Increase In Total Viable Count Research Articles

Evaluation of storage stability of poultry by-product meal incorporated fish feed under aerobic storage condition

The research focused on development of fish feed utilising poultry by-product meal (PBM) as a substitute for fish meal (FM) and evaluating its shelf life under aerobic packaging conditions. Initially, a basal diet (C) was formulated to meet the nutritional requirements for optimal growth of Tilapia by using FM as the major protein source. After analysing the nutritional composition of PBM, an isoproteinaceous diet (T) was formulated by replacing FM with PBM. The product was packed in HDPE bags and kept at room temperature and analysed for physico chemical and microbial characteristics for 45 days at weekly intervals. Moisture content of both C and T decreased significantly (p0.05) was found between C and T. The TBARS value of both C and T followed an increasing trend. This increase in C was not significant (p<0.01) between 28th and 35th day, and between 42nd and 45th day but that of T increased significantly (p<0.01) throughout the storage period. T consistently displayed the highest TBARS value during storage period. Tyrosine Value (TV) of both C and T also increased during storage and was significant (p<0.01) up to 42nd day of storage. C exhibited the highest TV throughout the storage period. Similarly, total viable count (TVC) of both C and T increased on storage. The increase in TVC for C was not significant (p<0.01) between 21st and 28th days, whereas that of T was significant (p<0.01) throughout the storage period. On 45th day, T exhibited highest count and was significantly different (p<0.01) from C. Throughout the 45-day storage period, no observable coliform count or yeast and mould count was noted in either C or T. The present study indicated that fish feed can be effectively prepared by utilising PBM and can be stored under room temperature up to 45 days. Keywords: Poultry by-product meal, fish meal, fish feed, storage stability

Antibacterial mechanism of atmospheric cold plasma against Pseudomonas fluorescens and Pseudomonas putida and its preservation application on in-packaged red shrimp paste

This study aimed to investigate the antibacterial mechanism of atmospheric cold plasma (ACP) against Pseudomonas fluorescens and Pseudomonas putida and its preservation effect on red shrimp paste. A reactive species (RS) assay showed that O3, H2O2, and total nitric oxide were generated after ACP treatment, which possessed great potential for antibacterial and food preservation. In vitro antibacterial results showed that excess RS inhibited bacterial activity through cell membrane damage. Molecular docking predictions and enzyme activity assays indicated that ACP-induced RS might deactivate dehydrogenases (such as malic dehydrogenase) by oxidatively modifying the active sites. Fluorescence quantification experiments validated the damage of RS to dsDNA. Further preservation tests on shrimp paste demonstrated that ACP treatment significantly delayed the increase in total viable count, Pseudomonas count, and total volatile basic‑nitrogen during refrigeration. This study deepened the understanding of the antibacterial mechanism of ACP and highlighted its potential application as a new preservation method.

An antibacterial film using κ-carrageenan loaded with benzyl isothiocyanate nanoemulsion: Characterization and application in beef preservation

Benzyl isothiocyanate (BITC) is a naturally active bacteriostatic substance and κ-carrageenan (KC) is a good film-forming substrate. In the present study, a nanoemulsion incorporating BITC was fabricated with a particle size of 224.1 nm and an encapsulation efficiency of 69.2 %. Subsequently, the acquired BITC nanoemulsion (BITC-NE) was incorporated into the KC-based film, and the light transmittance of the prepared composite films was lower than that of the pure KC film. Fourier transform infrared spectroscopy and scanning electron microscopy revealed that BITC-NE was compatible with the KC matrix. BITC-NE incorporation enhanced the tensile strength of the KC-based films by 33.7 %, decreased the elongation at break by 33.8 %, decreased the water vapor permeability by 60.1 %, increased the maximum thermal degradation temperature by 48.8 %, and decreased the oxygen permeability by 42 % (p < 0.05). Furthermore, the composite films showed enhanced antimicrobial activity against Staphylococcus aureus, Salmonella typhimurium, and Pseudomonas fluorescens. The developed KC-based composite films were applied to wrap raw beef, which significantly delayed the increase in total viable count, total volatile base nitrogen content, and thiobarbituric acid reactive substances, and prolonged the shelf-life of the raw beef by up to 10 days. These results indicated that the composite films prepared by incorporating BITC nanoemulsions into KC matrices have great antimicrobial application potential.

Mitigating quality deterioration in chilled pork by combining cinnamaldehyde nanoemulsions and a high-voltage electrostatic field

Cinnamaldehyde nanoemulsion (CNE) was obtained through ultrasonication, using Tween 80 as an emulsifier. The CNE was then applied to chilled pork in conjunction with a high-voltage electrostatic field (HVEF) to mitigate quality deterioration during refrigerated storage. The particle size of CNE ranged from 60 to 150 nm and was positively correlated with the amount of added cinnamaldehyde. The polydispersity index and zeta potential of CNE ranged from 0.25 to 0.30 and − 12 to −11 mV, respectively, indicating a narrow size distribution and stability. The CNE released the odor specific to cinnamaldehyde to pork in the first 4 days of chilling; however, it had little effect on the taste. HVEF pretreatment reduced the initial total viable count (TVC) in pork by 1.14 log cycle. The combination of CNE with HVEF successfully slowed down the loss of moisture, decrease in pH, and accumulation of total volatile basic nitrogen in pork during refrigeration. Furthermore, it mitigated the increase in TVC of pork. Therefore, this integrated method appears to be suitable for extending the shelf life of chilled pork.

Dynamic Changes in the Microbial Composition and Spoilage Characteristics of Refrigerated Large Yellow Croaker (Larimichthys crocea) during Storage.

The quality changes, dynamic changes in microbial composition, and diversity changes in large yellow croaker (Larimichthys crocea) during 4 °C refrigeration were studied using 16S rDNA high-throughput sequencing technology, and the total viable count (TVC), total volatile basic nitrogen (TVB-N), and thiobarbituric acid-reactive substances (TBARS) were determined. The results revealed a consistent increase in TVC, TVB-N, and TBARS levels over time. On the 9th day, TVC reached 7.43 lg/(CFU/g), while on the 15th day, TVB-N exceeded the upper limit for acceptable quality, reaching 42.56 mg/100 g. Based on the 16S rDNA sequencing results, we categorized the storage period into three phases: early storage (0th and 3rd days), middle storage (6th day), and late storage (9th, 12th, and 15th days). As the storage time increased, both the species richness and diversity exhibited a declining trend. The dominant genus identified among the spoilage bacteria in refrigerated large yellow croaker was Pseudomonas, accounting for a high relative abundance of 82.33%. A comparison was carried out of the spoilage-causing ability of three strains of Pseudomonas screened and isolated from the fish at the end of storage, and they were ranked as follows, from strongest to weakest: P. fluorescen, P. lundensis, and P. psychrophila. This study will provide a theoretical basis for extending the shelf life of large yellow croaker.

Synergistic Effect of Combined Treatment with Allicin and Antioxidant of Bamboo Leaves and Preservation of Bullfrogs (Lithobates catesbeiana) during Refrigeration Storage.

The effects of allicin and antioxidant of bamboo leaves (AOB) on the quality of bullfrogs (Lithobates catesbeiana) during refrigerated storage (4 °C) were investigated. The quality changes in samples treated with deionized water (CK), allicin solution (All), antioxidant of bamboo leaves (AOB), and allicin solution combined with AOB solution (AA) in microbiological, physicochemical, and sensory evaluation were analyzed, respectively. The results demonstrated that combination treatment inhibited the increase in total viable counts, delayed the decrease in amino acid content, and retarded the sensory deterioration. Preservative treatment has an inhibitory effect on the early storage of PBC, which can reduce PBC by about 1.0 log CFU/g. The reduction in thiobarbituric acid (TBA) content and total volatile basic nitrogen (TVB-N) content indicated that combination treatment could better restrain the lipid oxidation and degradation of protein than the CK group and single-treatment group. In addition, the TVB-N content in the AA group still did not exceed the threshold on the 14th day. As a consequence, combination treatment prolonged the shelf life of bullfrogs for another six days. Therefore, allicin and AOB with excellent antioxidant and antimicrobial activity could be an effective approach to delay the biochemical reaction of refrigerated bullfrogs. This study has provided a potential approach for increasing the shelf life of bullfrogs and preserving their quality during refrigerated storage.

The fabrication of films based on polymer and containing nanoclay, sodium diacetate, and tert‐butyl hydroquinone for packaging rainbow trout

This study investigates the fabrication of films based on a polymer containing nanoclay, sodium diacetate (SDA), and tert-butyl hydroquinone (TBHQ) for packaging rainbow trout fillets. The films were prepared by the addition of 2% SDA (SDA film), 2% TBHQ (TBHQ film), and a combination of both (1% SDA+1% TBHQ) into polyethylene polymer (93.00%) and montmorillonite nanoclay (5.00%). A film lack of nanoclay, SDA, and TBHQ was prepared and considered a control film. A film was also prepared by the addition of 95g polyethylene+5g nanoclay (Nanoclay). Morphological properties of the films were investigated by a scanning electron microscope (SEM). In vitro antioxidant properties and antibacterial activities of the films and their effects as the coating on fish samples were evaluated against Listeria monocytogenes, Salmonella typhimurium, and Escherichia coli. The effects of films on oxidative stability, antibacterial activity, pH, total volatile basic nitrogen (TVBN), and total viable count (TVC) of fish samples were assessed. The SEM results showed the homogenous dispersion of SDA and TBHQ into films. The SDA, TBHQ, and ST films showed antibacterial activity against L. monocytogenes, S. typhimurium, and E. coli compared with the control film as the coating and under in vitro conditions (p<0.05). The TBHQ and ST films exhibited higher antioxidant activity and prevented the oxidation as the coating. The films prepared from the SDA, TBHQ, and ST prevented an increase in TVC and TVBN (p<0.05). The ST films can prevent spoilage in fish samples and can be utilized in the food industry. PRACTICAL APPLICATION: We successfully prepared films with the help of nanoclay, sodium diacetate (SDA), and tert-butyl hydroquinone (TBHQ) on polyethylene for packaging fish fillets. Films containing SDA, TBHQ, and nanoclay showed antibacterial activity and prevented spoilage. The films can be used for packaging fish fillets.

Integration of fluorophore-based sensor spots into food packaging systems for the non-destructive real-time determination of oxygen

Oxygen is an important filling gas for modified atmosphere food packaging. To measure the oxygen amount non-destructively in the headspace, the integration of fluorescence material into the packaging system is a meaningful method, as oxygen serves as quencher for dynamic fluorescence. In this study, the integration of fluorescencent material into packaging films using a heat-sealing process was successfully demonstrated. Real-time determination of changes in oxygen partial pressure was also possible, with some limitations. The use of the technology for the determination of food quality changes (microbiological growth and color changes) were evaluated with high-oxygen stored minced beef (7 d, 4 °C), vacuum-packed sausage “Lyoner” type and beef steak (13 d, 4 °C). The increase in total viable count to the critical value of 107 CFU/g and the change of the surface color was well in common with the oxygen decrease for the high-oxygen packed minced beef. The vacuum packaged samples also showed correlations between reaching the critical microbiological value and a significant decrease of oxygen. However, no color changes were visible in that case.

Exploration of the roles of microbiota on biogenic amines formation during traditional fermentation of Scomber japonicus.

The influence of microbiota composition and metabolisms on the safety and quality of fermented fish products is attracting increasing attention. In this study, the total viable count (TVC), pH, total volatile base nitrogen (TVB-N) as well as biogenic amines (BAs) of traditional fermented Scomber japonicus (zaoyu) were quantitatively determined. To comprehend microbial community variation and predict their functions during fermentation, 16S rRNA-based high-throughput sequencing (HTS) and phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) were employed, respectively. The fresh samples stored without fermentation were used as controls. TVC and TVB-N values increased rapidly, and the content of BAs exceeded the permissible limit on day 2 in the controls, indicating serious spoilage of the fish. In contrast, a slower increase in TVC and TVB-N was observed and the content of BAs was within the acceptable limit throughout the fermentation of zaoyu. Significant differences in microbiota composition were observed between zaoyu and the controls. The bacterial community composition of zaoyu was relatively simple and Lactobacillus was identified as the dominant microbial group. The accumulation of histamine was inhibited in zaoyu, which was positively correlated with the relative abundance of Vibrio, Enterobacter, Macrococcus, Weissella, et al. based on Redundancy analysis (RDA), while Lactobacillus showed a positive correlation with tyramine, cadaverine, and putrescine. Functional predictions, based on Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis, revealed that the relative abundance of metabolic function exhibited a decreasing trend with prolonged fermentation time and the abundance of metabolism-related genes was relatively stable in the later stage of fermentation. Those metabolisms related to the formation of BAs like histidine metabolism and arginine metabolism were inhibited in zaoyu. This study has accompanied microbiota analysis and functional metabolism with the accumulation of BAs to trace their correspondences, clarifying the roles of microorganisms in the inhibition of BAs during fermentation of Scomber japonicus.

Effect of slightly acidic electrolyzed water（SAEW） combined with ultrasound sterilization on quality of Bigeye tuna (Thunnus obesus) during cryogenic storage

The quality, protein degradation, microstructure and moisture content of tuna fish were analyzed by using different concentrations of slightly acidic electrolyzed water (28, 55, 77 mg/mL) combined with 280 W ultrasonic treatment and single concentration of slightly acidic electrolyzed water (28, 55, 77 mg/mL). Fish freshness was evaluated by pH, TVB-N, TBA, color difference, TVC and texture. Protein degradation was studied by TCA-soluble peptide and myofibrin fragmentation index, and water status and tissue structure were evaluated by low field NMR and HE staining. The results showed that SAEW and SAEW+Ult treatment not only inhibited the increase of total viable counts (TVC), but also inhibited the increase of total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA) and pH. Among them, 55 mg/mL+Ult treatment had better inhibition of protein degradation, and the microstructure and texture of fish tissues maintained the best, and the water loss was the slowest. Therefore, 55 mg/mL+Ult treatment is an effective way to maintain the quality and prolong the shelf life of tuna during refrigeration.

신선식품 콜드체인 EPS 패키징 시스템의 택배 유통환경 계측

The food cold chain refers to a technology and distribution supply chain applied to maintain a constant temperature suitable for the product from production (harvest) to delivery to consumers. In particular, in Korea, the insulation material used in the food cold chain is mostly EPS (Expanded Polystyrene), which is used as a transport container for various food cold chains. However, according to the government's eco-friendly policy, companies charge environmental contributions to the use of EPS, but due to its low price and convenience of handling, it is still used as a container for delivering food. In this study, in order to measure the domestic delivery environment of general refrigerated foods, changes in impact, temperature, and humidity during transport of the EPS packaging system containing foods and ice pack refrigerants were measured. As a result, there were 2?3 sections in which a high impact force of 40 G or more was generated during transport. This can cause damage to the product and EPS container. The difference in temperature and humidity changes by parcel transport routes is more than 30%, so it is necessary to present accurate standards for the domestic cold chain distribution environment. As a result of microbial experiments. the transportation period had a dominant effect on the increase in total viable count and E. coli count.

Biological activity of biopolymer edible furcellaran-chitosan coatings enhanced with bioactive peptides

The aim of the study was to develop novel antimicrobial coatings which could be used for extending the microbiological quality of perishable food products. Seven different antimicrobial peptides (Lfcinβ, PLGG, MBP-1, LL-37, Cys-LL-37, RW4 and melittin) have been investigated as possible agents for implementation into the previously developed chitosan/furcellaran (CHIT/FUR) coatings. The study included several steps of microbiological analysis, starting with minimum inhibitory concentration (MIC) analysis of crude peptide solutions (concentration from 0.78 to 100 μg/mL) against selected pathogens. The analysis showed that only RW4 and melittin proved effective against all studied pathogens in the investigated doses, except for Aspergillus flavus. The second examination included in-vitro analysis regarding antimicrobial activity of developed coatings with peptides at a concentration of 5 μg/mL, against chosen pathogens. This analysis allowed to indicate a complementary effect of antimicrobial activity between all peptides and the CHIT/FUR complex since the coatings inhibited the growth of the tested pathogens. Afterwards, the coatings were used to coat smoked pork ham slices stored for 10 days and analysed for the increase in total viable counts (TVC). The analysis demonstrated a high efficiency of the CHIT/FUR complex, even without the addition of peptides. Only RW4 and LL-37 did not cause a decrease in antimicrobial power of the control coating. Therefore, in the final trial, the effect of different doses (1.25–10 μg/mL) of RW4 and LL-37 peptides on the TVC of cold-stored coated pork loins. The coatings almost completely inhibited the increase of TVC in the pork loins and the peptides were effective at all studied doses. The newly-developed coatings had strong antimicrobial properties and can be used to extend the shelf-life of perishable food products.

Combined effects of pectin–plant essential oil coating with vacuum packaging on the quality of large yellow croaker (Pseudosciaena crocea) during iced storage

AbstractThe study investigated the effects of pectin–plant essential oil coating combined with vacuum packaging on Pseudosciaena crocea during iced storage. Samples were immersed in sterile water (CK), 25% ethanol (E), pectin + 0.4% oregano essential oil (PO), and pectin + 0.4% ginger essential oil (PG), respectively. The results showed that compared with the CK group, PO and PG coatings could effectively inhibit the increase of total viable counts (TVC) and H2S‐producing bacteria counts by 1.25–1.64 log CFU/g and 1.18–1.37 log CFU/g, respectively. Meanwhile, PO and PG treatments could delay the increase of pH, thiobarbituric acid (TBA), and total volatile basic nitrogen (TVB‐N) value, which also inhibited the degradation rate of adenosine triphosphate (ATP) in fish. When samples treated with PO and PG, the shelf‐life of Pseudosciaena crocea could increase from 20 to 27 days and 24 days, respectively, which indicated that the combination of pectin–plant essential oil coating with vacuum packaging is a promising method for the preservation of Pseudosciaena crocea.

Bioremediation of Vegetable Oil Contaminated Soil with Two Microbial Isolates

Vegetable oil spills are becoming frequent and are potentially more challenging than petroleum hydrocarbon spills. Microbial lipases occupy a place of prominence among biocatalysts and are often used for the remediation of vegetable oil spills. There is a need for extensive characterisation of lipase for the treatment of vegetable oil-polluted sites. This work was carried out to monitor the degradation pattern of vegetable oil. Two microbial isolates previously isolated from an oil mill in Ibadan, Nigeria were used for the bioremediation experiment. Soil samples (with some purposely contaminated with 2 different vegetable oils) collected from the Nursery section of the Microbiology department as well as soil samples from the oil mill were all subjected to varied treatment processes. Field bioremediation using the isolates was carried out for 12 weeks. The isolates were identified, and microbial load and residual oil weight were determined during the degradation period using standard methods. The two isolates were identified as Pseudomonas fluoresecens and Candida parapsilosis. The result of sterile soil samples with and without mixing option, from palm oil and palm kernel purposely contaminated soils for all the various treatments, showed a general increase in total viable counts from the 2nd week to the 12th week, however in the non-sterile counterpart there was a steady increase from the 2nd week to the 8th week and subsequently, a gradual decrease from the 10th to the 12th week. The residual oil weight in the sterile purposely palm oil-contaminated soil, treated with the consortium (POC) non-mixed gave a reduction of value from 0.335 g on day 0 to 0.13025 g by the 12th week. From the oil mill non-sterile, treated with (POC) non-mixed sample, the residual weight after 12 weeks of treatment was 0.0043 g from an initial weight of 0.01 g. The microorganisms Pseudomonas fluoresecens and Candida parapsilosis had the potential for the degradation of fatty waste. They could therefore be employed in the environmental cleanup of the vegetable oil spill sites.

Effect of konjac glucomannan and chitosan-based film coatings on the quality of fresh sea bass (Lateolabrax maculatus) under refrigerated condition

• Film coating on the shelf-life enhancement of sea bass was studied. • Sea bass samples coated by chitosan-SPS presented minimum drip loss. • Coating is an effective way to prevent fish from lipid oxidation and muscle ageing. • Chitosan-based coating was good in retaining the texture parameters of fish. • TBA content of coated sea bass was lower as compared to the control. Sea bass ( Lateolabrax maculatus ) is one of the important seafood in China. Its shelf-life under refrigerated storage exponentially deteriorate due to the growth of spoilage microorganisms, protein degradation and lipid oxidation. In this study, 4 coating materials namely, konjac glucomannan-whey protein isolate (KGM-WPI) film, chitosan-sweet potato starch (CHI-SPS) film, chitosan-bamboo fungus (CHI-BF) film, and chitosan-boehmite alumina (CHI-BAH) have been explored to enhance the shelf life of sea bass during 8 days of refrigerated storage. Overall, CHI-BF was observed to be best in retaining hardness, gumminess and maintaining total volatile basic nitrogen value. Whereas CHI-SPS was found to retain chewiness and maintain lower values for drip loss and peroxide value. CHI-BAH coating was observed to maintain the lower values for pH and EC values of sea bass under refrigerated storage. However, the least increase in total viable count and minimum change in b * value was observed in the case of sea bass coated with KGM-WPI. The current research findings provide a new practical storage method for the entire fresh fish. The fresh fish can be coated with different coating materials and store on the ice at 4°C without packaging during retailing. These film coated whole fresh fish retains its microbial and sensory quality.

Combined effects of ultrasound and slightly acidic electrolyzed water on quality of sea bass (Lateolabrax Japonicus) fillets during refrigerated storage

A novel technique for sea bass (Lateolabrax Japonicus) fillets by combining ultrasound (US) and slightly acidic electrolyzed water (SAEW) to inactivate bacteria and maintain quality was developed. Samples were treated with distilled water (DW), US, SAEW and ultrasound combined with slightly acidic electrolyzed water (US + SAEW) for 10 min, respectively. The results suggested that US + SAEW treatment could retard the increase of total viable counts (TVC), Pseudomonas bacteria counts and H2S-producing bacteria counts, which also inhibit the rise of total volatile basis nitrogen (TVB-N), thiobarbituric acid (TBA), pH and K value. In addition, compared with SAEW or US treatment alone, US + SAEW treatment had distinctly effects on inhibiting protein degradation and maintaining better sensory scores. Compared with DW group, the shelf life of sea bass treated with US + SAEW was increased for another 4 days. It indicated that the combined treatment of US and SAEW could be used to the preservation of sea bass.

Effects of decontamination treatment combined with natural chemicals and/or ultra-high pressure on the quality and safety of ready-to-eat wine-pickled mud snails (Bullacta exarata)

Abstract Ready-to-eat wine-pickled mud snails (Bullacta exarata) typically host a large number of microorganisms and are frequently contaminated with pathogenic bacteria during processing, resulting in a higher risk for foodborne illness with consumption. In this study, the decontamination effects of different treatment methods, including the use of ultrasonic cleaning (USC), natural chemicals, and ultra-high pressure (UHP), on the quality and safety of pickled mud snails were investigated by assessing the total viable count (TVC), total volatile base nitrogen (TVB-N) content, thiobarbituric acid-reactive substance (TBARS), and pH value of the products after 12 months of storage at –20 °C. Treatment with 200 W USC for 5 min was the most effective approach for reducing TVC in raw mud snails, with a minimal change in food quality. Natural chemical treatment or UHP treatment significantly inhibited the increase in TVC, pH, and TBARS and TVB-N accumulation compared with the control group; however, their combined treatment had no synergistic effect. In contrast, the combined chemical treatment was more effective in inhibiting changes in the above indices in pickled mud snails than UHP treatment alone or combined chemicals+UHP treatment. In addition, the bacterial diversity of pickled mud snails before and after 12 months of storage at –20 °C was determined using Illumina MiSeq sequencing. Our results indicated that USC combined with natural chemicals can be utilized commercially to maintain the quality and safety of pickled mud snails during storage at –20 °C.

The impacts of salt with Chinese liquor on the inhibition of microbial spoilage and quality attributes of grass carp ( Ctenopharyngodon idellus ) fillets stored at 4°C

In order to clarify the action of a seasoning mixture of salt and Chinese liquor in maintaining the hygienic and quality characteristics of refrigerated grass carp, the changes in physicochemical properties, biogenic amines, and microbial growth in grass carp fillets during storage at 4°C for 30 days were investigated. Results showed that fillets lightly salted with Chinese liquor had lower values of total volatile basic nitrogen, drip loss, biogenic amines contents, and higher hardness as well as stable pH during storage, compared to the untreated or individual salted groups. The increase in total viable counts and total psychrophile counts were significantly inhibited by combined adding salt and Chinese liquor. Additionally, Illumina sequencing analysis showed Enterobacteriaceae and Carnobacteriaceae were the major spoilage bacteria species in untreated samples at the end of storage, but they were highly inhibited by adding salt and Chinese liquor. Practical applications Refrigerated storage can better maintain the fresh quality of fish because it is stored under nonfrozen conditions, but the shelf life is limited due to the action of microorganisms and endogenous enzymes. Food seasoning ingredients have the characteristics of high safety, low cost, and convenient application. The combination of salt with other ingredients in fish curing to develop low-salt preservation techniques has attached increasing interest. The present study showed that curing of grass carp using salt combined with Chinese liquor can largely delay chemical changes, lower the accumulation of putrescine and cadaverine, and inhibit the growth of spoilage microorganisms in refrigerated fish fillets compared to the untreated group. This study provided a promising cost-efficient and simple preservation technique of fish.

Effect of antibacterial treatments and natural chemicals on the quality and safety of marinated raw crab paste during storage at −20°C

AbstractThe effects of antibacterial treatments and several natural chemicals on the quality and safety of crab paste during storage at −20°C were investigated. All antibacterial treatments significantly reduced the bacterial total viable count (TVC) of swimming crabs, with sodium hypochlorite (NaClO) combined with ultrasonic cleaning having the best effects. Four chemicals significantly inhibited the increase in TVC, pH, and the accumulation of total volatile basic nitrogen (TVB‐N) compared to controls, and their combined treatment had synergistic effects. The L 9(3 4) orthogonal experiment showed that the optimum combination was A1B3C3D2 (i.e., 0.1 g kg−1 nisin, 0.4 g kg−1 ε‐polylysine hydrochloride, 0.3 g kg−1 tea polyphenol, and 0.5 g kg−1 citric acid). The TVC, TVB‐N concentration, and pH in A1B3C3D3‐treated samples remained far below the maximum acceptable limit for good‐quality marinated, raw, aquatic animal product after 12 months of frozen storage at −20°C. Furthermore, the combined treatment (A1B3C3D3) significantly inhibited the reproduction of foodborne pathogenic bacteria and spoilage bacteria. The antibacterial treatments and natural chemicals reduced foodborne pathogenic bacteria and inhibited microbial spoilage, and therefore maintained the quality and safety of crab paste during frozen storage. Antibacterial treatments and natural chemicals could be commercially utilized to maintain the quality and safety of crab paste.

Biogenic amines content in the fermented asian food in the Czech Republic

The aim of this work was to study the typical fermented Asian food (miso paste, soy sauce, rice vinegar, kimchi and tempeh) to monitor their microbial quality and presence of biogenic amines in relation to time and temperature of storage. This study is focused on microbiological research in order to determinate presence of selected indicator groups of microorganisms during storage of individual products at three different temperatures, 8 °C, 23 °C, 30 °C. It was found that the highest increase of total viable counts was observed in products stored in 23 °C and 30 °C, especially in tempeh and miso paste. In soy sauce and rice vinegar were observed only very low amounts of microorganisms through the storage period. In the second part of the experiment, the biogenic amines were analyzed using high performance liquid chromatography. It was found that the levels of biogenic amines in tested products were low and does not affect human health.