The use of starter cultures (Tetragenococcus halophilus TS71, Zygosaccharomyces rouxii A22, and Meyerozyma (Pichia) guilliermondii EM1Y52) in reduced-salt moromi fermentation was investigated. ...Reduced-salt moromi fermentation (12%NaCl) with starter cultures was monitored for changes of microbiological and biochemical properties including volatile flavor compounds (VFCs) and biogenic amines (BAs) during three months. The inoculation was done after one-month fermentation with two combinations: TS71 and A22 (L2); and TS71, A22 and EM1Y52 (L3). Controls were 12% salt (CL) and 18% salt traditional (CT) without inoculation. Total bacteria counts significantly increased (P < 0.05) in CL. Total lactic acid bacteria and total yeasts in the reduced-salt moromi with inoculation (L2 and L3) were significantly higher than both controls. Key VFCs including ethanol, 2-methyl-1-propanol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) and 3-hydroxy-2-methyl-4H-pyran-4-one (maltol) were detected in L2 and L3 at higher levels than the traditional CT. Lower amount of BAs was accumulated in the reduced-salt moromi fermentation, particularly with lactic acid bacterium (L3) than other fermentations. Hence, the reduced-salt moromi fermentation with using starter cultures was therefore feasible for the soy sauce production without undesirable impact on formation of VFCs and safety levels of BAs.
•Comparison of microbiological and biochemical properties of reduced salt and traditional soy sauce.•Zygosaccharomyces rouxii and Meyerozyma guilliermondii starter enhanced formation of volatile flavor compounds in soy sauce.•Low biogenic amines formation was observed in reduced salt soy sauce fermentation with Tetragenococcus halophilus starter.
Gelatins extracted from the skins containing fine scales of two species of bigeye snapper,
Priacanthus tayenus (GT) and
Priacanthus macracanthus (GM), were characterised. Both gelatins had the ...protein as the major component with high content of imino acids (proline & hydroxyproline) (186.29–187.42
mg/g). GT and GM contained calcium at levels of 6.53 and 2.92
g/kg, respectively. Both gelatins contained α1 and α2 chains as the predominant components and some degradation peptides. The absorption bands of both gelatins in Fourier transform infrared (FTIR) spectra were mainly situated in the amide band region (amide I and amide II). GT and GM had a relative solubility greater than 90% in the wide pH ranges (1–10). The bloom strength of GM (254.10
g) was higher than that of GT (227.73
g) (
P
<
0.05), but was slightly lower than that of commercial bovine gelatin (293.22
g) (
P
<
0.05). Finer gel structure with smaller strands and voids was observed in GM gel, in comparison with that observed in GT counterpart.
Zearalenone (ZEA) is a harmful secondary fungal metabolite, produced primarily by plant pathogenic fungi mostly belonging to the genus
. It is involved in reproductive disorders in animals since its ...structure is similar to the estrogen hormone. This induces precocious pubertal changes, fertility problems, and hyper estrogenic disorders. The main objectives of this study were to evaluate the ZEA removal capacity of plant-derived lactic acid bacteria (LAB) and to investigate the possible components and mechanisms involved in the removal of ZEA by physically and chemically treated plant-derived LAB. The bacterial cells were characterized using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), and the analysis of zeta potential, and hydrophobic index. Results revealed that 17 out of 33 plant-derived LAB exhibited ZEA removal from liquid medium. The percentage of removal ranged from 0.5-23% and
BCC 47723, isolated from wild spider flower pickle (Pag-sian-dorng), exhibited the highest removal. The alteration of proteins on
BCC 47723 structure by Sodium dodecyl sulphate (SDS) treatment was positively affected on ZEA removal, whereas that of lipids on ZEA removal was negatively observed. Heat treatment influenced the higher ZEA adsorption. SEM images showed that the morphologies of modified bacterial cells were distinctly deformed and damaged when compared with untreated control. FTIR analysis indicated that the original functional groups, which included amide (C=O, C-N), carboxyl (C=O, C-O, O-H), methylene (C=C), and alcohol (O-H) groups, were not changed after ZEA adsorption. The zeta potential indicated that electrostatic interaction was not involved in the ZEA removal, while hydrophobicity was the main force to interact with ZEA. These findings can conclude that adsorption by hydrophobicity is the main mechanism for ZEA removal of plant-derived
BCC 47723. The alteration of bacterial cell structure by heat treatment enhanced the efficiency of
BCC 47723 for ZEA reduction. Its activity can be protected by the freeze-drying technique. Hence, plant-derived
BCC 47723 can be considered as an organic adsorbent for ZEA reduction in food and feedstuff.
Effects of skipjack roe protein hydrolysate (SRPH) at various levels (0–3 g/100 g) on properties and oxidative stability of emulsion sausage from broadhead catfish (Clarias macrocephalus) fortified ...with skipjack tuna roe lipids were investigated. The addition of SRPH increased hardness, cohesiveness and resilience of sausage (p < 0.05). Finer fat globules were visualised in the sample added with SRPH at higher amounts. Nevertheless, the incorporation of SRPH at all levels had no impact on likeness of sausages. SRPH was shown to retard lipid oxidation of sausage during extended storage of 12 days as evidenced by the lower peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS), in comparison with the control. After 12 days, the sausage with 3 g/100 g SRPH had the retained docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), accounting more than 80%. Addition of SRPH had no effect on the organoleptic properties but could prevent the development of rancidity. Nevertheless, it showed no pronounced impact on microbial growth. SRPH could therefore be used as a natural antioxidative emulsifier in cooked fish emulsion sausage.
•Skipjack roe protein hydrolysate (SRPH) acted as emulsifier in emulsion sausage.•Addition of SRPH improved textural properties of fish emulsion sausage.•SRPH could retard lipid oxidation in emulsion sausage during the refrigerated stroage.
Gelatins from the skins of brownbanded bamboo shark (BBS;
Chiloscyllium punctatum) and blacktip shark (BTS;
Carcharhinus limbatus) were extracted using the distilled water at different temperatures ...(45, 60 and 75 °C) and times (6 and 12 h). Yields of gelatin from the skins of BBS and BTS were 19.06–22.81% and 21.17–24.76% (based on wet weight), respectively. Gelatins from both species extracted at 45 °C for 6 h exhibited the highest bloom strength (206–214 g), which was higher than that of commercial bovine bone gelatin (197 g) (
p < 0.05). Gelatin gels from BBS skin could set at room temperature (25–26 °C) within 24 min. However, gelatin gels from BTS skin was not able to set within 3 h at the same temperature. Scanning electron microscopic study showed that gelatin gel from BBS skin presented the thicker strand than those from BTS skin and bovine bone. Cross-linked components (β- and γ-chains) and α-chains were more degraded with increasing extraction temperatures, especially at 75 °C. Gelatin from BTS skin was more susceptible to hydrolysis than that from BBS skin. Fourier transform infrared (FTIR) study revealed that the major absorption bands of gelatin from the skins of both sharks shifted to a higher wavenumber, compared with their corresponding acid soluble collagen (ASC). Therefore, gelatins from the skin of BBS has a potential to replace mammalian for gelatin, due to its similarity in bloom strength and setting behavior to the commercial bovine bone gelatin.
Gelatins from the skin of some particular shark, which is the by-product from shark processing, exhibited the similar gel properties to those from the mammalian sources. Skin of brownbanded bamboo shark could be used as the potential and promising source for gelatin production due to the high extraction yield and its similarity in gel properties, particularly in terms of bloom strength and setting behavior, to bovine gelatin.
The safety of microbial cultures utilized for consumption is vital for public health and should be thoroughly assessed. Although general aspects on the safety assessment of microbial cultures have ...been suggested, no methodological detail nor procedural guideline have been published. Herein, we propose a detailed protocol on microbial strain safety assessment via whole-genome sequence analysis. A starter culture employed in traditional fermented pork production, nham, namely Lactobacillus plantarum BCC9546, was used as an example. The strain's whole-genome was sequenced through several next-generation sequencing techniques. Incomplete plasmid information from the PacBio sequencing platform and shorter chromosome size from the hybrid Oxford Nanopore-Illumina platform were noted. The methods for 1) unambiguous species identification using 16S rRNA gene and average nucleotide identity, 2) determination of virulence factors and undesirable genes, 3) determination of antimicrobial resistance properties and their possibility of transfer, and 4) determination of antimicrobial drug production capability of the strain were provided in detail. Applicability of the search tools and limitations of databases were discussed. Finally, a procedural guideline for the safety assessment of microbial strains via whole-genome analysis was proposed.
Prophylaxis and treatment of emerging zoonotic Streptococcus suis infection in agricultural and healthcare settings mainly rely on antibiotics. However, continued use of antibiotics contributing to ...emergence and widespread of antibiotic resistant S. suis becomes a significant challenge in many endemic countries, including Thailand. Meanwhile, the knowledge of antibiotic susceptibility patterns of bacterial pathogens is required for overcoming the antimicrobial resistance problem, the information of antibiotic susceptibility of S. suis strains isolated in Thailand remains limited. This study aims to assess the susceptibility of Thai-isolated S. suis strains to different antibiotic classes in order to gain an insight into the distribution of antibiotic-resistant patterns of S. suis strains in different regions of Thailand.
This study revealed the antimicrobial resistance and multidrug resistance of 262 S. suis strains isolated in different regions of Thailand. Susceptibility testing indicated widespread resistance to macrolides and tetracyclines of S. suis strains in the country. Beta-lactam antibiotic drugs (including cefotaxime and ceftiofur), vancomycin, chloramphenicol, as well as florfenicol were potentially the most effective therapeutic drugs for the treatment of S. suis infection in both pigs and humans. High prevalence of intermediate susceptibility of S. suis isolated from asymptomatic pigs for penicillin G, gentamicin, enrofloxacin, and norfloxacin could be the premise of the emergence of S. suis antibiotic resistance. Resistance was also found in S. suis strains isolated from asymptomatic pigs indicating that they could act as reservoirs of antibiotic resistance genes.
To the best of our knowledge, this is the first report on antimicrobial resistance of a large collection of S. suis strains isolated from pigs and humans in Thailand. It revealed the multidrug resistance of S. suis strains in pigs and humans. The information gained from this study raises an awareness and encourage best practices of appropriate antibiotic drug prescribing and use among human health and agriculture sectors.
Changes in chemical composition, physical properties and microstructure of duck egg, during salting for up to 14 days, were determined. Duck egg consisted of 10.87% shell, 54.73% egg white and 33.94% ...yolk. Salting resulted in an increase in weight proportion of egg white, but a decrease in yolk proportion. Moisture contents of both egg white and yolk decreased gradually with concomitant increases in salt and ash contents as the salting time increased. Protein and lipid contents increased slightly in both interior (viscous portion) and exterior (hardened portion) egg yolk with increasing salting time. Oil exudation was observed in yolk, particularly in exterior yolk. Triacylglycerols and phospholipid, found as the major lipids in egg yolk, underwent slight changes, but no differences in protein patterns of either egg white or egg yolk were observed during salting. Hardening ratio and hardness of egg yolk increased with increasing salting time. Adhesiveness and gumminess also increased, while springiness, cohesiveness and gumminess decreased slightly when the salting time increased. Scanning electron microscopic study revealed that yolk granule was polyhedral in shape and aligned closely when the salting proceeded. Protein spheres were distributed uniformly, together with oil droplets, in salted yolk, as visualised by transmission electron microscopy. Confocal laser scanning microscope (CLSM) micrographs indicated that the greater dehydration and release of lipids took place in egg yolk during salting.
Lactiplantibacillus pentosus
9D3, a prominent gamma-aminobutyric acid (GABA)-producing bacteria isolated from Thai pickled weed was characterized for its safety and probiotic properties
via
...whole-genome analysis and
in vitro
testing. The whole-genome sequence of
L. pentosus
9D3 was determined using a hybrid-sequencing approach, combining PacBio and Illumina technologies. A 3.81-Mbp genome of
L. pentosus
9D3 consisting of one 3.65-Mbp chromosome and six plasmids (1.9–71.9 Kbp) was identified with an estimated GC content of 46.09% and 3,456 predicted genes. The strain was confirmed to be
Lactiplantibacillus pentosus
according to the high average nucleotide identity value of >95% and digital DNA–DNA hybridization scores of >70% to the
L. pentosus
type strain. Comparative genome analysis with other
L. pentosus
strains showed that the GABA-producing capability was specific to the strain 9D3. Genes related to GABA biosynthesis and transport were identified on a plasmid, pLPE-70K, indicating the acquired nature of this property. The safety of
L. pentosus
9D3 was demonstrated through the lack of genes related to the production of toxins, biogenic amines, and antimicrobial drugs. Although the strain exhibited resistance to ampicillin and chloramphenicol, none of the antimicrobial resistance (AMR) genes were associated with mobile elements, i.e., plasmids and prophages. Therefore, the strain is considered to have low risk of transferring the AMR genes to other, potentially pathogenic bacteria. In addition,
L. pentosus
9D3 showed good survivability in the gastrointestinal tract environment and was able to adhere to the intestinal cell
in vitro.
Therefore,
L. pentosus
9D3 is concluded to be safe, with the potential to be used as a probiotic, exerting its health benefit through GABA production in the food system. The GABA-producing capability of the strain
in vivo
is the subject of further investigation.
Bioactive peptides from protein hydrolysate of defatted skipjack (Katsuwonus pelamis) roe with 5% degree of hydrolysis (DH) prepared by Alcalase digestion were isolated and characterised. Two active ...fractions with ABTS radical scavenging activity (973.01–1497.53 μmol TE/mg sample) and chelating activity (0.05–0.07 μmol EE/mg sample) from consecutive purification steps including ultrafiltration, cation exchange column chromatography and reverse phase high performance liquid chromatography (RP-HPLC), were subjected to analysis of amino acid sequence by LC–MS/MS. Seven dominant peptides with 6–11 amino acid residues were identified as DWMKGQ, MLVFAV, MCYPAST, FVSACSVAG, LADGVAAPA, YVNDAATLLPR and DLDLRKDLYAN. These peptides were synthesised and analysed for ACE-inhibitory activity and antioxidative activities. MLVFAV exhibited the highest ACE inhibitory activity (IC50 = 3.07 μM) (p < 0.05) with no antioxidative property, whilst DLDLRKDLYAN showed the highest metal chelating activity, ABTS radical and singlet oxygen scavenging activities. Therefore, peptides prepared from skipjack roe could be further employed as a functional food ingredient.
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