Reductions of Vibrio parahaemolyticus in Pacific oysters (Crassostrea gigas) by depuration at various temperatures

Consumption of raw oysters has been linked to several outbreaks of Vibrio parahaemolyticus infection in the United States. This study investigated effects of ice storage and UV-sterilized seawater depuration at various temperatures on reducing V. parahaemolyticus in oysters. Raw Pacific oysters (Crassostrea gigas) were inoculated with a mixed culture of five clinical strains of V. parahaemolyticus (10290, 10292, 10293, BE 98-2029 and 027-1c1) at levels of 10⁴⁻⁶ MPN/g. Inoculated oysters were either stored in ice or depurated in recirculating artificial seawater at 2, 3, 7, 10, 12.5, and 15 °C for 4–6 days. Holding oysters in ice or depuration of oysters in recirculating seawater at 2 or 3 °C for 4 days did not result in significant reductions (P > 0.05) of V. parahaemolyticus in the oysters. However, depuration at temperatures between 7 and 15 °C reduced V. parahaemolyticus populations in oysters by >3.0 log MPN/g after 5 days with no loss of oysters. Depuration at refrigerated temperatures (7–15 °C) can be applied as a post-harvest treatment for reducing V. parahaemolyticus in Pacific oysters.     

Occurrence and distribution of Vibrio parahaemolyticus in retail oysters in Sao Paulo State, Brazil

Vibrio parahaemolyticus is a potentially pathogenic bacterium that occurs naturally in estuarine environments worldwide, and is often associated with gastroenteritis in humans following consumption of raw bivalve mollusks, especially raw oysters. The occurrence of total and pathogenic V. parahaemolyticus in 74 samples of raw oysters collected in restaurants, supermarkets, groceries and beach huts in Sao Paulo State, was monitored between February 2006 and January 2007. Enumeration of V. parahaemolyticus was performed according to the most probable number (MPN) procedure. Five to ten typical colonies were selected from thiosulfate-citrate-bile salts-sucrose (TCBS) agar plates for confirmation by the presence of the species-specific gene tlh and the virulence genes tdh and trh by multiplex PCR. V. parahaemolyticus was detected in 100% of samples. The densities of total V. parahaemolyticus varied from 1.78 to 6.04 log₁₀ (MPN/g), with higher densities being detected in fall and summer, and lower densities in winter (P < 0.05). There was no statistical difference among densities of V parahaemolyticus regarding the site of collection. None of the 1943 V. parahaemolyticus isolates contained tdh and/or trh. These data provide information for the assessment of exposure to V. parahaemolyticus in oysters consumed in Sao Paulo, State, Brazil.     

Inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in oysters by high-hydrostatic pressure and mild heat

Several recent outbreaks associated with oysters have heightened safety concerns of raw shellfish consumptions, with the majority being attributed to Vibrio spp. The objective of this study was to determine the effect of high-hydrostatic pressure (HHP) followed by mild heating on the inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in live oysters. Inoculated oysters were randomly subjected to: a) pressurization at 200–300 MPa for 2 min at 21 °C, b) mild heat treatment at 40, 45 or 50 °C for up to 20 min and c) pressure treatment of 200–300 MPa for 2 min at 21 °C followed by heat treatment at 40–50 °C. Counts of V. parahaemolyticus and V. vulnificus were then determined using the most probable number (MPN) method. Pressurization at 200–300 MPa for 2 min resulted in various degrees of inactivation, from 1.2 to >7 log MPN/g reductions. Heat treatment at 40 and 45 °C for 20 min only reduced V. parahaemolyticus and V. vulnificus by 0.7–2.5 log MPN/g while at 50 °C for 15 min achieved >7 log MPN/g reduction. HHP and mild heat had synergistic effects. Combinations such as HHP at 250 MPa for 2 min followed by heat treatment at 45 °C for 15 min and HHP at 200 MPa for 2 min followed by heat treatment at 50 °C for 5 min reduced both V. parahaemolyticus and V. vulnificus to non-detectable levels by the MPN method (<3 MPN/g). HHP at ≥275 MPa for 2 min followed by heat treatment at 45 °C for 20 min and HHP at ≥200 MPa for 2 min followed by heat treatment at 50 °C for 15 min completely eliminated both pathogens in oysters (negative enrichment results). This study demonstrated the efficiency of HHP followed by mild heat treatments on inactivation of V. parahaemolyticus and V. vulnificus and could help the industry to establish parameters for processing oysters.     

A survey of oysters (Crassostrea gigas) in New Zealand for Vibrio parahaemolyticus and Vibrio vulnificus

A microbiological survey was conducted to determine the levels of total and pathogenic Vibrio parahaemolyticus (Vp) and Vibrio vulnificus (Vv) in Pacific oysters (Crassostrea gigas) collected from commercial growing areas in the North Island, New Zealand.The survey was intended to be geographically representative of commercial growing areas of Pacific oysters in New Zealand, while selecting the time frame most likely to coincide with the increased abundance of pathogenic vibrio species. Vp was detected in 94.8% of oyster samples examined (n = 58) with a geometric mean concentration of 99.3 MPN/g, while Vv was detected in 17.2% of oyster samples examined with a geometric mean concentration of 7.4 MPN/g. The frequency of Vp positive samples was 1.7 fold greater than reported in a study conducted three decades ago in New Zealand. Potentially virulent (tdh positive) Vp was detected in two samples (3.4%, n = 58) while no trh (another virulence marker) positive samples were detected. 16 S rRNA genotype could be assigned only to 58.8% of Vv isolates (8:1:1 A:B:AB ratio, n = 10). There was a good agreement [98.2% of Vp (n = 280) and 94.4% of Vv (n = 18) isolates] between molecular tests and cultivation based techniques used to identify Vibrio isolates and there was a significant (R² = 0.95, P < 0.001, n = 18) linear relationship between the MPN estimates by real-time PCR and cultivation. There was no significant correlation between any of the environmental parameters tested and Vp or Vv concentrations.     

Total and pathogenic Vibrio parahaemolyticus in shrimp: Fast and reliable quantification by real-time PCR

Vibrio parahaemolyticus is found in aquatic environments and is the leading cause of gastroenteritis due to seafood consumption worldwide. We evaluated a quantitative real-time PCR (Q-PCR) assay with hydrolysis probes, to determine whether this method could be used for the efficient counting of total, tdh and trh-positive V. parahaemolyticus in shrimps. We assessed the specificity of this assay, using 62 strains from 12 non target bacterial species of the Vibrio, Photobacterium, Shewanella and Aeromonas genera. Only V. parahaemolyticus with the appropriate target gene generated a fluorescent signal. We assessed the robustness of this assay, by analyzing spiked shrimps by Q-PCR and traditional culture methods, using most probable number (MPN)-PCR. After a 6 h enrichment period, the assay successfully detected total and pathogenic V. parahaemolyticus in shrimps samples spiked with less than 5 V. parahaemolyticus cells/g of shrimp. The Q-PCR results obtained were compared with those obtained by most probable number (MPN)-PCR format. An excellent correlation between the two methods was observed in all cases (R² > 0.9742). The application of this Q-PCR assay to 85 natural shrimp samples also resulted in the successful quantification of V. parahaemolyticus in this matrix, and the counts obtained were correlated with those obtained by (MPN)-PCR (P = 0.2598). Thus, this rapid and sensitive Q-PCR can be used to quantify V. parahaemolyticus in natural shrimp samples. This assay could be proposed, in response to the demands of the European Commission, as a tool for testing for the presence of vibrios in crustaceans, making it possible to legislate in this domain.     

Effect of High-Pressure Processing on Vibrio parahaemolyticus Strains in Pure Culture and Pacific Oysters

Different strains of Vibrio parahaemolyticus (Vp) in broth cultures and Vp‐inoculated live Pacific oysters (Crassostrea gigas) were subjected to high‐pressure processing (HPP) at 241, 276, 310, and 345 MPa. Results showed Vp numbers were reduced by HPP in both pure culture and whole oysters. Vp inactivation was dependent on time and pressure. Optimum conditions for reducing Vp in pure culture and oysters to nondetectable levels were achieved at 345 MPa for 30 and 90 s, respectively. Resistance variations were detected between Vp in pure culture and in oysters. HPP proved to be an efficient means of reducing Vp in oysters.     

Effect of high-pressure processing on reduction of Listeria monocytogenes in packaged Queso Fresco

The effect of high-hydrostatic-pressure processing (HPP) on the survival of a 5-strain rifampicin-resistant cocktail of Listeria monocytogenes in Queso Fresco (QF) was evaluated as a postpackaging intervention. Queso Fresco was made using pasteurized, homogenized milk, and was starter-free and not pressed. In phase 1, QF slices (12.7 × 7.6 × 1 cm), weighing from 52 to 66 g, were surface inoculated with L. monocytogenes (ca. 5.0 log₁₀ cfu/g) and individually double vacuum packaged. The slices were then warmed to either 20 or 40°C and HPP treated at 200, 400, and 600 MPa for hold times of 5, 10, 15, or 20 min. Treatment at 600 MPa was most effective in reducing L. monocytogenes to below the detection level of 0.91 log₁₀ cfu/g at all hold times and temperatures. High-hydrostatic-pressure processing at 40°C, 400 MPa, and hold time ≥15 min was effective but resulted in wheying-off and textural changes. In phase 2, L. monocytogenes was inoculated either on the slices (ca. 5.0 log₁₀ cfu/g; ON) or in the curds (ca. 7.0 log₁₀ cfu/g; IN) before the cheese block was formed and sliced. The slices were treated at 20°C and 600 MPa at hold times of 3, 10, and 20 min, and then stored at 4 and 10°C for 60 d. For both treatments, L. monocytogenes became less resistant to pressure as hold time increased, with greater percentages of injured cells at 3 and 10 min than at 20 min, at which the lethality of the process increased. For the IN treatment, with hold times of 3 and 10 min, growth of L. monocytogenes increased the first week of storage, but was delayed for 1 wk, with a hold time of 20 min. Longer lag times in growth of L. monocytogenes during storage at 4°C were observed for the ON treatment at hold times of 10 and 20 min, indicating that the IN treatment may have provided a more protective environment with less injury to the cells than the ON treatment. Similarly, HPP treatment for 10 min followed by storage at 4°C was the best method for suppressing the growth of the endogenous microflora with bacterial counts remaining below the level of detection for 2 out of the 3 QF samples for up to 84 d. Lag times in growth were not observed during storage of QF at 10°C. Although HPP reduced L. monocytogenes immediately after processing, a second preservation technique is necessary to control growth of L. monocytogenes during cold storage. However, the results also showed that HPP would be effective for slowing the growth of microorganisms that can shorten the shelf life of QF.     

Survival of Vibrio parahaemolyticus under environmental stresses as influenced by growth phase and pre-adaptation treatment

In this study, the susceptibility of Vibrio parahaemolyticus in different growth phases after exposure to lethal stresses including 47 °C and 8% ethanol was first investigated. The effect of a culture's growth phase on both the heat and ethanol shock response of V. parahaemolyticus was then examined. It was found that cells of V. parahaemolyticus in the mid-exponential phase, regardless of adaptation, were most susceptible to environmental stresses, while cells in the stationary phase were least susceptible to the lethal stresses examined. Adaptation with heat shock at 42 °C for 45 min or ethanol shock with 5% ethanol for 60 min induced an increased resistance of V. parahaemolyticus to subsequent lethal stresses at 47 °C and 8% ethanol. While the adaptation treatments resulted in a reduced resistance of the test organism to pH 4.4 and 20% NaCl. Generally, the extent of changes in the resistance of V. parahaemolyticus to lethal stresses between the adapted and control cells was found to be growth phase dependent. Compared with the respective control cells, the adapted late-exponential phase cells exhibited the greatest extent of change, while the adapted stationary phase cells showed the least change in their resistance to the lethal stresses examined.     

High hydrostatic pressure processing reduces Salmonella enterica serovars in diced and whole tomatoes

Fresh and fresh-cut tomatoes have been associated with numerous outbreaks of salmonellosis in recent years. One effective post harvest treatment to reduce Salmonella enterica in tomatoes may be high pressure processing (HPP). The objectives of the study were to determine the potential for HPP to reduce S. enterica serovars Newport, Javiana, Braenderup and Anatum in tryptic soy broth (TSB) and to determine the effect of HPP to reduce the most pressure resistant of the four serovars from fresh diced and whole tomatoes. To evaluate pressure resistance, TSB containing 8 log CFU/ml of one of the four serovars was packaged in sterile stomacher bags and subjected to one of three different pressures (350, 450 or 550 MPa) for 120 s. The most pressure resistant S. enterica serovar evaluated was Braenderup. Subjecting the broth culture to 350, 450 and 550 MPa resulted in a 4.53, 5.74 and 7.09 log reduction in S. Braenderup, respectively. Diced tomatoes (150 g) and whole red round tomatoes (approximately 150 g) were inoculated with 0.1 ml of 9.1 log CFU/ml S. Braenderup, and subjected to the same pressure treatments (350, 450 or 550 MPa). Significant reductions of S. Braenderup concentrations in diced tomatoes (P < 0.05) were seen after processing at 350 (0.46 CFU/g), 450 (1.44 log CFU/g), and 550 MPa (3.67 log CFU/g). In whole tomatoes, significant reductions (P < 0.05) were also seen at 350 (1.41 log CFU/g), 450 (2.25 log CFU/g) and 550 MPa (3.35 log CFU/g). HPP may be an effective post harvest strategy to reduce low levels of S. enterica contamination in whole and diced tomatoes.     

Biological characterization of two marine Bdellovibrio-and-like organisms isolated from Daya bay of Shenzhen, China and their application in the elimination of Vibrio parahaemolyticus in oyster

Bdellovibrio-and-like organisms (BALOs) are a group of highly motile delta-proteobacteria that prey on other gram-negative bacteria. However, nothing is known of the application potential of marine BALOs in safeguarding seafood safety. Here, biological characterization of two marine BALOs strains and their application in the elimination of Vibrio parahaemolyticus in oyster (Crassostrea ariakensis) at the laboratory scale were investigated.BALOs strains BDH12 and BDHSH06 were isolated from sediment of Daya bay in Shenzhen of China, with Shewanella putrefaciens strain 12 and V. parahaemolyticus strain SH06 as preys, respectively, when using double layer agar technique. They were identified as BALOs morphologically by transmission electron microscopy, while partial 16S rDNA sequencing analysis revealed that they showed no close relationships with members of the known genera Bdellovibrio, Bacteriolyticum, Bacteriovorax, or Peredibacter.Biological characterizations revealed that both strains had the optimal pH, salinity and temperature at 7.2, 3% and 30 °C, correspondingly. They could not utilize autoclaved, dead cells as hosts. Prey range analysis revealed that individually, BDH12 and BDHSH06 lysed 82.5% (47 strains) and 84.2% (48 strains) of the total 57 preys tested respectively. In combination, they lysed 98.2% (56 of 57) strains. All strains of V. parahaemolyticus, Vibrio cholerae and Vibrio alginolyticus tested could be lysed by both strains.A 7-day laboratory-scale V. parahaemolyticus elimination experiment in oyster showed that in the control, the cell counts of total vibrios and V. parahaemolyticus strain Vp plus in water and in oyster intestines were on the rise, whereas in the BALOs treated groups, their numbers were down from 8.09 ± 0.05 log CFU/ml and 8.02 ± 0.04 log CFU/ml to 2.39 ± 0.01 log CFU/ml and 2.33 ± 0.01 log CFU/ml, respectively. The same patterns could also be observed in oyster intestines. Results of this study indicate the feasibility of using BALOs to biologically control or even eliminate V. parahaemolyticus in seafood oyster.     

Combined pH and high hydrostatic pressure effects on Lactococcus starter cultures and Candida spoilage yeasts in a fermented milk test system during cold storage

The combined effects of high pressure processing (HPP) and pH on the glycolytic and proteolytic activities of Lactococcus lactis subsp. lactis, a commonly used cheese starter culture and the outgrowth of spoilage yeasts of Candida species were investigated in a fermented milk test system. To prepare the test system, L. lactis subsp. lactis C10 was grown in UHT skim milk to a final pH of 4.30 and then additional samples for treatment were prepared by dilution of fermented milk with UHT skim milk to pH levels of 5.20 and 6.50. These milk samples (pH 4.30, 5.20 and 6.50) with or without an added mixture of two yeast cultures, Candida zeylanoides and Candida lipolytica (10⁵ CFU mL⁻¹ of each species), were treated at 300 and 600 MPa (≤20 °C, 5 min) and stored at 4 °C for up to 8 weeks. Continuing acidification by starter cultures, as monitored during storage, was substantially reduced in the milk pressurised at pH 5.20 where the initial titratable acidity (TA) of 0.40% increased by only 0.05% (600 MPa) and 0.10% (300 MPa) at week 8, compared to an increase of 0.30% in untreated controls. No substantial differences were observed in pH or TA between pressure-treated and untreated milk samples at pH 4.30 or 6.50. The rate of proteolysis in milk samples at pH values of 5.20 and 6.50 during storage was significantly reduced by treatment at 600 MPa. Treatment at 600 MPa also reduced the viable counts of both Candida yeast species to below the detection limit (1 CFU mL⁻¹) at all pH levels for the entire storage period. However, samples treated at 300 MPa showed recovery of C. lipolytica from week 3 onwards, reaching 10⁶–10⁷ CFU mL⁻¹ by week 8. In contrast, C. zeylanoides did not show any recovery in any of the pressure-treated samples during storage.     

Sensitivity of Vibrio species in phosphate-buffered saline and in oysters to high-pressure processing

Multiple strains of Vibrio vulnificus, Vibrio parahaemolyticus, and Vibrio cholerae non-O1 were tested in phosphate-buffered saline for their sensitivity to high-pressure processing (HPP). Variability in sensitivity among strains was observed for all species; this variability decreased at higher pressures. V. vulnificus was the species that was most sensitive to treatment at 200 MPa (decimal reduction time [D] = 26 s), and V. cholerae was the species that was most resistant to treatment at 200 MPa (D = 149 s). The O3:K6 serotype of V. parahaemolyticus was more resistant to pressure than other serotypes of V. parahaemolyticus were. The results of studies involving V. vulnificus naturally occurring in oysters revealed that a pressure treatment of 250 MPa for 120 s achieved a > 5-log reduction in the levels of this bacterium. V. parahaemolyticus serotype O3:K6 in oysters required a pressure of 300 MPa for 180 s for a comparable 5-log reduction. When properly applied, HPP can be effective in improving the safety of shellfish with respect to Vibrio spp.     

Effect of high-pressure processing on Listeria spp. and on the textural and microstructural properties of cold smoked salmon

Investigation of the effect of high-pressure processing (HPP) at very short time on the inactivation of Listeria innocua was conducted as well as the effect on texture and microstructure. Lipid oxidation, colour and background bacterial flora were studied as well. HPP at 700-900 MPa for 10 s increased the inactivation of L. innocua in cold smoked salmon from 4500 cfu/g to nondetectable level (<0.3 cfu/g). L. innocua was more sensitive to HPP than the background flora tested. The product presented good microbiological quality and there was no indication of lipid oxidation. The effect of HPP on the redness of the product was not observed, however immediate effect on the lightness was noticed and the salmon becomes lighter in colour as a function of both time and pressure. The effects on the microstructure increased with both time and pressure and were most significant at 900 MPa and 60 s. The effect on microstructure coincides with the reduction of the bacteria. The knowledge from this study provides information for the industry on the development of HPP at 400-900 MPa with short pressure time of less than 60 s.     

High pressure induced changes in beef muscle proteome: Correlation with quality parameters

The relationship between pressure induced changes on individual proteins and selected quality parameters in bovine longissimus thoracis et lumborum (LTL) muscle was studied. Pressures ranging from 200 to 600 MPa at 20 °C were used. High pressure processing (HPP) at pressures above 200 MPa induced strong modifications of protein solubility, meat colour and water holding capacity (WHC). The protein profiles of non-treated and pressure treated meat were observed using two dimensional electrophoresis. Proteins showing significant differences in abundance among treatments were identified by mass spectrometry. Pressure levels above 200 MPa strongly modified bovine LTL proteome with main effects being insolubilisation of sarcoplasmic proteins and solubilisation of myofibrillar proteins. Sarcoplasmic proteins were more susceptible to HPP effects than myofibrillar. Individual protein changes were significantly correlated with protein solubility, L*, b* and WHC, providing further insights into the mechanistic processes underlying HPP influence on quality and providing the basis for the future development of protein markers to assess the quality of processed meats.     

Kinetics of the formation of radicals in meat during high pressure processing

The kinetics of the formation of radicals in meat by high pressure processing (HPP) has been described for the first time. A threshold for the radicals to form at 400 MPa at 25 °C and at 500 MPa at 5 °C has been found. Above this threshold, an increased formation of radicals was observed with increasing pressure (400–800 MPa), temperature (5–40 °C) and time (0–60 min). The volume of activation (ΔV^#) was found to have the value −17 ml mol⁻¹. The energy of activation (E_a) was calculated to be 25–29 kJ mol⁻¹ within the pressure range (500–800 MPa) indicating high independence on the temperature at high pressures whereas the reaction was strongly dependent at atmospheric pressure (E_a = 181 kJ mol⁻¹). According to the effect of the processing conditions on the reaction rate, three groups of increasing order of radical formation were established: (1) 55 °C at 0.1 MPa, (2) 500 and 600 MPa at 25 °C and 65 °C at 0.1 MPa, and (3) 700 MPa at 25 °C and 75 °C at 0.1 MPa. The implication of the formation of radicals as initiators of lipid oxidation under HPP is discussed.     

Effect of hydrostatic high-pressure processing on the chemical,functional, and rheological properties of starter-free Queso Fresco

Queso Fresco (QF), a popular high-moisture, high-pH Hispanic-style cheese sold in the United States, underwent high-pressure processing (HPP), which has the potential to improve the safety of cheese, to determine the effects of this process on quality traits of the cheese. Starter-free, rennet-set QF (manufactured from pasteurized, homogenized milk, milled before hooping, and not pressed) was cut into 4.5- × 4.5- × 15-cm blocks and double vacuum packaged. Phase 1 of the research examined the effects of hydrostatic HPP on the quality traits of fresh QF that had been warmed to a core temperature of 20 or 40°C; processed at 200, 400, or 600 MPa for 5, 10, or 20 min; and stored at 4°C for 6 to 8 d. Phase 2 examined the long-term effects of HPP on quality traits when QF was treated at 600 MPa for 3 or 10 min, and stored at 4 or 10°C for up to 12 wk. Warming the QF to 40°C before packaging and exposure to high pressure resulted in loss of free whey from the cheese into the package, lower moisture content, and harder cheese. In phase 2, the control QF, regardless of aging temperature, was significantly softer than HPP cheeses over the 12 wk of storage. Hardness, fracture stress, and fracture rigidity increased with length of exposure time and storage temperature, with minor changes in the other properties. Queso Fresco remained a bright white, weak-bodied cheese that crumbled and did not melt upon heating. Although high pressures or long processing times may be required for the elimination of pathogens, cheese producers must be aware that HPP altered the rheological properties of QF and caused wheying-off in cheeses not pressed before packaging.     

Effect of gamma and electron beam irradiation on the survival of pathogens inoculated into salted, seasoned, and fermented oyster

The objective of this study was to identify the efficacy of gamma and electron beam irradiation of the food-borne pathogens including 3-strain cocktail of Listeria monocytogenes (ATCC 19114, 19115, and 19111), Staphylococcus aureus (ATCC 6538, 25923, and 29213), and Vibrio parahaemolyticus (ATCC 17802, 33844, and 27969) in salted, seasoned, and fermented oyster (oyster Jeotkal, 8% salt), commercially available in the market. Irradiation (0, 0.5, 1, 2, and 5 kGy) significantly reduced the initial microbial level not only immediately after irradiation but also during storage at 10 °C for 4 weeks (P ≤ 0.05). No viable cell was detected at 5 kGy of irradiation at a detection limit of 10¹ CFU/g. Gamma irradiation was more effective than electron beam irradiation, and yielded D₁₀ values of 0.60, 0.71, and 0.29 kGy for L. monocytogenes, S. aureus, and V. parahaemolyticus, and those of electron beam irradiation were 0.69, 0.94, and 0.29 kGy, respectively. V. parahaemolyticus was most sensitive to irradiation and storage among all pathogens tested. Sensory quality was not affected by irradiation treatment. Results suggest that a low dose irradiation can improve the microbial quality and reduce the risk by the food-borne pathogens of oyster Jeotkal, which has limited alternative sterilization methods due to the temperature sensitivity of food products.     

Rapid and sensitive detection of Vibrio parahaemolyticus in sea foods by electrochemiluminescence polymerase chain reaction method

Vibrio parahaemolyticus has been considered as one of the most important food-borne bacterial pathogens. Because of the safety concerns, detection and characterization of V. parahaemolyticus have attracted much attention. In this study, electrochemiluminescence polymerase chain reaction (ECL-PCR) method combined with universal probes hybridization technique was applied to rapid detection of V. parahaemolyticus, infected and uninfected sea foods for the first time. Whether the sea food samples were infected was discriminated by detecting the gyrase B (gyrB) gene. We detect V. parahaemolyticus both in artificially contaminated sea foods and natural samples. The experiment results show that the infected and uninfected sea food samples can be clearly identified and the detection limit for V. parahaemolyticus is 1.6 pg purified genomic DNA in the presence of 1 μg non-specific background DNA. The technique may provide a new means in V. parahaemolyticus detection due to its simplicity and high efficiency.     

High pressure–temperature degradation kinetics of polyacetylenes in carrots

The present study assessed the effect of high pressure–temperature (HPT) processing on the levels of three polyacetylenes in carrot disks immediately after processing in comparison to sous-vide processing. The degradation kinetics of these compounds following processing at HPT was also investigated. The highest pressure–temperature combination which gave maximum retention during the time 10–30 min, for falcarinol it was 400 MPa, at 50 and 60 °C for 10 min; for falcarindiol it was 400 MPa, at 50 °C for 10 min and for falcarindiol-3-acetate was 400 MPa, at 50 °C for 10 min, respectively. Falcarindiol-3-acetate was found to be most barosensitive and falcarindiol was found to be most thermosensitive of the three polyacetylenes studied. When compared with sous-vide (SV) processed carrot disks, HPT processed samples showed higher retention of polyacetylenes. The changes in the levels of polyacetylenes during HPT treatment were adequately described by Weibull model function.