Exploring the Relationships Between Bacterial Community, Taste-Enhancing Peptides and Aroma in Thai Fermented Fish (Pla-ra).

As a traditional Thai condiment, Pla-ra is used to add flavor and richness to dishes. Nine treatment combinations of Pla-ra formulations created from 3 types of fish (Mor fish, Kradee fish, and Mor + Kradee fish) and 4 different carbohydrate sources (none, rice bran, roasted rice, and rice bran─roasted rice mixture) were studied through a 12 month fermentation period (1, 3, 5, 7, 8, 9, 10, 11, and 12 months). 16S rRNA Next Generation Sequencing (NGS) and LC-MS/MS techniques were used to analyze the microbial diversity and identify taste-enhancing peptides. Descriptive sensory analysis was performed on the extracts of the 108 Pla-ra samples mixed in a model broth. Koku perception and saltiness-enhancing attributes were clearly perceived and dominant in all samples, even though glutamyl peptides, including γ-Glu-Val-Gly, were found at subthreshold levels. The samples from mixed fish and Mor fish fermented with roasted ground rice and rice bran for 12 months had the most typical Pla-ra odors and tastes and had high taste-enhancing activities. NGS analysis revealed the presence of bacteria containing a large number of protease and aminopeptidase genes in the samples. Bacillus spp., Gallicola spp., and Proteiniclasticum spp. correlated well with the generation of glutamyl and arginyl peptides and typical odors in the samples. These results confirmed the typical sensory quality of Pla-ra depended on protein sources, carbohydrate sources, and bacteria communities. Further optimization of the microbial composition found could lead to the development of starter cultures to control and promote flavor development in fermented fish products.

Application of oil-in-water nanoemulsions based on grape and cinnamon essential oils for shelf-life extension of chilled flathead mullet fillets.

BACKGROUND: The effect of nanoemulsions prepared with grape seed and cinnamon essential oils on the shelf-life of flathead mullet (Mugil cephalus) fillets was evaluated by determining physicochemical (pH, free fatty acids, peroxide value, total volatile base nitrogen (TVB-N), and thiobarbituric acid reactive substances (TBARs)), sensory and microbiological (mesophilic aerobic bacteria, total psychrophilic bacteria, and Enterobacteriaceae counts) properties during 14 day storage at 2 °C. RESULTS: The nanoemulsions showed good stability and low average droplet size. The results indicated that nanoemulsion treatments significantly prolonged the shelf-life of the fillets. Treatment inhibited increases in pH and TVB-N, and retarded lipid oxidation and hydrolysis. Sensory assessment revealed that treatment induced shelf-life extension from 10 to 14 days, compared with controls. Microbiological analyses showed nanoemulsion treatment caused shelf-life extension from 10 to 12 days with reduction of microbiological contamination by up to 1 log cfu g-1 in mesophilic and 1.5 log cfu g-1 in psychrotrophic bacteria. CONCLUSION: Considering the results, grape seed and cinnamon essential oil nanoemulsions could be considered as novel antimicrobial and antioxidant materials for shelf-life extension of flathead mullet fillets during cold storage. © 2021 Society of Chemical Industry.

Optimization of the Maillard reaction of xylose with cysteine for modulating aroma compound formation in fermented tilapia fish head hydrolysate using response surface methodology.

Aroma defects limit the application of fish protein hydrolysates as flavourings. This study aimed to develop a flavour concentrate from fermented tilapia fish head hydrolysate bymaximising the Maillard reaction production of meaty and roasted aroma associated compounds. We studied the optimal conditions of the Maillard reaction of xylose with cysteine to form meat-like odorants using response surface methodology. A 3-factored and 3-leveled Box Behnken design was employed, where the independent variables were cysteine concentration (A, w/v, %), heating temperature (B, °C) and heating time (C, min). 2-Methyl-3-furanthiol and 2-furfurylthiol were used as response factors. The optimal conditions were obtained as follows: A, 0.80%; B, 183.80 °C; C, 89.34 min. Compared with the controls, Maillard reaction products enriched the meaty and roasted aroma associated compounds in the treated hydrolysate. In conclusion, the treated tilapia fish head hydrolysate may be used as a base in development of new fish-based flavourings.

Isolation, identification, and potential probiotic characterization of isolated lactic acid bacteria and in vitro investigation of the cytotoxicity, antioxidant, and antidiabetic activities in fermented sausage.

BACKGROUND: Probiotic bacteria can provide health benefits when delivered in functional foods. This study involved isolation of lactic acid bacteria (LAB) from traditionally dried and salted anchovy fish and characterization of their survival in simulated gastrointestinal digestion. Promising strains were used to prepare fermented fish sausages which were then evaluated for cytotoxicity activity against two cancer cell-lines, antidiabetic activity as determined by α-amylase and α-glucosidase inhibition, and antioxidant and proteolytic activities in vitro, as compared to non-fermented control sausages. RESULTS: Out of 85 LAB obtained, 13 isolates with high tolerance to simulated gastrointestinal digestion were obtained, which were identified as Enterococcus spp. Four E. faecium strains, one E. faecalis, and one E. durans were used separately to make fermented fish sausages. The α-amylase and α-glucosidase inhibition from fish sausages fermented by Enterococcus spp. ranged from 29.2 to 68.7% and 23.9 to 41.4%, respectively, during 21 days of storage. The cytotoxicity activities against Caco2 and MCF-7 cells of fish sausages fermented with Enterococcus spp. ranged from 18.0 to 24% and 13.9 to 27.9%, respectively. Cytotoxicity activities correlated positively with proteolysis and antioxidant activities, α-amylase and α-glucosidase inhibition activities, but negatively with the pH in fermented fish sausages. Strains also exhibited antimicrobial activity against foodborne pathogens and presented no significant concerns with regards to antibiotic resistance or virulence gene content. CONCLUSIONS: Fish sausages fermented by potential probiotic isolates of Enterococcus spp. from dried fish had valuable health-promoting benefits compared with non-fermented control sausages.

Chitosan and Oregano Oil Treatments, Individually or in Combination, Used To Increase the Shelf Life of Vacuum-Packaged, Refrigerated European Eel (Anguilla anguilla) Fillets.

We investigated the impact of chitosan and oregano essential oil (EO) individually or in combination on the quality of eel fillets in vacuum packaging (VP) and stored under refrigeration (4°C). Treatments studied were (i) control eel fillets stored in VP (E), (ii) eel fillets treated with 0.3% (v/w) oregano EO and stored in VP (E-OR), (iii) eel fillets treated with 2.0% (w/v) chitosan and stored in VP (E-CH), and (iv) eel fillets treated with 2.0% (w/v) chitosan and 0.3% (v/w) oregano EO and stored in VP (E-CH-OR). Treatments E-CH-OR and E-CH significantly reduced counts of mesophilic bacteria, Pseudomonas, Shewanella, and yeasts and molds during storage. Use of chitosan alone or in combination with oregano EO led to a significant reduction in concentrations of trimethylamine nitrogen and total volatile basic nitrogen in fillets, which led to lower concentrations of thiobarbituric acid reactive substances compared with the control samples. The eel samples in the E-CH and E-CH-OR groups were sensorially acceptable during the entire refrigerated storage period of 18 days. Presence of chitosan in the E-CH and E-CH-OR fillets did not negatively affect the taste of the fillets. E-CH fillets received a higher taste score than did E-CH-OR fillets probably because of the distinct and "spicy" lemon taste of chitosan, which was well received by the sensory panel. Based on overall sensory data (based on mean sensory scores of odor and taste), the shelf life was 6 days for the control fillets, 10 days for the E-OR fillets, and >18 days for the E-CH and E-CH-OR fillets stored in VP at 4°C. Overall, chitosan-treated eel fillets had lower microbial loads and a longer shelf life compared with the controls. Chitosan-treated eel fillets were preferred over oregano-treated fillets. Chitosan alone or in combination with oregano could be used as a preservative treatment and shelf-life extender for other seafoods.

Avaliação da qualidade microbiológica de carne mecanicamente separada (CMS) e de derivados do pescado provenientes de cinco municípios da Baixada Maranhense / Evaluation of the microbiological quality of mechanically recovered meat (MRM) and of fish by-products from five cities of the Baixada Maranhense

O objetivo desse trabalho foi avaliar a qualidade microbiológica da carne mecanicamente separada (CMS ) e derivados de pescado (fishburguer, nugget de peixe e linguiça de peixe) de cinco municípios da Baixada Maranhense. As contagens obtidas para coliformes totais nas amostras de CMS e derivados variaram de 43 a >1100 NMP/g. As contagens de coliformes termotolerantes variaram de 35 a >1100 NMP/g Em uma amostra de fish burguer do município de Bacurituba foi encontrado o valor de 3 x 103 UFC/g. Amostras provenientes dos cinco municípios apresentaram contaminação, encontrando-se em condições higiênico-sanitárias insatisfatórias, podendo representar riscos à saúde pública. Devem ser adotadas junto à comunidade envolvida na pesca artesanal e na produção desses alimentos, boas práticas de fabricação e condições adequadas de manipulação, armazenamento e conservação.

Efeito da utilização de própolis vermelha em salame de peixe no crescimento de bactérias láticas fermentadoras / Effect of the use of red propolis in salami of fish in the growth of fermenting lactic bacteria

O presente estudo teve como objetivo verificar a atividade antimicrobiana do extrato de própolis vermelha em salame de tilápia. Para isso, foram elaborados três tratamentos de salame: T1 = 0,1% de extrato de própolis, T2 = 0,2% de extrato de própolis e T3 = 0,2% de sal de cura (controle). Os tratamentos foram avaliados quanto a quantificação de bactérias mesófilas e bactérias láticas, e o pH durante 15 dias de maturação do salame. O extrato de própolis não interferiu no crescimento das bactérias láticas, mas também não inibiu a presença de bactérias mesófilas. Nos primeiros cinco dias de fermentação o pH diminuiu (pH 5,9 ), aumentando posteriormente ao final da maturação dos salames (pH 6,8). Conclui-se que é preciso testar concentrações mais altas da própolis vermelha em embutidos cárneos fermentados a fim de se obter uma ação mais eficiente contra bactérias mesófilas.

Efeito do processamento de defumação na qualidade de bijupirá (Rachycentron canadum): atributos bacteriológicos, químicos e sensoriais / Effect of smoking-method on the keeping quality of cobia (Rachycentron canadum): bacteriological, chemical and sensory attributes

O objetivo do presente trabalho foi desenvolver a carne de bijupirá defumada, assim como avaliar o rendimento, a qualidade bacteriológica, a composição centesimal e a aceitabilidade do produto. Análises microbiológicas de pesquisa de Salmonella sp. e contagens de Staphylococcus aureus, coliformes totais e Escherichia coli foram realizadas. Foi determinada a composição centesimal e realizado o teste de aceitação do produto. O rendimento médio da carne após a salga foi de 83,41%, com base no peso do charuto. A análise microbiológica da carne defumada apresentou-se positiva em apenas uma amostra para Staphylococcus aureus e negativa para as demais bactérias. O produto possui boa qualidade nutricional e alcançou 97% de aceitação para o aspecto global, atingindo média de 6,26 (± 0,99). A carne de bijupirá defumada obteve condições higiênico-sanitárias satisfatórias, boa qualidade nutricional, além de alto índice de aceitação sensorial, destacando-se os atributos textura e sabor. Evidenciou-se, assim, que esse tipo de processo pode ser realizado em escala artesanal ou industrial.(AU)

The objective of the study was to develop the smoked cobia meat and to evaluate the yield, the bacteriological quality, the centesimal composition, and the acceptability of the product. Microbiological analysis of Salmonella sp. and Staphylococcus aureus, total coliforms and Escherichia coli counts were performed. The centesimal composition was determined and the acceptance test was performed. The average yield of the product after salting was 83.41% based on the fish roll weight. The microbiological analysis of the smoked meat showed positive in only one sample for Staphylococcus aureus and negative for the other bacteria. The product has a good nutritional quality and was accepted obtaining 97% for the overall aspect, average of 6.26 (± 0.99). The smoked cobia meat obtained satisfactory hygienic-sanitary conditions, good nutritional quality, besides a high index of sensorial acceptance emphasizing the texture and flavor attributes. Smoked process can be easily carried out on an artisanal or industrial scale.(AU)

Use of modified Richards model to predict isothermal and non-isothermal microbial growth

Abstract Mathematical models are often used to predict microbial growth in food products. An important class of these models involves the adaptation of classical sigmoid functions, such as the Gompertz and logistic functions. This study aimed to validate the use of the modified Richards model in various situations, which have not previously been tested. The model was obtained through solving a system of two differential equations and could be applied to both isothermal and non-isothermal environments. To test and validate this model, we used published datasets containing data for the growth of Pseudomonas spp. in fish products. The results obtained after fitting the model showed that it could be effectively used to describe and predict the Pseudomonas growth curves under various temperature regimens. However, the influence of the shape parameter on the growth curve is an issue that needs further evaluation.

Lentibacillus alimentarius sp. nov., isolated from Myeolchi-jeotgal, a traditional Korean high-salt fermented anchovy.

A Gram-positive, motile, endospore-forming, rod-shaped bacterium, designated strain M2024T, was isolated from Myeolchi-jeotgal, a traditional Korean high-salt fermented anchovy and was characterised using a polyphasic taxonomic approach. Comparative 16S rRNA gene sequence analysis showed that strain M2024T belongs to the genus Lentibacillus in the family Bacillaceae of the Firmicutes. The 16S rRNA gene sequence analysis showed that strain M2024T is closely related to Lentibacillus populi WD4L-1T (95.5%), Lentibacillus garicola SL-MJ1T (95.2%) and Virgibacillus siamensis MS3-4T (95.1%). The chemotaxonomic properties of strain M2024T are consistent with those of members of the genus Lentibacillus: the quinone system has MK-7 as the predominant menaquinone and anteiso-C15:0 and anteiso-C17:0 are the predominant cellular fatty acids. The major polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The G+C content of the genomic DNA was determined to be 36.2 mol%. Differential phenotypic properties compared with closely related type strains support the conclusion that strain M2024T can be separated from previously described members of the genus Lentibacillus. The strain thus represents a novel species in this genus, for which the name Lentibacillus alimentarius sp. nov. is proposed. The type strain is M2024T (= KEMB 9001-124T = JCM 16521T).

Regenerative and Antibacterial Properties of Acellular Fish Skin Grafts and Human Amnion/Chorion Membrane: Implications for Tissue Preservation in Combat Casualty Care.

BACKGROUND: Improvised explosive devices and new directed energy weapons are changing warfare injuries from penetrating wounds to large surface area thermal and blast injuries. Acellular fish skin is used for tissue repair and during manufacturing subjected to gentle processing compared to biologic materials derived from mammals. This is due to the absence of viral and prion disease transmission risk, preserving natural structure and composition of the fish skin graft. OBJECTIVES: The aim of this study was to assess properties of acellular fish skin relevant for severe battlefield injuries and to compare those properties with those of dehydrated human amnion/chorion membrane. METHODS: We evaluated cell ingrowth capabilities of the biological materials with microscopy techniques. Bacterial barrier properties were tested with a 2-chamber model. RESULTS: The microstructure of the acellular fish skin is highly porous, whereas the microstructure of dehydrated human amnion/chorion membrane is mostly nonporous. The fish skin grafts show superior ability to support 3-dimensional ingrowth of cells compared to dehydrated human amnion/chorion membrane (p < 0.0001) and the fish skin is a bacterial barrier for 24 to 48 hours. CONCLUSION: The unique biomechanical properties of the acellular fish skin graft make it ideal to be used as a conformal cover for severe trauma and burn wounds in the battlefield.

Biosurfactant production by Pseudomonas aeruginosain kefir and fish meal

The aim of this study was to increase rhamnolipid production by formulating media using kefir and fish meal for Pseudomonas aeruginosa strains isolated from different environmental resources. The strains, named as H1, SY1, and ST1, capable of rhamnolipid production were isolated from soil contaminated with wastes originating from olive and fish oil factories. Additionally, P. aeruginosa ATCC 9027 strain, which is known as rhamnolipid producer, was included in the study. Initially, rhamnolipid production by the strains was determined in Mineral Salt Medium (MSM) and then in media prepared by using kefir and fish meal. The obtained rhamnolipids were purified and quantified according to Dubois et al. (1956). The quantity of rhamnolipids of ATCC, H1 and SY1 strains in kefir media were determined as 11.7 g/L, 10.8 g/L and 3.2 g/L, respectively, and in fish meal media as 12.3 g/L, 9.3 g/L and 10.3 g/L, respectively. In addition, effect of UV light exposure on rhamnolipid production was also investigated but contrary a decrease was observed. The results indicate that P. aeruginosa strains isolated from various environmental resources used in this study can be important due to their rhamnolipid yield, and fish meal, which is obtained from waste of fish, can be an alternative source in low cost rhamnolipid production.

Tannins and extracts of fruit byproducts: antibacterial activity against foodborne bacteria and antioxidant capacity.

The shelf life of fresh fish and meat transported over long distances could be extended by using plant-based extracts to control spoilage bacteria. The goals of the present study were to identify plant-based extracts that effectively suppress the main spoilage bacteria of chilled fish and lamb and to assess their antioxidant capacity. The phenolic compounds in wood-based tannins and extracts isolated from byproducts of the fruit processing industry were identified and/or quantified. The total phenol content, but not the flavonoid to total phenol ratio, was strongly associated with higher antibacterial activity against several fish and lamb spoilage bacteria in zone of inhibition and minimum inhibitory concentration assays as well as greater antioxidant capacity in the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical assay. The most promising compounds in both cases, and thus good candidates for antibacterial packaging or antioxidant dietary supplements, were mango seed extract and tannic acid containing mostly polygalloyl glucose type phenols.

An educationally inspired illustration of two-dimensional Quantitative Microbiological Risk Assessment (QMRA) and sensitivity analysis.

Quantitative Microbiological Risk Assessment (QMRA) is a structured methodology used to assess the risk involved by ingestion of a pathogen. It applies mathematical models combined with an accurate exploitation of data sets, represented by distributions and - in the case of two-dimensional Monte Carlo simulations - their hyperparameters. This research aims to highlight background information, assumptions and truncations of a two-dimensional QMRA and advanced sensitivity analysis. We believe that such a detailed listing is not always clearly presented in actual risk assessment studies, while it is essential to ensure reliable and realistic simulations and interpretations. As a case-study, we are considering the occurrence of listeriosis in smoked fish products in Belgium during the period 2008-2009, using two-dimensional Monte Carlo and two sensitivity analysis methods (Spearman correlation and Sobol sensitivity indices) to estimate the most relevant factors of the final risk estimate. A risk estimate of 0.018% per consumption of contaminated smoked fish by an immunocompromised person was obtained. The final estimate of listeriosis cases (23) is within the actual reported result obtained for the same period and for the same population. Variability on the final risk estimate is determined by the variability regarding (i) consumer refrigerator temperatures, (ii) the reference growth rate of L. monocytogenes, (iii) the minimum growth temperature of L. monocytogenes and (iv) consumer portion size. Variability regarding the initial contamination level of L. monocytogenes tends to appear as a determinant of risk variability only when the minimum growth temperature is not included in the sensitivity analysis; when it is included the impact regarding the variability on the initial contamination level of L. monocytogenes is disappearing. Uncertainty determinants of the final risk indicated the need of gathering more information on the reference growth rate and the minimum growth temperature of L. monocytogenes. Uncertainty in the dose-response relationship was not included in the analysis, hence the level of its influence cannot be assessed in the present research. Finally, a baseline global workflow for QMRA and sensitivity analysis is proposed.

UV-C radiation as a factor reducing microbiological contamination of fish meal.

Fish meals, added to feeds as a source of protein, may contain pathogenic bacteria. Therefore, effective methods for their sanitizing, such as UV-C radiation, are needed to minimize the epidemiological risk. The objective of this study was to evaluate the effect of UV-C radiation on the sanitary state of fish meals. The research materials included salmon and cod meals. Samples of the fish meals were inoculated with suspensions of Salmonella, E. coli, enterococci, and C. sporogenes spores and exposed to the following surface UV-C fluencies: 0-400 J·m⁻² for bacteria and 0-5000 J·m⁻² for spores. For the vegetative forms, the highest theoretical lethal UV-C dose, ranging from 670.99 to 688.36 J·m⁻² depending on the meal type, was determined for Salmonella. The lowest UV-C fluency of 363.34-363.95 J·m⁻² was needed for the inactivation of Enterococcus spp. Spores were considerably more resistant, and the UV-C doses necessary for inactivation were 159571.1 J·m⁻² in salmon meal and 66836.9 J·m⁻² in cod meal. The application of UV-C radiation for the sanitization of fish meals proved to be a relatively effective method for vegetative forms of bacteria but was practically ineffective for spores.

Microbiological quality of salmon (Salmo salar) sold in cities of the state of São Paulo, Brazil

The present paper evaluated the microbiology of salmon by quantifying mesophilic heterotrophic microorganisms, total and thermotolerant coliforms, and the presence of Vibrio parahaemolyticus, Staphylococcus aureus, Salmonella sp., Escherichia coli and Aeromonas sp. in the meat. This study can provide technical support for the suggestion of a new regulation of a Brazilian legislation through specific microbiological standards concerning the consumption of raw fish. A number of 31 (16 cooled and 15 frozen) samples of salmon were collected in the retail market network of a few cities in the State of São Paulo, Brazil. Results presented populations of mesophilic heterotrophic microorganisms ranging from 1.0 x 10 and 3.9 x 10(6) CFU/g, total and thermotolerant coliforms in 32.25% and 19.35% of the samples, respectively, and Aeromonas sp. in 41.95% of the samples with a populational variation ranging from 2.0 x 10² to 8.0 x 10³ CFU/g. Staphylococcus aureus was found in one sample whereas Vibrio parahaemolyticus, Salmonella sp. and Escherichia coli were not found. These results demonstrated the presence of potencially pathogenic microorganisms in fresh fish consumed in Brazil, highlighting the necessity of control measures to avoid public health problems related to the consumption of raw fish.

Control of Listeria monocytogenes and spoilage bacteria on smoked salmon during storage at 5 °C after X-ray irradiation.

In this study, smoked salmon fillets were artificially inoculated with Listeria monocytogenes (3.7 ± 0.2 log CFU g(-1)) and treated with X-ray irradiation generated by a RS 2400 X-ray machine (Rad Source Technologies Inc.) using doses of 0.0, 0.1, 0.5, 1.0, and 2.0 kGy. Unirradiated and irradiated samples were then stored at 5 °C for 35 days and tested for L. monocytogenes count after 0, 5, 10, 15, 20, 25, 30, and 35 days. Also, uninoculated-untreated and uninoculated-treated samples with the lowest and highest X-ray doses (0.1 and 2.0 kGy) were stored at 5 °C and examined for psychrotrophs and mesophiles counts after 0, 5, 10, 15, 20, 25, 30, and 35 days. The initial L. monocytogenes population (3.7 log CFU g(-1) ) was significantly (p < 0.05) reduced to an undetectable level (<1.0 log CFU g(-1)) by treatment with 1.0 kGy X-ray. Treatment with 0.1 kGy X-ray significantly reduced the initial psychrotrophs and mesophiles counts from 5.3 and 3.0 to 3.3 and 2.3, respectively. However, L. monocytogenes, psychrotrophs and mesophiles counts were gradually increased during storage. Treatment with 2.0 kGy X-ray kept the L. monocytogenes population under detectable level until 35 days. Treatment with 2.0 kGy X-ray kept the mesophiles and psychrotrophs counts within the acceptable level until 35 days. These results revealed that treatment with X-ray irradiation can significantly reduce the risk of listeriosis and extend the shelf life of smoked salmon during storage at 5 °C.

Antimicrobial activity of Chinese bayberry extract for the preservation of surimi.

BACKGROUND: Chemical preservatives such as sodium nitrite and potassium sorbate have been widely used to keep surimi products fresh. However, the potential harmfulness to human health cannot be ignored. This study was conducted to develop natural preservatives for the storage of Collichthys surimi. RESULTS: Among the eight Chinese traditional herbs and fruits, Chinese bayberry extract showed the greatest inhibitory effect against surimi spoilage bacteria Serratia marcescens and Pseudomonas aeruginosa. Moreover, N-butanol phase extract of bayberry (NB) showed the greatest activity among the different phases of bayberry extract. When Chinese bayberry extract was combined with tea polyphenol, an additive inhibitory effect was observed on growth of Hansenula anomala, Micrococcus luteus, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Our results further indicated that the shelf life of surimi products stored at room temperature can be extended when supplemented with Chinese bayberry extract. CONCLUSION: Our results suggest that Chinese bayberry extract can be used as a natural preservative for the storage of Collichthys surimi.

[Antibacterial activity of essential oil vapor for histamine-producing bacteria].

In this study, we evaluated the antibacterial activity of essential oil vapors against histamine-producing bacteria Morganella morganii NBRC3848 and Raultella planticola NBRC3317. We measured the minimum inhibitory dose (MID) of 14 essential oils towards these two strains. Allyl isothiocyanate (AIT) and salicylaldehyde (SA) vapors showed higher antibacterial activity than the other 12 essential oil vapors. Both AIT and SA vapors suppressed growth of total aerobic bacteria and histamine-producing bacteria in bigeye tuna and mackerel meat during storage at 12°C. These vapors also inhibited histamine accumulation in bigeye tuna meat and mackerel meat. Thus, application of AIT and SA vapors is effective for preventing increase of histamine-producing bacteria and histamine formation in fish meat.

Estudio de la estabilidad microbiológica de la barracuda a través del tiempo de almacenaje en Costa Rica / Microbiological stability through storage period of Sphyraena ensis in Costa Rica

En el presente estudio se evaluaron algunos de los cambios microbiológicos y bioquímicos producidos en una especie de pez de consumo frecuente en Costa Rica, como lo es la barracuda Sphyraena ensis. Se evaluaron muestras de barracuda obtenidas durante la estación lluviosa y durante la estación seca. A cada una de éstas se le realizó un recuento aerobio psicrófilo, recuento e identificación de Vibrio, Enterococcus y Pseudomonas durante 6 días de almacenaje a dos temperaturas, 2 y 7ºC. Así también, se le realizó a cada una, la evaluación de la concentración de histamina producida mediante un inmunoensayo enzimático comercial. Los resultados obtenidos ponen de manifiesto que se da un incremento en los recuentos obtenidos a través del tiempo de almacenaje, dicho crecimiento es mayor al aumentar la temperatura de refrigeración. La mayoría de muestras mantenidas a 7ºC presentan recuentos superiores a 106 UFC/g luego de tres días de almacenaje, situación que no se presenta en las muestras mantenidas a 2ºC. No obstante, luego de 6 días de almacenaje, todas las muestras, independientemente de la temperatura de almacenaje, sobrepasan este valor. De la misma manera, se da un incremento en la concentración de histamina producida a través del tiempo de almacenaje, especialmente al conservar el producto a mayor temperatura debido al aumento de bacterias capaces de descarboxilar la histidina. No existe una diferencia estadísticamente significativa entre los recuentos obtenidos en estación lluviosa con respecto a la estación seca, no obstante, sí existe una diferencia con respecto a los géneros bacterianos aislados.

At the present study some of the microbiological and biochemical changes that occur through storage period in Sphyraena ensis, a fish specie of frequent consumption in Costa Rica were studied. Samples of S. ensis obtained during rainy and dry season were evaluated. Analysis included aerobic psychrotrophic count, identification and count of Vibrio, Enterococcus and Pseudomonas through a six day storage period at two different refrigeration temperatures, 2 and 7ºC. Same time, a commercial enzymatic immunoassay was used for the evaluation of the variation on the concentration of histamine produced in the different samples. Results obtained show that there is an increase on the bacteriological counts through the storage period, this increase is bigger as refrigeration temperature increases. Most of the samples maintained at 7ºC showed counts above 106 CFU/g after three days of storage, those stored at 2ºC did not present such high population levels. Nevertheless, after 6 days of storage, all samples, despite the storage temperature used, presented levels above the described one. Also, an histamine concentration increased through storage time, especially when the product was conserved at the higher temperature due to an increase in the number of histidine descarboxilating bacteria. There is no statistical difference between the counts obtained during rainy or dry season; nevertheless, there is a difference assicieated to the bacterial genera isolated.