Total Volatile Basic Nitrogen Research Articles

Development of a comprehensive classification model for determining the storage day of frigate tuna (Auxis thazard) for freshness evaluation using a portable electronic nose

SummaryEnsuring the freshness of fish is essential to guaranteeing safer products for consumers. A classification model was developed using the PEN3 electronic nose to predict fish freshness with its storage day. Frigate tuna (Auxis thazard) was used for odour sampling along with the total volatile base nitrogen (TVB‐N), at 4 °C for 14 days every other day. Random forest and support vector machine (SVM) were performed to develop freshness classification models based on PEN3 data and 100% and 99.8% accuracies were obtained, respectively, in distinguishing the eight storage day classes. The PEN3 sensors including W2S, W1S, W1W, W3S, and W6S were identified as key sensors for fish freshness. TVB‐N analysis advances the freshness prediction of e‐nose and three freshness levels were identified as ‘Fresh’, applicable from the 0th to the 6th day; ‘Moderately fresh’, lasting from the 7th to the 9th day; and ‘Unsuitable for consumption’, applicable from the 10th day onwards.

Effects of packaging methods and temperature variations on the quality and microbial diversity of grouper (Epinephelus Lanceolatus) during cold storage

Microbial growth and its metabolism are the primary reasons for fish spoilage. In this study, the effects of temperature fluctuations and modified atmosphere packaging (MAP) on the quality and microbial diversity of grouper (Epinephelus lanceolatus) during cold storage were investigated. Fish fillets were packed in air packaging (AP), vacuum packaging (VP), MAP1 (40% CO2/55% N2/5% O2), and MAP2 (60% CO2/35% N2/5% O2), and stored at T1 (4 °C) and T2 (4–8 °C temperature fluctuations), respectively. Total viable counts (TVC), psychrophilic bacteria count, Pseudomonas count, and H2S-producing bacteria count all increased during cold storage. Pseudomonas, Serratia, and Carnobacterium were the dominant genera in AP, VP, and MAP2 at T1 storage, with relative abundances of 82.7%, 54.5%, and 57.3%, respectively. Temperature fluctuations accelerated the spoilage process of the grouper, and increased the relative abundance of Serratia in the samples, but had less effect on the composition of these spoilage bacterial members. The microbial community was more affected by the different gas atmospheres. MAP inhibited the growth of Pseudomonas and increased the relative abundance of Carnobacterium and Psychrobacter in the samples. Low temperature and MAP effectively suppressed the rise of pH, total volatile basic nitrogen (TVB-N), trimethylamine (TMA), thiobarbituric acid reactive substances (TBARs), and K values and maintained the water holding capacity (WHC) and sensory quality of the samples. Grouper had the longest shelf life under MAP2-T1 treatment. The MAP2-T1 samples maintained lower levels of TVB-N (151.8 mg/kg), TMA (7.6 mg/kg), TBARs (0.90 mg MDA/kg), and K value (48.5%) and higher levels of WHC (77.6%) on the 18th day, with a lower degree of spoilage compared to other samples.

Curcumin-loaded food-grade nano-silica hybrid material exhibiting improved photodynamic effect and its application for the preservation of small yellow croaker (Larimichthys polyactis)

Two types of curcumin-loaded food-grade nano-silica (F-SiO2) hybrid materials were successfully synthesized using the rotary evaporation method (F-SiO2@Cur) and the adsorption method (Cur@F-SiO2). The microstructure and spectral analyses confirmed that the curcumin in F-SiO2@Cur was loaded within the nanopores in a non-aggregate form rather than being adsorbed onto the surface (Cur@F-SiO2). Additionally, F-SiO2@Cur exhibited remarkable water solubility (1510 ± 50.33 µg/mL) and photostability (a photodegradation ratio of only 59.22 %). Importantly, F-SiO2@Cur obtained a higher capacity for the generation of singlet oxygen (1O2) compared to control groups. Consequently, F-SiO2@Cur-mediated photodynamic inactivation (PDI) group attained the highest score in sensory evaluation and the best color protection effect in PDI experiment of small yellow croaker (Larimichthys polyactis) at 4 °C. Moreover, F-SiO2@Cur could effectively controlled total volatile basic nitrogen (TVB-N) content, pH, and total viable count (TVC), thereby prolonging the shelf life. Therefore, F-SiO2@Cur-mediated PDI is an effective fresh-keeping technology for aquatic products.

Comparative study of a liposome and emulsion system with cinnamon essential oil on the quality and proteolysis of refrigerated minced pork.

Essential oils have been recognized for their strong antibacterial property, making them an innovative approach for preserving meat. However, their chemical instability and direct impact on meat proteins limit their application. To overcome these limitations, various loading systems have been explored. This study aimed to compare the effect of cinnamon essential oil (CEO) loaded in a liposome and emulsion system on the proteolysis of minced pork and to evaluate the advantages of each delivery system in preventing microorganism-induced quality deterioration of meat. Minced pork treated with CEO-liposomes exhibited lower pH, total volatile basic nitrogen (TVB-N), and total viable count (TVC) values than CEO-emulsions and provided better protection against microorganisms. SDS-polyacrylamide gel electrophoresis (PAGE) analysis confirmed that CEO-liposome was more effective in protecting proteins from degradation. Moreover, CEO-liposome produced lower amount of bitter amino acids and harmful biogenic amines. Antibacterial mechanisms indicated that CEO-liposome exhibited a stronger inhibitory effect against major spoilage bacteria in meat products by increasing cell membrane permeability. The membrane damage was further supported by an increase in conductivity and the leakage of nucleic acids. Compared to the CEO-emulsion system, CEO-liposome emerged as an effective preservative for minced pork. These results provided important theoretical support for using a bioactive compound delivery system to prevent microorganism-induced quality deterioration in meat.

Antibacterial activity of angelica essential oil, its mechanism against Pseudomonas fluorescens, and its application in the preservation of chilled fresh beef

The mechanism by which Angelica essential oil (AEO) can act as an antimicrobial agent at cellular and metabolic levels to inhibit Pseudomonas fluorescens (P. fluorescens), and its effectiveness in beef preservation, were investigated and evaluated in this study. Our results showed that the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AEO to P. fluorescens were 12.5 μL/mL and 25 μL/mL, respectively, at which AEO could effectively inhibit P. fluorescens reproduction and retard its growth (p < 0.05). Severe morphological damage to the AEO-treated cells of the microorganism, including cell walls and membranes, were observed via scanning electron microscopy (SEM). AEO treatment was also seen to lead to an increase in alkaline phosphatase (AKPase) activity and conductivity, and a significant leakage of intracellular macromolecular components (such as nucleic acids and proteins), providing further evidence of damage to the integrity of cell wall and cell membrane. Metabolomics analysis revealed that the differential metabolites in the AEO hindered nucleic acid synthesis and expression in the P. fluorescens, leading to tricarboxylic acid (TCA) cycle blockage and amino acid restriction, energy metabolism disorders and membrane damage, mainly through nucleotide metabolism, amino acid metabolism, carbohydrate metabolism and membrane transport. Moreover, application testing demonstrated the efficacy of AEO in slowing the increase of beef pH and total volatile basic nitrogen (TVB-N), extending the shelf life of chilled beef by 5.39 d, and effectively maintaining the organoleptic quality of beef. These results lay a foundation for the development of AEO as a natural bacteriostatic agent.

Preservation strategies for processed grass carp products: Analyzing quality and microbial dynamics during chilled and ice temperature storage

This study investigated the impact of ice temperature storage on quality and bacterial composition of processed fish paste products (PFP). Freezing curve revealed the ice temperature was −1 °C. Electric nose (e-nose) showed significant changes in volatile components within 8 days. Results of total volatile basic nitrogen (TVB-N) showed that PFP stored at 4 °C reached its limit after 2 days, whereas PFP stored at ice temperature remained stable for 6 days. Thiobarbituric acid reactive substances (TBARS) demonstrated delayed oxidation in PFP stored at ice temperature compared to 4 °C. TCA-soluble peptides indicated that the protein degradation was suppressed by ice temperature. Additionally, ice temperature inhibited microbial growth and altered bacterial composition. High-throughput sequencing revealed that Pseudomonas, Brochothrix, Carnobacterium were dominant at 4 °C, while Acinetobacter, Pseudomonas, Janthinobacterium and Brochothrix were dominant at ice temperature. In summary, ice temperature might be a potential method for maintaining the freshness of PFP.

Effects of cold plasma and ultra-high-pressure sterilization on the quality, flavor, and safety of semi-dried golden pompano

This investigation aimed to assess the impact of cold plasma (CP) and ultra-high-pressure (UHP) treatment on the quality, flavor, and safety of semi-dried golden pompanos during the storage period. The results showed the highest severity of lipid oxidation in the CP group, whereas alternation in protein structure and protein oxidation were the most apparent in the UHP group. Compared with CP, UHP better inhibited the accumulation of total volatile basic nitrogen and biogenic amines. The shelf life of samples was prolonged by 10–12 and 12–17 days upon treatment with CP and UHP, respectively. Furthermore, the freshness preservation effect of UHP was superior. Compared with CP, UHP better mitigated the loss of free amino acids and showed the best inhibitory effect on the production of bad odor-producing compounds, such as 3-methyl-butanal, 2,3-butanediol, acetic acid, and trimethylamine.

Preparation, characterization, and coating effect of bio-active nano-emulsion based on combined plant essential oils on quality of grass carp fillets

This study aimed to develop a satisfactory essential oil (EO) nano-emulsion through high pressure microjet technology and explore its physiochemical properties and synergistic coating effects on grass carp fillets. The optimal conditions for oregano/litsea cubeba (6:4, wt%/wt%) nano-emulsion were shown to be 80 s high pressure microjet pretreatment time, 9000 lb per square inch pretreatment pressure, 6 % oil phase, and 3:2 Km (mass ratio of surfactant to co-surfactant). The obtained nano-emulsion exhibited 100.42 ± 0.96 nm oil diameter at 4 °C after 15-day storage, coupled with high stability after centrifugation, freeze–thaw and heating treatment. Compared with untreated samples at day 6 storage, the nano-emulsion-treated grass carp fillets exhibited improved textural properties, higher water-holding capacity (74.23 % ± 0.80 %), lower total volatile basic nitrogen (TVB-N, 13.46 ± 0.30 mg/100g)/thiobaric acid (TBA,0.43 ± 0.02 mgMDA/100g), and lower total viable spoilage bacteria count (4.98 ± 0.21 lgCFU/g). This study facilitates understanding the combined EOs nano-emulsion on improving the shelf life of grass carp fillets.

Combined Effect of an Active AgIon® Absorbent Pad and a Chitosan Coating on the Preservation of Fresh Beef.

In the present study, the combined effect of an AgIon® antimicrobial absorbent (Ζ) pad and a chitosan coating (C) on the preservation of fresh beef stored aerobically at 5 °C was investigated. Microbiological, physicochemical, and sensory attributes were monitored for up to 10 days of storage. The microbiological data indicated that the C and chitosan coating plus absorbent pad (CZ) treatments were the most efficient in reducing total viable counts (TVC) by 4.09 and 3.53 log cfu/g compared to the control W and Z treatments on day 4 of storage (p < 0.05). An analogous reduction in the counts of the other microbial groups monitored was recorded. pH values were ca. 5.7 for treatments W and Z and 5.45 for treatments C and CZ on day 4 of storage (p < 0.05). The total volatile basic nitrogen (TVB-N) values remained <20 mg/100 g for all treatments on day 4 and for treatments C and CZ on day 10 of storage. The total color difference values decreased (p < 0.05) during storage for treatments W and Z, but remained constant for treatments C and CZ. Based on sensory, microbiological and physico-chemical data, beef shelf life was ca ^# + 3 days for samples W and Z and at least 10 + 3 days for samples C and CZ. Between the two antimicrobial treatments, chitosan was considerably more effective than the AgIon® antimicrobial absorbent pad, which showed practically no antimicrobial activity in direct contact with beef meat.

Effect of gelatin-chitosan-Cyclocarya paliurus flavonoids edible coating film on the preservation of chilled beef

The effect of gelatin-chitosan (GEL-CS) films supplemented with different concentration (0.1%, 0.2%, 0.3%) of Cyclocarya paliurus flavonoid (CPF) on the freshness of beef was investigated for 14 days at 4 °C. The results showed that CPF-added GEL-CS film maintained the freshness of beef better than GEL-CS film. The beef coated with CPF-added film maintained good color, pH, and texture during storage, and the total volatile base nitrogen (TVB-N) was 15.517 mg/100 g at day 14, which was 36.75 mg/100 g lower than that of the control group. In addition, the CPF-added film retarded the oxidation of lipids and proteins in beef compared to the GEL-CS film and promoted the retention of beef quality by inhibiting the deterioration reaction, with a TBA value of 0.33 mg MDA/kg at 14 days of storage, which was 2.081 mg MDA/kg lower than that of the control group. In addition, the CPF-added film showed higher antimicrobial activity against spoilage microorganisms compared to the GEL-CS film, thus further ensuring the edible quality of chilled beef. In conclusion, this study shows that CPF-added GEL-CS film can be used as a packaging film for beef preservation and effectively extend the shelf life of beef up to 14 days.

Novel colorimetric indicators based on alginate hydrogel beads containing anthocyanin for visual freshness monitoring of shrimp and minced chicken

Novel colorimetric indicators were developed by incorporating anthocyanins into alginate hydrogel beads through electrostatic extrusion for intelligent packaging. Two different sizes of hydrogel beads were produced and applied into shrimp and minced chicken packaging to visually detect freshness status during 4 °C storage. To assess the freshness of the products, the viable count of various types of bacteria (psychrotrophic, H2S-producing, mesophilic, and Pseudomonas spp.), total volatile basic nitrogen (TVB-N) content, pH, K-value, H-value, and biogenic amines level were analyzed. The indicators' color change (ΔE) was then correlated with these parameters. Color analysis of the indicators during storage indicated ΔE values below 10 and over 30 in the hydrogels incorporated into minced chicken and shrimp packaging, respectively. The color change of both indicators integrated into the shrimp package was strongly correlated with the change in viable counts, TVB-N, pH, K-value, and H-value (r ≥ 0.8, p < 0.016), as well as biogenic amines (r = 0.7, p < 0.05). The indicators applied to minced chicken packaging showed subtle color changes during storage, while those in shrimp packaging consistently reflected shelf-life variations. This innovative approach shows potential for improving food safety and quality monitoring, particularly in seafood packaging, where indicators have been effective in visually signaling product freshness.

The quality and nutritional value of beef from Angus steers fed different levels of humate (K Humate S100R)

This study compared the effect of four levels of K Humate S100R (potassium humate) supplementation on the quality, shelf-life, and nutritional properties of beef. Angus steers (n = 40) were individually housed and fed either 0, 35, 70, or 140 g K Humate S100R/animal/day for 100 days, following a 30 day adjustment period. The steers were slaughtered at the completion of the feeding study. The left m. longissimus lumborum (LL) was collected at 24 h post-mortem and aged for either 2 or 6 weeks before analysis. K Humate S100R supplementation did not affect beef drip loss, cooking loss, shear force, sarcomere length, ultimate pH, intramuscular fat content, or total volatile basic nitrogen concentrations (P > 0.05). Steers supplemented with 70 g/day K Humate S100R produced beef with higher a* values on Days 1 and 3 of retail display (P < 0.05). Beef mineral composition was unchanged by K Humate S100R supplementation (P > 0.05), but there were minor changes to the fatty acid profile. Specifically, the ratio of omega-6 to omega-3 (P < 0.05) and C20:2n-6 concentrations (P < 0.05) increased with supplementation level. Together, these results demonstrate no detrimental effects on beef quality and shelf-life as a result of K Humate S100R supplementation.

Effect of Neutral Protease on Freshness Quality of Shucked Pacific Oysters at Different Storage Conditions.

The aim of this study was to investigate the effect of neutral protease treatment on the biochemical properties of various parts of Pacific oysters (Crassostrea gigas) under different storage conditions. The mechanism of quality degradation in the mantle, adductor muscle, gill, and trunk of treated oysters stored at -1.5 °C (superchilling) or 4 °C (refrigeration) for several days using different storage methods was studied. The results showed that the oyster treated with the enzyme exhibited higher glycogen content, flavor nucleotide content, and sensory scores compared to the control group. Superchilling at -1.5 °C was observed to slow the increase in total volatile basic nitrogen (TVB-N), total viable count (TVC), and pH, while maintaining sensory scores better than refrigeration at 4 °C. Both wet superchilling (WS) and dry exposed superchilling (DeS) methods effectively preserved freshness and quality at -1.5 °C. The freshness of the oysters' body trunk changed most significantly. K value, K' value, and AEC value, as the evaluation indexes of oyster freshness, were affected by the storage medium. Therefore, neutral protease enhances the flavor of oysters in a short time, and oysters stored in wet superchilling or dry exposed superchilling conditions have an extended shelf life.

The Effects of Four Different Thawing Methods on Quality Indicators of Amphioctopus neglectus.

Amphioctopus neglectus is a species of octopus that is favored by consumers due to its rich nutrient profile. To investigate the influence of different thawing methods on the quality of octopus meat, we employed four distinct thawing methods: air thawing (AT), hydrostatic thawing (HT), flowing water thawing (FWT), and microwave thawing (MT). We then explored the differences in texture, color, water retention, pH, total volatile basic nitrogen (TVB-N), total sulfhydryl content, Ca2+-ATPase activity, and myofibrillar protein, among other quality indicators in response to these methods, and used a low-field nuclear magnetic resonance analyzer to assess the water migration that occurred during the thawing process. The results revealed that AT had the longest thawing time, leading to oxidation-induced protein denaturation, myofibrillar protein damage, and a significant decrease in water retention. Additionally, when this method was utilized, the content of TVB-N was significantly higher than in the other three groups. HT, to a certain extent, isolated the oxygen in the meat and thus alleviated protein oxidation, allowing higher levels of Ca2+-ATPase activity, sulfhydryl content, and springiness to be maintained. However, HT had a longer duration: 2.95 times that of FWT, resulting in a 9.84% higher cooking loss and a 28.21% higher TVB-N content compared to FWT. MT had the shortest thawing time, yielding the lowest content of TVB-N. However, uneven heating and in some cases overcooking occurred, severely damaging the protein structure, with a concurrent increase in thawing loss, W value, hardness, and shear force. Meanwhile, FWT improved the L*, W* and b* values of octopus meat, enhancing its color and water retention. The myofibrillar protein (MP) concentration was also the highest after FWT, with clearer subunit bands in SDS-PAGE electrophoresis, indicating that less degradation occurred and allowing greater springiness, increased Ca2+-ATPase activity, and a higher sulfhydryl content to be maintained. This suggests that FWT has an inhibitory effect on oxidation, alleviating protein oxidation degradation and preserving the quality of the meat. In conclusion, FWT outperformed the other three thawing methods, effectively minimizing adverse changes during thawing and successfully maintaining the quality of octopus meat.

Contribution of mono- and co-culture of Pseudomonas paralactis, Acinetobacter MN21 and Stenotrophomonas maltophilia to the spoilage of chill-stored lamb

Exploring the contribution of common microorganisms to spoilage is of great significance in inhibiting spoilage in lamb. This work investigated the extent of protein degradation and profile changes of free amino acids (FAAs), free fatty acids (FFAs) and volatile organic compounds (VOCs) in lamb caused by single- and co-culture of the common aerobic spoilage bacteria, P. paralactis, Ac. MN21 and S. maltophilia. Meanwhile, some key VOCs produced by the three bacteria during lamb spoilage were also screened by orthogonal partial least square discriminant analysis and difference value in VOCs content between inoculated groups and sterile group. Lamb inoculated with P. paralactis had the higher total viable counts, pH, total volatile base nitrogen and TCA-soluble peptides than those with the other two bacteria. Some FAAs and FFAs could be uniquely degraded by P. paralactis but not Ac. MN21 and S. maltophilia, such as Arg, Glu, C15:0, C18:0 and C18:1n9t. Co-culture of the three bacteria significantly promoted the overall spoilage, including bacterial growth, proteolysis and lipolysis. Key VOCs produced by P. paralactis were 2, 3-octanedione, those by Ac. MN21 were 1-octanol, octanal, hexanoic acid, 1-pentanol and hexanoic acid methyl ester, and that by S. maltophilia were hexanoic acid. The production of extensive key-VOCs was significantly and negatively correlated with C20:0, C23:0 and C18:ln9t degradation. This study can provide a basis for inhibiting common spoilage bacteria and promoting high-quality processing of fresh lamb.

Effectiveness of a formulation based on Ocimum gratissimum essential oil and cashew gum as inhibitors of quality loss and melanosis in shrimp

In this study, two nanoemulsions were formulated with essential oil (EO) of Ocimum gratissimum with (EON) or without (EOE) cashew gum (CG). Subsequently, inhibition of melanosis and preservation of the quality of shrimp stored for 16 days at 4 ± 0.5 °C were evaluated. A computational approach was performed to predict the system interactions. Dynamic light scattering (DLS) and atomic force microscopy (AFM) were used for nanoparticle analysis. Gas chromatography and flame ionization detector (GC-FID) determined the chemical composition of the EO constituents. Shrimps were evaluated according to melanosis's appearance, psychrotrophic bacteria's count, pH, total volatile basic nitrogen, and thiobarbituric acid reactive substances. EON exhibited a particle size three times smaller than EOE. The shrimp treated with EON showed a more pronounced sensory inhibition of melanosis, which was considered mild by the 16th day. Meanwhile, in the other groups, melanosis was moderate (EOE) or severe (untreated group). Both EON and EOE treatments exhibited inhibition of psychrotrophic bacteria and demonstrated the potential to prevent lipid oxidation, thus extending the shelf life compared to untreated fresh shrimp. EON with cashew gum, seems more promising due to its physicochemical characteristics and superior sensory performance in inhibiting melanosis during shrimp preservation.

Novel insights into the microbial succession and quality variation of golden pompano (Trachinotus ovatus) driven by storage temperatures based on high-throughput sequencing

Changes in the microbial diversity of golden pompano (Trachinotus ovatus) under different temperature conditions, including room temperature (RT, 20 °C), refrigerated temperature (RF, 4 °C), and supercooling preservation temperature (SP, −1 °C), were investigated using high-throughput sequencing (HTS). The results showed that the total viable count (TVC) and total volatile basic nitrogen increased as the storage period was extended. TVC results suggested that the shelf-life of golden pompano was 30 h, 8 days, and 21 days for RT, RF, and SP, respectively. HTS analysis of the samples revealed that the microbial community diversity decreased as the storage time increased, and the decrease was delayed by low temperatures. Significant differences at the genus level of the dominant bacteria were also observed among the groups exposed to different storage conditions. The dominant spoilage bacteria for golden pompano stored at 20 °C was Photobacterium, those of the 4 °C sample were Shewanella, Pseudomonas, and Psychrobacter, and that of the −1 °C sample was Pseudomonas. This study provides a basis for developing strategies to control bacterial growth.

Ammonia-responsive chitosan/polymethacrylamide double network hydrogels with high-stretchability, fatigue resistance and anti-freezing for real-time chicken breast spoilage monitoring

Hydrogels are a promising option for detecting food spoilage in humid conditions, but current indicators are prone to mechanical flaws, posing a concern for packaging systems that require strong mechanical properties. Herein, a double network hydrogel was prepared by polymerizing methacrylamide in a chitosan system with aluminum chloride and glycerol. The resulting hydrogel demonstrated high stretchability (strain >1500 %), notch insensitivity, excellent fatigue resistance, and exceptional anti-freezing capabilities even at −21 °C. When incorporating bromothymol blue (BB) or methyl red (MR), or mixtures of these dyes into the hydrogels as indicators, they exhibited sensitive colorimetric responses to pH and NH3 levels at different temperatures. Hydrogels immobilizing BB to MR ratios of 1:1 and 1:2 displayed clearer and more sensitive color responses when packed into chicken breast, with a sensitivity level of 1.5 ppm of total volatile basic nitrogen (TVB-N). This color response correlated positively with the accumulation of TVB-N on the packaging during storage at both 25 °C and 4 °C, providing sensitive indications of chicken breast deterioration. Overall, the developed hydrogels and indicators demonstrate enhanced performance characteristics, including excellent mechanical strength and highly NH3-sensitive color responses, making significant contributions to the food spoilage detection and intelligent packaging systems field.

Exploring the potential of melittin peptide: Expression, purification, anti-pathogenic properties, and promising applications as a bio-preservative for beef slices

Melittin peptide is a short cationic linear peptide derived from honey bee venom with 26 amino acids, demonstrates potential in controlling and eliminating pathogens. In this study, the genetic sequence of melittin was inserted into the pcDNA3.1+ plasmid and expressed in HEK-293 cells with a His-tag. Purification was done through affinity chromatography and a nickel column. In this study, the antimicrobial effect of melittin in beef sirloin was first investigated, and the minimum inhibitory concentration (MIC) was determined. Then, the effect of combining it with nanochitosan (n-CH) coating, melittin (0.1% and 0.2%v/v), and nanochitosan alone on the physicochemical, microbiological, and sensory properties of beef was examined over a 9-day at 4 °C. At the end of the storage period, the coated samples effectively prevented an increase in pH (5.75 ± 0.06) and showed a significant decrease in the peroxide value (PV) (4.50 ± 0.07). The most favorable result was observed when using the n-CH+0.2%M, which led to malondialdehyde level of 0.44 ± 0.0.05 mg/kg in the amount of thiobarbituric acid reactant. Additionally, the total volatile base nitrogen content in the treatment involving 0.2%M and n-CH+0.2% and 0.1%M was deemed acceptable. Although the total viable count (TVC) of microorganisms in samples covered with melittin increased over time (7.88 ± 0.12 CFU/g), the microbial growth rate in these samples was lower than the control sample (12.10 ± 0.13 CFU/g). Therefore, the use of nanochitosan based edible coatings in combination with melittin in meat packaging reduces microbial population and increases its shelf life.

Inhibitory effects of glutathione peroxidase on microbial spoilage of crayfish (Procambarus clarkii) during refrigerated storage

The variety of enzyme-based biological preservatives is limited. This study evaluated the effects of glutathione peroxidase (GSH-Px) on the quality of crayfish during refrigerated storage by measuring the pH, total volatile basic nitrogen, trimethylamine, and microbial contamination in crayfish muscle simulation system. The results revealed that 0.3% GSH-Px (CK3) not only suppressed the degradation of nitrogenous substances but also decreased the contamination levels of total viable, Enterobacteriaceae, and Pseudomonas counts (P < 0.05). Furthermore, the populations of Lactococcus, Aeromonas, and Massilia differed in the CK3 group compared to the other groups (P < 0.05) at the end of the storage (day 15). Moreover, the principal coordinate analysis showed that the colony composition of CK3 stored for 15 days was similar to that of the control group stored for 10 days. Therefore, GSH-Px exhibits antibacterial activity against Gram-negative bacteria and has good application potential in freshwater aquatic product preservation.