Psychrotrophic Bacteria Counts Research Articles

Determination of Spoilage Microbiota of Pacific White Shrimp During Ambient and Cold Storage Using Next-Generation Sequencing and Culture-Dependent Method.

This study was conducted to determine the initial and spoilage microbiota of Pacific white shrimp during ambient and cold storage using next-generation sequencing (NGS) and a culture-dependent method. The quality changes were also evaluated by sensory analysis and total volatile basic nitrogen (TVB-N) values. After 1 d of storage, the psychrotrophic bacteria were only 5.97 log CFU/g, accounting for 1.1% of the mesophilic bacteria counts (7.94 log CFU/g). The psychrotrophic bacteria counts exceeded the counts of mesophilic bacteria for shrimp stored at 4 °C after 6 d of storage, indicating that psychrotrophic bacteria became predominant. The NGS was used to identify the bacterial species in samples stored at 25 and 4 °C. The results showed that the dominant microorganisms were Vibrio at 25 °C, and Acinetobacter, Psychrobacter, and Shewanella at 4 °C. By the culture-dependent method based on 16S rRNA gene and VITEK®2 CompactA system, it showed that the dominant microorganisms were Proteus spp. at 25 °C, and Shewanella putrefaciens, Acinetobacter johnsonii, and Aeromonas sobria at 4 °C. In conclusion, differences in results of microbiota analyzed by culture dependent and independent approaches were observed. The combination of both methodologies may provide more comprehensive information about the dominant spoilage microbiota in Pacific white shrimp during ambient and cold storage.

Short communication: Variation in the composition and properties of Swedish raw milk for ultra-high-temperature processing

The composition and properties of raw milk are of great importance for the quality and shelf life of the final dairy product, especially in products with a long shelf life [e.g., ultra-high-temperature (UHT)-treated milk]. The objective of this study was to investigate the compositional variation in raw milk samples before processing at the dairy plant. Moreover, we wanted to investigate the effect of the UHT process on this variation (i.e., if the same variation could be observed in the corresponding UHT milk). The quality traits analyzed included detailed milk composition, counts of total and psychrotrophic bacteria, proteolytic activity, and color, as well as predictive measures of stability (i.e., ethanol stability and heat coagulating time). Samples of raw milk and the corresponding produced UHT milk were collected and analyzed on a monthly basis during 1 yr. Principal component analysis was used to identify months showing similarities and differences with respect to total variation. In contrast to previous studies, we observed only small variations between months and no clear effect of season for the raw milk. For the UHT milk, July and the winter months (December, January, and February) tended to separate from the other months. Quality traits showing significant variation were only to some extent identical in raw milk and UHT-processed milk. A better understanding of the natural variation in raw milk quality will provide opportunities to improve the shelf life of UHT-treated milk products.

Effect of Farsi gum-based antimicrobial adhesive coatings on the refrigeration shelf life of rainbow trout fillets

The present study aimed to evaluate the effects of antimicrobial and antioxidant adhesive coatings prepared from the water-soluble fraction of Farsi gum (WFG) on the refrigerated shelf-life of rainbow trout fillets. Antimicrobial and antioxidant characteristics were developed through incorporating cinnamon (CEO) and Shirazi thyme (SEO) essential oils, individually or in combination with each other. Coated fish fillets and control samples, stored at 4 ± 1 °C, were subjected to various microbiological (namely total viable count (TVC), psychrotrophic and lactic acid bacteria counts) as well as physicochemical (including peroxide value (PV), thiobarbituric acid reactive substances (TBARS), total volatile basic-nitrogen (TVB-N) and pH) evaluations during storage. Moreover, sensory characterisation were performed for texture, odour, colour and overall acceptability. Essential oils incorporation into WFG-based coatings had significant (p < 0.05) effects on decreasing total viable, psychrotrophic and lactic acid bacteria counts. The application of coating significantly (p < 0.05) reduced TVB-N, peroxide and TBARS values. Texture, odour, colour and overall acceptability of coated samples were much better than those of control samples. The results of this study showed that WFG could be used as a novel biopolymer source for introduction of EOs.

Use of Vinegar and Jasmine Tea Extract to Control Foodborne Pathogens and Spoilage Micro-Organisms in Fresh Chicken Sausage

ObjectivesConsumer demand for natural preservatives is on rise. Verdad Avanta F100 is a natural vinegar blended with jasmine tea extract (VJTE) and has excellent antimicrobial and antioxidant properties. Salmonella can be a serious problem in fresh poultry products such as fresh chicken sausage. Under abusive temperature storage conditions, Salmonella can grow in poultry products. Aerobic plate counts (APC), Psychrotrophic, Enterobacteriacae and Lactic acid bacteria (LAB) counts are reported to determine the shelf life of the fresh chicken sausage. This study evaluates the impact of vinegar and jasmine tea extract on the shelf life of fresh ground chicken sausage. The objective is to validate the efficacy of vinegar and jasmine tea extract for Salmonella control and shelf-life extension of fresh ground chicken sausage. Materials and MethodsFresh bone-in, skin-on chicken thighs were deboned and ground to 4 mm and mixed with additional ingredients (water, salt, garlic powder, black pepper, onion powder, mustard powder) for control, and 2 levels of VJTE (0.70% and 1.00%). A 5 strain cocktail of Salmonella spp. was used in this study; including: Salmonella enterica; subsp. enterica; serovar Enteritidis, Salmonella enterica; subsp. Enterica; serovar Enteritidis, Salmonella enterica; subsp. Enterica; serovar Typhimurium, Salmonella enterica; subsp. Enterica; serovar Typhimurium and Salmonella enterica; subsp. Enterica; serovar Heidelberg. For inoculated chicken samples approximately 1,000 g of mixed sausage was placed in a plastic bag along with 1 mL of 4.5 log CFU/mL of Salmonella cocktail and mixed together to achieve a final count of 2.5 log CFU/g of Salmonella in the sausage. Inoculated samples were stored at 4 and 15.4°C for 27 and 13 d, respectively. Non inoculated samples were stored at 4°C for 27 d. pH, moisture, water activity were measured for all treatments. The plating for each microflora was done independently- in duplicate and at approximately 0, 7, 11, 20, and 27 d for the non-inoculated samples and at approximately 0, 5, 8, 13 d for the Salmonella inoculated samples. ResultsSalmonella has been shown not to grow under refrigerated temperatures and our results show no growth for any samples over 13 d during refrigerated storage. Salmonella growth indicates that even under temperature abused conditions (15.4°C) vinegar and jasmine tea extract were able to limit the growth of Salmonella for 13 d whereas the control reached 6.54 log CFU/g in 5 d. APC growth kinetics indicate vinegar and jasmine tea extract extended the shelf life of chicken sausage for the full 27 d whereas the control showed 7.00 log CFU/g increase at 11 d. Enterobacteriaceae growth data indicates that use of vinegar and jasmine tea extract inhibited the outgrowth over the shelf life to the initial level, while the control treatment had 7.08 log CFU/g increase in 14 d. ConclusionThis research validates the antimicrobial efficacy of Vinegar and jasmine tea extract (VJTE) in chicken sausage to control the growth of Salmonella under abused temperature conditions and to extend the shelf-life of fresh chicken sausage and provides the meat industry with a highly effective natural antimicrobial to assure the food safety as well the shelf life of the product.

The effect of different gas permeability of packaging on physicochemical and microbiological parameters of pork loin storage under high O2 modified atmosphere packaging conditions.

The aim of this study was to determine the influence of different packaging materials on meat quality during cold storage. Therefore pork loins (m. longissimus thoracis et lumborum) obtained from crossbred pigs (Polish Landrance x Duroc, n = 6) were stored at 2 ℃ in modified atmosphere packs (80% O2, 20% CO2) in four types of trays, which differ in gas permeability. Physicochemical (headspace gas composition, pH, colour, drip loss, cooking loss, shear force, the basic composition and fatty acid profile) and microbiological ( Salmonella spp., Escherichia coli, Enterobacteriaceae, total aerobic plates count, total psychrotrophic bacteria count, the number of lactic acid bacteria, Pseudomonas spp., the general amount of yeast and mold) parameters were monitored for up to 12 days. At the end of the storage period no differences in most physicochemical properties of pork loin due to type of packaging were found, however trays with high gas permeability had the greatest impact on total aerobic plates count and Pseudomonas spp. growth.

Physicochemical Properties, Microbial Profile, and Biogenic Amines Content of Barramundi (Lates calcarifer Bloch) Fillets Wrapped in Selected Packaging Films Under Modified Atmosphere Packaging

The purpose of this study was to investigate the effect of packaging film on physicochemical properties, microbial profile, and biogenic amines content of barramundi (Lates calcarifer Bloch) fillets packed in polyamide, polypropylene, and low-density polyethylene films and kept at 8°C more than 20 days under modified atmosphere packaging. Putrescine and cadaverine were the most abundant amines, whereas the concentration of histamine ranged from less than 0.5 (not detected) to 198.0, 264.3, and 308.5 mg/kg for polyamide, polypropylene, and polyethylene (low-density polyethylene) films, respectively. Among the three, the psychrotrophic bacteria count was initially 4.26 log colony forming units/g and exceeded the acceptable limit of 7 log colony forming units/g on the 16th day of storage for polyamide and on 12th day of storage for polypropylene and polyethylene. However, the total plate count, among the three packaging films, was initially 3.54 log colony forming units/g and exceeded the acceptable limit of 6 log colony forming units/g on the 12th day of storage. The histamine-forming bacteria count was significantly (p < 0.05) lower in barramundi fillets packaged with polyamide compared to polypropylene and polyethylene. The significant difference (p < 0.05) was observed between the concentration of amines in polyamide as compared with polypropylene and polyethylene. Among the three packaging materials, polyamide was found to be the best for prolonging the storage of barramundi fillets.

Sanitary aspects and technological challenges of whole milk microfiltration at low temperatures

Abstract: The objective of this work was to evaluate the effects of whole milk microfiltration at low temperatures on bacterial counts and on its shelf life. The microfiltration process was evaluated at two temperatures (30 and 50ºC) and compared with the slow pasteurization process. Both slow pasteurization and microfiltration reduced the initial counts of aerobic mesophilic and psychrotrophic bacteria, as well as total coliforms in whole milk. Microfiltration at 50ºC was as effective as the pasteurization process, since it reduced the initial count of aerobic mesophilic bacteria in 4.4 log cycles; increased the product's shelf life, which reached 30 days without exceeding 1,000 CFU mL-1; and eliminated coliform counts at the temperatures of 35 and 45ºC, established by the Brazilian legislation. Microfiltration at 30°C reduced the aerobic mesophilic bacteria counts by 2.2 log cycles; however, Escherichia coli was found in the product, which exhibited a shelf life of less than five days. Therefore, microfiltration at 30ºC can be associated with thermal treatments, but, when applied alone, it shows unsatisfactory results.

Quality indicators and shelf life of red octopus (Octopus maya) in chilling storage

There are no precedents concerning the quality of Octopus maya during chilled storage. This study evaluated the shelf life of the red octopus in chilling storage (4oC) and the correlation of the sensory quality index with microbiological counting and the biochemical indicators (hypoxanthine, histamine and volatile amines). A total of 112 whole raw octopi (average weight of 896 g) were randomly selected from seven batches and exposed to 4°C for 18, 24, 48, 72, 84, 96, and 100 h. The histamine concentration (91.7%), followed by the counts of psychrotrophic bacteria (5.5%) and hypoxanthine (2.2%), were the predictors from the redundancy analysis that better explained the changes taking place during the chilling hours. After 72 h of chilling, the microbial count was determined to be log 4.7 CFU/g, and the octopus samples were classified as B quality (minor sensory quality defects) based on the sensory quality scale. Although the samples were not classified as unacceptable at 100 h of refrigeration by the sensory index, the level of histamine reached the defect action level (5 mg/100 g) as ruled by the International Food Safety Authorities. The shelf life of the red octopus in chilling storage was predicted to be 119 h.

Quality assessment of shrimps preserved with orange leaf essential oil incorporated gelatin

Assessment of edible gelatin coating solution enriched with essential oil obtained from orange (Citrus sinensis (L.) Osbeck) leaves on the quality and shelf life of cold stored deep water pink shrimp (Parapenaeus longirostris Lucas 1846) was studied. Gelatin (G) and 2% orange leaf essential oil incorporated gelatin (G+OL) solution, which was selected after antimicrobial and antioxidant analysis, were used for coating. Microstructure characterization of the gelatin films was done by Scanning Electron Microscopy. Sensory and melanosis, microbiological [total viable counts (TVC), psychrotrophic bacteria counts (PBC), Enterobacteriaceae (EB)], chemical [sulphur dioxide (SO2), pH, total volatile base nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), thiobarbituric acid (TBA), peroxide value (PV)] and physical (color) analysis were carried out for control and coated samples and shelf-life was determined throughout the storage period of 14 days.The results indicate that the edible gelatin coating solutions enriched with orange leaf essential oil has noticeable effects on the quality and shelf life of shrimps when compared to control group. It was determined that edible gelatin coating solutions used were effective in all groups particularly on melanosis which may occur in shrimps and edible gelatin coating solutions with orange leaf essential oil preserved the quality of shrimp better.

Evaluation of the antimicrobial activity of pecan nut [Carya illinoinensis (Wangenh) C. Koch] shell aqueous extract on minimally processed lettuce leaves

Pecan nutshell is a residue from food industry that has potential to be used as biopreservative in foods. The objective of this study was to evaluate the antimicrobial activity of pecan nutshell aqueous extract in vitro and its effectiveness to inhibit spoilage microorganisms on lettuce leaves. The results indicate that the aqueous extract presents inhibitory activity against important foodborne pathogenic bacteria such as Listeria monocytogenes, Salmonella Enteritidis, Staphylococcus aureus, Bacillus cereus, Aeromonas hydrophila and Pseudomonas aeruginosa. Antimicrobial activity was not observed against Corynebacterium fimi, Clostridium perfringens, Escherichia coli, and the phytopathogenic fungi tested. When applied onto lettuce leaves, pecan nutshell extract reduced the counts of mesophilic and psychrotrophic bacteria in 2 and 4 log CFU/g, respectively, during storage of leafy for 5 days at refrigeration temperature (5 °C). The extract was not effective to inhibit yeast on lettuce leaves. Thus, the aqueous extract of pecan shell showed great potential to be used as a natural preservative in foods, acting mainly in the inhibition of spoilage and pathogenic bacteria.

English

This paper identified the bacterial flora composition and its influence on the microbiological spoilage process in economically important fish species: Filhote (Brachyplatystoma filamentosum) and Dourada (Brachyplatystoma rousseauxii) in the Amazon region. Microbiological characterization was performed: counts of total mesophilic aerobic bacteria, psychrotrophic bacteria and coliforms at 35 and 45°C, respectively. Bacteria were also isolated through seeding in agar surface using Violet Red Bile Glucose (VRBG) for enterobacteria strains and Baird-Parker Agar with Egg-Yolk Tellurite for Staphylococcus species, both with incubation at 36°C for 48 h. The bacteria isolated were identified using the API 20E kit (Enterobacteria), and Gram-positive bacteria with API Staph (Staphylococci). Finally, the lag phase for strain growth was measured using spectrophotometry readings (620 nm) at different temperatures (10, 15 and 37°C). The mesophilic aerobic bacteria counts for fresh fish samples ranged from 5.21 to 7.64. The count ranges of psychrotrophic aerobic bacteria found were 5.11 – 6.91 log CFU/g. They also had an average score above 103 MPN/g for total coliforms. The most predominant were Hafnia alvei, Pseudomonas luteola, Staphylococcus xylosus and Staphylococcus lugdunensis. When subjected to temperature of 10°C, the strains achieved growth after 6 h (p<0.05). Key words: Spoilage, catfish, Brachyplatystoma filamentosum, Brachyplatystoma rousseauxii.

Development and Application of the Quality Index Method (QIM) for Farmed Tambaqui (Colossoma macropomum) Stored Under Refrigeration

This research aimed to assess the freshness of farmed tambaqui (Colossoma macropomum) eviscerated and stored in ice for 30 days. The changes observed in the fish over storage were monitored through sensory evaluation Quality Index Method (QIM), pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), and microbiological analyses (coagulase-positive staphylococcus, Salmonella spp., coliforms at 45C, and mesophilic and psychrotrophic bacteria counts). The Quality Index (QI) showed a linear increase, ranging from 0 (maximum freshness) to 34 (total loss of freshness), with a strong correlation (R2 = 0.988) with storage time. The microbiological analyses showed that the psychrotrophic bacteria count went over the recommended limit after the 26th day. TVB-N ranged from 4.01 to 15.92 mg/100 g; pH, from 6.01 to 6.57; and TBARS, from 0.01 to 0.14 mg MDA/kg between the 1st and 30th days of storage. The sensory, physicochemical, and microbiological analyses established that eviscerated tambaqui stored in ice is appropriate for consumption up until the 22nd day. Practical Applications The QIM takes into account the diversity among species and defines the sensory quality parameters for fish freshness. Sensory analysis has been shown to be an important tool to assess sensory quality of fresh fish and is largely used by sanitary inspection agencies. The QIM established that eviscerated tambaqui (C. macropomum) stored in ice at 0C remained proper for consumption until the 22nd day. The results of the application of QIM to marketed fish species can establish the product's shelf life which is a very important for the industry and for consumers. QIM: Development and Application of a Sensory Protocol for Farmed Tambaqui (C. macropomum).

Inhibitory Effect of Lactococcin BZ Against Listeria innocua and Indigenous Microbiota of Fresh Beef.

In this study, the effect of lactococcin BZ on microbiological quality of fresh beef is investigated. For this purpose, the meat samples were treated with various amounts of lactococcin BZ (200-2500 AU/mL), a bacteriocin produced by Lactococcus lactis spp. lactis BZ, and kept at 4-5 °C for 12 days. During storage, the microbiological properties of the meat samples with or without lactococcin BZ were determined. Inhibitory effect of lactococcin BZ depended on its amount. The higher the amount of lactococcin BZ, the higher the inhibitory activity. Treatment with lactococcin BZ at the level of 2500 AU/mL resulted in 4.87, 3.50 and 3.94 log cycle decrease in the counts of mesophilic, psychrotrophic and lactic acid bacteria, respectively, and 1.90·104 and 1.04·102 CFU/g reduction in coliform and faecal coliform bacteria, respectively, at the end of storage as compared to their initial numbers in the control sample. However, the counts of these bacteria in control samples increased during storage. Also, lactococcin BZ at 1600 AU/mL showed very strong antilisterial effect against Listeria innocua in fresh meat and reduced the cell numbers from 6.04 log CFU/g to undetectable level on the 6th day of storage. In conclusion, lactococcin BZ has a potential use as a biopreservation agent to improve safety and shelf life of raw beef.

Analysis of Vacuum Packed Beef Regarding Psychrotrophic Bacteria Growth and Biogenic Amines Content

It has been recognized that biogenic amines (BA) content in meat can be considered a freshness marker. Considerable amounts of some BAs can appear during food storage under certain conditions, according to the handling of the raw material, technology applied, storage temperature and time, packaging condition, mainly if amino acid - decarboxylase positive microorganisms are present. The aim of this study was to evaluate the psychrotrophic bacteria growth and metabolic production of BAs during chill storage of beef. The vacuum packed beef cuts (Longissimus dorsi muscle) were analyzed during storage at 7 °C at 0, 15, 30, 45, and 60 d, to determine the psychrotrophic bacteria growth and the BAs amount. The BAs considered were: putrescine, cadaverine, histamine, spermidine, and spermine. The BAs quantitative determination was carried out by reversed phase high-performance liquid chromatography (HPLC) with UV detection. Statistic procedures were performed using SAS statistical software. The growth parameters of psychrotrophic bacteria including lag phase, maximum specific growth rate, maximum bacterial cell density, initial population, mean square error, and coefficient of determination were determined according to Baranyi and Roberts model. The values of histamine and spermidine increased significantly (P < 0.0001) during storage time, while the levels of spermine decreased (P < 0.0001). Psychrotrophic bacteria counts increased significantly (P < 0.0001) reaching 7.6 log cfu/g over time. The counts of this group positively correlated to histamine and spermidine (r = 0.68 and 0.61, respectively), while spermine showed a negative correlation (r = -0.70). Conversely, no significant correlation was found between psychrotrophics counts and putrescine or psychrotrophics counts and cadaverine.

A chitosan-based coating with or without clove oil extends the shelf life of cooked pork sausages in refrigerated storage

Chitosan coatings, with and without clove oil, were investigated for effects on quality and shelf life of cooked pork sausages stored at a refrigerated temperature (4±2°C). The various treatments of cooked pork sausages were: untreated (control), coating with 2% chitosan (CS), and coating with a mixture having 2% chitosan and 1.5% clove oil (CS+CO). Various microbiological, physical, chemical and sensory properties were monitored over 25days of storage. The total viable count, the psychrotrophic bacteria count, the L* value, peroxide value and the thiobarbituric acid reactive substances increased, while the a* value, the b* value, the pH and the sensory scores decreased with storage time, across all treatments. However, these changes were slowest with the CS+CO treatment. Based on sensory evaluation and microbiological quality, the shelf lives were 14days for control, 20days for CS, and 20days for CS+CO treated samples, under refrigerated storage.

Effect of Lyophilized Water Extract of U rtica dioica L. on the Shelf Life of Vacuum-Packaged Beef Steaks

In this research, the effects of lyophilized Urtica dioica L. water extract (LUDWE) on the shelf life of vacuum-packaged beef steaks were evaluated. For this purpose, beef steaks were arranged as control (vacuum packaging, VP), 150 ppm LUDWE + VP, 300 ppm LUDWE + VP and 450 ppm LUDWE + VP, and were stored at 2 ± 0.5C for 21 days. During storage, psychrotrophic bacteria, lactic acid bacteria, Pseudomonas, Enterobacteriaceae counts, pH, color and thiobarbituric acid reactive substances (TBARS) values of beef steaks were determined. By adding LUDWE in the beef steaks, TBARS values decreased (P < 0.01), and minimum values were determined in 450 ppm LUDWE + VP groups (P < 0.05). Depending on the increase in the LUDWE level, psychrotrophic (P < 0.01), Pseudomonas (P < 0.01), Enterobacteriaceae (P < 0.01) and lactic acid bacteria (P < 0.01) counts decreased, and the highest counts of these parameters were determined in the control group. LUDWE also had significant effects on L* (P < 0.01), a* (P < 0.01) and b* (P < 0.01) values of vacuum-packaged beef steaks. Practical Applications Beef steak is more susceptible to microbial spoilage and lipolytic reactions; these can lead to a shorter shelf life with potential risks for human health during storage at low temperatures. In beef steaks, lipid oxidation can be decreased and spoilage bacterial counts can be suppressed using natural antioxidants and antimicrobials such as lyophilized Urtica dioica L. water extract (LUDWE). This work clearly showed that LUDWE could be used as a good natural antioxidant and antimicrobial agent in fresh meat products such as beef steaks.

Effect of rosemary in combination with yeast extract on microbiology quality, oxidative stability and color of non-fermented cooked salami “Inovec”

The aim of this study was to determine antimicrobial and antioxidant effect of dried rosemary (1 g/kg) in combination with yeast extract 1 g/kg (1st experimental group) and 2 g/kg (2nd experimental group) in compare to control sample (without rosemary extract and treated with E316 and E621) in non-fermented heat-treated product Inovec salami. Inovec salami is a product produced all over the Slovakia. The similar product can be found in Polish (Polish salami) or in the Czech Republic (Vysocina salami). The samples were vacuum packaged and were kept at 4 °C for 30 days. Determination of psychrotrophic bacteria count (PBC), count of Enterobacteriaceae family (ETB), yeast and moulds, Lactobacillus spp. bacteria count (LAB) was done by cultivation methods. Oxidative stability was determined by TBARS value. Color spaces L*, a*, b* of Inovec salami was determined by CM 2600D spectrophotometer (Konica Minolta, Germany). It was found non-significant (p &gt;0.05) color loss (decrease in redness) over time, and the treatments had a non-significant impact (p &gt;0.05) on redness of the salami in compare to control sample. TBARS values of the rosemary treated cooked salami with different amount of yeasts extracts were significantly lower compare to control sample at the end of the shelf life. Also, lower value of TBARS was determined in salami with rosemary in combination with higher amount of yeast extract. The lowest count of PBC was determined in the second experimental group after 15 days. The rosemary extract in combination of yeast extract treatments were not able to influence the growth of the yeasts and moulds. It was found that rosemary extract in combination with yeast extract in the salami of the second experimental group after 15 days of storage significantly (p &lt;0.05) decrease count of Lactobacillus bacteria.

Physicochemical and microbial changes during storage of smoke-flavoured salmon obtained by a new method

The aim of this study was to evaluate the effect of a new smoking-salting method employing water vapour permeable (WP) bags on the physicochemical and microbial quality of smoke-flavoured salmon in refrigerated storage. Fresh salmon was subjected to a smoking process in the WP at 5 °C. Physicochemical and microbiological analyses were periodically carried out during the subsequent 40 days of refrigerated storage of the product. The WP bags enabled the evaporation of the exudate during the smoking-salting stage, enabling the drying of the product to take place at the same time. A slight increase of trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) contents was observed over the storage period. The concentration of TVB-N ranged from 14.26 to 21.48 mg N/100 g of fish, values far below the upper limits of acceptability. The low values of the thiobarbituric acid (TBA) index (final level of 0.71 mg MDA/kg) indicate that the lipid oxidation in the smoke-flavoured salmon was limited throughout the period studied. The initial K1-value was high and only a slight increase was observed during storage. Counts of mesophilic, psychrotrophic, Enterobacteriaceae and lactic acid bacteria were low throughout the study. Given the changes observed for the physicochemical and microbiological parameters, it can be said that no spoilage took place in the smoke-flavoured salmon during the 40 days of storage. This new method could be of interest to producers as it enables smoke-flavoured salmon to be produced to a good standard of hygiene, minimizing handling and reducing processing steps and brine wastes.

English

The Amazon offers great potential for fishery activities but the fish fauna&rsquo;s specific microbiota is not yet known. This paper identified the bacterial flora composition and the influence of this process on the microbiological spoilage in economically important fish species in the Amazon region: butterfly peacock bass (Cichla ocellaris) and piramutaba (Brachyplatystoma vailantii). To this end, microbiological characterization was performed: counts of total mesophilic aerobic bacteria, psychrotrophic bacteria and coliforms at 35 and 45&deg;C. Bacteria were also isolated through seeding in agar surface using violet red bile glucose (VRBG) for enterobacteria strains and Baird-Parker Agar with egg-yolk tellurite for Staphylococcus species, both with incubation at 36&deg;C for 48 h. The bacteria isolated were identified using the API 20E kit (Enterobacteria), and Gram-positive with API Staph (Staphylococci). Finally, the limit temperature for strain growth was tested using spectrophotometry readings at 554 nm at 10 and 15&deg;C at three different times: 0, 3 and 6 h. The mesophilic aerobic bacteria counts for fresh fish samples ranged from 6.03 - 8.23 log CFU/g for piramutaba and 4.52 - 7.24 log CFU/g for butterfly peacock bass. The count ranges of psychrotrophic aerobic bacteria found were 6.14 - 8.56 log CFU/g and 4.52 - 7.24 log CFU/g for piramutaba and butterfly peacock bass, respectively. They also had an average score above 103 MPN/g for total coliforms. Sixteen different strains were isolated. The most predominant were Staphylococcus hominis, Staphylococcus aureus, Stenotrophomonas maltophilia and Enterobacter intermedius. When subjected to temperatures of 10 and 15&deg;C, the strains did not achieve growth for 6 h at a 95% significance level. Key words: Fish, Cichla ocellaris, Brachyplatystoma vailantii, microflora.

Antimicrobial and aromatic edible coating on fresh-cut pineapple preservation

The present research aimed to develop an edible coating incorporated with mint essential oil, evaluate its effectiveness in inhibiting in vitro microbial development, and improve both quality and shelf-life of fresh-cut pineapple. Mint essential oil-containing edible coatings showed in vitro antimicrobial efficiency against Escherichia coli and Salmonella Enteritidis. Titratable acidity, pH, and texture were not affected (P&gt;0.05) by coating or storage time. Mass loss was not higher than 1.0% after the 6th day of storage. No effect of storage time and coating on total soluble solids was observed. Mint essential oil-containing coatings inhibited the growth of yeasts and molds in fresh-cut pineapple. Compared to uncoated and control-coated samples, mint essential oil-containing coatings lessened psychrotrophic bacteria counts throughout storage. Counts of thermotolerant coliforms were not higher than 3.0MPN·g-1 in all treatments, whereas no Salmonella sp. was detected during the 6-day storage. Mint essential oil provided a strong flavor to the fruit, as shown by sensory evaluations.