Editorial: Biogenic amines in foods

Rapid discrimination of Lentilactobacillus parabuchneri biofilms via in situ infrared spectroscopy

Microbial contamination in food industry is a source of foodborne illnesses and biofilm-related diseases. In particular, biogenic amines (BAs) accumulated in fermented foods via lactic acid bacterial activity exert toxic effects on human health. Among these, biofilms of histamine-producer Lentilactobacillus parabuchneri strains adherent at food processing equipment surfaces can cause food spoilage and poisoning. Understanding the chain of contamination is closely related to elucidating molecular mechanisms of biofilm formation. In the present study, an innovative approach using integrated chemical sensing technologies is demonstrated to fundamentally understand the temporal behavior of biofilms at the molecular level by combining mid-infrared (MIR) spectroscopy and fluorescence sensing strategies. Using these concepts, the biofilm forming capacity of six cheese-isolated L. parabuchneri strains (IPLA 11151, 11150, 11129, 11125, 11122 and 11117) was examined. The cut-off values for the biofilm production ability of each strain were quantified using crystal violet (CV) assays. Real-time infrared attenuated total reflection spectroscopy (IR-ATR) combined with fluorescence quenching oxygen sensing provides insight into distinct molecular mechanisms for each strain. IR spectra showed significant changes in characteristic bands of amides, lactate, nucleic acids, and extracellular polymeric substances (i.e., lipopolysaccharides, phospholipids, phosphodiester, peptidoglycan, etc.), which are major contributors to biofilm maturation involved in the initial adhesion processes. Chemometric methods including principal component analysis and partial least square-discriminant analysis facilitated the rapid determination and classification of cheese isolated L. parabuchneri strains unambiguously differentiating the IR signatures based on their ability to produce biofilm. All biofilms were morphologically characterized by confocal laser scanning microscopy on relevant industrial equipment surfaces. In summary, this innovative approach combining MIR spectroscopy with luminescence sensing enables real-time insight into the molecular composition and formation of L. parabuchneri biofilms.

Biogenic Amine Content Analysis of Three Chicken-Based Dry Pet Food Formulations

The pet food market is constantly expanding, and more and more attention is paid to the feeding of pets. Dry foods stand out and are often preferred due to their long shelf life, ease of administration, and low cost. In this context, dry foods are formulated from fresh meats, meat meals, or a mix of the two. These raw materials are often meat not fit for human consumption; they might be subject to contamination and proliferation of microorganisms which, by degrading the organic component, can lead to the formation of undesirable by-products such as biogenic amines. These nitrogenous compounds obtained by decarboxylation of amino acids can therefore be found in high-protein foods, and their ingestion in large quantities can cause intoxication and be harmful. This study aims at analyzing the possible presence of biogenic amines in three different formulations of chicken-based kibbles for pets: one obtained from fresh meat, one from meat meal, and one from a mix of the two. This study is also focused on the presence of free amino acids as they represent the key substrate for decarboxylating enzymes. Mass spectrometry (Q-TOF LC/MS) was used to analyze the presence of biogenic amines and free amino acids. The results show that fresh-meat-based products have a lower content of biogenic amines, and at the same time a higher quantity of free amino acids; on the contrary, meat-meal- and mix-based products have a greater quantity of biogenic amines and a lower concentration of free amino acids, suggesting that there has been a higher microbial proliferation as proved by the total aerobic mesophilic bacteria counts. It is therefore clear that fresh-meat-based kibbles are to be preferred when they are used for preparing dry pet food due to the lowest concentration of biogenic amines.

Influence of Brewing Process on the Profile of Biogenic Amines in Craft Beers

The evaluation of the biogenic amines (BAs) profile of different types of craft beers is herein presented. A previously developed and validated analytical method based on ion-pair chromatography coupled with potentiometric detection was used to determine the presence of 10 BAs. Good analytical features were obtained for all amines regarding linearity (R² values from 0.9873 ± 0.0015 to 0.9973 ± 0.0015), intra- and inter-day precision (RSD lower than 6.9% and 9.7% for beer samples, respectively), and accuracy (recovery between 83.2-108.9%). Detection and quantification limits range from 9.3 to 60.5 and from 31.1 to 202.3 µg L^-1, respectively. The validated method was applied to the analysis of four ale beers and one lager craft beer. Ethylamine, spermidine, spermine, and tyramine were detected in all analyzed samples while methylamine and phenylethylamine were not detected. Overall, pale ale beers had a significantly higher total content of BAs than those found in wheat pale and dark samples. A general least square regression model showed a good correlation between the total content of BAs and the brewing process, especially for Plato degree, mashing, and fermentation temperatures. Knowledge about the type of ingredients and manufacturing processes that contribute to higher concentrations of these compounds is crucial to ensuring consumer safety.

Biogenic amine production from processed animal and plant protein-based foods contaminated with Escherichia coli and Enterococcus feacalis

The aim of the study was to investigate biogenic amine production in different types of cooked protein foods. The food samples were incubated at varying temperatures (4, 37 and 55 °C) on different microbiological media for 48, 72 and 180 h. Resulting bacteria were isolated and characterized using cultural, biochemical and molecular methods, further screened for production of biogenic amines in decarboxylase broth media supplemented with 0.4% of histidine, tyrosine, lysine and ornithine. The samples were incubated at 25 °C for 48 h and the biogenic amine concentration in each food sample determined by means of HPLC. There was a high prevalence of the isolates among the food samples. All the isolates except Klebsiella sp. and Pseudomonas sp. were positive for decarboxylase activity indicating 84.6% of the isolates capable of biogenic amine production. The amine concentration varied among the types of food and methods of cooking. Histamine was detected in 41.67% of the inoculated food samples (9.2 ± 1.2-100.95 ± 0.1 µg/g) while putrescine was the least detected (41.67%) in the inoculated food sample (7.7 ± 0.1-8.8 ± 0.2 µg/g). Cadaverine and histamine were detected in 16.4% (2.6 ± 0.2-49.9 ± 0.9 µg/g) and 7.5% (1.4 ± 0.1-20.4 ± 0.3 µg/g) of the foods, respectively. Microbial contamination of the cooked protein foods led to high levels of biogenic amines irrespective of the cooking methodology adopted and type of foods investigated.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05576-0.

Safety evaluation and anti-inflammatory activity of Lactobacillus johnsonii IDCC 9203 isolated from feces of breast-fed infants

This study evaluated the safety of Lactobacillus johnsonii IDCC 9203 and investigated its anti-inflammatory activity in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. Genomic analysis revealed that this strain has no virulence and antibiotic resistance gene except tetW, which is a tetracycline resistance gene. Minimum inhibitory concentration data showed that the strain is resistant to tetracycline and aminoglycosides. Further analysis indicated that the transferability of the tetW gene is extremely low, and resistance to aminoglycosides is due to the intrinsic resistance of L. johnsonii IDCC 9203. Phenotypic safety assessment showed that the strain has neither β-hemolytic nor β-glucuronidase activity, and no biogenic amine production. When LPS-induced RAW 264.7 cells were treated with L. johnsonii IDCC 9203, the level of nitric oxide and expression of pro-inflammatory cytokines significantly decreased (p < 0.05). Therefore, L. johnsonii IDCC 9203 strain is considered as safe and beneficial probiotic for human consumption.

The Prescriber's Guide to the MAOI Diet-Thinking Through Tyramine Troubles

This review article features comprehensive discussions on the dietary restrictions issued to patients taking a classic monoamine oxidase inhibitor (phenelzine, tranylcypromine, isocarboxazid), or high-dose (oral or transdermal) selegiline. It equips doctors with the knowledge to explain to their patients which dietary precautions are necessary, and why that is so: MAOIs alter the capacity to metabolize certain monoamines, like tyramine, which causes dose-related blood pressure elevations. Modern food production and hygiene standards have resulted in large reductions of tyramine concentrations in most foodstuffs and beverages, including many cheeses. Thus, the risk of consequential blood pressure increases is considerably reduced-but some caution remains warranted. The effects of other relevant biogenic amines (histamine, dopamine), and of the amino acids L-dopa and L-tryptophan are also discussed. The tables of tyramine data usually presented in MAOI diet guides are by nature unhelpful and imprecise, because tyramine levels vary widely within foods of the same category. For this reason, it is vital that doctors understand the general principles outlined in this guide; that way, they can tailor their instructions and advice to the individual, to his/her lifestyle and situation. This is important because the pressor response is characterized by significant interpatient variability. When all factors are weighed and balanced, the conclusion is that the MAOI diet is not all that difficult. Minimizing the intake of the small number of risky foods is all that is required. Many patients may hardly need to change their diet at all.

Effect of Lactic Acid Fermentation on Legume Protein Properties, a Review

Legume proteins have a promising future in the food industry due to their nutritional, environmental, and economic benefits. However, their application is still limited due to the presence of antinutritional and allergenic compounds, their poor technological properties, and their unpleasant sensory characteristics. Fermentation has been traditionally applied to counteract these inconveniences. At present, lactic acid fermentation of legumes is attracting the attention of researchers and industry in relation to the development of healthier, tasty, and technologically adapted products. Hence, we aimed to review the literature to shed light on the effect of lactic acid fermentation on legume protein composition and on their nutritional, functional, technological, and sensorial properties. The antimicrobial activity of lactic acid bacteria during legume fermentation was also considered. The heterogenicity of raw material composition (flour, concentrate, and isolate), the diversity of lactic acid bacteria (nutriment requirements, metabolic pathways, and enzyme production), and the numerous possible fermenting conditions (temperature, time, oxygen, and additional nutrients) offer an impressive range of possibilities with regard to fermented legume products. Systematic studies are required in order to determine the specific roles of the different factors. The optimal selection of these criteria will allow one to obtain high-quality fermented legume products. Fermentation is an attractive technology for the development of legume-based products that are able to satisfy consumers’ expectations from a nutritional, functional, technological, and sensory point of view.

Dynamics and correlation of microbial communities and metabolic compounds in doenjang-meju, a Korean traditional soybean brick

To investigate the general fermentation characteristics of doenjang-meju (a Korean traditional soybean brick), they were periodically collected from eight different manufacturers during all fermentation stages, and their microbial communities and metabolic compounds (metabolites and volatile compounds) were analyzed. Bacillus and/or lactic acid bacteria (LAB, mainly Enterococcus) and Aspergillus were abundant during fermentation. Fructose and glucose; glycerol; acetate and lactate; and cadaverine, putrescine, tyramine, and histamine were identified as the major sugars, carbon compound, organic acids, and biogenic amines, respectively. Tetramethylpyrazine, butyric acid, butyl butyrate, butanol, acetic acid, 2-methylbutyrate, acetoin, 2,3-butandiol, and nonadecane were the major volatile compounds. However, the profiles of microbial communities, metabolites, and volatile compounds during fermentation varied significanlty among samples. Principal component analysis revealed that doenjang-meju had two differentiated fermentation features, Bacillus-dominated fermentation and LAB (mainly Enterococcus)-dominated fermentation, each having different metabolite and volatile compound profiles. Particularly, fewer volatile compounds were detected in LAB-dominated doenjang-meju samples. Correlation analysis showed a strong negative correlation between Bacillus and LAB, and bacteria and fungi were less correlated with each other. Enterococcus, LAB, and Bacillus were positively correlated with lactate, flavonoid aglycones, and putrescine, respectively, suggesting that they might be mainly responsible for producing the compounds during fermentation. This study provides insights into the general fermentation characteristics of doenjang-meju.

A comprehensive review of spermidine: Safety, health effects, absorption and metabolism, food materials evaluation, physical and chemical processing, and bioprocessing

Spermidine, a natural autophagy inducer, has a variety of health effects, such as antitumor, antiaging, anti-inflammation, cardiovascular protection, and neuromodulation. It has been a hot topic in the field of food processing, and current research findings suggest that spermidine-rich foods may be used in intervention and prevention of age-related diseases. In this article, recent findings on the safety, health effects, absorption and metabolism of spermidine were reviewed, and advances in food processing, including the raw materials evaluation, physical and chemical processing, and biological processing of spermidine, were highlighted. In particular, the core metabolic pathways, key gene targets, and efficient metabolic engineering strategies involved in the biosynthesis of spermidine and its precursors were discussed. Moreover, limitations and future perspectives of spermidine research were proposed. The purpose of this review is to provide new insights on spermidine from its safety to its food processing, which will advance the commercial production and applications of spermidine-rich foods and nutraceuticals.

Preliminary Investigation of Biogenic Amines in Type I Sourdoughs Produced at Home and Bakery Level

During a survey for isolating sourdough lactic acid bacteria (LAB), 20 dough samples produced at the bakery level (BL) or home-made (HM) were collected. An enzyme-based colorimetric method revealed a total biogenic amines (BAs) concentration in the range 41.4–251.8 ppm for six (three BL and three HM) sourdoughs characterised by unpleasant odours. Eight BAs generally investigated in foods were identified and quantified from these six samples by ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS). Only one HM sample contained almost all analysed BAs. Tryptamine was exclusively detected in HM sourdoughs (0.71–24.1 ppm). Putrescine, tryptamine, spermidine, and spermine were the only BAs detected in BL sourdoughs. MiSeq Illumina analysis was applied to study the total bacterial community of sourdoughs. LAB accounted from 67.89 to 92.17% of total bacterial diversity, and Levilactobacillus brevis was identified in all six sourdoughs. Leuconostoc, Pediococcus, and Weissella were also dominant. Plate counts detected neither the presence of Pseudomonas nor members of the Enterobacteriaceae family, and LAB levels were, on average, barely 5.89 Log CFU/g for BL, and 7.33 Log CFU/g for HM sourdoughs. Data suggested that the microorganisms mainly imputable of BAs formation in sourdough are members of the LAB community.

Wireless Tags with Hybrid Nanomaterials for Volatile Amine Detection

Quality control in the production and processing of raw meat is currently one of the biggest concerns for food industry and would benefit from portable and wireless sensors capable of detecting the onset of spoilage. Raw meat is a natural source of biogenic and volatile amines as byproducts of decarboxylation reactions, and the levels of these compounds can be utilized as quality control parameters. We report herein a hybrid chemiresistor sensor based on inorganic nanofibers of SiO₂:ZnO (an n-type material) and single-walled carbon nanotubes functionalized with 3,5-dinitrophenyls (a p-type material) with dosimetric sensitivity ∼40 times higher for amines than for other volatile organic compounds, which also provides excellent selectivity. The hybrid nanomaterial-based chemiresistor sensory material was used to convert radio-frequency identification tags into chemically actuated resonant devices, which constitute wireless sensors that can be potentially employed in packaging to report on the quality of meat. Specifically, the as-developed wireless tags report on cumulative amine exposure inside the meat package, showing a decrease in radio-frequency signals to the point wherein the sensor ceased to be smartphone-readable. These hybrid material-modified wireless tags offer a path to scalable, affordable, portable, and wireless chemical sensor technology for food quality monitoring without the need to open the packaging.

Au@ZIF-8 SERS paper for food spoilage detection

Putrescine and cadaverine are important volatile indicators for the evaluation of food spoilage. In this study, a metal-organic framework (MOF)-coated surface-enhanced Raman scattering (SERS) paper platform for the detection of putrescine and cadaverine is developed. Au@ zeolite imidazolate framework-8 (ZIF-8) SERS paper is fabricated by the coating of ZIF-8 layer on a Au nanoparticle-impregnated paper that is prepared by dry plasma reduction. The Au@ZIF-8 SERS paper is characterized by scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction, and N₂ sorption isotherm. The ZIF-8 layer enables the accumulation of gaseous molecules and also provides enhancement of SERS signals. The fluorescence, SERS, and simulation results prove the improved detection ability of the Au@ZIF-8 platform for the volatile molecules. For the selective detection of putrescine and cadaverine, the Au@ZIF-8 SERS paper is functionalized with 4-mercatobenzaldehyde (4-MBA). The 4-MBA molecule acts as a Raman reporter and also a specific receptor for the volatile amine molecules. Using the intensity ratiometric detection of 4-MBA-functionalized Au@ZIF-8 SERS paper, putrescine and cadaverine are quantitatively detected with detection limits of 76.99 and 115.88 parts per billion, respectively. Furthermore, the detection of volatile amine molecules released from spoiled salmon, chicken, beef, and pork samples is demonstrated. It is anticipated that the MOF-coated SERS paper platforms will be applicable not only in food safety but other applications including disease diagnosis and environmental monitoring.

Genomic characterization and probiotic potential of Lactobacillus casei IDCC 3451 isolated from infant faeces

Probiotics play an important role in health benefits on the host. However, they also possess potentials for infectivity or in situ toxin production; thus, requiring a comprehensive assessment of their safety. In this study, we report genomic characteristics of a newly isolated Lactobacillus casei IDCC 3451 from infant faeces. Phenotypic assays based on enzyme activities and carbohydrate fermentation profiles represented metabolic features of the strain. Safety evaluation for antimicrobial resistance, biogenic amines production and cytotoxicity to a murine mouse model suggested its safe use as a probiotic strain. Our findings on the genetic background of L. casei IDCC 3451 and its potential features provide a promising functional and safe probiotic strain for the human consumption.

Plant-based proteinaceous snacks: Effect of fermentation and ultrasonication on end-product characteristics

The study aimed at the development of a sufficient technology to improve sensory, textural, physical, and microbiological properties of peas snacks (Ps) using solid-state fermentation (SSF) and submerged fermentation (SMF) with two different lactic acid bacteria (LAB) strains (Lactobacillus casei LUHS210 and Lactobacillus uvarum LUHS245) for 24 hr and ultrasonication (10, 20, and 30 min). To ensure safety of the used technologies, microbiological characteristics and biogenic amines (BAs) content in treated Ps were analyzed. Additionally, a different salt content (3.6 and 1.0 g/100 g) was used for snacks preparation. The obtained results revealed that used treatments reduced enterobacteria in Ps, while in fermented Ps, yeast/moulds were not found. Ps with the lower salt content were more acidic and harder (0.90 mJ), and there was a significant effect (p < .05) due to the fermentation method, LAB strains, and ultrasonication on the texture of final product. Different salt content significantly affected the color coordinates of the Ps tested (p < .05). The predominant biogenic amines in Ps were phenylethylamine and spermidine. However, the reduction of some BAs after samples fermentation was observed. To conclude, acceptable formulations of Ps can be obtained with 1.0 g/100 g salt, and by using fermentation, as the end-product is more attractive to consumers than those prepared with 3.6 g/100 g salt and using ultrasonication.

Challenges Associated with Byproducts Valorization-Comparison Study of Safety Parameters of Ultrasonicated and Fermented Plant-Based Byproducts

In order to promote the efficient use of byproducts from the production of plant-based beverages, which still contain a large amount of nutritional and functional compounds, microbiological and chemical safety characteristics should be evaluated and, if needed, improved. Many challenges are associated with byproducts valorization, and the most important ones, which should be taken into account at the further steps of valorization, are biological and chemical safety. For safety improving, several technological treatments (biological, physical etc.) can be used. In this study, the influence of low-frequency ultrasonication (US) and fermentation with Lactobacillus casei LUHS210 strain, as physical and biotechnological treatments, on the safety characteristics of the byproducts (BYs) from the processing of rice, soy, almond, coconut, and oat drinks was compared. Ultrasonication, as well as fermentation, effectively improved the microbiological safety of BYs. Ultrasonication and fermentation reduced the concentration of deoxynivalenol, on average, by 24% only in soy BYs. After fermentation, 15-acetyldeoxynivalenol was formed in all samples (<12 µg kg-1), except for soy BYs. The lowest total biogenic amines content was found in fermented rice BYs and ultrasonicated coconut BYs. When comparing untreated and fermented BYs, significant changes in macro- and micro-elements content were found. Ultrasonication at 37 kHz did not significantly influence the concentrations of macro- and micro-elements, while fermentation affected most of the essential micro-elements. Consequently, while ultrasonication and fermentation can enhance the safety of BYs, the specific effects must be taken into account on biogenic amines, mycotoxins, and micro and macro elements.

Reduction in biogenic amines in douchi fermented by probiotic bacteria

Ecology studies showed that esophageal and gastric cancers are directly correlated with the consumption of processed foods. The carcinogenicity of traditional Chinese fermented foods such as douchi (fermented black beans or fermented black soybeans) is due to the presence of carcinogenic N-nitroso compounds, which are derived from biogenic amines. Among the various biogenic amines that can act as precursors of N-nitroso compounds, histamine and tyramine are considered to be the most toxic and are of public health concern when present in food. We have examined some douchi products on the market, and significant amounts of histamine and tyramine were found. The use of fermentation starters generated by subculturing fermented products with unknown microbiota would induce the risk of biogenic amines. As the microbiota used in fermentation is a crucial factor in determining the biogenic amines of fermented food, it is hypothesized that the possible harmful effects of douchi can be minimized through the use of fermentation starters composed of probiotic bacteria. This is the first study to investigate the potential of using probiotic bacteria in manufacturing douchi. Lactobacillus rhamnosus GG (LGG), Lactobacillus casei Shirota (LcS) and Escherichia coli Nissle 1917 (EcN) were used to ferment black beans in this study, and no tyramine was detected in black bean samples incubated with these three strains anaerobically at 37°C or 20°C. The starter culture strains, temperature and presence of oxygen during the incubation period were found to be critical to the generation of biogenic amines. The findings of this study can provide evidence-based insights and warrant further investigations on the potential of reducing the harmful compounds in food fermented with probiotic bacteria as well as the sensory evaluation of douchi fermented with probiotic bacteria.

Biogenic Amine Contents and Microbial Characteristics of Cambodian Fermented Foods

Naturally fermented foods are an important part of the typical diet in Cambodia. However, the food safety status of these products has not been widely studied. The aim of this study was, therefore, to provide an overview of the quality of these foods in relation to microbiology and biogenic amines. Additionally, the obtained results were compared to the habits and practices of Cambodians in handling this type of food. A total of 57 fermented foods (42 fishery and 15 vegetable products) were collected from different retail markets in the capital of Cambodia. Pathogenic Salmonella spp., Listeria spp., and Listeria monocytogenes were not detected in 25 g samples. Generally, less than 102 cfu/g of Staphylococcus aureus, Escherichia coli, Pseudomonas spp., Enterobacteriaceae, and molds were present in the fermented foods. Bacillus cereus group members (<102 to 2.3 × 104 cfu/g), lactic acid bacteria (<102 to 1.1 × 107 cfu/g), halophilic and halotolerant bacteria (<102 to 8.9 × 106 cfu/g), sulfite-reducing Clostridium spp. (<102 to 3.5 × 106 cfu/g), and yeasts (<102 to 1.1 × 106 cfu/g) were detected in this study. Still, the presence of pathogenic and spoilage microorganisms in these fermented foods was within the acceptable ranges. Putrescine, cadaverine, tyramine, and histamine were detected in 100%, 89%, 81%, and 75% of the tested products, respectively. The concentrations of histamine (>500 ppm) and tyramine (>600 ppm) were higher than the recommended maximum levels in respectively four and one of 57 fermented foods, which represents a potential health risk. The results suggest that the production process, distribution, and domestic handling of fermented foods should be re-evaluated. Further research is needed for the establishment of applicable preservation techniques in Cambodia.

Catabolism of biogenic amines in Pseudomonas species

Biogenic amines (BAs; 2-phenylethylamine, tyramine, dopamine, epinephrine, norepinephrine, octopamine, histamine, tryptamine, serotonin, agmatine, cadaverine, putrescine, spermidine, spermine and certain aliphatic amines) are widely distributed organic molecules that play basic physiological functions in animals, plants and microorganisms. Pseudomonas species can grow in media containing different BAs as carbon and energy sources, a reason why these bacteria are excellent models for studying such catabolic pathways. In this review, we analyse most of the routes used by different species of Pseudomonas (P. putida, P. aeruginosa, P. entomophila and P. fluorescens) to degrade BAs. Analysis of these pathways has led to the identification of a huge number of genes, catabolic enzymes, transport systems and regulators, as well as to understanding of their hierarchy and functional evolution. Knowledge of these pathways has allowed the design and collection of genetically manipulated microbes useful for eliminating BAs from different sources, highlighting the biotechnological applications of these studies.

Evaluation of the Biogenic Amines and Microbial Contribution in Traditional Chinese Sausages

Biogenic amines (BAs) in sausages represent a health risk for consumers, and thus investigating the BAs accumulation mechanism is important to control the BAs. In this study, the BAs profiles of 16 typical Chinese sausage samples were evaluated, and 8 kinds of common BAs were detected from different samples. As a whole, the BAs contents of the majority of Chinese sausage samples were within the safe dosage range, except that the total BAs and histamine concentrations of sample HBBD were above the toxic dosage levels. Furthermore, the bacterial and fungal communities of the Chinese sausage samples were investigated by high-throughput sequencing analysis, and Staphylococcus, Bacillus, Lactococcus, Lactobacillus, Debaryomyces, and Aspergillus were identified as the predominant genera. Accordingly, 13 representative strains were selected from the dominant genera, and their BAs formation and degradation properties were evaluated. Finally, the results of fermented meats model experiment indicated that the Staphylococcus isolates including Staphylococcus pasteuri Sp, Staphylococcus epidermidis Se, Staphylococcus carnosus Sc1, Staphylococcus carnosus Sc2, and Staphylococcus simulans Ss could significantly reduce BAs, possessing the potential as the starter cultures to control the BAs in fermented meat products. The present study not only helped to explain the BAs accumulation mechanism in Chinese sausage, but also developed the candidates for potential BAs control in fermented meat products.

Role of Starter Cultures on the Safety of Fermented Meat Products

Starters are microbial cultures used to promote and conduct the fermentation of meat products. Bacteria, particularly lactic acid bacteria (LAB) and coagulase-negative staphylococci (CNS), as well as yeasts and molds, may be used as starters. They can increase the safety of fermented meat products by means of rapid matrix acidification or due to the production of antimicrobial substances, such as bacteriocins. Besides, starters may help to standardize product properties and shorten ripening times. Safety of fermented meat products may be jeopardized by microbiological, namely foodborne pathogens (Salmonella spp., Listeria spp., etc), and chemical hazards, particularly biogenic amines, nitrosamines, polycyclic aromatic hydrocarbons (PAH), and mycotoxins. Biogenic amines (BA) are potentially unsafe nitrogenous compounds that result from the decarboxylation of some amino acids. Some microorganisms may be responsible for their formation. Starters can cause a fast pH decrease, inhibiting the development of microorganisms with amino acid decarboxylative ability, thus preventing the accumulation of BA in fermented meat products. Besides, starters can compete with the autochthonous, non-starter microbiota throughout ripening and storage, thus reducing BA production. Some strains of Lactobacillus sakei and Lactobacillus plantarum have been shown to reduce the formation/accumulation of BA. On the other hand, Staphylococcus xylosus and Debaryomyces hansenii strains have been reported to degrade BA in food. PAH are organic compounds containing multiple aromatic rings and produced by the incomplete combustion of organic matter, such as the wood used for smoking meat. Mixed starters containing Lactobacillus spp., Gram-positive catalase-positive cocci and yeasts have been used in the manufacturing of traditional meat sausages. However, the effect of starters on reducing the accumulation of PAH is poorly understood. Starters may also be engaged in competitive exclusion, outcompeting the spoiling or deteriorating autochthonous microbiota. For example, Pediococcus acidilactici has been shown to inhibit Listeria monocytogenes in meat products. Additionally, the role of molds, such as Penicillium nalgiovense, in the competitive exclusion of undesired filamentous fungi, has also been demonstrated. Most of these undesired fungi produce mycotoxins, secondary metabolites capable of causing disease. The current review addresses the role of starters on the microbiological and chemical safety of fermented meat products.

Genomic and metabolic features of Tetragenococcus halophilus as revealed by pan-genome and transcriptome analyses

The genomic and metabolic diversity and features of Tetragenococcus halophilus, a moderately halophilic lactic acid bacterium, were investigated by pan-genome, transcriptome, and metabolite analyses. Phylogenetic analyses based on the 16S rRNA gene and genome sequences of 15 T. halophilus strains revealed their phylogenetic distinctness from other Tetragenococcus species. Pan-genome analysis of the T. halophilus strains showed that their carbohydrate metabolic capabilities were diverse and strain dependent. Aside from one histidine decarboxylase gene in one strain, no decarboxylase gene associated with biogenic amine production was identified from the genomes. However, T. halophilus DSM 20339^T produced tyramine without a biogenic amine-producing decarboxylase gene, suggesting the presence of an unidentified tyramine-producing gene. Our reconstruction of the metabolic pathways of these strains showed that T. halophilus harbors a facultative lactic acid fermentation pathway to produce l-lactate, ethanol, acetate, and CO₂ from various carbohydrates. The transcriptomic analysis of strain DSM 20339^T suggested that T. halophilus may produce more acetate via the heterolactic pathway (including d-ribose metabolism) at high salt conditions. Although genes associated with the metabolism of glycine betaine, proline, glutamate, glutamine, choline, and citrulline were identified from the T. halophilus genomes, the transcriptome and metabolite analyses suggested that glycine betaine was the main compatible solute responding to high salt concentration and that citrulline may play an important role in the coping mechanism against high salinity-induced osmotic stresses. Our results will provide a better understanding of the genome and metabolic features of T. halophilus, which has implications for the food fermentation industry.

Tetragenococcus halophilus MJ4 as a starter culture for repressing biogenic amine (cadaverine) formation during saeu-jeot (salted shrimp) fermentation

Biogenic amines (BAs) are frequently present in traditionally fermented salted foods. In this study, a Tetragenococcus halophilus strain (MJ4) with no BA-producing ability was isolated from a fish (anchovy) sauce. Strain MJ4 did not produce BAs from supplied precursors and no BA-producing genes were identified in its genome. Bacterial community analysis showed that in non-inoculated saeu-jeot (shrimp sauce) fermentation, Tetragenococcus predominated after 82 days, while in strain MJ4-inoculated saeu-jeot, Tetragenococcus predominated during the entire fermentation. Strain MJ4 repressed the growth of T. muriaticus, a known BA producer, during fermentation, but metabolite analysis demonstrated that metabolite profiles, including amino acids, were similar regardless of MJ4 inoculation. The metabolite analysis also showed that strain MJ4 clearly repressed the formation of cadaverine during fermentation. This study suggests that the use of strain MJ4 as a starter culture in salted fish fermentation may be a good strategy for the reduction of BA formation.

What We Know and What We Need to Know about Aromatic and Cationic Biogenic Amines in the Gastrointestinal Tract

Biogenic amines derived from basic and aromatic amino acids (B/A-BAs), polyamines, histamine, serotonin, and catecholamines are a group of molecules playing essential roles in many relevant physiological processes, including cell proliferation, immune response, nutrition and reproduction. All these physiological effects involve a variety of tissue-specific cellular receptors and signalling pathways, which conforms to a very complex network that is not yet well-characterized. Strong evidence has proved the importance of this group of molecules in the gastrointestinal context, also playing roles in several pathologies. This work is based on the hypothesis that integration of biomedical information helps to reach new translational actions. Thus, the major aim of this work is to combine scientific knowledge on biomolecules, metabolism and physiology of the main B/A-BAs involved in the pathophysiology of the gastrointestinal tract, in order to point out important gaps in information and other facts deserving further research efforts in order to connect molecular information with pathophysiological observations.

Biogenic amines analysis and microbial contribution in traditional fermented food of Douchi

Biogenic amines (BAs) have been reported to threaten the Douchi safety, while the BAs formation mechanism and corresponding control method have not been clarified for Douchi. The present study aims to investigate the microbial contribution to BAs in Douchi, and to find the beneficial strain for BAs control. Firstly, the BAs profiles of 15 Douchi samples were analyzed, and common 6 kinds of BAs were detected from different samples. All the samples showed the total BAs contents within the safe dosage range, while the histamine concentrations in 2 samples and β-phenethylamine in 6 samples were above the toxic level. Then, the bacterial and fungal communities were investigated by high-throughput sequencing analysis, and Bacillus and Candida were identified as the dominant bacteria and fungi genus, respectively. Furthermore, nineteen strains were selected from the dominant species of Douchi samples, including 14 Bacillus strains, 2 Staphylococcus strains, 1 Enterococcus strain and 2 Candida strains, and their BAs formation and degradation abilities were evaluated. B. subtilis HB-1 and S. pasteuri JX-2 showed no BAs producing ability, and B. subtilis GD-4 and Candida sp. JX-3 exhibited high BAs degradation ability. Finally, fermented soybean model analysis further verified that B. subtilis HB-1 and S. pasteuri JX-2 could significantly reduce BAs. This study not only contributed to understanding the BAs formation mechanism in Douchi, but also provided potential candidates to control the BAs in fermented soybean products.

Evaluation of the diagnostic potential of urinary N-Acetyltyramine-O,β-glucuronide (NATOG) as diagnostic biomarker for Onchocerca volvulus infection

Background

Onchocerciasis, also known as river blindness is one of the neglected tropical diseases affecting millions of people, mainly in sub-Saharan Africa and is caused by the filarial nematode Onchocerca volvulus. Efforts to eliminate this disease are ongoing and are based on mass drug administration programs with the microfilaricide ivermectin. In order to monitor the efficacy of these programs, there is an unmet need for diagnostic tools capable of identifying infected patients. We have investigated the diagnostic potential of urinary N-acetyltyramine-O,β-glucuronide (NATOG), which is a promising O. volvulus specific biomarker previously identified by urine metabolome analysis.

Methods

A liquid chromatography tandem mass spectrometry (LC-MS/MS) method was used to assess the stability characteristics of NATOG and to evaluate the levels of NATOG in study samples. An LC-fluorescence method was also developed.

Results

Stability characteristics of NATOG were investigated and shown to be ideally suited for use in tropical settings. Also, an easy and more accessible method based on liquid chromatography coupled to fluorescence detection was developed and shown to have the necessary sensitivity (limit of quantification 1 μM). Furthermore, we have evaluated the levels of NATOG in a population of 98 nodule-positive individuals from Ghana with no or low levels of microfilaria in the skin and compared them with the levels observed in different control groups (endemic controls (n = 50), non-endemic controls (n = 18) and lymphatic filariasis (n = 51). Only a few (5 %) of nodule-positive individuals showed an increased level (> 10 μM) of NATOG and there was no statistical difference between the nodule-positive individuals and the control groups (P > 0.05).

Conclusions

Results of the present study indicate the limited potential of NATOG as a diagnostic biomarker for O. volvulus infection in amicrofilaridermic individuals.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1582-6) contains supplementary material, which is available to authorized users.