Radiation-resistant Macrococcus caseolyticus (A) isolated from radiation-processed semidried prawns.

A radiation-resistant bacterial isolate from gamma-radiation-processed (5 kGy) semidried prawns was identified as a new strain of Macrococcus caseolyticus and was designated as M. caseolyticus (A) on the basis of morphological and biochemical characterization and 16S rRNA sequencing. DNA-DNA hybridization studies with M. caseolyticus DSM 20597(T) further confirmed the isolate as M. caseolyticus. Major fatty acids present in M. caseolyticus (A) were C14:0, C16:1ω11c, and C18:1ω9c, whereas C15:0anteiso, C16:0iso, and C18:0iso were absent. The closest match for the isolate, as per fatty acid methyl ester analysis, was M. caseolyticus DSM 20597(T). However, the similarity index was significantly low (0.112), which indicates that the isolate could be a new strain of M. caseolyticus. The decimal reduction dose (D10) for M. caseolyticus (A), M. caseolyticus JCSC5402, and Staphylococcus aureus MTCC96 was 1.18, 0.607, and 0.19 kGy, respectively. This is the first report on radiation resistance of M. caseolyticus. Macrococcus caseolyticus (A) is more resistant to gamma and UV radiation stress than are M. caseolyticus JCSC5402 and S. aureus MTCC96; however, it is sensitive to heat as well as desiccation stress.

An investigation into gamma-ray treatment of shellfish using electron paramagnetic resonance spectroscopy.

BACKGROUND: Gamma irradiation is a safe method for the decontamination of shellfish, and its technical feasibility and safety have been endorsed (FAO/IAEA/WHO). In order to implement proper food-processing regulations, the identification of radiation treatment is required. In this study, electron paramagnetic resonance (EPR) spectroscopy was employed to identify the irradiation of seven different types of commonly consumed shellfish. RESULTS: Characteristics (g factor and signal intensity) of the EPR spectra of control and irradiated samples were recorded in order to clarify the gamma-ray treatment of shellfish. Radiation-specific signals around g = 2.0038 ± 0.0006 (g1) and g = 1.9996 ± 0.0002 (g2 and g3) were observed for all shellfish samples irradiated with absorbed doses of 3 and 6 kGy. The X-ray diffraction (XRD) spectra of some shellfish samples were recorded to investigate their mineral profiles. CONCLUSION: The EPR spectroscopic results indicated that carbonate minerals were the source of the paramagnetic species that were produced upon irradiation, entrapped in the shellfish and showed radiation-specific asymmetric signals whose intensities increased quantitatively with the absorbed radiation dose. The XRD analysis revealed that aragonite and calcite minerals were present in the shells of shellfish.

Impact of irradiation on fish and seafood shelf life: a comprehensive review of applications and irradiation detection.

Irradiation is one of the most important and effective methods towards food preservation despite the consumer lack of trust and aversion towards this method. Irradiation effectiveness greatly depends on the dose provided to food. This review aims at summarizing all available information regarding the impact of irradiation dose on the shelf life and microflora and sensory and physical properties of fish, shellfish, molluscs, and crustaceans. The synergistic effect of irradiation in conjunction with other techniques such as salting, smoking, freezing, and vacuum packaging was also reported. Another issue covered within the frame of this review is the detection (comparison of methods in terms of their effectiveness and validity) of irradiated fish and seafood. The information related to fish and seafood irradiation and its detection is presented by means of 11 comprehensive tables and 9 figures.

[Constant direct action of the magnetic field on the brain fabric].

The important role of direct action of a constant magnetic field (CMF) on a fabric of a brain in its realization neural-effects under condition of an irradiation of a head of an animal is shown. In experiments on rabbits it is statistically proved, that a various degree of neural isolation of a bark of a brain, not only does not interfere with display of reaction of its bioelectric activity on CMF, but also does by its more precise (unequivocal, intensive, short-latent), in comparison with corresponding answers of intact brain. The comparative analysis of bioelectric activity of intact brain, a preparation "cerveau isole", the neural-isolated strip of a bark (at rabbits) and completely isolated nervous system (a chain of a river cancer) in conditions of action CMF proves the above-stated position.

The effect of electron beam irradiation on IgG binding capacity and conformation of tropomyosin in shrimp.

To evaluate the effect of electron beam (EB) irradiation on IgG binding capacity and conformation of tropomyosin in shrimp (Solenocera melantho), shrimp meat was irradiated with different doses (0, 1, 3, 5, 7, 9 kGy) of EB. IgG binding capacity of TM from shrimp meat was detected by western blot and indirect enzyme-linked immunosorbent assay. The conformation of TM was analyzed with circular dichroism and Fourier transform infrared spectroscopy. Results showed that there was a significant decrease in IgG binding capacity of TM from shrimp meat treated with EB irradiation, with the most significant effect observed at 7 kGy. At this dose, the IgG binding capacity of TM decreased by 59% when compared to the control group. The structural changes were consistent with changes in IgG binding capacity of TM. It was concluded that EB irradiation can reduce the immunoreactivity of shrimp TM by altering its structure.

Rapid and Reliable Method for Determining Irradiation Histories of Ground Beef and Prawns by Measuring 5,6-Dihydrothymidine.

A rapid and reliable method for determining irradiation histories of ground beef and prawns was developed on the basis of a method for determining the irradiation history of beef liver by liquid chromatography-tandem mass spectrometry (LC-MS/MS) of 5,6-dihydrothymidine (DHdThd). Improvements in the method included the following: (1) 50% ethanol precipitation in the DNA extraction step was conducted before the RNase step, (2) snake venom phosphodiesterase I was used for DNA digestion to boost liberation of DHdThd, and (3) a matrix-matched calibration curve was used for determining DHdThd by LC-MS/MS analysis. This method successfully determined irradiation histories of ground beef and prawns. Furthermore, a close correlation between the formation of DHdThd and 2-alkylcyclobutanones, which are an established index of irradiation histories, was observed in ground beef. DHdThd in DNA could be a promising candidate for a new index of irradiation histories of various foods.

Inactivation by ionizing radiation of Salmonella enteritidis, Salmonella infantis, and Vibrio parahaemolyticus in oysters (Crassostrea brasiliana).

Irradiation is considered one of the most efficient technological processes for the reduction of microorganisms in food. It can be used to improve the safety of food products, and to extend their shelf lives. Oysters are considered one of the most important vehicles for pathogenic bacteria because of their feeding characteristics. The aim of this study was to evaluate the influence of a gamma radiation process on high levels of Salmonella Enteritidis, Salmonella Infantis, and Vibrio parahaemolyticus incorporated by oysters (Crassostrea brasiliana), as well as the effects of the process on the survival of the oysters and on their sensory attributes. The oysters were exposed to gamma radiation (60Co) in doses ranging from 0.5 to 3.0 kGy. A dose of 3.0 kGy was generally sufficient to reduce the level of Salmonella serotypes by 5 to 6 log10 units. A dose of 1.0 kGy was sufficient to produce a 6-log10 reduction in the level of V. parahaemolyticus. The highest irradiation dose did not kill the oysters or affect their sensory attributes. Hence, a dose of 3.0 kGy can be considered effective in inactivating Salmonella and V. parahaemolyticus in oysters without changing their odor, flavor, or appearance.

Long-term decline of radiocesium concentration in seafood from the Ligurian sea (northern Italy) after Chernobyl.

The activity of 137Cs, 134Cs and 40K in tissues from fish, molluse and shellfish of the Ligurian sea was measured during 1987-1988. The mean annual concentrations in 1987 were 5.92 +/- 4.1 Bq/kg (wet tissue) for 137Cs and 2.7 +/- 1.5 Bq/kg for 134Cs and 2.46 +/- 1.82 and 0.33 +/- 0.57 Bq/kg respectively in 1988. The mean value of 40K activity was 138.6 +/- 22.1 Bq/kg. Contamination was significantly higher in the littoral area up to 1000 m from the coast (8.39 +/- 7.6 and 1.74 +/- 2.08 Bq/kg respectively versus 2.91 +/- 1.87 and 0.58 +/- 0.59 Bq/kg respectively in the open sea). The common octopus (Octopus vulgaris) had the highest radioactivity values and could be utilized as an indicator of radioactivity pollution. There were no significant differences regarding the trophic level, the seafood phylum, or the east and west Ligurian sea areas. Long-term reduction in the sea habitat was estimated at about 200 days for 137Cs and 110 days for 134Cs, reflecting differences in the physical half-life of these radionuclides. These values were lower than those found in terrestrial foodstuff and could have reflected dilution of the contaminants in the open sea. The effective dose equivalent for the Ligurian population of radiocesium originating from seafood was estimated at 1.3 microSv in 1987 and 0.5 microSv in 1988. These va ues represent 0.8 and 0.3% respectively of the annual dose (180 microSv/year) due to 40K intake with the diet.

Determination of hydroxytryptophan isomers in gamma-irradiated egg white, chicken meat, and shrimps.

The radiation induced products of tryptophan (TRP) were determined in gamma-irradiated egg white, chicken meat and shrimps using RP-HPLC and electrochemical detection. A two-step hydrolysis with proteinase K and carboxypeptidase A was developed to release the radiation products from egg white and chicken meat and with proteinase K and pronase E from shrimps. The four hydroxytryptophan isomers (OH-Trp) were identified and quantified as radiation products in all samples. The amounts ranged between 0.02 and 1.97 mg/kg protein. A significant difference between irradiated and unirradiated samples was found for irradiation doses of more than 3 kGy for egg white and chicken meat. For shrimps no significant increase of OH-Trp isomers was measured up to a radiation dose of 5 kGy.

A point about electron paramagnetic resonance detection of irradiated foodstuffs.

This paper makes a point about the identification of irradiated foodstuffs by means of electron paramagnetic resonance (EPR) or electron spin resonance (ESR). EPR is the most accurate method for such routine applications since radicals are stabilised for a long time in all (or part of) foods that are in solid and dry states; consequently, EPR can be applied to meat and fish bones, fruit and relative products (from vegetal origin). More details are given for mollusc shells, such as oysters and mussels.

Current status of the EPR method to detect irradiated food.

This review gives a brief outline of the principles of the EPR detection method for irradiated foods by food type. For each food type, the scope, limitations and status of the method are given. The extensive reference list aims to include all which define the method, as well as some rarely cited works of historical importance.

Ultraviolet irradiation and gradient temperature assisted autolysis for protein recovery from shrimp head waste.

A novel autolysis method using ultraviolet (UV) irradiation and gradient temperature was investigated to efficiently recover proteins from the head of the shrimp Penaeus vannamei. The proteolytic activity of shrimp head subjected to 30W UV irradiation for 20 min was increased by 62%, compared with that of untreated samples. After irradiation, the enzymes remained active across a wide range of temperatures (45-60°C) and pH (7-10). An orthogonal design was used to optimize autolysis condition. After 5h autolysis, protein recovery from the UV-heat treated samples was up to 92.1%. These results indicate the potential of using UV irradiation in combination with gradient temperatures to improve recovery of proteins from shrimp head waste.

Cholesterol oxidation and astaxanthin degradation in shrimp during sun drying and storage.

Dried salted shrimps are made from raw shrimps, which are cooked and dried under direct sunlight. The preparation and storage include treatments and conditions that can promote oxidative changes in different components. The aim of this study was to monitor the formation of major cholesterol oxidation products and the changes in the astaxanthin content and fatty acid profile in dried salted shrimp during cooking, sun drying and storage. During sun drying, most of the astaxanthin (75%) was degraded in cooked shrimp, while cholesterol oxidation products (COPs) showed a dramatic increase (8.6-fold), reaching a total concentration of 372.9 ± 16.3 µg/g of lipids. Further storage favoured both astaxanthin degradation (83%) and COPs formation (886.6 ± 97.9 µg/g of lipids after 90 days of storage). The high degradation of astaxanthin and the elevated formation of COPs during sun drying and storage indicate the necessity to re-evaluate the processing and storage conditions of salted dried shrimp.

Identifying irradiated oysters by luminescence techniques (TL & PSL).

This study shows an exhaustive comparison of different methods, based on luminescence techniques, to identify X-ray irradiated oysters at five different dose levels in the range 0.1-2 kGy and suggests a simple, fast and sequential routine analysis protocol. A total number of 50 oysters from North Sea, including 10 control samples, were analysed by using two photo-stimulated luminescence (PSL) methods (named A and B) and three thermoluminescence (TL) methods (named C, D and E), either on constituents or contaminating minerals from shells and intestines. Setting a lower threshold value T1 (1000 counts/60s) all of control specimens gave negative screening results while photo counts from irradiated samples were found to be higher than upper threshold T2 (4000 counts/60s), except at the lowest dose level 0.1 kGy for procedure A. All PSL calibrated analysis were successful and a sensitivity index was also determined to better classify obtained data according to the revised European Standard (EN 13751:2009). TL ratios, Glow 1 over second Glow 2, the latter after irradiating at 1 kGy and remeasuring the same minerals for each sample, showed values less than 0.1 related to untreated samples or higher than 0.1 for irradiated ones. Reported procedures were also tested over 60 days, longer than oyster shelf life confirming the applicability and feasibility of the proposed methods.

Pulsed ultraviolet light reduces immunoglobulin E binding to Atlantic white shrimp (Litopenaeus setiferus) extract.

Pulsed ultraviolet light (PUV), a novel food processing and preservation technology, has been shown to reduce allergen levels in peanut and soybean samples. In this study, the efficacy of using PUV to reduce the reactivity of the major shrimp allergen, tropomyosin (36-kDa), and to attenuate immunoglobulin E (IgE) binding to shrimp extract was examined. Atlantic white shrimp (Litopenaeus setiferus) extract was treated with PUV (3 pulses/s, 10 cm from light source) for 4 min. Tropomyosin was compared in the untreated, boiled, PUV-treated and [boiled+PUV]-treated samples, and changes in the tropomyosin levels were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). IgE binding of the treated extract was analyzed via immunoblot and enzyme-linked immunosorbent assay (ELISA) using pooled human plasma containing IgE antibodies against shrimp allergens. Results showed that levels of tropomyosin and IgE binding were reduced following PUV treatment. However, boiling increased IgE binding, while PUV treatment could offset the increased allergen reactivity caused by boiling. In conclusion, PUV treatment reduced the reactivity of the major shrimp allergen, tropomyosin, and decreased the IgE binding capacity of the shrimp extract.