Shelf-life extension of herring (Clupea harengus) using in-package atmospheric plasma technology

Atmospheric cold plasma is a green and emerging technology, highly interesting to the food industry for its application. Dielectric Barrier Discharges (DBD) can generate atmospheric cold plasma inside sealed packages filled with air through the use of high voltages. This study investigated the use of a large gap DBD design to generate a plasma discharge within the headspace of packaged herring fillets, and its effects on microbiological and quality markers of the fish stored for 11 days at 4 °C. DBD plasma treatment conditions were 70 kV or 80 kV for 5 min treatment time.Results showed that the microbial load (total aerobic mesophilic, total aerobic psychrotrophics, Pseudomonas, lactic acid bacteria and Enterobacteriaceae) were significantly (p < 0.05) lower in the treated samples compared to the control samples. However, samples exposed to the lowest applied voltage better retained key quality factors (lower oxidation and less colour modification). DBD-treatment caused a reduction in trapped water in the myofibrillar network (T21), identified using low-field nuclear magnetic resonance of protons (¹H LF NMR).The results indicate that in-package plasma treatment could be employed as an effective treatment for reducing spoilage bacteria in fish.Industrial relevanceDielectric Barrier Discharge (DBD) was evaluated as a treatment for highly perishable fish products. DBD's is a safety and lower costs alternative for processing industry. DBD has been scarcely tested on fish; this work showed results on quality and shelf-life of a highly perishable fish species, which might serve as reference for processing optimisation of fish products minimally processed by DBD.     

Inactivation effect of dielectric barrier discharge plasma against foodborne pathogens on the surfaces of different packaging materials

The usefulness of dielectric barrier discharge (DBD) plasma for surface disinfection of the common food packaging materials, namely glass, polyethylene, polypropylene, nylon, and paper foil was evaluated. DBD plasma was generated by applying a pulsed DC voltage of 10 kV and at a power of 208 W. The separation distance between the electrodes was 2.65 mm. On exposure of food pathogens-loaded packaging materials to the plasma, > 4 log/cm² reduction (99.99%) in viable cell counts of Escherichia coli O157:H7 was observed in 10 min. The other two tested pathogen strains, Salmonella typhimurium and Staphylococcus aureus, were inactivated in the range 3.0–3.5 log/cm². The inactivation pattern of the pathogens fitted well to the log-linear and tail model. Compared to unexposed packaging materials, no significant (p > 0.05) changes in the surface temperatures, optical characteristics, tensile strengths, and strain-induced deformation were observed for the DBD plasma-exposed materials. Therefore, the DBD plasma can be used to disinfect surfaces of different food packaging materials harboring moderate levels of bacterial contaminants without adversely affecting their physicomechanical properties.Industrial relevanceTraditionally, dry heat, steam, UV light and chemicals like ethylene oxide and hydrogen peroxide have been used as surface sterilants and disinfectants for packaging materials in the food industry. However, certain limitations have motivated the search for new approaches. Cold plasma technology is an emerging, green process for surface sterilization. The DBD plasma was found to be effective in reducing the bacterial food pathogens on different food packaging materials. As the technology is simple and scalable, it can be readily applied industrially.     

Cold plasma treatment for fresh-cut melon stabilization

The aim of this study was to evaluate the effect of gas plasma treatment on fresh-cut melon stability during controlled storage. Plasma treatments of 15 + 15 and 30 + 30 min were conducted on fresh cut melon using a dielectric barrier discharge (DBD) generator. Samples were packed and stored for 4 days at 10 °C and evaluated for qualitative, metabolic and microbiological indexes. Qualitative parameters of fresh-cut melon (titratable acidity, soluble solid content, dry matter, colour, texture) were only weakly affected by plasma treatment. Peroxidase (POD) and pectin methylesterase (PME) activities were slightly inhibited by the treatment up to respectively about 17 and 7%. Tissue metabolic heat production decreased proportionally to the treatment duration, while a partial conversion to anaerobic metabolism was observed. Microbial results showed that a significant increase in microbial shelf-life was achieved following the 15 + 15 min plasma treatment due to a delayed growth of spoilage mesophilic and psychrotrophic microflora.Industrial relevanceThe demand for fresh-cut products characterized by high qualitative and nutritional values and an acceptable shelf-life has promoted the research for non-thermal treatments.Fresh-cut melon is considered to be highly perishable and potentially hazardous food because it can support the growth of spoilage microflora and several pathogens.Cold plasma has shown its potentiality as an antimicrobial treatment and has been tested on different food products, but the impact on product quality and metabolism is still scarcely known.The results obtained in this study contributed to deepen the knowledge on the effect of plasma treatment on microbial, qualitative and metabolic aspects of fresh-cut melon.     

Physicochemical characterization of plasma-treated sodium caseinate film

Sodium caseinate films were physico-chemically characterized for the effects of atmospheric dielectric barrier discharge (DBD) plasma as function of applied voltage and treatment times. Surface roughness of plasma treated films at both 60 and 70 kV was found to be significantly (p ≤ 0.05) higher than the control. Glass transition temperature of all the films after plasma treatment was found to be less than the control film. The increase in the O/C atomic ratio shows the formation of new oxygen-containing groups on the film surface. XRD and FT-IR spectra suggest a disruption in the inter-helical structure without any change in the helical configuration of the protein molecules. Increase in the hydrophilicity of the sodium caseinate film was also observed after DBD plasma, but no significant (p > 0.05) increase in the WVTR and OTR was noticed, showing the suitability of the film for novel processes such as in-package plasma decontamination of food.     

Rapid and real-time prediction of lactic acid bacteria (LAB) in farmed salmon flesh using near-infrared (NIR) hyperspectral imaging combined with chemometric analysis

In this study, hyperspectral imaging working in near-infrared (NIR) region (900–1700 nm) was applied to evaluate surface lactic acid bacteria (LAB) spoilage of farmed salmon flesh during cold storage. Hyperspectral images of salmon samples were acquired at different storage times. Spectral information within regions of interest (ROIs) of images were extracted to relate to reference LAB values measured by standard pour plate method. Least-squares support vector machine (LS-SVM) algorithm was used to calibrate the full NIR range spectral data, resulting in regression coefficients of prediction (R_P) of 0.929 with root mean square error of prediction (RMSEP) of 0.515. Competitive adaptive reweighted sampling (CARS) algorithm was employed to reduce the spectral redundancy and identify the most informative wavelengths (MIWs) most related with LAB prediction across the whole wavelength range. Eight individual MIWs at 1155 nm, 1255 nm, 1373 nm, 1376 nm, 1436 nm, 1641 nm, 1665 nm and 1689 nm were finally selected from the full 239 wavelengths. Based on the selected MIWs, a new optimised model named CARS-LS-SVM was established, leading to R_P of 0.925 with RMSEP of 0.531. At last, the CARS-LS-SVM model was transferred to each pixel of hyperspectral images of samples and colour maps were generated for visualising the LAB spoilage process in salmon flesh. The overall results indicated that NIR hyperspectral imaging is very potential and could be used as a rapid, non-destructive and efficient technique for LAB evaluation in salmon flesh.     

Effect of gutting on microbiological,chemical, and sensory properties of aquacultured sea bass (Dicentrarchus labrax) stored in ice

The effect of gutting on microbiological, chemical, and sensory properties of aqua-cultured sea bass (Dicentrarchus labrax) stored in ice was studied. Pseudomonads and H₂S-producing bacteria (including Shewanella putrefaciens) were the dominant bacteria at the end of the 16-day storage period in ice for both whole ungutted and gutted sea bass. Brochothrix thermosphacta and Enterobacteriaceae were also found in the spoilage microflora of ungutted and gutted sea bass but their counts were always less than those of Pseudomonads and H₂S-producing bacteria. Bacterial counts of whole ungutted sea bass were always higher than those obtained for gutted sea bass samples. Mesophilic counts for gutted and ungutted fish exceeded 7 log cfu g⁻¹ after 9 and 15 days of ice storage, respectively. Of the chemical indicators of spoilage, TMA values of ungutted sea bass increased very slowly whereas for gutted samples higher values were obtained reaching a final value of 0.73 and 4.39 mg N 100 g⁻¹, respectively (day 16). TVB-N values showed no significant increase for whole ungutted sea bass during storage reaching a value of 27.7 mg N 100 g⁻¹ (day 16) whereas for gutted fish 36.9 mg N 100 g⁻¹ was recorded. TBA values remained low for ungutted sea bass samples until day 16 of storage, whereas for gutted fish were variable. Of the chemical indices used, none proved useful means of monitoring early ungutted and gutted sea bass freshness in ice. Sensory assessment using the EC freshness scale gave a grade E for up to 5 days for the ungutted sea bass, a grade A for a further 2 days and a grade B for an additional 4 days, after which sea bass was graded as C (unfit). Gutted sea bass was given a grade E for up to 3 days, a grade A for the 4–7th days, and a grade B for the 8–10th days of storage, whereas on day 11 it was graded as unfit. Acceptability scores for odor, taste and texture of cooked ungutted and gutted sea bass decreased with time of storage. Results of this study indicate that the shelf-life of whole ungutted and gutted sea bass stored in ice as determined by the overall acceptability sensory scores and microbiological data is 13 and 8 days, respectively.     

Preservation of salted,vacuum-packaged,refrigerated sea bream (Sparus aurata) fillets by irradiation: microbiological,chemical and sensory attributes

The effect of gamma irradiation (1 and 3 kGy) on the shelf-life of salted, vacuum-packaged sea bream (Sparus aurata) fillets stored under refrigeration was studied by monitoring the microbiological, chemical and organoleptic changes occurring in fish samples. Non-irradiated, salted, vacuum-packaged fish served as control samples. Irradiation affected populations of bacteria, namely, Pseudomonas spp., H₂S-producing bacteria, Brochothrix thermosphacta, Enterobacteriaceae and lactic acid bacteria. The effect was more pronounced at the higher dose (3 kGy) applied. Of the chemical indicators of spoilage, trimethylamine (TMA) values of non-irradiated, salted sea bream increased slowly to 8.87 mg N (100 g)⁻¹ flesh (whereas for irradiated, salted samples significantly lower values were obtained, reaching a final TMA value of 6.17 and 4.52 mg N (100 g)⁻¹ flesh at 1 and 3 kGy, respectively (day 42). Total volatile base nitrogen values increased slowly attaining a value of 60.52 mg N (100 g)⁻¹ for non-irradiated, salted sea bream during refrigerated storage whereas for irradiated fish, lower values of 48.13 and 37.21 mg N (100 g)⁻¹ muscle were recorded at 1 and 3 kGy, respectively (day 42). Thiobarbituric acid values for irradiated, salted sea bream samples were higher than respective non-irradiated (salted) fish, and increased slowly until day 28 of storage reaching final values of 1.01 (non-irradiated, salted), 2.15 (1 kGy) and 3.26 mg malonaldehyde kg⁻¹ flesh (3 kGy), respectively (day 42). Sensory evaluation (taste) showed a reasonably good correlation with bacterial populations. On the basis of sensorial evaluation, a shelf-life of 27–28 days was obtained for vacuum-packaged, salted sea bream irradiated at 1 or 3 kGy, compared to a shelf-life of 14–15 days for the non-irradiated, salted sample.     

Effect of high pressure (HP) on the quality and shelf life of red mullet (Mullus surmelutus)

The effect of different temperature/time/pressure high hydrostatic pressure (HP) treatment on the quality and shelf life of red mullet were studied. Different high pressure treatments (at 3, 7, 15 and 25 °C, 5 to 10 min and 220, 250 and 330 MPa) were tested to establish the best processing conditions for the quality of red mullet. The effect of the process on the quality of the sample was examined by colour, Trimethylamine nitrogen (TMA-N) and Thiobarbituric acid number (TBA) analysis. Based on the results of the parameters, the best combinations of HP treatments were determined as 220 MPa/5 min/25 °C and 330 MPa/5 min/3 °C for red mullet. The effects of this combination treatment on sensory, chemical and microbiological properties of red mullet stored at 4 °C were studied. The results obtained from this study showed that the shelf life of untreated and HP treated stored at 4 °C, as determined by overall acceptability of sensory and microbiological data, are 12 days for untreated red mullet and 14 days for treated red mullet at 220 MPa for 5 min at 25 °C and 15 days for treated red mullet at 330 MPa for 5 min at 3 °C.Industrial relevanceFresh fish have short shelf life. HP treatment has shown to be an effective method to control pathogen and spoilage microorganisms in fish and fish products. However, high pressure treatment can promote colour and oxidation changes that could modify their sensory characteristics. The main objective of the first part of this study was to detect the best combination among the applied pressure (220, 250 and 330 MPa), temperature (3, 7, 15 and 25 °C) and time (5 and 10 min) combinations. The treatment ranges were chosen according to the unchanging colour, lower TBA value and TMA stability by HP and considering the economical aspects of HP processing. In the second part of the study, HP was applied on the selected samples and a shelf-life study was performed by measuring the changes in the quality parameters, of the samples throughout their storage. The storage conditions were set so as to achieve refrigeration handling (4 °C). Shelf-life estimation was performed according to the data obtained. HP (at 220 MPa for 5 min at 25 °C and at 330 MPa for 5 min at 3 °C) treatment is the most effective treatment for shelf-life extension as compared to non-treated red mullet.     

The potential of atmospheric air cold plasma for control of bacterial contaminants relevant to cereal grain production

The aim of this work was to investigate the efficacy of dielectric barrier discharge atmospheric cold plasma (DBD ACP) against bacteria associated with grains quality and safety. ACP inactivation efficacy was tested against biofilms formed by different strains of E. coli, Bacillus and Lactobacillus in grain model media and against B. atrophaeus endospores either in grain media or attached on abiotic surfaces. Effects were dependent on bacterial strain, media composition and mode of ACP exposure. ACP treatment for 5 min reduced E. coli spp., B. subtilis and Lactobacillus spp. biofilms by > 3 log₁₀, whereas insignificant reductions were achieved for B. atrophaeus. ACP treatment of 5–20 min reduced B. atrophaeus spores in liquids by > 5 log₁₀. Treatment for 30 min reduced spores on hydrophobic surface by > 6 log₁₀, whereas maximum of 4.4 log reductions were achieved with spores attached to hydrophilic surface. Microscopy demonstrated that ACP caused significant damage to spores. In package ACP treatment has potential to inactivate grain contaminants in the form of biofilms, as well as spores and vegetative cells.Industrial relevanceThis study demonstrates that ACP technology is a promising tool for effective bio-decontamination which offers a wide range of possible applications including inactivation of microorganisms on cereal grains. However, due to the nature of the microbial contamination of grains and complex grain structures it may be necessary to optimise the potential for surface inactivation at several stages of grain processing and storage to enhance ACP efficacy against bacterial endospores.     

Effect of high voltage electrostatic field thawing on the lipid oxidation of frozen tuna fish (Thunnus albacares)

Changes in the quality, such as color, and TBA values are compared between tuna fish (Thunnus albacares) cuts thawed by high voltage electrostatic field (HVEF) and those thawed conventionally as control. The tuna cubes (2 × 4 × 4 cm³) are thawed under HVEF at three different voltages from the corona starting to the breakdown voltage one with electrode gaps of 3, 4.5, and 6 cm. The control specimens are subjected to no HVEF but thawed conventionally at 20 °C. The results show that thawing under HVEF increases significantly the TBA and ΔE values of the frozen tuna fish cubes (p < 0.05). Tuna fish cubes were observed to oxidize faster at high electrostatic field intensities than at lower ones. Among the two models considered in this study (zero-order and first-order), the first yielded excellent fits for the TBA value experiment.Industrial relevanceThe degree of fish oxidation due to application of a high-voltage electrostatic field method for fish thawing is an important issue that needs serious attention. Application of HVEF thawing is found to lack the potential to extend the freshness of thawed tuna fish due to lipid oxidation and color changes.     

Atmospheric cold plasma dissipation efficiency of agrochemicals on blueberries

Cold plasma has emerged as a potential bio-decontamination technology for microbial and chemical risks associated with food products such as fruits and vegetables. This study investigated the efficacy of cold plasma treatment for the degradation of pesticides (boscalid and Imidacloprid) on blueberries in tandem with the need to retain critical quality attributes of a fresh high value berry product post treatment. An in-package high voltage dielectric barrier discharge plasma reactor was employed for this study. The degradation efficacy of pesticides after 80 kV and 5 min of cold plasma treatment were found to be 80.18% for boscalid and 75.62% for Imidacloprid. Total phenol and flavonoid contents of blueberries increased significantly for 1 min treated samples for all applied voltages. However, plasma treatment significantly decreased the ascorbic acid at longer plasma doses. There was no significant effect on physical parameters such as color while acceptable changes were observed in blueberry firmness. This study demonstrates effective chemical decontamination of blueberries whilst maintaining critical nutritional and physical quality parameters, offering an alternative process for quality retention of processing sensitive high value berry products.     

Cold atmospheric pressure plasma processing of insect flour from Tenebrio molitor: Impact on microbial load and quality attributes in comparison to dry heat treatment

In this study, the applicability of semi-direct cold atmospheric pressure plasma (CAPP) during postharvest processing of Tenebrio molitor flour is investigated. Besides analyzing the decontamination efficacy, plasma-induced impact on techno-functionality, protein solubility, composition and structure was determined and compared to heat induced effects.Following CAPP treatment, the total microbial load of the Tenebrio flour of 7.72 log₁₀ cfu/g was reduced to 7.10 (1 min), 6.72 (2.5 min), 5.79 (5 min), 5.19 (7.5 min), 5.21 (10 min) and 4.73 (15 min) log₁₀ cfu/g. With increasing exposure to CAPP, protein solubility at pH 4 almost linearly decreased to a minimum of 54%. Water binding capacity decreased from 0.79 to 0.64 g_water/g whereas oil binding capacity increased from 0.59 to 0.66 g_oil/g. Gel electrophoresis revealed a decrease of all protein fractions at pH 4 whereas at pH 10 the band pattern significantly shifted to protein fractions with higher molecular weights.Industrial relevanceEdible insects are rich in valuable protein, fat, fibre, minerals and micronutrients. Although a wide range of species represent a valuable alternative protein source that could contribute to food and feed security, they are industrially hardly exploited. The tailored application of proper processing technologies could lead to novel insect-based high-protein food and feed products with unique functional properties supporting the increase in acceptability among potential consumers. Current research concentrates on developing processing chains including innovative nonthermal approaches. Cold atmospheric pressure plasma (CAPP) has gained attention as an effective technology for the decontamination and modification of fresh and dry agricultural products. In the postharvest chain of edible insects, the application of CAPP could contribute to the development of safe and high-quality insect-based products in the food and feed sector.     

Inactivation of Salmonella Enteritidis PT30 on the surface of unpeeled almonds by cold plasma

The contamination of nut products, like almonds, with human pathogens is a reoccurring concern in the food industry. In this study the inactivation of Salmonella Enteritidis PT 30 (ATCC BAA-1045) on the surface of unpeeled almonds by cold atmospheric pressure plasma was investigated. Air, O₂, N₂, CO₂ and 90% CO₂ + 10% Ar were used as process gas. Inoculum preparation and inoculation of almonds was done according to the guidelines recommended by the Almond Board of California. Furthermore, impact of plasma treatment on product color was measured. All plasma treatments inactivated Salmonella. Maximum achieved inactivation depends on the used process gas. Air plasma inactivated > 5.0 log₁₀, O₂ plasma 4.8 and N₂ plasma 2.0 log₁₀ after 15 min treatment. The plasma treatment with air and N₂ resulted in a browning of the unpeeled almond's surface color. Whereas the other used plasma did not alter the color considerably.Industrial RelevanceThe contamination of raw nuts with human pathogens is an on-going food safety concern. The application of cold atmospheric pressure plasma has a high potential as a gentle technology for the surface decontamination. The results of this study suggest that a cold plasma treatment could be an alternative technology for the pasteurization of almonds. The use of air plasma achieved more than a 5 log₁₀, which is in general required by the U.S. Food and Drug Administration for the approval as an alternative inactivation technology for food products. However, the scale up to commercial treatment levels requires the complete understanding of the involved product-plasma interactions.     

Mandarin preservation by microwave-powered cold plasma treatment

Cold plasma treatment (CPT) was investigated as a nonthermal method for inhibiting Penicillium italicum and improving storability of mandarins (Citrus unshiu Marc.). Whole mandarin fruits or the peels were treated with cold plasma at 0.7 kPa using a microwave CPT system. The treatment variables were plasma-forming gases, plasma generation power, and treatment time. Nitrogen (N₂)-CPT at 900 W for 10 min, resulted in the highest inhibition of P. italicum (84% reduction in disease incidence), significantly increased the total phenolic content and antioxidant activity of mandarin peel after the treatment (p < 0.05), but did not significantly affect CO₂ generation, weight loss, content of soluble solids, titratable acidity, pH, ascorbic acid concentration (flesh), or surface color during storage at 4 and 25 °C. These results demonstrate the potential for CPT application as a postharvest technology for preserving mandarins, increasing the total phenolic content and antioxidant activity of mandarin peel.     

Afterglow corona discharge air plasma (ACDAP) for inactivation of common food-borne pathogens

Atmospheric pressure cold plasma technology is becoming increasingly popular for microbiological decontamination of food and bio-materials. In the present study, afterglow corona discharge air plasma (ACDAP) was used for the inactivation of most common food-borne pathogens, namely pathogenic Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Bacillus cereus, Listeria monocytogenes, and Vibrio parahaemolyticus. Corona discharge plasma was generated at an output voltage of 20 kV DC, and a frequency of 58 kHz. And, a centrifugal blower that provides an airflow velocity of 2.5 m/s at electrode tip level was used for generating the flowing afterglow of the plasma. During plasma exposure, about 20 °C rise in temperature and a 50% decrease in relative humidity were observed in a treatment chamber within 3 h of exposure. Upon ACDAP exposure, as high as 3.5-log (99.97%) reduction in viable cell counts of tested food pathogens, especially E. coli O157:H7, was observed over a 24-hour exposure. The pathogen inactivation pattern was better explained by using the Singh–Heldman model, which belongs to pseudo-first-order kinetics. In conclusion, ACDAP was shown to be effective for the inactivation of common food-borne pathogens.     

Inhibition of mackerel (Scomber scombrus) muscle lipoxygenase by green tea polyphenols

The high polyunsaturated fatty acid content of oily fish such as mackerel (Scomber scombrus) makes it particularly susceptible to oxidative degradation. We have shown previously the presence of lipoxygenase (LOX), a lipid oxygenase, in mackerel muscle. In the current study, commercially available green tea polyphenols were shown to effectively inhibit the LOX activity of mackerel muscle. EGCG (epigallocatechin gallate) was the strongest inhibitor tested with an IC₅₀ (concentration for half maximal inhibition) value of 0.13 nM. All the tea catechins showed a mixed non-competitive type inhibition. In addition, antioxidants such as BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), esculetin, caffeic acid, ascorbic acid, and ethylene diamine tetraacetic acid (EDTA) were effective to varying degrees (IC₅₀ values between 0.02 and >50 μM) in the inhibition of mackerel muscle LOX. Nordihydroguaiaretic acid (NDGA), a classical LOX inhibitor and potassium cyanide (KCN), a heme protein inhibitor were assayed for their inhibitory activities for comparison.Post harvest spoilage of fish account for loss of as much as 10% of the world’s catches of cultured fish. This data indicates that the green tea polyphenols, nature’s very potent antioxidants, may be used as an effective and natural means of reducing post harvest spoilage in fish.     

Protective role of vacuum vs. atmospheric frying on PUFA balance and lipid oxidation

The effect of vacuum frying processing on proximate composition, fatty acid profile, oxidative status and sensorial properties of fish patties, was evaluated as compared with conventional (atmospheric) frying.Vacuum frying procedure was carried out at 80 mmHg (water boiling point: 42 °C) and oil temperature (107 °C) determined to obtain an equivalent thermal driving force (Δ65 °C) of that of the atmospheric frying conditions used (165 °C). Frying times of 2, 4, 6, 8 and 10 min were investigated.Vacuum frying significantly prevented degradation of EPA (Eicosapentaenoic acid) and DHA (Docosahexaenoic acid), reducing the polyene index and maintaining a lower ω6/ω3 fatty acid ratio in samples, while no significant differences with conventional frying in total oil content were observed. The use of vacuum also reduced formation of peroxides and carbonyl derivatives. Tocopherol levels decreased in all samples regardless of the frying conditions used, although vacuum-fried samples maintained higher tocopherol levels after processing. These samples also showed higher lightness and lower a* and b* values, which can be associated to lower non-enzymatic browning levels.These results support the applicability of vacuum frying technology for fish patties, since it prevents colour changes, improves juiciness and reduces oxidation when compared to conventionally (atmospheric) fried counterparts.Industrial relevanceConsumers are increasingly aware of the link between food and health, maintaining a high demand for healthy products. In this regard, consumption of fatty fish, with healthy properties widely known, is lower than recommended by health authorities, especially in children. Novel processing technologies focused on increasing the appealing of products based on fatty fish can help in ameliorating this deficient consumption. Vacuum frying is a promising way of obtaining attractive products, due to some product modification after the deep-fat frying process, and yet retaining natural colour, juiciness and healthy properties to a high extent. Vacuum frying allows reducing ω3 fatty acids and tocopherol degradation, differentiating fish products so obtained, which can be launched into the market and benefit from this technology. Compared to conventional frying, the results are better nutritional and sensory properties in a final product.     

Influence of different shrinking temperatures and vacuum conditions on the ability of psychrotrophic Clostridium to cause ‘blown pack’ spoilage in chilled vacuum-packaged beef

This study determined the ability of psychrotrophic Clostridium strains isolated from vacuum-packaged beefs and abattoir environments to cause ‘blown-pack’ spoilage of vacuum-packaged beef stored at 2 and 15 °C. The influence of shrinking temperatures (83, 84 and 87 °C) and vacuum pressure (6 and 9 mbar) on the occurrence of such spoilage as well as the effects of simulated transportation (500 km) on the integrity of packages was determined. At 15 °C and 2 °C, twelve and six strains caused ‘blown-pack’ spoilage, respectively. The combination of vacuum pressure (9 mbar) combined with shrinking temperature (87 °C) retarded the occurrence of spoilage. The simulated transportation under the experimental conditions did not affect the integrity of packages. More studies that assess the factors that may contribute for the occurrence of ‘blown-pack’ spoilage should be performed to avoid the occurrence of such spoilage during its shelf-life.     

Post-thawing quality changes of common carp (Cyprinus carpio) cubes treated by high voltage electrostatic field (HVEF) during chilled storage

In recent years, high voltage electrostatic field (HVEF) technology has been demonstrated to be a viable alternative to high-temperature treatments in processing for inhibiting microbial growth and maintaining post-thawing quality of foods. In this study, common carp (Cyprinus carpio) meat cubes were treated with HVEF, and compared to air-thawed and running tap water-thawed controls to investigate how HVEF affects common carp meat quality after thawing and low-temperature storage (4 °C). The results showed that thawing under − 6, − 12 kV HVEF and running tap water significantly decreased the thawing time by 30, 50 and 45 min, respectively, compared to air thawing control. In addition, − 12 kV HVEF treatment also reduced the moisture loss, which the initial drip loss of it was lower by 2.95% than CK. The initial total viable counts, Aeromonas, Pseudomonas, and lactic acid bacteria were 3.58, 3.15 2.88 and 3.25 log CFU/g in CK after thawing, respectively, which were higher than that in the cube thawed by − 12 kV HVEF (3.11, 2.93 2.71 and 2.91 log CFU/g). Additionally, − 12 kV HVEF treatment enhanced adenosine monophosphate deaminase (AMP-deaminase) activity, reduced acid phosphatase (ACP) activity and delayed the degradation of inosine monophosphate (IMP) to hypoxanthine (Hx). These results suggested that HVEF treatment could be useful in the thawing and storage of frozen common carp fish.Industrial relevanceThe study investigated the effects of high voltage electrostatic field (HVEF) thawing on the water-holding capacity, adenosine triphosphate degradation and microbial community changes of frozen common carp (Cyprinus carpio) cubes when stored at 4 °C. HVEF under − 12 kV was found to have positive influence on reducing the thawing time, maintaining water-holding capacity, decreasing the level of microbe, and delaying adenosine triphosphate (ATP) degradation. A potential application for HVEF in the thawing and storage of frozen aquatic product was highlighted in food industry.     

Atmospheric pressure plasma jet inactivation of Pseudomonas aeruginosa biofilms on stainless steel surfaces

This study established the efficacy of atmospheric pressure plasma jet on Pseudomonas aeruginosa on stainless steel types 316 and 304; with different finishes namely, mirror (MR), hairline (HL) and 2B surfaces. A cocktail of four strains of P. aeruginosa in the mid-stationary growth phase were allowed to attach on the test surfaces, and subjected to atmospheric pressure plasma jet treatment with an air injection rate of 5 l/min, output power of 360 W at 4.22 cm source-to-surface distance. Attachment rates were significantly affected by surface finish, rather than by stainless steel type. The D-values on the 316 stainless steel type ranged from 2.53 s (MR) to 3.16 s (2B); while those on the 304 type ranged from 1.95 s (HL) to 3.27 s (2B). Variations in D-values were observed between surface finishes within a specific stainless steel type. However, significant variations were not observed between the same surface finish of different steel types. The observed antimicrobial efficacy was attributed to the generation of reactive oxygen species, ultraviolet-C rays, and rapid temperature increase (final temperature of 143.42 °C to 174.05 °C) within 15 s of treatment. In the absence of heating, the D-value increased to 16.45 s, but a 5-log (99.999%) reduction in the population was observed in a relatively short treatment time of 90 s.Industrial relevanceThe results obtained in this work demonstrated the potential of using atmospheric pressure plasma jet technology as a non-chemical, non-thermal, and thermal stainless steel food contact surface decontamination against Pseudomonas aeruginosa, a common biofilm-producing bacterium. Such a technology shall help the industry address the challenge of cross contamination in the food manufacturing and food service settings.