Fish Spoilage Research Articles

Solid- and Vapor-Phase Antibacterial Activities and Mechanisms of Essential Oils Against Fish Spoilage Bacteria

Essential oils (EOs), regarded as secondary metabolites from plants, possess effective antibacterial properties. This study investigates the antibacterial efficacy of seven citrus EOs against six spoilage bacteria: Vibrio parahaemolyticus, V. harveyi, Photobacterium damselae, Shewanella putrefaciens, Carnobacterium divergens, and Lactobacillus pentosus. The antibacterial activity of these EOs was evaluated using solid- and vapor-phase applications. All tested EOs demonstrated effective antibacterial activity at a concentration of 294 μL/L against Gram-negative bacteria. Notably, lemon and orange EOs exhibited dose-dependent inhibition in both solid- and vapor-phase applications, with minimum effective concentrations ranging from 29.4 to 58.8 μL/L. Following treatment with lemon and orange EOs for 6 h at 1/4 minimum inhibitory concentration, leakage of intracellular DNA and proteins was observed, indicating damage to the cell membrane/wall. Proteomic analysis revealed distinct mechanisms: lemon EO impaired bacterial antioxidant defenses, while orange EO disrupted cell division, leading to reduced bacterial viability. These findings provide valuable insights into the potential of different EO application forms in controlling spoilage bacteria.

Colorimetric core/shell ZIF-8/PEO/PDA nanofibers for detection of fish spoilage

Here, colorimetric nanofibers (NFs) based on polydiacetylene (PDA), zeolitic imidazolate framework-8 (ZIF-8), and poly(ethylene) oxide (PEO) were developed. First, the successful synthesis of ZIF-8 was illustrated with structural and morphological analysis. Next, shell/core PDA/PEO/ZIF-8 NFs, namely PPZ0, PPZ5, PPZ15, and PPZ25, were fabricated by coaxial electrospinning at various ZIF-8 concentrations in the core. PPZ5 NFs exhibited a 63 % increase in tensile strength while PPZ25 NFs showed the highest thermal resistance. PPZ15 NFs with the best physicochemical and colorimetric properties were selected to evaluate food spoilage. The change in color difference values of PPZ15 NFs was correlated well with total viable count (TVC) and total volatile basic nitrogenous (TVB-N) in fish samples during chilled storage, reaching TVC to 6.69 log CFU/g, and TVB-N to 33.13 mg N/100 g on day 6. Ultimately, the PPZ15 NFs were successfully utilized to provide a real-time, quantitative assessment of fish freshness.

Antimicrobial efficacy of carvacrol-loaded curdlan hydrogels for enhancing shelf-life in seafood packaging applications

As global warming and the energy crisis receive increasing attention, the development of ecofriendly functional food packaging materials has also garnered significant interest. In this study, curdlan was combined with foaming agents (Cremodan and xanthan) and a crosslinking agent (sodium trimetaphosphate) to form a porous curdlan hydrogel. The material properties of the curdlan hydrogels were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and a thermogravimetric analysis (TGA). Results showed that the 2 % curdlan hydrogel exhibited a high water content (96.2 %), and swelling (89.2 %) and reswelling abilities (89.5 %), with a distinctly porous structure and excellent thermostability. These properties make it suitable for loading carvacrol, resulting in the formation of a carvacrol/curdlan hydrogel. In the results of antimicrobial testing, the carvacrol/curdlan hydrogel showed greater antimicrobial properties against Shewanella putrefaciens (32.3 mm) and Vibrio harveyi (33.1 mm) compared to V. parahaemolyticus (24.5 mm) in inhibition zone test. Noteworthy was the certain degree of antimicrobial ability of the carvacrol/curdlan hydrogel, which continuously exhibited microbial inhibition of the total viable count (TVC) of the no-inoculated and V. parahaemolyticus-inoculated group on sea bass fillets during 6 days of storage. In addition, the carvacrol/curdlan hydrogel inhibited the S. putrefaciens-caused microbial spoilage of fish. However, the continuous antibacterial ability of carvacrol/curdlan hydrogel needs to be improved. In future work, changing the porous size of curdlan hydrogel to control the carvacrol release for elongating the durability and long-term usage will be accomplished to fit the need in functional packaging applications.

Detection of Illicit Conservation Treatments in Sea Bass (Dicentrarchus labrax): Application and Data Integration of NIR Spectrometers.

Global fish and seafood consumption is increasing annually, frequently leading to the emergence of food fraud, mainly related to mislabeling and adulteration like, for example, the use of illicit/unauthorized food additives to mask or delay fish spoilage. Among the available diagnostic tools for control purposes, spectroscopic techniques have often been proposed to identify these kinds of illicit practices in fish and seafood products. The presented study aims to test two cheap and portable near infrared (NIR) spectrometers, a handheld MicroNIR and a pocket-sized SCiO, to uncover use of the illicit food additive Cafodos, a mixture of sodium citrate and hydrogen peroxide used to preserve some fish characteristics (like smell, color, na dtexture). The NIR spectroscopy in combination with chemometric approaches, allowed the successfully classification of (81-100%) samples of sea bass (Dicentrarchus labrax) treated with Cafodos. The study highlights the potential of this technique that, by not requiring pre-treatment of samples with further reagents, is cheaper and safer for the environment. In conclusion, the study confirmed the potential of portable devices for rapid NIR spectroscopy analysis to identify food fraud and ensure consumer safety.

Rancang Bangun Cooler Box Portable Menggunakan Peltier

Technological developments and modern industrial needs increasingly demand high energy efficiency in refrigeration machine operations. In this context, the development of a more efficient cooling machine control system is very necessary. Portable cooler boxes using Thermoelectric Cooler (TEC) technology are an innovation to improve the quality and durability of fish caught by fishermen in Surabaya. This research aims to design and test a cooler box that can maintain low temperatures for a long time. This research method uses experimental methods, a series of tools and uses two test plans, namely: static and dynamic testing. The components used are three Peltier elements supported by a 12V 54A power supply, a 10K NTC temperature sensor, and a passive thermal regulator heatsink with fan. Precision testing data on the comparison sensor (thermodigital), obtained an average value of 3.75%. The error value is still categorized as a safe difference value and the tool works according to its function. Test data shows that the Cooler box can maintain a temperature between 5°C to 10°C, this temperature is ideal for slowing down the process of fish spoilage. Testing was carried out by integrating an Arduino Nano for real-time temperature monitoring which is displayed on the LCD and stored on a MicroSD. Test results show that this cooling system is effective in maintaining a stable temperature under various conditions of use, with an electrical energy consumption of 3111.38Wh per 6 hours.

Double-walled encapsulation of curcumin in starch and cellulose, its characterization and application as a sensing material to monitor food quality

The curcumin was encapsulated within a double-layered complex shell of nano-sized cellulose as the primary layer and the native starch (MDC) or the nano-sized starch (NDC) as the secondary layer to improve its stability, decreasing its release rate, while masking bitterness. The double-walled curcumin capsules were studied for encapsulation efficiency, colour behaviour at different pH and characterization using FTIR, DSC & FESEM. The encapsulation efficiency for NDC and MDC was 97.11 % & 90.46 %. The FTIR showed a shift of peaks to higher wavelength particularly at 1043 cm −1 and most of the curcumin peaks disappeared or had low intensity as enclosed within the layers of the capsules. Further, fish fillets were coated in starch paste containing 20 % double-walled curcumin capsules and the visible colour change was observed during a 7-day storage period at refrigerated conditions that could confirm the spoilage of fish to consumers without opening the package.

Effects of Chemically and Green Synthesized Zinc Oxide Nanoparticles on Shelf Life and Sensory Quality of Minced Fish (Pangasius hypophthalmus).

The purpose of this study was to investigate the effect of chemically and green synthesized zinc oxide nanoparticles (ZnO-NPs) on the shelf life and sensory quality of fish meat. In this study, ZnO-NPs were synthesized by employing the colloidal chemistry (CZnO-NPs) and green synthesis (GZnO-NPs) methods, and they were also characterized to assess their morphology. The synthesized ZnO-NPs, ZnO, and zinc acetate (ZnA) were used for the preservation and fortification of fish (Pangasius hypophthalmus) meat at 20 mg/kg of Zn. In a six-day storage study at 4 °C, the fish samples were evaluated for their sensory attributes (color and odor), physicochemical quality (pH and total volatile base nitrogen), oxidative changes (thiobarbituric acid-reactive substances and peroxide value), and microbial loads at 0, 3, and 6 days of storage. The fortification of raw fish with the synthesized CZnO-NPs produced better sensory attributes (color and odor) and maintained a pH non-conducive to microbial growth throughout the entire storage period compared with the control, ZnO, and ZnA-fortified samples. The GZnO-NPs largely did not provide any added advantage over CZnO-NPs but sometimes responded better than the control, ZnO, and ZnA samples. Oxidative status and total volatile base nitrogen were lower for CZnO-NPs in refrigerated fish compared with the other treatments. The ZnO-NP-fortified fish had the lowest counts of total viable bacteria, coliforms, Staphylococcus spp., and Vibrio spp. Hence, the fortification of fish with synthesized CZnO-NPs is promising as a food additive to reduce microbial spoilage and lipid peroxidation of fish in storage.

Use of Fruit Waste as Natural Dyes in pH-Sensitive Colorimetric Sensors for Tilapia Fillets Quality Decline

Graphical Abstract Highlight Research 1. The use of dragon fruit peel, mangosteen peel and onion peel waste as natural dyes in colorimetric sensors was analyzed in this study. 2. Natural dyes are added to bioplastics with kappa carrageenan polymer, a mixture of corn starch and kappa carrageenan, and corn starch to determine the characteristics of the best bioplastic to be used as a colorimetry sensor. 3. The quality of the fish fillet compared to the color changes in colorimetry sensor was analysed in this study. 4. Mixture of kappa carrageenan and corn starch as bioplastic with casting method was analyzed in this study. Abstract Tilapia fillet aimed to prolonging shelf life, may still experience quality deterioration posing food safety risks. Colorimetric pH indicators offer a simple and affordable solution to the food industry to evaluating fish spoilage. Natural dyes reduce potential health risks associated with synthetic dyes. Anthocyanin sources haven’t been explored like dragon fruit rind, mangosteen rind, and red onion skin serve as real time quality and safety assessment tools for consumers. This study explores the potential of anthocyanin extracted from dragon fruit rind, mangosteen rind, and red onion skin as colorimetric sensors for evaluating the quality and safety of tilapia fillets. The anthocyanin-based sensors developed using kappa carrageenan and corn starch polymers to achieve sustainability fisheries program and were characterized according to the Japanese Industrial Standard for bioplastics. The results show that anthocyanin from dragon fruit skin exhibited the best color change in response to pH changes in the tilapia fillet, indicating its potential as a reliable indicator of spoilage. This research highlights the feasibility of using natural dyes as colorimetric sensors, reducing the risk of health hazards associated with synthetic dyes. This study also shows that different polymers give different characteristic of bioplastic. Carrageenan bioplastic shows best thickness values of 0,118 mm; Carrageenan and corn starch bioplastics shows best tensile strength values of 20,62 MPa; Carrageenan bioplastic shows best elongation values of 254%; and All polymers shows the same biodegradation rate values of 14,29%. Further studies are needed to explore other natural dyes and optimize the polymers for optimal bioplastic characteristics.

Development and characterization of a double-layer smart packaging system consisting of polyvinyl alcohol electrospun nanofibers and gelatin film for fish fillet

This study aimed to develop a double-layer film composed of an intelligent, gelatin-based film integrated with active polyvinyl alcohol electrospun nanofibers (PVANFs). Eggplant skin extract (ESE), a colorimetric indicator, was incorporated into the gelatin-based film at varying concentrations ranging from 0 % to 8 % w/w. The gelatin film containing 8 % ESE was identified as the optimal formulation based on its superior color indication, water barrier, and mechanical properties. Savory essential oil (SEO)-loaded PVANFs were electrospun onto the optimized gelatin film to fabricate the double-layer film. Analysis of the chemical and crystalline structures and the double-layer film's thermal properties confirmed the gelatin film's physical integration with PVANFs. Morphological examination revealed a smooth surface on the film and a uniform fibrillar structure within the PVANFs. Furthermore, the developed double-layer film effectively detected spoilage in trout fish while controlling pH, oxidation, and microbial changes during storage.

Acetic and citric acids effect the type II secretion system and decrease the metabolic activities of salmon spoilage-related Rahnella aquatilis KM05

Rahnella aquatilis causes seafoods to spoil by metabolizing sulfur-containing amino acids and/or proteins, producing H2S in products. The type II secretion system (T2SS) regulates the transport of proteases from the cytoplasm to the surrounding environment and promotes bacterial growth at low temperatures. To prevent premature fish spoilage, new solutions for inhibiting the T2SS of bacteria should be researched. In this study, global transcriptome sequencing was used to analyze the spoilage properties of R. aquatilis KM05. Two of the mapped genes/coding sequences (CDSs) were matched to the T2SS, namely, qspF and gspE, and four of the genes/CDSs, namely, ftsH, rseP, ptrA and pepN, were matched to metalloproteases or peptidases in R. aquatilis KM05. Subinhibitory concentrations of citric (18 µM) and acetic (41 µM) acids caused downregulation of T2SS-related genes (range from − 1.0 to -4.5) and genes involved in the proteolytic activities of bacteria (range from − 0.5 to -4.0). The proteolytic activities of R. aquatilis KM05 in vitro were reduced by an average of 40%. The in situ experiments showed the antimicrobial properties of citric and acetic acids against R. aquatilis KM05; the addition of an acidulant to salmon fillets limited microbial growth. Citric and acetic acids extend the shelf life of fish-based products and prevent food waste.

FABRICATION OF CU MODIFIED NANO CHITOSAN WITH BROMOCRESOL GREEN AS INTELLIGENT PACKAGING

In recent advancements, the development of smart packaging systems for food has focused on utilizing composite materials to enhance functionality and sustainability. In this study, the composite film from chitosan and PVA was combined at various concentrations (ranging from 0.1% to 0.5%) with the addition of Cu(500mM) and 1% STPP at a 5:1 ratio. An additional indicator was included to detect fish spoilage. The synthesized chitosan material was then blended with PVA to form a composite film. The film was characterized using FTIR, which confirmed the presence of fingerprint vibrations indicating the cross-linking between TPP, chitosan, and Cu. These bonds were observed at wave numbers 1118 cm-1, 879 cm-1, and 603 cm-1. SEM analysis revealed that the film had particle sizes ranging from 865 nm to 1.49 μm. XRD analysis showed distinctive features of pure chitosan and chitosan composite. The composite film K-05 produced an amorphous structure, indicating decreased crystallinity due to the addition of STPP and Cu. The water uptake test demonstrated that an increased concentration of chitosan in the composite led to higher absorption and solubility effects. Conversely, the addition of chitosan in the film decreased water vapor permeability as determined by the water vapor permeability test. The antibacterial test conducted on all films (concentration of 0.1% to 0.5%) indicated that the films K-01 and K-02 exhibited the best zone of inhibition against Escherichia coli. This study sucessfully synthesized and characterized a smart packaging film composed of polyvinyl alcohol (PVA), chitosan, copper (Cu), and bromocresol green (BCG) indicator, designed to monitor food freshness through visual pH changes and inhibition of microbial growth.

DESIGN OF LPG GAS OVEN TECHNOLOGY AS AN EFFORT TO INCREASE SALTED FISH PRODUCTION IN SUMEDANG, INDONESIA

Processing salted fish is one of the traditional ways of preserving fish carried out by the community when the fish harvest is abundant. However, traditional processing of salted fish is not always hygienic and can cause health problems if not done properly. In this context, Liquefied petroleum gas (LPG) gas ovens are a technology that can help increase the productivity of hygienic processing of salted fish. LPG gas oven is a drying oven that uses gas energy to dry fish. By using an LPG gas oven, drying fish can be done quickly and hygienically, thereby reducing fish spoilage and damage. This research succeeded in designing and assembling an LPG gas oven and providing technical training to the community in its use. This will help increase peoples knowledge and skills in using LPG gas ovens to dry and make salted fish hygienically. Using LPG gas ovens as a salted fish processing technology can be the best solution to overcome excess catches that have not been sold on the market and produce more hygienic salted fish production. Thus, LPG gas ovens can help increase the productivity and welfare of the community around the Jatigede Dam, Sumedang Regency, who depend on the fish catch from Lake Jatigede as their source of livelihood. Another advantage of processing salted fish using an LPG gas oven is that it overcomes the weakness of traditional drying, namely when it rains suddenly, causing the humidity in the fish to increase produces salted fish that is more hygienic, free from dust, and free from flies landing which will produce eggs, which is the cause of salted fish worming and becoming rotten and wasted and overcoming the storage process, where some traders actually store it in the refrigerator, which is limited in nature and in ultimately affects changes in the aroma and taste of the product after being processed/re-dried.

Real-time tracking of fish quality using a cellulose filter paper colorimetric indicator incorporated with prickly pear fruit betacyanins

In the present work, a freshness indicator was developed by immobilizing extracted betacyanins from prickly pear fruit (PFB) onto cellulose filter paper to visually determine fish spoilage. Various properties of the prepared indicator, including color stability, moisture uptake, sensivity to hydrogen sulfide (H2S) gas and pH changes, and chemical analysis were studied. The PFB-based indicator exhibited good color stability at various temperatures and times, with no significan color changes observed during storage at 25, 4, and −18 °C for 8 days. The moisture absorption of the indicator based on PFB was lower than that of cellulose paper, which is crucial for colorimetric indicators. Basic nitrogen and sulfur compounds are the main volatile compounds produced during fish spoilage. The results of the present study showed that both total volatile basic nitrogen (TVB-N) and H2S gas produced during fish spoilage contributed to the color changes of betacyanin-based colorimetric indicators. The prepared freshness indicators were pH-sensitive, with significant color changes due to TVB-N and H2S production during fish storage. A significant correlation was observed between fish quality (pH, TVB-N and total viable count) and the visible color changes of the indicators. The color of the designed indicator shifted from dark pink to pale pink/white during fish storage. These prepared freshness indicators were inexpensive, easy to use, and non-toxic, making them suitable for assessing the quality and shelf life of fish fillets.

Visual tracking of real-time freshness of fish using an agar hydrogel colorimetric indicator containing CuNPs/NCQDs

A simple, selective, and affordable dual fluorescence-colorimetric indicator for hydrogen sulfide was developed based on a complex of copper nanoparticles and N-doped carbon quantum dots (CuNPs/NCQDs). Real-time and visual freshness tracking of fish was done using a colorimetric indicator by incorporating CuNPs/NCQDs into agar hydrogel (AH-CuNPs/NCQDs). The fluorescence response of the CuNPs/NCQDs solution is quenched upon exposure to H2S. The field-emission scanning electron microscopy image of the AH-CuNPs/NCQDs film revealed a unified structure. The prepared indicator exhibited a good and irreversible response to H2S, with a LOD of 91.36 and a LOQ of 276.86 μM, based on the localized surface plasmon resonance (LSPR) mechanism. The X-ray photoelectron spectrometer and Fourier transform infrared spectrometer results confirmed the formation of a CuS bond in the colorimetric indicator exposed to fish spoilage. The prepared indicator demonstrated good stability and remained unaffected by pH or other volatile compounds. Notably, there was a strong correlation between ΔΕ and fish freshness parameters (pH, TV-BN, and TVC). Light green, pale yellow, and dark yellow colors, respectively, indicated freshness, semi-freshness, and spoilage of fish during storage in the refrigerator. Overall, the prepared indicator can be effectively used for detecting spoilage in meat products as a highly sensitive freshness indicator.

Chemical components and antibacterial activity of huajiao essential oils and its inhibitory mechanism against Pseudomonas putida

Pseudomonas putida is known to cause spoilage in edible mushrooms and fish. Huajiao essential oil (HEO), extracted from the pericarp of Huajiao, exhibits broad-range antimicrobial properties. This study investigated the chemical composition of HEO and its inhibitory effects and potential antimicrobial mechanism against P. putida. The major components of HEO were found to be linalool (33.65%), d-limonene (15.17%), and sabinene (14.22%). The minimum inhibitory concentration of HEO against P. putida was determined to be 10 mg/mL. Treatment with HEO resulted in intracellular substance leakage, compromised cell membrane integrity, increased membrane fluidity, and reduced cell viability. HEO also led to the accumulation of intracellular reactive oxygen species and inhibited metabolic enzyme activity. Additionally, electron microscopy revealed significant disruption of cell morphology. Molecular docking analysis suggested that linalool, d-limonene, and sabinene may inhibit genetic material replication and expression. These findings indicate that HEO can target multiple pathways to inhibit P. putida, making it a potential natural drug candidate against this bacterium.

The effectiveness of garlic extracts on biogenic amine formation by foodborne pathogens and fish spoilage bacteria

SummaryImpacts of aqueous and ethanolic extracts of garlic were investigated in suppressing bacterial growth and biogenic amine (BA) formation by selected foodborne pathogens (Candida albicans, Salmonella paratyphi A, Escherichia coli and Staphylococcus aureus) and fish spoilage bacteria (Enterococcus faecalis, Photobacterium damselae and Pseudomonas luteola). The spread‐plate method was used to monitor bacterial growth in histidine decarboxylase broth (HDB), whereas the rapid high‐performance liquid chromatographic (HPLC) method was used for BA analysis. Bacterial growth and their ammonia and BA production were monitored using HDB. The results showed that bacterial growth on HDB was in the range from 9.13, for P. luteola, to 9.54 log CFU (colony‐forming units) mL−1, for S. aureus and C. albicans. The presence of garlic extracts in HDB resulted considerably in lowering bacterial growth and BA formation (P < 0.05). The highest inhibitory activities of ethanolic and water garlic extracts were obtained for Gram‐positive S. aureus with 1.4 and 1.5 logarithmic reduction on bacterial growth, followed by Gram‐negative Salmonella Paratyphi A and E. coli. Application of garlic extracts, mainly ethanolic ones, showed a significant inhibitory effect on bacterial ammonia production, with 4‐100‐fold lower ammonia accumulation (P < 0.05). Bacteria produced all tested BAs, mainly dopamine, agmatine and tryptamine. The highest levels of histamine and tyramine (61.99 and 36.45 mg L−1) were produced by S. aureus. In the presence of aqueous or ethanolic garlic extracts, putrescine production by E. faecalis was around 110‐fold lower than that of the control group. Results revealed that both garlic extracts are potent antimicrobials that can control the growth of foodborne pathogens and their harmful BA formation.

Inter-facility characterization of bacteria in seafood processing plants: Exploring potential reservoirs of spoilage organisms and the resistome

A study was conducted in fish processing facilities to investigate the microbial composition, microbial metabolic potential, and distribution of antibiotic resistance genes. Whole metagenomic sequencing was used to analyze microbial communities from different processing rooms, operators and fish products. Taxonomic analyses identified the genera Pseudomonas and Psychrobacter as the most prevalent bacteria. A Principal Component Analysis revealed a distinct separation between fish product and environmental samples, as well as differences between fish product samples from companies processing either Gadidae or Salmonidae fish. Some particular bacterial genera and species were associated with specific processing rooms and operators. Metabolic analysis of metagenome assembled genomes demonstrated variations in microbiota metabolic profiles of microbiota across rooms and fish products. The study also examined the presence of antibiotic-resistance genes in fish processing environments, contributing to the understanding of microbial dynamics, metabolic potential, and implications for fish spoilage.

PH-indicator based on delignified jute fiber and red cabbage anthocyanins for monitoring fish spoilage using a smartphone application

Halochromic materials that show visible color changes in response to changes in pH are suitable for the real-time monitoring of fish spoilage. In this study, an easy-to-use, simple, inexpensive, and non-toxic fish freshness indicator was fabricated by combining delignified jute (Corchorus olitorius) fibers and anthocyanins (halochromic materials) from red cabbage (DFA: Delignified jute fibers incorporated with anthocyanins). A single-step decolorization/delignification using solar irradiation along with NaOH and H2O2 treatment was used for modifying the jute fibers. This method helps to overcome the self-color, mitigates the lack of affinity of jute fibers towards anthocyanins and preserves the lignin so that the strength of the fiber is not impacted. A smartphone-based color analysis was used for real-time fish quality monitoring using DFA. To the best of our knowledge, there are no reports on the use of jute fibers as substrates to incorporate anthocyanins for food spoilage monitoring. The indicator displayed an observable color response to the pH and varying concentrations of amine compounds. During the storage of fish (mackerel), the colorimetric indicator showed a visible color change from pink (for fresh fish) to blue (for spoiling fish) and then to green (for spoiled fish), corresponding to changes in pH and total volatile basic nitrogen. To offer a straightforward quantitative assessment of color changes, we utilized the freely available Android application Color Grab to measure the color using RGB and L*, a*, and b* indices. The DFA indicator providing naked-eye analysis has the potential to be an effective tool for real-time monitoring of on-site food spoilage by non-specialized personnel in resource-limited areas.

Effect of Antigonon leptopus extract in corn starch-glycerol based film as colourimetric indicator film for monitoring fish freshness

A colourimetric indicator can be used to test the freshness of fish in a rapid, straightforward and non-destructive manner. Anthocyanin, a natural dye found in Antigonon leptopus flowers, has a sensitive colour reactivity to a wide range of pH levels and can be made into colourimetric indicator films on a laboratory scale, making it a viable replacement for artificial dyes. The study's purpose was to see how the concentration of A. leptopus extract affected the colourimetric assessment of fish freshness. Ethanol was used to extract anthocyanin from A. leptopus. FTIR and pHrespond spectroscopies were used to characterise the extracts. Colourimetric indicator films were developed to assess fish freshness by incorporating A. leptopus extract into a corn starch-glycerol matrix via the solution casting method, with concentrations of 10%, 30% and 50%, respectively. The effect of A. leptopus extract on visual aspects, thickness, morphology, FTIR spectra, UV-Vis spectra and colour responses was analysed. Microbial analysis, TVB-N contents, firmness, and pH of the fish samples were analysed after storage. The colour of the original films became darker as the extracted content increased. There was no significant (p>0.05) effect of A. leptopus extract on film thickness. SEM micrographs revealed that the composite films had homogeneous and whitish granules on the surface and that increasing the A. leptopus extract concentration caused the films to become rougher. FTIR and UV-Vis spectroscopies showed successful binding between A. leptopus extracts and corn starch-glycerol film. With increasing pH, the colour change of the films exposed to pH = 3-11 solutions was no significant difference due to improper storage. An increase in the microbial population, TVB-N content and pH was observed over the storage period as a result of fish deterioration. Colour changes were also identified in the film which became darker. Overall, colourimetric indicator film with 50% A. leptopus extract was found to be the optimal formulation since it had the highest values in ∆E* during progressive spoilage of fish.

Mechanisms underlying the potent antimicrobial effects of plasma-activated seawater (PASW) on fish spoilage bacterium Shewanella putrefaciens

Plasma-activated seawater (PASW) presents a promising approach for marine fish preservation, yet its antimicrobial efficacy and mechanisms remain unclear. This study found that PASW exhibits superior bactericidal properties against the fish spoilage bacterium Shewanella putrefaciens compared to plasma-activated water (PAW), and increased effectiveness in preserving fish fillets. To clarify the mechanisms, a detailed investigation was conducted, including the generation of reactive oxygen/nitrogen species (ROS/RNS) and active halogen species in PASW, and their antimicrobial efficacy. Findings showed greater nitrite and hydrogen peroxide production in PASW relative to PAW, as well as the conversion of chloride/bromide ions into active species, which collectively enhanced PASW's antimicrobial activity. The synergistic action of ROS/RNS and active chlorine/bromine species in PASW promoted the generation of intracellular ROS, causing increased membrane damage, redox imbalance, and consequently higher bacterial mortality. This study enhances our understanding of PASW's antimicrobial effects and highlights its potential applications in the seafood industry.