Influence of vacuum and modified atmosphere packaging in combination with UV-C radiation on the shelf life of rainbow trout (Oncorhynchus mykiss) fillets

The effects of UV-C radiation, modified atmosphere packaging (MAP) and their combination on rainbow trout (Oncorhynchus mykiss) fillets quality were examined during a period of 22 days. The samples were submitted to five packaging conditions: (AP) aerobic packaging; (VP) vacuum packaging; (VP + UV-C) vacuum packaging + UV-C radiation; (MAP) modified atmosphere packaging (80% CO₂/20% N₂) and (MAP + UV-C) modified atmosphere packaging + UV-C radiation (80% CO₂/20% N_2; 106.32 mJ/cm²) and storaged at 4 °C. The samples were analyzed daily for microbiological (mesophilic, psychrotrophic and Enterobacteriaceae counts) and chemical (pH, TMA-N, TBV-N, lipid oxidation, ammonia and biogenic amines) parameters. Overall, UV-C radiation promoted lag phase formation in mesophilic and psychrotrophic groups. Mesophilic and psychrotrophic groups presented significant lower (P < 0.05) growth rate and colony forming units in the stationary phase in the samples submitted to MAP. MAP significantly reduced (P < 0.05) total mesophilic count and MAP + UV-C total mesophilic and psychrotrophic counts. Values of pH decreased at all packaging conditions except in the case of aerobic packaging. TBARS value increased faster in samples subject to MAP and MAP + UV-C whereas TMA-N, TVB-N and ammonia values increased slowly. Lower production of putrescine and cadaverine was observed in MAP and VP samples. MAP reduced total production of ammonia, TVB-N and putrescine, whereas MAP + UV-C reduced total production of TVB-N and cadaverine during entire the storage time. Results of the current study suggest that MAP retarded microbial growth and delayed chemical changes enhancing the shelf life of rainbow trout fillets at least twice.     

Effect of high pressure processing on the quality of herring (Clupea harengus) and haddock (Melanogrammus aeglefinus) stored on ice

Fresh herring and haddock were vacuum-packed and subjected to high pressure processing (200, 250 and 300 MPa at 10 °C for both 1 and 3 min) or left untreated as controls. The samples were stored in ice at 2 °C for up to 14 days, during which time the changes in microbial quality, total volatile base nitrogen (TVBN) and trimethylamine (TMA) production were monitored. Microbial shelf-life was determined as the storage time required for psychrotrophic counts to reach 10⁶ CFU g^?1, while chemical shelf-life was estimated as the time taken for TVBN and TMA values to reach 35 mg N 100 g^?1 and 15 mg N 100 g^?1 respectively.High pressure significantly delayed microbial growth (p < 0.05) in both herring and haddock. In the case of herring the microbiological shelf-life was extended from ～4 days in controls to ?13 days in fish pressure-treated at 200 MPa/3 min. Microbial numbers in all the haddock samples tended to be lower throughout the storage period, compared to herring, irrespective of pressure treatment, and none of the pressure-treated samples reached unacceptable psychrotrophic numbers until 14 days in ice compared to 10 days in the controls. The microflora of both the control and pressure-treated herring and haddock at day 0 were predominantly Gram-positive cocci (Micrococcus spp. and Staphylococcus spp.) and spore-forming rods (Clostridium spp. and Bacillus spp.). This microflora did not change significantly during storage of the fish in ice at 2 °C for 10 days.Pressure treatment also delayed TVBN and TMA production in the fish. In the case of herring, predicted values did not reach unacceptable levels until at least 18 days (200 MPa/3 min) compared to 5.5 days in controls. With haddock, TMA and TVBN values in control samples reached unacceptable limits between 6 and 10 days of storage. However, the levels remained below the limits of acceptability in all pressure-treated samples during storage, apart from on day 14, when the TVBN value in samples treated at 200 MPa/1 min exceeded the level of acceptability.Overall, taking account of the various spoilage indicators, the minimum treatment required to increase shelf-life in herring and haddock to ～13 days on ice was found to be 200 MPa for 3 min.     

Quality differences of whole ungutted sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) while stored in ice

The aim of this study is to determine the quality changes in whole ungutted sea bass and sea bream while stored in ice. Changes in chemical quality were determined by using pH, total volatile basic nitrogen (TVB-N, mg N/100 g), trimethylamine (TMA-N, mg/100 g), thiobarbituric acid (TBA, mg malonaldehyde/kg), water activity (a_w), color measurement, and sensory analysis. Changes in microbiological quality were determined by using the analysis of total viable mesophilic and psychrophilic bacterial counts. Result of this study indicated that the shelf life of sea bass and sea bream stored in ice as determined by overall acceptability sensory scores and microbiological data was 15 days.     

Microbiological changes in farm reared freshwater prawn (Macrobrachium rosenbergii de Man) in ice

The microbiological changes in farm reared freshwater prawn (Macrobrachium rosenbergii de Man) during ice storage were studied. A total of 156 bacterial cultures from fresh and ice-stored farmed freshwater prawn were isolated and characterized. Total aerobic, mesophilic and psychrotrophic counts and hydrogen sulphide producing bacterial counts were determined. The total aerobic counts at 20 and 37 °C on fresh prawn was in the range of 4–5 log₁₀ cfu g⁻¹. Aerobic counts on M. rosenbergii at 20 °C and 7 °C exceeded 10⁷ cfu g⁻¹ by the end of storage, of which 40–52% were H₂S producers. Gram-negative bacteria constituted 73% of the total flora of fresh prawn and Enterobacteriaceae and Aeromonadaceae dominated. After 19 days of iced storage, more than 80% of the bacterial flora of prawn were Gram-negative. Pseudomonas, Aeromonas hydrophila, A. veronii boivar sobria and Shewanella putrefaciens were identified as the dominant spoilage organisms of farm reared M. rosenbergii stored in ice. This study confirms that freshwater prawn carry significant numbers of motile aeromonads capable of growth at low temperature. The results of the study indicated that the shelf-life of freshwater prawn as determined by microbiological data is 12–16 days. Immediate icing of harvested M. rosenbergii is essential to improve the microbiological stability.     

Physicochemical and microbial changes during storage of smoke-flavoured salmon obtained by a new method

The aim of this study was to evaluate the effect of a new smoking-salting method employing water vapour permeable (WP) bags on the physicochemical and microbial quality of smoke-flavoured salmon in refrigerated storage. Fresh salmon was subjected to a smoking process in the WP at 5 °C. Physicochemical and microbiological analyses were periodically carried out during the subsequent 40 days of refrigerated storage of the product. The WP bags enabled the evaporation of the exudate during the smoking-salting stage, enabling the drying of the product to take place at the same time. A slight increase of trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) contents was observed over the storage period. The concentration of TVB-N ranged from 14.26 to 21.48 mg N/100 g of fish, values far below the upper limits of acceptability. The low values of the thiobarbituric acid (TBA) index (final level of 0.71 mg MDA/kg) indicate that the lipid oxidation in the smoke-flavoured salmon was limited throughout the period studied. The initial K₁-value was high and only a slight increase was observed during storage. Counts of mesophilic, psychrotrophic, Enterobacteriaceae and lactic acid bacteria were low throughout the study. Given the changes observed for the physicochemical and microbiological parameters, it can be said that no spoilage took place in the smoke-flavoured salmon during the 40 days of storage. This new method could be of interest to producers as it enables smoke-flavoured salmon to be produced to a good standard of hygiene, minimizing handling and reducing processing steps and brine wastes.     

Changes in microbiological,physicochemical and muscle proteins of post mortem large yellow croaker (Pseudosciaena crocea)

This study was devoted to the identification of changes in microbiological, physicochemical and proteins which could be used as freshness indicators in large yellow croaker. The parameters that proved to be most sensitive to variations over storage time were total viable count, Shewanella putrefacents, Photobacterium phosphoreum, TVB-N, PV and K value. They might therefore be considered as good indicators for evaluating spoilage of large yellow croaker during refrigerated storage for 20 days. The proteins including MHC, actin, tropomyosin, protein bands of 14 ～ 15 kDa, 32 ～ 33 kDa, 35 ～ 36 kDa and 41 ～ 42 kDa could be used as the potential freshness markers of large yellow croaker. The results of these analyses indicated optimal quality for large yellow croaker stored under these conditions and established a shelf-life of 12 days.     

Quality predictive models of grass carp (Ctenopharyngodon idellus) at different temperatures during storage

To study quality changes in cold chain circulation, kinetic models were developed to predict the freshness changes of grass carp at different temperatures during storage. Sensory assessment, total aerobic count (TAC), K value, total volatile basic nitrogen (TVB-N) and 2-Thiobarbituric acid (TBA) at ?3, 0, 3, 9 and 15 °C were accessed to investigate the relation between the freshness changes and temperature. The kinetic models of sensory assessment, TAC, K value, TVB-N and TBA with respect to storage time and temperature were developed based on Arrhenius equation. The high regression coefficients (R² > 0.9) indicated the acceptability of the first-order reaction and Arrhenius model for predicting the quality changes of grass carp. Activation energies (E_A) of sensory assessment, TAC, K value, TVB-N and TBA are 114.38, 75.88, 57.11, 111.55, 63.09 kJ mol^?1, and corresponding rate constants (k₀) are 2.97 × 10²⁰, 1.12 × 10¹³, 8.30 × 10⁹, 8.34 × 10¹⁹, 9.06 × 10¹⁰ respectively. Relative errors between predicted and observed freshness indictors values of TAC, K value and TVB-N are all within ±10%. Therefore the quality changes of grass carp can be predicted based on the prediction model of TAC, K value and TVB-N within ?3–15 °C.     

A simple method to evaluate the shelf life of refrigerated rabbit meat

The shelf life of rabbit meat during refrigerated storage was investigated under industrial conditions. Rabbit carcasses were bulk packed (BP), packed under air (PUA) and under modified atmosphere (MAP) (30% O₂:40% CO₂:30% N₂). The main groups studied were mesophilic aerobes, psychrotrophic aerobes, Pseudomonas spp., lactic acid bacteria, yeast and moulds and Enterobacteriaceae. The microorganisms that showed faster growth were psychrotrophic aerobes (growth rate of 0.36 ± 0.09 day⁻¹) for BP, Pseudomonas (0.26 ± 0.03 day⁻¹) for PUA, and lactic acid bacteria (0.22 ± 0.01 day⁻¹) for MAP, and the lag phases were 4, 4 and 8 days, respectively. The main effect of MAP was the increase in lag phase from 4 to 8 days, for lactic acid bacteria, psychrotrophic and mesophilic aerobes. The respective growth rates were similar to those observed with PUA. In addition, MAP inhibited Pseudomonas growth during 18 days. Considering 6 log CFU g⁻¹ as maximum tolerable microbial load, the calculated values of shelf life in BP, PUA and MAP were 6, 7 and 12 days, respectively, when considering the fastest growing microorganisms.     

Limited microbial growth in Atlantic salmon packed in a modified atmosphere

This study examined the dynamics of microbial growth in fresh chilled Atlantic salmon (Salmo salar) packed in a modified atmosphere. Atlantic salmon were harvested, handled, transported, and processed under optimal conditions to produce skinless fillet portions packed in pouches containing 96% CO₂ at gas: product ratios of greater than 5:1 (v/w) and stored for 38 days at less than 1 °C. Microbial analysis was conducted using psychrotrophic and mesophilic plate counts and DNA-based techniques. Results revealed initial microbial counts at day 0 of 10² CFU g⁻¹ and sequences from the genera Luteimonas, Pseudorhodoferax, Aequorivita, Gillisia, Gramella, Micrococcus, Acidovorax and Achromobacter. An extended lag phase was observed of 10 (psychrotrophic) or 15 (total) days with total plate count numbers reaching 10⁶ CFU g⁻¹ after 21 (psychrotrophic) and 25 days (total) and stabilising at 10⁸ CFU g⁻¹ after 31 days. At 31 days the microbial community was dominated by Pseudomonas spp. as determined by identification of isolates and sequencing of a 16S rRNA gene clone library. No Photobacterium spp., including the specific spoilage organism Photobacterium phosphoreum, were identified during the study.     

Comparing the effectiveness of chitosan and nanochitosan coatings on the quality of refrigerated silver carp fillets

The coating effects of chitosan and chitosan nanoparticles on the quality of silver carp (Hypophthalmicthys molitrix) fillets during refrigerated storage at 4 °C were compared. Solutions of Chitosan (2%, w/v) and nanochitosan (2%, w/v) were used for the coating. The control and the coated fish samples were analyzed periodically for microbiological (total mesophilic and psychrotrophic count), physicochemical (pH, TVB-N, TBARS), and sensory attributes. The results indicated that both chitosan and nanochitosan coating were effective for the preservation of silver carp fillets during refrigerated storage. However, nanochitosan exhibited higher antimicrobial activity than chitosan during the storage period. Furthermore, nanochitosan showed a stronger ability to inhibit the TVB-N content than chitosan. Therefore, to extend the shelf life and delay the deterioration of fresh silver carp fillets during refrigerated storage, nanochitosan coating is more effective.     

The efficacy of grape seed extract,citric acid and lactic acid on the inactivation of Vibrio parahaemolyticus in shucked oysters

The efficacy of grape seed extract (GE), citric acid (CA) or lactic acid (LA) on the inactivation of Vibrio parahaemolyticus in shucked oysters was studied. The minimum inhibitory concentration (MIC) of GE, CA or LA against V. parahaemolyticus in TSB-1% NaCl was also determined. The shucked oysters were artificially inoculated with V. parahaemolyticus, the inoculated shucked oysters (25 g) were then dipped in solution of GE (0.0, 10.0, 20.0, 50.0, 100, 200, 300 and 500 mg mL⁻¹), CA (0.0, 5.0, 10.0, 15.0, 20.0, 50.0, 100, 200 and 300 mg mL⁻¹) or LA (0.0, 1.0, 5.0, 10.0, 15.0, 20.0, 50.0, 100 and 150 mg mL⁻¹) for 10 min. The population of V. parahaemolyticus in shucked oysters was determined. The MICs of GE, CA or LA against V. parahaemolyticus were 10.0, 5.0 or 1.0 mg mL⁻¹, respectively. A 500, 300 or 150 mg mL⁻¹ GE, CA or LA solutions were needed to reduce the population of V. parahaemolyticus to below the detection level (1.0 log g⁻¹) in shucked oysters.     

A multicommuted flow system for fast screening/sequential spectrophotometric determination of dichromate,salicylic acid,hydrogen peroxide and starch in milk samples

In this work a multicommuted flow system for the sequential screening/determination of dichromate, salicylic acid, hydrogen peroxide and starch in milk samples was developed. The concept of multicommutation in flow injection analysis was chosen, resulting in an environmentally friendly system with minimal consumption of reagents and waste generation. The proposed approach is based on a simple binary DETECT or NO-DETECT response, thereby making it possible to determine analytes quickly, with high performance and easy operation. For dichromate determination, the proposed method was based on the reaction between Cr(VI) and 1,5-diphenylcarbazide, enabling a linear working range response, between 1.0 and 10.4 mg L⁻¹, (R = 0.999). In order to determine salicylic acid, the proposed method was based on a complexation reaction of Fe(III) and salicylic acid, with the linear working range response from 103.6 to 414.3 mg L⁻¹ (7.5 × 10⁻⁴–3.0 × 10⁻³ mol L⁻¹) (R = 0.999). The hydrogen peroxide determination was based on the oxidation reaction of hydrogen peroxide with vanadium oxide (V) in an acid environment, with a linear working range of 10.0–200.0 mg L⁻¹ (R = 0.996). Starch determination was based on the complex reaction of starch and triiodide, with a linear working range of 12.5–150.0 mg L⁻¹ (R = 0.999). The mean sampling rate for the four species was 83 determinations per hour. Performance curves were used to verify the quantity of false positives and false negatives. Addition and recovery tests were used for validation of the proposed procedures, resulting in variation between 90.1 and 108.7% for three different samples.     

A survey study on safety and microbial quality of “gluten-free” products made in Italian pasta factories

The rising prevalence of celiac disease leads to an increased demand of “gluten-free” products. A survey study on the gluten content and on the microbiological quality of “gluten-free” flour, and processing flour products, was carried out from 2010 to 2015 in Northern Italy. Overall 12,419 samples were analyzed, and 94.7% contained a gluten concentration less than 5 mg kg⁻¹ (lower limit of detection). Only 0.1% of samples showed a gluten concentration above 80 mg kg⁻¹ (maximum limit of detection). In the remaining 5.2%, the gluten concentration was between 5 and 80 mg kg⁻¹, underlining how a gluten-free diet completely devoid of gluten is unrealistic. The microbiological quality of these products was investigated.Overall, the majority of samples revealed microbial loads of less than 1 l g CFU g⁻¹ (lower limit of detection). High levels of spoilage bacteria were found in egg-containing products. Total mesophilic bacteria were counted in all analyzed food categories with concentrations up to about 6, 8 and 9 l g CFU g⁻¹ in dry pasta, flours and egg products respectively. Listeria monocytogenes was found only in one sample, whereas Salmonella spp. was never found.Buckwheat flour was the most frequently contaminated product by presumptive Bacillus cereus, with a prevalence of 12.5%. Also, a contamination by Coagulase-Positive Staphylococci was found during this investigation, especially in buckwheat dry pasta and flour and in egg dry pasta, with a prevalence of 54.7%.This study aimed to enhance the knowledge about the “gluten-free” products which are still poorly studied, even if their impact on the food market is increasingly considerable.     

Saturated aqueous ozone degradation of deoxynivalenol and its application in contaminated grains

Deoxynivalenol (DON) is a secondary metabolite produced by Fusarium graminearum in grains, food and contaminated feed, which can lead to many adverse health effects to humans and livestock. The degradation of DON in different contaminated grains oxidated by saturated aqueous ozone (80 mg L⁻¹) was monitored by ultra-high-performance liquid chromatography, tandem-quadrupole-detection mass spectrometry (UPLC–TQD-MS). Results suggest that ozone has a significant effect on DON reduction in solution. When 80 mg L⁻¹ gaseous ozone was used to treat 10 mg L⁻¹ of DON solution, the degradation rate of DON reached 83% within 7 min, while the respective detoxification rates of contaminated wheat, corn and bran by saturated aqueous ozone (80 mg L⁻¹) were 74.86%, 70.65% and 76.21 in 10 min. Ozone at 80 mg L⁻¹ was applied on various DON solution concentrations at 1 mg L⁻¹, 10 mg L⁻¹ and 20 mg L⁻¹ in ultra-pure water. In this paper, the degradation procedure for DON is calculated and described by a first-order kinetic equation. At lower levels (20 mg L⁻¹) of aqueous ozone, intermediate degradation products were observed by ultra-ne quickly and effectively degrades DON and toxicity in various contaminated grains in a matter of minutes. Therefore, ozonation is projected to be an effective, fast, and safe method for DON degradation.     

Determination of the shelf life of sardine (Sardina pilchardus) marinades in tomato sauce stored at 4 °C

In this study the shelf life of sardine marinades in tomato sauce was investigated. After the marination process, sardine fillets were packed into the glass jars with 2% acetic acid and 4% sodium chloride with tomato sauce and spices. The effect of pasteurization at 70 °C for 20 min on the shelf life of the sardine marinades was determinated. At the end of 6 months storage the differences between TBA, FA(free), FA(total) and pH value of pasteurized and non-pasteurizated marinades were not significantly (p > 0.05) different, while the difference between TVB-N, TMA-N, total plate count and lactic acid bacteria count of pasteurized and non-pasteurized marinades were significant (p < 0.05). Shelf life of pasteurized and non-pasteurized sardine marinades in tomato sauce was found to be 6 months at 4 °C.     

Chlorpyrifos residue levels on field crops (rice,maize and soybean) in China and their dietary risks to consumers

In this study, chlorpyrifos residue levels in field crops of rice, maize and soybean were investigated according to the “Guideline on Pesticide Residue Trials” of China. On the basis of the residual results, human dietary risks were further evaluated. Chlorpyrifos residues of harvest grains were firstly prepared by QuEChERS method and analyzed using Gas Chromatography Tandem Mass Spectrometry (GC–MS/MS). Dietary risks were assessed by a deterministic approach. The median residues in field trials of rice, maize and soybean were 0.617, 0.0227 and 0.0136 mg kg⁻¹, respectively. The highest residues in field trials of rice, maize and soybean were 3.23, 0.114 and 0.102 mg kg⁻¹, respectively. Chronic intake assessment indicated that only 39.0% of acceptable daily intake (ADI, 0–0.01 mg kg bw⁻¹ day⁻¹) was consumed through rice, maize and soybean. The acute hazard indexes (aHI) of adults was 26.1% of acute reference dose (ARfD, 0–0.1 mg kg bw⁻¹) and aHI of children was 63.5% of ARfD in dietary exposure assessment through rice, maize and soybean consumption. Single pathway risk assessment indicated that chlorpyrifos application on field crops in manner of the good agricultural practices didn't pose public health risks.     

Effect of Citrus wilsonii Tanaka extract combined with alginate-calcium coating on quality maintenance of white shrimps (Litopenaeus vannamei Boone)

The combined effect of Citrus wilsonii extract and alginate-calcium film coating on microbiological, chemical and sensory changes of white shrimps (Litopenaeus vannamei) was studied over 6 days of storage at 4 °C. A specific spoilage microorganism Lysinibacillus sphaericus S1 was isolated from local shrimp samples, which could cause the appearance of orange spoilage spots. The methanol extract of C. wilsonii exhibited significant antimicrobial activity against L. sphaericus S1, as well as several other food-borne pathogens. GC–MS analysis showed a high percent of furandione and furfural compounds in the extract. The extract with edible alginate-calcium coating was effective in delaying the quality deterioration of the shrimps stored at 4 °C. Total viable count of the treated shrimps was more than 10 times lower than the negative untreated control. The lower rate of the increase in pH and total volatile base nitrogen (TVB-N) was also observed in shrimps treated with the extract compared to the control group shrimps. After 6 days of refrigerated storage, shrimps treated with the extract combined with coating had the significant higher sensory score for odor, color and texture. The results suggest that the methanol extract from C. wilsonii may be promising to be developed as a new eco-friendly preservative that might be applied to extend the shelf life of shrimps maintaining good quality.     

Use of impedance spectroscopy for predicting freshness of sea bream (Sparus aurata)

In the present study, the use of a rapid portable system based on impedance spectroscopy to assess fish freshness has been tested. The evolution of different physical and chemical parameters (moisture, fat, pH and TVBN) and impedance measurements (modulus and phase at different frequencies) of six different batches of sea bream (Sparus aurata) were analysed. Impedance spectroscopy was able to classify raw matter into six groups according to composition differences, and also to classify those samples stored for a time of between 0 and 15 days into different groups according to degree of freshness. TVB-N is one of the most usual parameters to assess shelf life periods of fish samples; the coefficient of determination (R²) of 0.72 obtained in the Partial Least Squares regression for this parameter confirmed the potential application of the impedance spectroscopy for predicting sea bream freshness.     

Effect of an icing medium containing the alga Fucus spiralis on the microbiological activity and lipid oxidation in chilled megrim (Lepidorhombus whiffiagonis)

The present study provides a first approach on the employment of an icing medium including Fucus spiralis, an alga exhibiting antimicrobial and antioxidant activities, for the preservation of fish quality during chilled storage. For it, two different concentrations of a F. spiralis extract (0.67 and 2.50 g lyophilized alga L⁻¹ aqueous solution; F-1 and F-2 batches, respectively) were tested as icing medium for the chilled storage of megrim (Lepidorhombus whiffiagonis) for 14 days. The effects of the alga were compared with a counterpart batch stored in traditional ice prepared only from water (F-0 batch). A significant (p < 0.05) inhibition of microbial activity (aerobes, psychrotrophs, proteolytic bacteria, lipolytic bacteria; pH and trimethylamine formation) in F-1 batch and, especially in F-2 batch, was concluded. Concerning lipid oxidation development, a significantly (p < 0.05) lower formation of interaction compounds (fluorescence assessment) in samples corresponding to the F-2 batch was also observed, proving the inhibitory effect of F. spiralis on the formation of tertiary lipid oxidation compounds in chilled megrim. The icing medium proposed in this study may open the way to the development of a natural biopreservation strategy for chilled seafood based on algae.