scholarly journals The effects of Lactococcus lactis subsp. lactis and its supernatant on some bacteriological and sensory values in Rainbow trout (Onchorhynchus mykiss) fillets

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Asad Abbaspour Anbi ◽  
Vadood Razavilar ◽  
Moslem Neyriz Naghadehi ◽  
Masoud Seidgar ◽  
Ali Nekuiefard ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Lactococcus Lactis ◽  
Storage Time ◽  
Culture Medium ◽  
Live Cells ◽  
Human Consumption ◽  
Lactococcus Lactis Subsp ◽  
Live Bacteria ◽  
And Control ◽  
Control Samples

Lactic Acid Bacteria (LAB) have a great potential as bio-preservatives. The live cells and supernatant Lactococcus lactis subsp. lactis induced bacteriological changes in Onchorhynchus mykiss fillet by spray and immersion methods was studied during vacuum- packaged storage at 4 °C for 15 days. 40 kg of O. mykiss were prepared from a culture farm in Oshnavieh (Northwest Iran) and 112 fillet samples (100g) were prepared by aseptic method. L. lactis subsp. lactis (PTCC1336) bacteria was cultured in MRS culture medium. Its supernatant (2%, 4%) was extracted and 106 CFUml-1 dilutions of LAB were prepared and tested on the fillets to enhance their shelf life. All samples were evaluated regarding to growth of psychrotrophic, psychrophilic, mesophilic bacteria, molds and yeasts. Four characteristics including of odor, flavor, texture and color of fillets after and before cooking were evaluated for sensory analysis on days 1, 5, 10 and 15 and compared with control samples. The 4% supernatant and live bacteria were more effective than that of 2% and control (P<0.05). The amounts of corrosive bacteria in 4% and live cells in storage time were less than human consumption limits (7log CFUg-1), whereas in control and 2% supernatant treatments were more than that limits. The results showed that increasing the percentage of supernatant was more effective on bacteriologic factors and enhanced sensory characteristics of rainbow trout fillets (P<0.05).

scholarly journals Effects of monoacylglycerols and chitosan on the biogenic amine formation in the flesh of rainbow trout (Oncorhynchus mykiss)

2020 ◽  
Vol 38 (No. 3) ◽  
pp. 164-170
Author(s):  
Kateřina Matějková ◽  
Martin Křížek ◽  
Eva Dadáková ◽  
František Vácha ◽  
Tamara Pelikánová
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Biogenic Amines ◽  
Biogenic Amine ◽  
Storage Time ◽  
Sensory Properties ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Fish Flesh ◽  
Control Samples

Contents of eight biogenic amines (putrescine, cadaverine, spermidine, spermine, histamine, tyramine, tryptamine and phenylethylamine) were determined in vacuum-packed fillets of rainbow trout (Oncorhynchus mykiss). Fish flesh was treated using a solution of chitosan (2%, w/v) or monoacylglycerols (monocaprylin C8, monocaprin C10, 5%, w/v). The control and treated packs were stored at 3.5 °C for up to 25 days. Samples of good quality did not contain more than 30 mg kg–1 of either putrescine or cadaverine. Exceeding this limit was usually followed by a worsening of the sensory properties of samples. Chitosan was found to be the most potent additive, prolonging the storage time of fillets by approximately four times, compared to control samples. Histamine was not found in any sample treated with chitosan. of the monoacylglycerols, C8 was more efficient compared to C10. All additives are easily applicable to the surface of fish flesh.

Recirculation versus flow-through rainbow trout laboratory Flavobacterium columnare challenge

2020 ◽  
Vol 139 ◽  
pp. 213-221
Author(s):  
C Birkett ◽  
R Lipscomb ◽  
T Moreland ◽  
T Leeds ◽  
JP Evenhuis
Keyword(s):  
Rainbow Trout ◽  
Environmental Parameters ◽  
Cumulative Effects ◽  
Flavobacterium Columnare ◽  
Replacement Rate ◽  
Bacterial Concentration ◽  
Water Replacement ◽  
Dose Concentration ◽  
Flow Through ◽  
And Control

Flavobacterium columnare immersion challenges are affected by water-related environmental parameters and thus are difficult to reproduce. Whereas these challenges are typically conducted using flow-through systems, use of a recirculating challenge system to control environmental parameters may improve reproducibility. We compared mortality, bacterial concentration, and environmental parameters between flow-through and recirculating immersion challenge systems under laboratory conditions using 20 rainbow trout families. Despite identical dose concentration (1:75 dilution), duration of challenge, lot of fish, and temperature, average mortality in the recirculating system (42%) was lower (p < 0.01) compared to the flow-through system (77%), and there was low correlation (r = 0.24) of family mortality. Mean days to death (3.25 vs. 2.99 d) and aquaria-to-aquaria variation (9.6 vs. 10.4%) in the recirculating and flow-through systems, respectively, did not differ (p ≥ 0.30). Despite 10-fold lower water replacement rate in the recirculating (0.4 exchanges h-1) compared to flow-through system (4 exchanges h-1), differences in bacterial concentration between the 2 systems were modest (≤0.6 orders of magnitude) and inconsistent throughout the 21 d challenge. Compared to the flow-through system, dissolved oxygen during the 1 h exposure and pH were greater (p ≤ 0.02), and calcium and hardness were lower (p ≤ 0.03), in the recirculating system. Although this study was not designed to test effects of specific environmental parameters on mortality, it demonstrates that the cumulative effects of these parameters result in poor reproducibility. A recirculating immersion challenge model may be warranted to empirically identify and control environmental parameters affecting mortality and thus may serve as a more repeatable laboratory challenge model.

Changes in the Population Density of Pathogenic Microorganisms in Response to the Allelopathic Effect of Thypha Latifolia

2014 ◽  
Vol 1 (1) ◽  
pp. 31-36 ◽  
Author(s):  
O. Zhukorskiy ◽  
O. Gulay ◽  
V. Gulay ◽  
N. Tkachuk
Keyword(s):  
Cell Density ◽  
Allelopathic Effect ◽  
Pathogenic Microorganisms ◽  
Sterile Water ◽  
Erysipelothrix Rhusiopathiae ◽  
Pathogenic Leptospira ◽  
Favorable Conditions ◽  
And Control ◽  
The Impact ◽  
Control Samples

Aim. To determine the response of the populations of Erysipelothrix rhusiopathiae and Leptospira interrogans pathogenic microorganisms to the impact of broadleaf cattail (Thypha latifolia) root diffusates. Methods. Aqueous solutions of T. latifolia root diffusates were sterilized by vacuum fi ltration through the fi lters with 0.2-micron pore diameter. The experimental samples contained cattail secretions, sterile water, and cultures of E. rhusiopathiae or L. interrogans. The same amount of sterile water, as in the experimental samples, was used for the purpose of control, and the same quantity of microbial cultures was added in it. After exposure, the density of cells in the experimental and control samples was determined. Results. Root diffusates of T. latifolia caused an increase in cell density in the populations of E. rhusiopathiae throughout the whole range of the studied dilutions (1:10–1:10000). In the populations of the 6 studied serological variants of L. interrogans spirochetes (pomona, grippotyphosa, copenhageni, kabura, tarassovi, canicola), the action of broadleaf cattail root diffusates caused the decrease in cell density. A stimulatory effect was marked in the experimental samples of the pollonica serological variant of leptospira. Conclusions. The populations of E. rhusiopathiae and L. interrogans pathogenic microorganisms respond to the allelopathic effect of Thypha latifolia by changing the cell density. The obtained results provide the background to assume that broadleaf cattail thickets create favorable conditions for the existence of E. rhusiopathiae pathogen bacteria. The reduced cell density of L. interrogans in the experimental samples compared to the control samples observed under the infl uence of T. latifolia root diffusates suggests that reservoirs with broadleaf cattail thickets are marked by the unfavorable conditions for the existence of pathogenic leptospira (except L. pollonica).

scholarly journals A Legionnaires’ Disease Cluster in a Private Building in Italy

2021 ◽  
Vol 18 (13) ◽  
pp. 6922
Author(s):  
Maria Luisa Ricci ◽  
Maria Cristina Rota ◽  
Maria Grazia Caporali ◽  
Antonietta Girolamo ◽  
Maria Scaturro
Keyword(s):  
Severe Pneumonia ◽  
Control Measures ◽  
Health Concern ◽  
Human Consumption ◽  
Domestic Water ◽  
Quality Of Water ◽  
Legionnaires Disease ◽  
Prevention And Control Measures ◽  
Private Homes ◽  
And Control

Legionnaires’ disease (LD) is a severe pneumonia caused by bacteria belonging to the genus Legionella. This is a major public health concern and infections are steadily increasing worldwide. Several sources of infection have been identified, but they have not always been linked to human isolates by molecular match. The well-known Legionella contamination of private homes has rarely been associated with the acquisition of the disease, although some patients never left their homes during the incubation period. This study demonstrated by genomic matching between clinical and environmental Legionella isolates that the source of an LD cluster was a private building. Monoclonal antibodies and sequence-based typing were used to type the isolates, and the results clearly demonstrated the molecular relationship between the strains highlighting the risk of contracting LD at home. To contain this risk, the new European directive on the quality of water intended for human consumption has introduced for the first time Legionella as a microbiological parameter to be investigated in domestic water systems. This should lead to a greater attention to prevention and control measures for domestic Legionella contamination and, consequently, to a possible reduction in community acquired LD cases.

scholarly journals Sugar and no sugar added fruit microalgae-enriched jams: a study about their physicochemical, rheological, and textural properties

2021 ◽  
Author(s):  
Zaida Natalia Uribe-Wandurraga ◽  
María Bravo-Villar ◽  
Marta Igual ◽  
Carmen Savall ◽  
Purificación García-Segovia ◽  
...  
Keyword(s):  
Food System ◽  
Textural Properties ◽  
Arthrospira Platensis ◽  
Microalgae Biomass ◽  
Textural Parameters ◽  
Weak Gel ◽  
Biomass Extract ◽  
And Control ◽  
Colour Coordinates ◽  
Control Samples

AbstractJams are preparations of fruits whose main preserving agent is sugar. Due to this, health concerns of consumers have resulted in a sugar reduction, and its replacement using alternative sweeteners and introducing new ingredients enhancing nutritional properties. In this study, four types of fruits jams (plum, strawberry, apple, and peach), with or without sugar, were prepared using two microalgae biomass, Arthrospira platensis (Spirulina) and Chlorella vulgaris, and Dunaliella salina extract as ingredients at different mix levels of concentrations, 0.10%–0.10%–0.05% respectively, for plum; 0.04%–0.00%–0.01 respectively, for strawberry; 0.06%–0.04%–0.00% respectively, for apple and 0.00%–0.01%–0.04% respectively, for peach. Physicochemical, rheological, and textural parameters were evaluated. Substitution of sugar/fructose syrup in the jam’s preparation caused changes in pH values, solid soluble content, and rheological and textural properties compared to sugar jams. Using sugar or sweeteners as isomalt, stevia and sucralose and microalgae biomass or extract showed significant changes in colour coordinates, however, these differences were not perceptible by the human eye. Jams containing microalgae biomass-extract showed higher G', G'', G*, and η* values than their corresponding control samples. All the jams presented weak-gel characteristics, distinguishing fruit jams. However, the results of weak-gel model analysis suggest that the influence of the different ingredients in the food system depends not only on their concentration but also on the interactions in the gel structure. Strawberry and apple jams showed no significant differences between microalgae biomass-extract samples and control samples, for both sugar and no sugar added jams being the best-obtained samples.

Growth, nisA Gene Expression, and In Situ Activity of Novel Lactococcus lactis subsp. cremoris Costarter Culture in Commercial Hard Cheese Production

2017 ◽  
Vol 80 (12) ◽  
pp. 2137-2146 ◽  
Author(s):  
Dimitrios Noutsopoulos ◽  
Athanasia Kakouri ◽  
Eleftheria Kartezini ◽  
Dimitrios Pappas ◽  
Efstathios Hatziloukas ◽  
...  
Keyword(s):  
Gene Expression ◽  
Lactococcus Lactis ◽  
Starter Culture ◽  
Fold Increase ◽  
Raw Milk ◽  
Good Growth ◽  
Lactococcus Lactis Subsp ◽  
Quantitative Expression ◽  
Hard Cheese

ABSTRACT This study evaluated in situ expression of the nisA gene by an indigenous, nisin A–producing (NisA+) Lactococcus lactis subsp. cremoris raw milk genotype, represented by strain M78, in traditional Greek Graviera cheeses under real factory-scale manufacturing and ripening conditions. Cheeses were produced with added a mixed thermophilic and mesophilic commercial starter culture (CSC) or with the CSC plus strain M78 (CSC+M78). Cheeses were sampled after curd cooking (day 0), fermentation of the unsalted molds for 24 h (day 1), brining (day 7), and ripening of the brined molds (14 to 15 kg each) for 30 days in a fully controlled industrial room (16.5°C; 91% relative humidity; day 37). Total RNA was directly extracted from the cheese samples, and the expression of nisA gene was evaluated by real-time reverse transcription PCR (qRT-PCR). Agar overlay and well diffusion bioassays were correspondingly used for in situ detection of the M78 NisA+ colonies in the cheese agar plates and antilisterial activity in whole-cheese slurry samples, respectively. Agar overlay assays showed good growth (&gt;8 log CFU/g of cheese) of the NisA+ strain M78 in coculture with the CSC and vice versa. The nisA expression was detected in CSC+M78 cheese samples only, with its expression levels being the highest (16-fold increase compared with those of the control gene) on day 1, followed by significant reduction on day 7 and almost negligible expression on day 37. Based on the results, certain intrinsic and mainly implicit hurdle factors appeared to reduce growth prevalence rates and decrease nisA gene expression, as well as the nisin A–mediated antilisterial activities of the NisA+ strain M78 postfermentation. To our knowledge, this is the first report on quantitative expression of the nisA gene in a Greek cooked hard cheese during commercial manufacturing and ripening conditions by using a novel, rarely isolated, indigenous NisA+ L. lactis subsp. cremoris genotype as costarter culture.

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