scholarly journals Behaviour of Listeria monocytogenes and Natural Microflora during the Manufacture of Riojano Chorizo (Spanish Dry Cured Sausage)

2021 ◽  
Vol 9 (9) ◽  
pp. 1963
Author(s):  
Elena Gonzalez-Fandos ◽  
Maria Vazquez de Castro ◽  
Alba Martinez-Laorden
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Low Temperature ◽  
Water Activity ◽  
Low Temperatures ◽  
Production Method ◽  
Starter Cultures ◽  
Natural Microflora ◽  
Traditional Technologies ◽  
Traditional Production

Riojano chorizo is a dry cured sausage manufactured with traditional technologies without adding starter cultures at low temperatures. Its characteristics differ from other types of chorizo since sugars and nitrites are no added and processing temperatures are low- This work evaluates the behaviour of Listeria monocytogenes during the processing of inoculated Riojano chorizo as well as the natural microflora that can play a technological role or be of interest as indicators. The sausage mixture was inoculated with a cocktail of three selected strains of L. monocytogenes (CECT 932, CECT 934 and CECT 4032) (4 log10 CFU/g) and after processed following the traditional production method. Samples were taken before inoculation, after inoculation, after stuffing (day 0) and on days 6, 13, 21 and 28 of processing. L. monocytogenes, mesophiles, Micrococcaceae, lactic acid bacteria, Enterobacteriaceae, S. aureus, sulfite-reducing clostridia and molds and yeast counts were evaluated. Furthermore, pH, water activity and humidity were determined. No growth of L mocytogenes was observed during the first 6 days, when the temperature of processing was 4 °C. The low temperature in the initial stages was a relevant hurdle to control L. monocytoegenes growth. A significant decrease (p ≤ 0.05) in L. monocytogenes counts was observed on day 13 compared to the initial counts. During drying (days 6 to 21) a reduction in this pathogen of 1.28 log CFU/g was observed. The low water activity below 0.92 on day 13 and 0.86 on day 21 seems to be critical for the reduction of L. monocytogenes.

Behavior of Listeria monocytogenes in Skim Milk during Fermentation with Mesophilic Lactic Starter Cultures

1988 ◽  
Vol 51 (8) ◽  
pp. 600-606 ◽  
Author(s):  
MICHELLE M. SCHAACK ◽  
ELMER H. MARTH
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Lactic Acid Bacteria ◽  
Skim Milk ◽  
Starter Cultures ◽  
Plate Count ◽  
Inoculum Level ◽  
Plate Count Agar ◽  
Streptococcus Lactis ◽  
Streptococcus Cremoris

The ability of Listeria monocytogenes to grow and compete with mesophilic lactic acid bacteria was examined. Autoclaved skim milk was inoculated with 103 cells of L. monocytogenes (strain V7 or Ohio)/ml, and with 5.0, 1.0, 0.5 or 0.1% of a milk culture of either Streptococcus cremoris or Streptococcus lactis. Inoculated milks were fermented for 15 h at 21 or 30°C, followed by refrigeration at 4°C. Samples were plated on McBride Listeria Agar to enumerate L. monocytogenes and on either APT Agar or plate count agar to enumerate lactic acid bacteria. L. monocytogenes survived in all fermentations, and commonly also grew to some extent. Incubation at 30°C with 5% S. lactis as inoculum appeared to be the most inhibitory combination for strain V7, causing 100% inhibition in growth based on maximum population attained. S. cremoris at the 5.0% and 0.1% inoculum levels, was slightly less inhibitory to L. monocytogenes at 37°C, but it was slightly more inhibitory to L. monocytogenes at the 1.0% inoculum level than was S. lactis. In general, S. lactis reduced the pH of fermented milks more than did S. cremoris. The population of L. monocytogenes began to decrease before 15 h in only one test combination, which was use of a 5.0% inoculum of S. cremoris and 30°C incubation. In most instances, growth of the pathogen appeared to be completely inhibited when the pH dropped below 4.75.

Relationship Between Water Activity, Salts of Lactic Acid, and Growth of Listeria monocytogenes in a Meat Model System

1992 ◽  
Vol 55 (8) ◽  
pp. 574-578 ◽  
Author(s):  
NING CHEN ◽  
LEORA A. SHELEF
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Moisture Content ◽  
Water Activity ◽  
Sodium Lactate ◽  
Model System ◽  
Cell Numbers ◽  
Maximum Cell ◽  
The Relationship ◽  
Control Samples

The relationship between water activity (aw), lactate, and growth of Listeria monocytogenes strain Scott A was studied in a meat model system consisting of cooked strained beef ranging in moisture content from 25 to 85% (wt/wt). Lactate (4%) depressed meat aw, and differences between aw values in control and lactate-treated samples at each moisture level increased progressively with decrease in moisture, from 0.003 (85% moisture) to 0.046 (25% moisture). Maximum cell numbers per g in control samples stored at 20°C for 7 d were about 109 (45–85% moisture, aw= 0.981–0.994) and 107 (35% moisture, aw = 0.965); there was no growth in meat with 25% moisture (aw = 0.932). Sodium lactate (4%) suppressed listerial growth at >55% and inhibited growth in samples with 25–55% moisture (a < 0.964). Lactate concentrations less than 4% were not listeristatic, but combinations of 2 or 3% lactate with 2% NaCl in samples with 55% moisture inhibited growth. Potassium and calcium lactate were as effective as the sodium salt in suppressing growth and aw.

scholarly journals Non-thermal inactivation of Listeria spp. in a typical dry-fermented sausage: “Bergamasco” salami

2019 ◽  
Vol 8 (3) ◽  
Author(s):  
Erica Tirloni ◽  
Vanessa Di Pietro ◽  
Giuseppe Rizzi ◽  
Francesco Pomilio ◽  
Patrizia Cattaneo ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Lactic Acid Bacteria ◽  
Production Process ◽  
Water Activity ◽  
Growth Potential ◽  
Worst Case ◽  
Fermented Sausage ◽  
Dry Fermented Sausage ◽  
Control Samples

Aim of the present study was the evaluation of the growth potential of Listeria spp. inoculated in the typical North Italian dry fermented sausage “Bergamasco” salami during its production. As it was necessary to carry out the challenge test in the production line of the industry, according to the guidelines of the European Reference Laboratory for Listeria monocytogenes, a non-pathogenic “surrogate” microorganism was used: for the inoculum, two strains of Listeria innocua (1 ATCC, 1 strain isolated from a similar substrate) were used. The inoculation of the samples occurred during grinding and mixing of the sausage mass, before the filling. To avoid cross-contamination, the control samples were produced before the contaminated ones. After the dripping, salamis were subjected to the normal production process (drying and maturation in five steps at specific temperatures and humidity rates). The inoculated products were subjected to the enumeration of Listeria spp. at T0 (day of inoculation) and at T4 (post-drying), and every 10 days during curing (T10, T20, T30, T40, T50, T60, T70, T80 and T90), as this salami is generally sold as whole piece with varying levels of curing (from T20 to T90). Since the product may be cut in half and vacuumpacked, at each of the times starting from T20, half salami was vacuum-packed and stored for 30 days at 12°C, at the end of the which Listeria spp. enumeration was performed again. At all times and for each type of samples of each of the three batches, the enumeration of the natural microflora (Total Viable Count, lactic acid bacteria, Pseudomonas spp., Enterobacteriaceae) and the determination of water activity and pH were performed on control samples. The product was characterized by a high concentration of microflora (8-8.5 Log UFC/g), consisting mainly of lactic acid bacteria, added to the mixture at the beginning of the production process. The pH showed a decrease over time, expected for this type of products, due to the development of lactic acid bacteria (final pH: 5.42-5.55). The water activity reached values able to inhibit the development of Listeria spp. (final aw: 0.826-0.863). Listeria counts in the tested batches of “Bergamasco” salami showed the absence of significant growth in the product with a reduction of loads if compared to T0, between -0.59 and -1.04 Log CFU/g. Even in the samples subjected to vacuum packaging and storage at 12°C, the absence of significant increase of lactic acid bacteria in the product was highlighted with further decrease of bacterial loads (-0.70/-0.79 Log CFU/g if compared to T20). Considering the worst case scenario (thus the batch with the highest growth potential), in the products stored in the curing room at 14-16°C, at humidity of 80% and in the samples stored at 12°C and vacuum packaged, the threshold indicated by the EURL Lm guidelines (+0.5 Log CFU/g) for the growth of Listeria spp. was not reached, allowing to classify “Bergamasco” salami in the category 1.3 of the EC Reg. 2073/2005 as “Ready-to-eat food unable to support the growth of Listeria monocytogenes”.

scholarly journals Effects of wild type lactic acid bacteria on histamine and tyramine formation in sucuk

2021 ◽  
Vol 71 (4) ◽  
pp. 2553
Author(s):  
Y. N. DOĞAN ◽  
Ö. F. LENGER ◽  
M. DÜZ ◽  
I. DOĞAN ◽  
Z. GÜRLER
Keyword(s):  
Amino Acids ◽  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Starter Cultures ◽  
Acid Decarboxylase ◽  
Lactobacillus Curvatus ◽  
Amino Acid Decarboxylase ◽  
Lactobacillus Sake ◽  
Natural Microflora ◽  
Fermented Products

Biogenic amines (BAs) are formed by the decarboxylation of amino acids in fermented products and accumulate in these products due to the fermentation conditions, the natural microflora of the product, and the diversity of amino acids. Although they are inhibited by the human body, they are a hazard to public health. Starter cultures used in fermented sucuk should not have amino acid decarboxylase properties. The aim of the present study was to determine proteolytic activity, histidine and tyrosine decarboxylase enzyme activities of Lactobacillus plantarum, Lactobacillus sake, and Lactobacillus curvatus species and to evaluate the level of BA in sucuk groups containing these lactic acid bacteria (LAB). It was determined that none of the LAB generated these activities. While histamine values were not statistically significant in the sucuk groups (P> 0.05), tyramine values showed statistically significant differences (P<0.05). The tyramine values of GI ( = 1.43 ± 0.75) and GIII ( = 2.73 ± 1.02) groups were lower than C ( = 8.97 ± 5.29) and GII ( = 7.58 ± 2.90) groups. According to the results of the study, L. plantarum or L. curvatus can provide more reliable fermented products with respect to tyramine formation. L. plantarum, L. sake, and L. curvatus could reduce histamine and tyramine formation in fermented sucuk.

scholarly journals In vitro evaluation of bacteriocin-like inhibitory substances produced by lactic acid bacteria isolated during traditional Sicilian cheese making

2016 ◽  
Vol 5 (1) ◽  
Author(s):  
Giusi Macaluso ◽  
Gerlando Fiorenza ◽  
Raimondo Gaglio ◽  
Isabella Mancuso ◽  
Maria Luisa Scatassa
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Lactic Acid Bacteria ◽  
Salmonella Enteritidis ◽  
Raw Milk ◽  
Starter Cultures ◽  
Proteinase K ◽  
Alternative Methods ◽  
Diffusion Assay

Bacteriocins are antimicrobial proteins produced by bacteria that inhibit with a bactericidal or bacteriostatic mode of action, the growth of other bacteria. Many lactic acid bacteria (LAB) produce a high diversity of different bacteriocins. Bacteriocinogenic LAB are generally recognized as safe (GRAS) and useful to control the frequent development of pathogens and spoilage microorganisms; for this reason they are commonly used as starter cultures in food fermentations. In this study, the authors describe the results of a screening on 699 LAB isolated from wooden vat surfaces, raw milk and traditional Sicilian cheeses, for the production of bacteriocin-like inhibitory substances (BLIS), by comparing two alternative methods. The antagonistic activity of LAB and its proteinaceous nature were evaluated using the <em>spot on the lawn</em> and the <em>well-diffusion assay</em> and the sensitivity to proteolytic (proteinase K, protease B and trypsin), amylolytic (α-amylase) and lipolytic (lipase) enzymes. The indicator strains used were: <em>Listeria monocytogenes</em>, <em>Staphylococcus aureus</em>, <em>E. coli</em>, <em>Salmonella enteritidis</em>. A total of 223 strains (belonged to the species <em>Enterococcus</em> spp., <em>Lactobacillus</em> spp., <em>Pediococcus</em> spp., <em>Streptococcus</em> spp., <em>Leuconostoc</em> spp. and <em>Lactococcus lactis</em>) were found to inhibit the growth of <em>Listeria monocytogenes</em> by using the <em>spot on the lawn</em> method; only 37 of these were confirmed by using the well-diffusion assay. The direct addition of bacteriocin-producing cultures into dairy products can be a more practical and economic option for the improvement of the safety and quality of the final product.

Control of Natural Microbial Flora and Listeria monocytogenes in Vacuum-Packaged Trout at 4 and 10° C Using Irradiation

2002 ◽  
Vol 65 (3) ◽  
pp. 515-522 ◽  
Author(s):  
IOANNIS N. SAVVAIDIS ◽  
PANAGIOTIS SKANDAMIS ◽  
KYRIAKOS A. RIGANAKOS ◽  
NIKOLAOS PANAGIOTAKIS ◽  
MICHAEL G. KONTOMINAS
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Gamma Irradiation ◽  
Shelf Life ◽  
Unirradiated Sample ◽  
Bacterial Populations ◽  
Natural Microflora ◽  
Lower Temperature ◽  
And Storage ◽  
Higher Sensitivity

The effect of gamma irradiation on the natural microflora of whole salted vacuum-packaged trout at 4 and 10°C was studied. In addition, the effectiveness of gamma irradiation in controlling Listeria monocytogenes inoculated into trout was investigated. Irradiation at doses of 0.5 and 2 kGy affected populations of bacteria, namely, Pseudomonas spp., Brochothrix thermosfacta, lactic acid bacteria, H2S-producing bacteria typical of Shewanella putrefaciens, and Enterobacteriaceae, at both 4 and 10°C. This effect was more pronounced at the higher dose (2 kGy) and the lower temperature (4°C). Pseudomonads, H2S-producing bacteria typical of S. putrefaciens, and Enterobacteriaceae showed higher sensitivity to gamma irradiation than did the rest of the microbial species. Sensory evaluation did not show a good correlation with bacterial populations. On the basis of sensory odor scores, a shelf life of 28 days (2 kGy, 4°C) was obtained for salted vacuum-packaged freshwater trout, compared with a shelf life of 7 days for the unirradiated sample. Under the same conditions, the growth of L. monocytogenes inoculated into the samples was suppressed by 2 log cycles after irradiation (2 kGy) and storage for up to 18 days at 4°C.

scholarly journals Effects of Lactobacillus plantarum on the Fermentation Profile and Microbiological Composition of Wheat Fermented Silage Under the Freezing and Thawing Low Temperatures

2021 ◽  
Vol 12 ◽  
Author(s):  
Miao Zhang ◽  
Lei Wang ◽  
Guofang Wu ◽  
Xing Wang ◽  
Haoxin Lv ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Low Temperature ◽  
Low Temperatures ◽  
Fungal Pathogens ◽  
Animal Feed ◽  
Ammonia Nitrogen ◽  
Poor Quality ◽  
Freezing And Thawing ◽  
Silage Fermentation ◽  
Repeated Freezing

The corruption and/or poor quality of silages caused by low temperature and freeze-thaw conditions makes it imperative to identify effective starters and low temperature silage fermentation technology that can assist the animal feed industry and improve livestock productivity. The effect of L. plantarum QZ227 on the wheat silage quality was evaluated under conditions at constant low temperatures followed by repeated freezing and thawing at low temperatures. QZ227 became the predominant strain in 10 days and underwent a more intensive lactic acid bacteria fermentation than CK. QZ227 accumulated more lactic acid, but lower pH and ammonia nitrogen in the fermentation. During the repeated freezing and thawing process, the accumulated lactic acid in the silage fermented by QZ227 remained relatively stable. Relative to CK, QZ227 reduced the abundance of fungal pathogens in silage at a constant 5°C, including Aspergillus, Sporidiobolaceae, Hypocreaceae, Pleosporales, Cutaneotrichosporon, Alternaria, and Cystobasidiomycetes. Under varying low temperature conditions from days 40 to days 60, QZ227 reduced the pathogenic abundance of fungi such as Pichia, Aspergillus, Agaricales, and Plectosphaerella. QZ227 also reduced the pathogenic abundance of Mucoromycota after the silage had been exposed to oxygen. In conclusion, QZ227 can be used as a silage additive in the fermentation process at both constant and variable low temperatures to ensure fast and vigorous fermentation because it promotes the rapid accumulation of lactic acid, and reduces pH values and aerobic corruption compared to the CK.

Impact inoculum dosage of lactic acid bacteria on oat and wheat silage fermentation at ambient and low temperatures

2018 ◽  
Vol 69 (12) ◽  
pp. 1225
Author(s):  
Miao Zhang ◽  
Zhongfang Tan ◽  
Xiaojie Wang ◽  
Meiyan Cui ◽  
Yanping Wang ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Low Temperature ◽  
Lactic Acid Bacteria ◽  
Ambient Temperature ◽  
Low Temperatures ◽  
Raw Materials ◽  
Antimicrobial Properties ◽  
Alpine Regions ◽  
Silage Quality

Lactic acid bacteria (LAB) can be used as silage additives to ensure rapid and vigorous fermentation at early stages of ensiling. We predicted that the optimal LAB inoculation dosage for forage at ambient temperature (15–38°C) would be different from that at cold temperature (4°C). In this study, Lactobacillus plantarum QZ227, isolated from a wheat landrace in alpine regions of Qinghai, China, and commercial L. plantarum FG1 were used as inoculum, with sterile water as control. The effects of inoculum dosage on the fermentation quality of oat (Avena sativa L. cv. Qinghai) and wheat (Triticum aestivum L. cv. Yumai No. 1) silage at ambient temperature (15–38°C) and at 4°C were investigated in laboratory experiments. Little or no improvement in silage quality occurred upon increasing the inoculum dosage at ambient temperature. By contrast, a lower pH and NH3-N content, and a higher LAB count and lactic acid content, were observed at 4°C. Furthermore, the growth of Escherichia coli was inhibited effectively at the lower temperature, and silage quality was positively correlated with increasing inoculum dosage (P&lt;0.05). These results suggest that increasing the inoculum dosage could improve the quality of silage at lower temperatures of 4°C, whereas an appropriate dosage was a key factor for silage at ambient temperature. In this study, oat forage could be used as raw materials for ensiling only at low temperature but was not suitable for ensiling at ambient temperature without wilting due to the high moisture content (86.55%). QZ227 isolated from the roots of wheat in alpine regions displayed superior antimicrobial properties against yeast at ambient temperature and E. coli at 4°C compared with commercial strain FG1. This is the first study to explore the effects of inoculum dosage on silage quality at low temperatures, and provides a basis for low-temperature silage technologies.

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