in the detoxification of these substances. The aim of this paper is to give an overview on the presence of these compounds in dry fermented sausages and to discuss the most important factors influencing their accumulation. These include process and implicit factors as well as the role of starter and nonstarter microflora growing in the different steps of sausage production. Moreover, the role of microorganisms with amino oxidase activity as starter cultures to control or reduce the accumulation of biogenic amines during ripening and storage of sausages is discussed.