Determination of indole in shrimps by differential-pulse voltammetry in an emulsified medium.

A method has been developed to determine indole in shrimps by differential-pulse voltammetry at a Pt electrode in an emulsified medium, after extraction into hexane - ethyl acetate (49 + 1). The standard additions method was used in order to minimise the matrix effect. Recoveries at the concentration levels of 11.71 and 0.94 micrograms g-1 of shrimp were 82 and 75%, respectively. The relative standard deviations were 3.5 and 4.0%, respectively. The accuracy of the proposed method was verified by comparing the results obtained from the analysis of shrimp samples allowed to decompose at room temperature for 1, 3 and 4 d, with those obtained from a spectrophotometric method by applying Student's t-test.

Effect of cooking on availability and in vitro nitrosation of precursors of volatile N-nitroso compounds in seafood.

Aqueous extracts of uncooked and cooked samples of squid and shrimp, characterized by their high amine content, were exposed to nitrate. The samples were cooked following traditional Italian recipes: stewing, grilling and deep-frying for squid; boiling, grilling and deep-frying for shrimp. Incubation of the aqueous extracts with nitrite in acidic medium yielded appreciable amounts of N-nitrosodimethylamine. Ascorbic acid and alpha-tocopherol were effective in preventing nitrosation of seafood amines only in the presence of molar excesses of these vitamins. An attempt at modulating nitrosation through the use of food ingredients naturally rich in vitamin C was unsuccessful.

Determination of total sulfite in shrimp, potatoes, dried pineapple, and white wine by flow injection analysis: collaborative study.

A method for the determination of total sulfite in shrimp, potatoes, dried pineapple, and white wine by flow injection analysis (FIA) was collaboratively studied by 8 laboratories. In the method, the sample solution is reacted with sodium hydroxide to liberate aldehyde-bound sulfite. The sample stream is acidified to produce SO2 gas, which diffuses across a Teflon membrane in the gas diffusion cell into a flowing stream of malachite green. The degree of discoloration of the malachite green is proportional to the amount of sulfite in the sample solution. Red wine was included in the study but interlaboratory precision for these samples was not satisfactory and correlation with Monier-Williams results was poor. The present method is not recommended for use with these samples. For shrimp, potatoes, dried pineapple, and white wine, average reproducibility (RSDR) of results was 25% for samples at 10 ppm SO2 and 10% for samples at greater than 50 ppm. Overall average reproducibility was 14%. Recoveries of sulfite added to samples averaged 80%. Comparison of FIA with the Monier-Williams method indicated comparable results by the 2 methods. The FIA method has been adopted official first action for determination of greater than or equal to 5 ppm total sulfite in shrimp, potatoes, dried pineapple, and white wine.

Extraction from prawn shells of substances cryoprotective for Vibrio cholerae.

Substances cryoprotective for Vibrio cholerae were detected from prawn shells immersed in phosphate-buffered saline. This cryoprotective activity was heat resistant and sensitive to treatment with trypsin. For the exhibition of its full activity, the presence of Mg ion was indispensable. The cryoprotective activity of this substance was more active than that of other known cryoprotectants, like glycerol or serum.

[Fluoride contents in tea and Sakura-shrimp in relation to other inorganic constituents].

The purpose of this study is to determine the fluoride contents of shrimp and of tea samples obtained from Shizuoka prefecture which is famous for tea products area and fishery market and to examine the relations between fluoride and other mineral contents, such as calcium, magunesium and phosphorus. Fluoride contents in tea produced in this area have been reported by Matsuura and Kokubu and other investigators, but more recent data are scarce. Samples were taken from a kind of shrimp known as Sakura-shrimp and from 4 kinds of commercial tea (coarse tea, 2 kinds of green tea and refined green tea). After having been dried and powdered, 1g of each sample was reduced to ashes at 550 degrees C for 10 hours with Ca(OH)2 as a fluoride fixative. Fluoride was distilled from each ash sample at about 140 degrees C with HClO4, and about 200 ml of distillate was collected from each sample. Fluoride contents were determined by means of ion-specific electrode. Calcium and magnesium contents were determined by atomic absorption spectrophotometry, and phosphorus contents were determined by Chen, Toribara and Warner's method. Total fluoride contents of the samples were as follows: 61.73ppm in shrimp, 180.16ppm in coarse tea, 72.62ppm and 89.02ppm in the 2 kinds of green tea, and 71.11ppm in refined green tea. More than 99% of the total fluoride was obtained from 150ml distillate of each sample. Calcium contents were extremely high in shrimp (21,822ppm) and 2,106-2,693ppm in tea samples. Magnesium contents were highest in shrimp (3,088ppm) and lowest in coarse tea (1,333ppm).(ABSTRACT TRUNCATED AT 250 WORDS)

Sensitivity to sulfited foods among sulfite-sensitive subjects with asthma.

Eight individuals with asthma who had been diagnosed as sulfite sensitive on the basis of double-blind capsule-beverage challenges were subjected to challenges with various sulfited foods, including lettuce, shrimp, dried apricots, white grape juice, dehydrated potatoes (as mashed potatoes), and mushrooms. Four of these patients failed to respond to challenges with any of the sulfited foods. The other four patients experienced a decrease in pulmonary function on double-blind challenges with sulfited lettuce. Two of three of these patients reacted to challenges with dried apricots and white grape juice; the fourth patient has not yet been challenged with these products. Only one of these four patients reacted to challenges with dehydrated potatoes and mushrooms, and, in this case, the response to double-blind challenges with dehydrated potatoes was not consistent. None of the sulfite-sensitive subjects with asthma responded to challenges with sulfited shrimp. It is concluded that sulfite-sensitive subjects with asthma will not necessarily react after ingestion of sulfited foods. The likelihood of a reaction is dependent on the nature of the food, the level of residual sulfite, the sensitivity of the patient, and perhaps on the form of residual sulfite and the mechanism of the sulfite-induced reaction.

Presence and significance of lithium in the brown shrimp, Crangon crangon (L.).

1. In female (non-ovigerous and ovigerous) brown shrimps, Crangon crangon, whole animal lithium levels are about 20% higher than in males, which indicates that lithium has a special function in the female reproductive system. 2. Decreasing lithium levels in larger males suggest that with males a substantial part of the lithium present may be passively absorbed to the exoskeleton. 3. At low temperatures internal lithium concentrations are strongly increased. In response to external salinity the internal lithium concentrations show a typical regulation pattern. The effects of temperature and salinity clarify that lithium must be involved in metabolic processes. 4. Apart from a special function in the reproductive system, lithium can probably replace other ions in their function, e.g. in regulating the activity of enzymatic processes.

Chitin structure and chitinase activity: isolation of structurally intact chitins.

Assessment of chitinase kinetics and mechanism in vitro has been hampered by lack of suitable substrates. We have previously reported rapid linear initial chitinase velocity with chitin substrate isolated from insect larval cuticle. Such chitin is shown to be fibrous in the light microscope. Methods are described for preparing fibrous chitins from any animal source including calcified carapaces. Evidence is given that chitin native fine structure in situ is maintained by structural proteins which in the fibrous chitin isolates are functionally replaced by covalently bound ester groups. Chitin fiber analogues thus reconstructed appear to have retained their native fine structure.

Identification of a shrimp-derived allergen as tRNA.

During an attempt to isolate shrimp allergens, evidence was obtained that shrimp ribonucleic acid was capable of eliciting a specific IgE response in man and an experimental animal model system. The shrimp ribonucleic acid was extracted from boiled whole shrimp (Peneaus indicus), and was isolated by salt precipitation and sequential chromatography over DEAE-Sephacel and BioGel P-100. The allergenic material was identified as a ribonucleic acid based on the following criteria: a maximal absorption at 258 nm, failure to stain positively with Coomassie Brilliant Blue on slab gel electrophoresis, positive staining with ethidium bromide, co-migration with yeast tRNA on submerged gel electrophoresis in 1.5% Agarose M, and sensitivity to ribonuclease T2 and 0.3 M NaOH. Treatment with protease did not alter its allergenic activity. The RNA was capable of binding allergen-specific IgE in sera from two shrimp-sensitive patients, as demonstrated by microELISA and solid-phase radioimmunoassay (SPRIA) using antigen-coated nitrocellulose filter paper discs and purified 125I-labeled goat anti-human IgE. RNA isolated from shrimp by a conventional tRNA isolation procedure also had the ability to specifically bind IgE in the sera of shrimp-sensitive patients. IgE antibodies to shrimp RNA did not recognize yeast tRNA or salmon testes DNA, and were not detected in sera of other subjects. The shrimp-derived RNA was further able to induce a reaginic response in mice. A combination of in vitro aminoacylation of shrimp tRNA and SPRIA resulted in the identification of the allergenic tRNA as tRNA(Tyr) and tRNA(Arg). Thus, shrimp tRNA is capable of inducing a specific IgE response in man.

Differential pulse polarographic determination of sulfites in foods: collaborative study.

A differential pulse polarographic (DPP) method for the determination of "free" and "total" sulfite in foods was collaboratively studied by 8 laboratories. The collaborators analyzed blind duplicate samples of shrimp, orange juice, peas, dried apricots, and dehydrated potatoes. Collaborators also analyzed the same samples spiked with sulfites at 2 levels, which ranged from 10 to 1100 micrograms added SO2/g. The variability of free SO2 results was excessive for quantitative analysis, but the method can be used for qualitative detection of free SO2. The method for total SO2 determination was suitable for as low as approximately 10 micrograms/g. Recoveries are comparable to those for the official Monier-Williams method at high levels and are superior at low levels. The method has been adopted official first action for determination of total SO2 in the foods studied.

Adaptation of a quantitative programme for the X-ray analysis of solubilized tissue as microdroplets in the transmission electron microscope: application to the moult cycle of the shrimp Crangon crangon (L).

A quantitative programme for X-ray microanalysis is used in a non-standard manner on solubilized tissue which has been spiked with cobalt and sprayed as microdroplets on electron microscope grids. During the procedure the count time and the concentration of cobalt is related to the peak integral and, from the relative efficiencies, the concentrations of other elements are computed from the peak integrals. Absorption is taken into account but the X-ray background is not used to estimate the total mass and the beam current is not measured. The method is applied to the hepatopancreas and blood from individual shrimps, Crangon crangon, to give the concentrations of sodium, magnesium, silicon, phosphorus, sulphur, potassium and calcium at different stages of the moult cycle. In the hepatopancreas the absolute and relative quantities of phosphorus, sulphur and other elements change in phase with the moult cycle. This situation must be linked with fluctuations in levels of metabolic activity and may affect the metal-binding capacity of the tissue which is known to fluctuate. The hepatopancreas accumulates lipid and phosphorus during the intermoult period, but the level of phospholipid phosphorus remains as a constant proportion of the tissue wet weight. The gland does not store calcium for hardening the new exoskeleton after ecdysis. Magnesium is a more important and variable component and could be linked with metabolic activity. The blood composition remains more stable. However, sulphur concentration is high and variable and this may, to some extent, reflect changes in the concentration of taurine. The concentration of copper increases towards the end of the moult cycle and decreases during moulting; opposite changes occur in the hepatopancreas.

[Technochemical characteristics of canned "Natural Antarctic shrimp meat" and its nutritive value]. / Tekhnokhimicheskaia kharakteristika konservov "Miaso antarkticheskoi krevetki (krilia) natural'noe" i ikh pishchevaia tsennost'.

The authors studied the technochemical characteristics and biological value of the canned food prepared from Antarctic krill--a new type of raw material. Lipids were assayed by thin-layer chromatography, fatty acids by means of a G-180 Yanako chromatograph, the amino acid composition of proteins by a metry. It was shown that the chemical composition of the canned food "Natural Antarctic Krill Meat" is similar to that of the canned food manufactured from crabs. Protein was found to be a predominant component of solid substances. Proteins were discovered to contain all essential amino acids. The protein efficacy of the krill meat slightly decreases in the course of canned food sterilization, However, their biological value remains high, being inferior to casein but insignificantly. The content of toxic elements contained by mineral substances does not exceed the maximal allowable concentration. The diet containing canned food manufactured from krill reduces the blood cholesterol content.

Amino acid sequence of the beta chain of sarcoplasmic calcium binding protein (SCP) obtained from shrimp tail muscle.

The amino acid sequence of the beta chain of shrimp SCP has been determined. It is composed of 192 amino acid residues and is acetylated at the N-terminus. The molecular weight was determined to be 21,960. The sequence difference with the aB chain of the same shrimp, of which the sequence was determined previously (J Biochem. (1984) 95, 1603-1615), is 19% (37 non-identical residues out of 192 residues). The shrimp SCPs have three EF-hand type Ca2+ binding sites, however, from comparison with the amino acid sequences of SCPs of scallop (Takagi et al., Biochim. Biophys. Acta in press) and of sandworm (Kobayashi et al., manuscript in preparation), it is reasonable to think that SCP originally had four Ca2+ binding sites, and in the case of shrimp SCPs, one of them (site IV) may have lost the affinity to Ca2+ on amino acid replacements during evolution.

An unusual glucocerebroside in the crustacean nervous system.

High concentrations of glucocerebroside (glucosylceramide) were found in the ventral nerve cord, brain, optic nerve, and antenna, but not in the nonneural tissue, of the brown shrimp Penaeus aztecus aztecus. This lipid contained unusual sphingoid bases consisting of 14-, 15-, and 16-carbon sphinganines and sphingenines. The fatty acids were mainly nonhydroxylated homologs 22 carbons long and longer, similar to those found in galactocerebroside but differing from those in glucocerebroside in mammalian nervous systems.

Modification of the AOAC gas-liquid chromatographic method for indole in shrimp: collaborative study.

Several changes were suggested for standardization of the AOAC official final action gas chromatographic method for the determination of indole in shrimp. In a collaborative study, 3 FDA laboratories compared the modified method with the current method. At a 95% confidence level, the same results were obtained for each respective sample by the AOAC or the modified method, which had the following changes. The cleanup column was standardized by drying the silica gel for 2 h at 125 degrees C and equilibrating with 3 g of water/25 g of silica gel. Concentrated ethyl acetate shrimp extracts were treated with anhydrous sodium sulfate before column cleanup and indole was eluted from the column with 15% ethyl ether/hexane. A reduced amount of the internal standard, 2-methylindole, was used to improve peak height measurements at the 25 microgram% indole level. The modified method has been adopted official first action to replace method 18.075.