Antimicrobial effects of cinnamon bark oil on microbial composition and quality of grass carp (Ctenopharyngodon idellus) fillets during chilled storage

In this study, 11 essential oils were initially screened for antimicrobial activity against Aeromonas veronii, Acinetobacter johnsonii, Shewanella putrefaciens, and Pseudomonas jessenii. Cinnamon bark oil exhibited the highest antimicrobial activity and was used as a natural preservative in grass carp fillets stored at 4 ± 1 °C. Sensory assessment, total volatile basic nitrogen (TVB-N), color, biogenic amines, adenosine triphosphate (ATP)-related compounds, K-value, and presence of microbiota were analyzed during storage. Cinnamon bark oil treatment was found to be effective in enhancing organoleptic quality, inhibiting microbial growth, and delaying the increase of TVB-N, putrescine, cadaverine and K-value. Based on sensory analysis, shelf-life of grass carp fillets was 8 days for the control and 12 days for the treatment group. According to high-throughput sequencing, Aeromonas and Pseudomonas were the predominant microbiota in fresh grass carp. As storage time progressed, the microbial composition of both control and treatment samples became less diverse. Pseudomonas followed by Aeromonas were dominant in spoiled control samples. However, there were significant differences in microbial composition between control and treatment samples at the end of storage. Cinnamon bark oil treatment inhibited the growth of Aeromonas and Shewanella, and Pseudomonas was the only predominant microbiota found in spoiled treatment samples.     

Effect of starter culture, spice mix and storage time and temperature on biogenic amine content of dry fermented sausages

Two types of dry fermented sausage differing in spicing mixture and the diameter (low content of red pepper + diameter 80 mm, H-sausage; high content of red pepper + diameter 55 mm, P-sausage, respectively) were produced in parallel with two different starter cultures (Pediococcus pentosaceus + Staphylococcus carnosus, B-samples and S. carnosus + Staphylococcus xylosus + Lactobacillus farciminis, F-samples, respectively). The sausages were ripened 21 days and subsequently stored 91 days at the room temperature. Concentration of both most abundant amines, putrescine and tyramine (y; mg/kg DM) increased significantly (P<0.01) in HB-sausage during ripening (x; days): y=2.5+18.13x−0.3144x² (R²=0.99) and y=0.7+8.17x−0.1130x² (R²=0.99), and also during storage: y=127.3+5.123x (R²=0.79) and y=26.0+3.211x (R²=0.74), respectively. At the end of ripening, putrescine (247 mg/kg DM) and tyramine (123 mg/kg DM) content in the HB-sausage was higher (P<0.05) than in the PB-sausage (12 and 9 mg/kg DM, respectively), concentration of either of these amines was negligible (1 mg/kg DM) in either type of F-inoculated sausage. Both starter culture and sausage type influenced significantly (P<0.001) both putrescine and tyramine content in the sausage; starter accounted for 57% and 55% of total variability in putrescine and tyramine content, respectively. Due to the significant (P<0.05) increase of total aerobic counts in the HB-sausage between the end of ripening and the 7th day of storage, followed by the significant (P<0.01) increase of the sum of total biogenic amines between the end of ripening (425 mg/kg DM) and the end of storage (1029 mg/kg DM), the storage of the dry fermented sausages at the room temperature should not be recommended.     

Production of biogenic amines by lactic acid bacteria and enterobacteria isolated from fresh pork sausages packaged in different atmospheres and kept under refrigeration

The occurrence of in vitro amino acid activity in bacterial strains associated with fresh pork sausages packaged in different atmospheres and kept in refrigeration was studied. The presence of biogenic amines in decarboxylase broth was confirmed by ion-exchange chromatography and by the presence of the corresponding decarboxylase genes by PCR. From the 93 lactic acid bacteria and 100 enterobacteria strains analysed, the decarboxylase medium underestimates the number of biogenic amine-producer strains. 28% of the lactic acid bacteria produced tyramine and presented the tdc gene. All the tyramine-producer strains were molecularly identified as Carnobacterium divergens. Differences on the relative abundance of C. divergens were observed among the different packaging atmospheres assayed. After 28 days of storage, the presence of argon seems to inhibit C. divergens growth, while packing under vacuum seems to favour it. Among enterobacteria, putrescine was the amine more frequently produced (87%), followed by cadaverine (85%); agmatine and tyramine were only produced by 13 and 1%, respectively, of the strains analysed. Packing under vacuum or in an atmosphere containing nitrogen seems to inhibit the growth of enterobacteria which produce simultaneously putrescine, cadaverine, and agmatine. Contrarily, over-wrapping or packing in an atmosphere containing argon seems to favour the growth of agmatine producer-enterobacteria. The production of putrescine and cadaverine was associated with the presence of the corresponding amino acid decarboxylase genes. The biogenic amine-producer strains were included in a wide range of enterobacterial species, including Kluyvera intermedia, Enterobacter aerogenes, Yersinia kristensenii, Serratia grimesii, Serratia ficaria, Yersinia rodhei, Providencia vermicola and Obesumbacterium proteus.     

Determination of biogenic amines in foods using ultra-performance liquid chromatography (UPLC)

A rapid ultra-performance liquid chromatographic (UPLC) method for the determination of biogenic amines (putrescine, cadaverine, spermidine, spermine, phenylethylamine, histamine, tyramine and tryptamine) in selected food samples is described. The eight biogenic amines, which are the most important to be determined in food samples, were derivatized with dansyl chloride prior to UPLC separation. The dansylated amines were separated on an Agilent Zorbax Eclipse XDB – C18 column (50 × 4.6 mm ID, 1.8 μm) using gradient elution with a binary system of acetonitrile–water, a flow rate of 1.0 ml/min and UV detection at 225 nm. The analysis is very fast, all amines are well resolved and are eluted from the column in less than 6 min. The average repeatability of the method ranged between 1.02% and 2.14%. Limits of detection (LODs) for considered amines ranged between 0.032 and 0.098 μg/l; calibration curves showed very good linearity (r = 0.9994–1.0000). The method was applied to the analysis of amines in pork, beef, chicken and fish meat, cheese and edible mushrooms.     

Identification and decarboxylase activities of bacteria isolated from decomposed mahimahi (Coryphaena hippurus) after incubation at 0 and 32°C

Identification and amine-forming ability of bacterial isolates from decomposed mahimahi (Coryphaena hippurus) were studied in order to identify spoilage microflora and determine the potential for a chemical index of spoilage based on the metabolites produced. Mesophilic bacteria isolated from a fish incubated at 32°C for 24 h were essentially all Gram-negative rods; 89% of these were Vibrio alginolyticus. Strong histamine-forming (> 100 mg/100 ml) mesophiles consisted of eight cultures of Morganella morganii and one of Proteus mirabilis. Weak histamine-forming (< 10 mg/100 ml) mesophiles were all V. alginolyticus, and these comprised 15% of the isolates assigned to that species. Decarboxylation of ornithine and lysine occurred in 38 and 92%, respectively, of the mesophilic isolates. Psychrotrophic isolates obtained from a fish incubated 14 days at 0°C were predominantly Gram-negative genera. Of these, 9% were histamine-forming cultures of Alteromonas putrefaciens, a weak histamine former that produced < 1 mg/100 ml at 5 and 20°C. Decarboxylation of ornithine and lysine occurred in 13 and 15%, respectively, of the psychrotrophic isolates.     

Genetic screening of biogenic amines production capacity from some lactic acid bacteria strains

There is an increasing interest for using lactic acid bacteria (LAB) as a starter and adjunct cultures for producing novel foods with particular functional traits. The ability of the starter to produce biogenic amines (BA) should be taken into account wherein protective starters should be selected to avoid hygienic and toxicological risks. This work aimed to study the possibilities of forming BA (histamine, putrescine, agmatine and tyramine) from thirty two LAB strains belonging to species of the genera Lactobacillus and Streptococcus that used in food products as well as strains isolated from healthy breast-fed infants. The analytical protocol involved using polymerase chain reaction (PCR) and thin layer chromatography (TLC) techniques to determine the ability of LAB strains to form BA. The presence of key genes involved in the biosynthetic pathways of the BA was also assessed by PCR. Six LAB strains gave positive results for putrescine production wherein the maximum level was 14.6 mg/kg. Six strains gave positive results for histamine production (maximum level was 31.7 mg/kg) and were positive for the presence of histidine decarboxylase (HDC) gene. Seven strains exhibited positive results for tyramines production (maximum level was 2.85 mg/kg) and were positive for the presence of tyrosine decarboxylase (TDC) gene. Eight strains gave positive results for agmatine production (maximum level was 174.5 mg/kg) and were positive for the presence of dihydrolase (deiminase) gene that responsible for agmatine formation. It could be concluded that the microorganisms used in food and dairy production should be screened carefully by PCR for their ability to produce BA.     

A new fear in wine: Isolation of Staphylococcus epidermidis histamine producer

Biogenic amines (BAs) are undesirable compounds in all foods and beverages because they may induce food-borne intoxications when consumed at high concentrations. The aim of this study was to identify the organism responsible for the synthesis of histamine in a Tempranillo red wine from Ribera de Duero D.O. (Denomination of origin), Spain. Bacteria present in wines after malolactic fermentation were isolated, identified and typed. Four strains of the species Oenococcus oeni and two strains of Staphylococcus epidermidis were found. None of the O. oeni strains produced histamine, cadaverine or putrescine, but one of the S. epidermidis strains (Pa) was able to produce all three in synthetic medium and grape must, although not in wine. From the data obtained in this work, histamine present in Tempranillo wine B was produced by the S. epidermidis strain Pa. This is the first report in which the presence of S. epidermidis has been reported in wine and whose ability to produce histamine, putrescine and cadaverine has been demonstrated in grape must.     

Production of biogenic amines “in vitro” in relation to the growth phase by Enterobacteriaceae species isolated from traditional sausages

Histidine, lysine, ornithine and tyrosine decarboxylase activities were tested in 79 strains of Enterobacteriaceae (41 of Hafnia alvei, 17 of Serratia liquefaciens, 5 of Enterobacter cloacae, 4 of Citrobacter braakii, 2 of Proteus vulgaris, 2 of Proteus mirabilis, 2 of Providencia stuartii, 2 of Klebsiella terrigena, 1 of Rahnella aquatilis, 1 of Salmonella arizonae, 1 of Citrobacter youngae and 1 of Escherichia coli) isolated from Botillo, a Spanish traditional sausage. In general, the strains were positive for all four activities, with the exception of two strains of H. alvei and the E. coli strain, which did not display histidine decarboxylase activity. The strains of P. mirabilis and P. stuartii did not exhibit any of the four activities tested.     

Biogenic amine content in dry fermented sausages as influenced by a producer,spice mix,starter culture,sausage diameter and time of ripening

Sixteen types of dry fermented sausages were commercially produced as combinations of two producers (designated K and R), two starter cultures (Pediococcus pentosaceus, C; Lactobacillus curvatus + Staphylococcus carnosus, F), two spicing mixtures (H; P) and two casing diameters (4.5 cm, T; 7 cm, W), and were sampled at days zero, 14, 28 (end of ripening), 49, 70, 91 and 112 (samples were stored at 15 °C and relative humidity of 70% between days 28 and 112). Tyramine and putrescine content (Y, mg kg⁻¹) increased (P < 0.01) with increasing time of ripening/storage (X, days): Y = 52.0 + 5.19X − 0.0275X² (R² = 0.60) and Y = 37.0 + 3.45X − 0.0192X² (R² = 0.23), respectively. Smaller diameter (T), spice mix containing red pepper (P) and starter culture C decreased (P < 0.05) both tyramine and putrescine content in the sausages as compared to the W, H and F counterparts, respectively; content of both amines was lower (P < 0.05) in the K-sausages than in the R-sausages. Tyramine content in the sausages at the time interval 28 days of ripening + 21 days of storage was in the range from 170 (KHCU sausage combination) to 382 (RHFS) mg kg⁻¹.