Biofilm formation by Vibrio parahaemolyticus on food and food contact surfaces increases with rise in temperature

Vibrio parahaemolyticus is recognized as a human foodborne pathogen that is mostly associated with seafood. This pathogen can form a mature biofilm on food and food contact surfaces during food processing. The present study investigated V. parahaemolyticus biofilm formation at various temperatures on shrimp, crab, and stainless steel coupons, using the biofilm formation index (BFI) method on microtiter plates. The results were also confirmed by field emission scanning electron microscopy. Both the BFI values and cultural counts revealed that V. parahaemolyticus biofilm formation was stronger at higher temperatures than at lower temperatures. Biofilm formation differed according to the growth surface type and growth temperature. It was found that higher temperatures (15–37 °C) induced stronger biofilm formation whereas 4 and 10 °C resulted in attachment of the bacterial cells as monolayers. It could be concluded that temperatures of 25–37 °C result in significantly stronger biofilm formation as well as exoprotease and AI-2 production on food and food contact surfaces, indicating that these temperatures might be threatening conditions for food safety.     

Chemicals and biological products used in south-east Asian shrimp farming, and their potential impact on the environment — a review

A wide variety of chemicals and biological products are used to treat the water and sediment of ponds in semi-intensive and intensive south-east Asian shrimp farming. These products are also often used in shrimp hatcheries and to disinfect equipment for shrimp pond management. In spite of the size and importance of the shrimp farming industry in several south-east Asian countries, documentation of the quality and quantity of chemicals and biological products used during farming is scarce. This paper is a compilation of the literature available on substances used in shrimp farming, and the possible environmental effects of these products are analysed to the extent allowed by the limited information. The role of shrimp farm managers, the chemical industry, governments, inter-governmental organisations and scientists in the development of a sustainable practice is discussed. It is concluded that shrimp farmers should reduce the use of chemicals and biological products because of the risks to the environment, human health and to production, and also, because many chemicals and biological products used in pond management have not been scientifically shown to have a positive effect on production. Clearly, the use of some chemicals, i.e. certain antibiotics, poses a risk of danger towards human health. Some chemicals used in shrimp farming, such as organotin compounds, copper compounds, and other compounds with a high affinity to sediments leave persistent, toxic residues, and are likely to have a negative impact on the environment. However, to assess the reality of these risks, substantial new information about the quantity of chemicals used in marine south-east Asian shrimp farming is needed.     

The effect of several cooking treatments on subsequent chilled storage of thawed deepwater pink shrimp (Parapenaeus longirostris) treated with different melanosis-inhibiting formulas

This work deals with the effect that different cooking methods have on quality of shrimps (Parapenaeus longirostris) during the chilled storage. Vacuum-cooking (sous-vide) and steaming were compared with the traditional cooking process in boiling water. The effect of prior treatment with several melanosis-inhibiting agents (with a commercial sulphite- or 4-hexylresorcinol-based formula) was also tested. Neither the melanosis-inhibiting blends nor the cooking methods used significantly affected the water-holding capacity, firmness or moisture content of the cooked shrimps. Spraying with a 4-hexylresorcinol-based formula was effective in preventing microbial growth during storage. Vacuum-cooking was also shown to be the most effective way of preventing microbial growth although the TVB-N content of cooked shrimps increased significantly. By discriminant analysis, a combination of prior spraying with 4-hexylresorcinol-based formula followed by vacuum-cooking, proved to be the best method for obtaining shrimps with a very good appearance and high microbial quality. The foregoing may be very important for the cooking industries.     

Kinetic modeling of mass transfer during deep fat frying of shrimp nugget prepared without a pre-frying step

The objective of this study was to evaluate the effect of different batter formulation on mass transfer during deep fat frying of shrimp nuggets prepared without a pre-frying step. The effects of soy and corn flour (5, 10%) addition to the batter formulation, frying temperature and time on mass transfer were determined. The results showed an interaction effect of these processing conditions on mass transfer. The most reduction in fat absorption was observed when samples were coated with batter contained 10% soy flour and fried at 190 °C. The first order kinetic based on the Fick's law were used to describe moisture transfer data. The effective moisture diffusivity ranged between 2.05 × 10⁻⁸ and 5.71 × 10⁻⁸ m²/s with R² between 0.91 and 0.98, and fat transfer rate constant was between 3.5 × 10⁻³ and 7.8 × 10⁻³ s⁻¹ with R² from 0.82 to 0.99. Activation energy obtained from the Arrhenius plot for the effective moisture diffusivity ranged between 18.42 and 23.84 kJ/mol.     

A predictive model for assessment of decontamination effects of lactic acid and chitosan used in combination on Vibrio parahaemolyticus in shrimps

Vibrio parahaemolyticus is a major causative agent of human gastroenteritis in seafood products including shrimps. Lactic acid and chitosan are natural antimicrobials for food decontamination in the washing process of seafood. In this research, a 4-factor response surface model based on the Box–Behnken experimental design was developed to evaluate the effects of lactic acid (1%, 2%, and 3%, v/v), chitosan (0.4%, 1%, and 1.6%, w/v), rotational rate (90, 110, and 130 rpm) and washing time (10, 20, and 30 min) on reduction of V. parahaemolyticus inoculated in raw shrimps. These treatments achieved 2.2 to 4.3 log₁₀ CFU/g reduction of V. parahaemolyticus in shrimps. Stepwise stratification led to a simplified model that has a satisfactory performance as evidenced by statistical indices (R² = 0.92; p < 0.0001; RMSE = 0.196) and external validation parameters [bias factor (B_f) = 1.01; accuracy factor (A_f) = 1.05]. The model generated an optimum treatment combination (3% lactic acid, 1.6% chitosan, and rotational rate at 110 rpm) that could achieve greatest bacterial reduction of 4.5 log₁₀ CFU/g. Among the four factors, lactic acid and chitosan were the major contributors for bacterial decontamination. Analysis of variances showed a significant interactive inactivation effect (p < 0.05) from combined use of lactic acid and chitosan. The treatments did not have adverse effects on the quality attributes such as color and pH of the shrimps.     

Supercritical fluid extraction in situ derivatization for simultaneous determination of chloramphenicol,florfenicol and thiamphenicol in shrimp

The applicability of supercritical fluid extraction in situ derivatization was investigated for determination of trace amounts of amphenicols (chloramphenicol, florfenicol and thiamphenicol) in shrimp. Quantification was performed by using electron-capture negative chemical ionisation-gas chromatography/mass spectrometry (NCI–GC/MS). The parameters of supercritical fluid extraction (addition of modifier, temperature, pressure, extraction time and extraction mode) and in situ derivatization (collection solvent and derivatization reagent) were varied with control. The optimum extractions were obtained using 600 μL ethyl acetate as a modifier for supercritical carbon dioxide with static extraction for 5 min, then dynamic extraction for 10 min at 25 MPa and 60 °C. The conditions for in situ derivatization were 200 μL N,O-bis(trimethylsilyl) trifluoroacetamide containing 1% trimethylchlorosilane in 20 mL ethyl acetate as collection solvent. The new method of supercritical fluid extraction in situ derivatization was found to be linear over the concentration range of 20–5000 pg/g, with detection limits ranging from 8.7 to 17.4 pg/g (using the selective ion monitoring mode), with a R.S.D. (relative standard deviation) less than 15.3% (n = 5). Analysis of spiked shrimp samples revealed that matrix had little effect on extraction. The results presented here indicate that supercritical fluid extraction in situ derivatization is for the trace analysis of amphenicol bacteriostats in shrimp samples.     

Effect of cooking conditions on the flavour compounds and composition of shrimp (Parapenaeus longirostris) broth

 To achieve a shrimp broth with the best flavour, the whole shrimp must be cooked at 85°C for 30 min in a 0.5% NaCl solution in proportions 1 : 2 (w : v). Quantitatively, the main components of the broth were nitrogen substances, the most abundant of these being peptides of molecular weight less than 600 Da. Levels of ATP metabolites were also determined [the more abundant compounds were inosine, guanosine 5′-monophosphate (GMP) and inosine 5′-monophosphate (IMP)], as were free sugars (glucose, fructose and ribose) and fat content. The free amino acid composition was also determined. A significant correlation (P <0.0001) between cooking temperature and different nitrogen fractions was observed. Received: 22 September 1997 / Revised version: 13 November 1997     

Lipid Adaptation of Shrimp Rimicaris exoculata in Hydrothermal Vent

The shrimp Rimicaris exoculata is the most abundant species in hydrothermal vents. Lipids, the component of membranes, play an important role in maintaining their function normally in such extreme environments. In order to understand the lipid adaptation of R. exoculata (HV shrimp) to hydrothermal vents, we compared its lipid profile with the coastal shrimp Litopenaeus vannamei (EZ shrimp) which lives in the euphotic zone, using ultra performance liquid chromatography electrospray ionization‐quadrupole time‐of‐flight mass spectrometry. As a result, the following lipid adaptation can be observed. (1) The proportion of 16:1 and 18:1, and non‐methylene interrupted fatty acid (48.9 and 6.2 %) in HV shrimp was higher than that in EZ shrimp (12.7 and 0 %). While highly‐unsaturated fatty acids were only present in the EZ shrimp. (2) Ceramide and sphingomyelin in the HV shrimp were enriched in d14:1 long chain base (96.5 and 100 %) and unsaturated fatty acids (67.1 and 57.7 %). While in the EZ shrimp, ceramide and sphingomyelin had the tendency to contain d16:1 long chain base (68.7 and 75 %) and saturated fatty acids (100 and 100 %). (3) Triacylglycerol content (1.998 ± 0.005 nmol/mg) in the HV shrimp was higher than that in the EZ shrimp (0.092 ± 0.005 nmol/mg). (4) Phosphatidylinositol and diacylglycerol containing highly‐unsaturated fatty acids were absent from the HV shrimp. (5) Lysophosphatidylcholine and lysophosphatidylethanolamine were rarely detected in the HV shrimp. A possible reason for such differences was the result of food resources and inhabiting environments. Therefore, these lipid classes mentioned above may be the biomarkers to compare the organisms from different environments, which will be benefit for the further exploitation of the hydrothermal environment.     

Effect of Garlic Oil and Modified Atmosphere Packaging on the Quality of Chilled Shrimp

This research aimed to investigate the effect of essential oils extracted from garlic (Allium sativum L.) and modified atmospheric (MA) conditions on maintaining the quality of chilled Pacific white shrimps (Litopenaeus vannamei). Clean fresh shrimps (headless, shell‐off and devein) were dipped into 15 mg/ml of garlic oil for 15 min. Approximately 100 g of shrimps with or without dipping into the garlic oil was placed on polyethylene terephthalate trays and packed under two MA conditions (modified atmosphere packaging 1: 40% CO₂ + 60% N₂ and modified atmosphere packaging 2: 60% CO₂ + 40% N₂) using nylon/PE pouches. The shrimps with or without dipping into the garlic oil packed under normal atmospheric condition using PE pouches were prepared as the control. The samples were then stored at 8°C ± 2°C for three weeks and taken every two times a week. Shrimp samples were subjected to physical, chemical and microbiological analysis as well as sensory evaluation. The results showed that either garlic oil or MA conditions had proven to help preserving the quality of chilled white shrimps because they slowed down both chemical degradation and microbial spoilage. The shrimps dipped in garlic oil and/or packed under MA conditions had lower pH, total volatile base nitrogen and trimethylamine values as well as total viable counts than the control sample. 60% CO₂ + 40% N₂ in combination of garlic oil helped prolonging the shelf life of the shrimps stored at 8°C ± 2°C from 6 to 18 days. Thus, applying both garlic oil and low O₂ atmospheric conditions were more effective on maintaining shrimp quality than applying only garlic oil or MA conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

CAROTENOPROTEIN FROM TROPICAL BROWN SHRIMP SHELL WASTE BY ENZYMATIC PROCESS

While extraction of carotenoprotein from brown shrimp (Metapenaeus monoceros) shell waste, trypsin showed maximum recovery (55%) of carotenoid pigment in 4 hours at (28±2°C); but pepsin and papain showed about 50% recovery during the same period. The yield of protein paste by trypsin was maximum. The average protein content in the protein paste was about 450 g kg^-1. The percent of recovery of protein by papain and pepsin was close to that of trypsin. During storage at ambient temperature (28±5°C) loss of carotenoids from cake prepared by trypsin was minimum. The cost of trypsin is twenty times that of papain. Thus papain, easily available and the cheapest enzyme, can be used suitably for moderate recovery of carotenoids and good recovery of protein from shrimp shell waste at tropical ambient temperature. The dried colorless solid residue after extraction of carotenoprotein and protein, can be used as raw materials for chitin/chitosan.