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SUMMARY The effect of frozen storage and different glazes on the denaturation of fish proteins was studied. The solubility of proteins was affected less when glazes were used. The denaturation of proteins was restricted to the actomyosin fraction of proteins; the sarcoplasmic fraction remained unchanged. The total actomyosin denaturation was not closely related with either the decrease in apyrase activity of the muscle brei or with the contractility of the muscle fiber.

The addition of L-ascorbic acid (AsA) and dehydro-L-ascorbic acid (DAsA), after adjustment to pH 6.4 and 4.3 with sodium hydroxide respectively, to Alaska pollack brayed meat caused increase in the strength of the gel. Both AsA and DAsA had improving action on the gel strength, but DAsA was more potent than AsA. About 80% of added AsA was recovered as the reduced form in the gel when AsA was added to the brayed meat. On the other hand, about 20% of added DAsA was reduced to AsA when DAsA was added to the meat. These results suggest that the improving action of AsA in the gel formation may be due to the oxidation of sulfhydryl groups in fish proteins by DAsA. When AsA was heated with actomyosin in solution at 80°C for 20 minutes, AsA was almost completely recovered as the reduced form. On the other hand, when DAsA was heated with actomyosin at 80°C, some of it was reduced rapidly to AsA by the reaction with actomyosin during the first 5 minutes. These results suggest that DAsA may oxidize sulfhydryl groups in the actomyosin molecule.

IT IS universally recognized that the nutritive value of fish meals varies considerably and that this variation may be attributed to the initial differences in the raw materials and to the effects of processing and handling (Ousterhout and Snyder, 1962). Review of the literature on fish meal proteins as sources of amino acids reveals that little is known regarding the amino acid inadequacies of fish meal. Laksesvela (1958) showed tryptophan to be first limiting in condensed herring solubles but was unable to show, with the possible exception of histidine, a first limiting amino acid in a heated herring meal. Lysine or methionine supplementation of the heated fish meal, either singly or in combination, seemed to depress growth even though chemical analysis indicated a 40% decrease in “available lysine” in the heated sample. Tarr et al. (1954) reported that the addition of lysine to an overheated herring meal improved its nutritive…

Present trends in the global animal production of fats and protein are reviewed. The dominance of the West and the temperate latitudes is underlined, and the uniqueness of China and Japan are analyzed. The global disparities are based primarily on the ample soil resources in the West allowing for extensive production of feed crops, led by oilseeds. A second major input is fish protein, half the catches of fish from the oceans being converted into meal and oil. This kind of secondary or even tertiary production is unlikely to be copied under the parsimonious conditions of the poor world. The relative roles of oilseed and fish proteins are analyzed. Future trends are discussed on the basis of the FAO projections presented in the Indicative World Plan.

Addition of formaldehyde to fresh cod muscle, to give concentrations of 10 to 200 ppm, brought about marked decreases in the extractable protein content during holding periods of 24 hr or less at 0 C. Similar levels of formaldehyde, produced during frozen storage of gadoid (Atlantic cod, Gadus morhua, pollock, Pollachius virens, cusk, Brosme brosme, and silver hake, Merluccius bilinearis), fillets at −5 C, brought about similar reductions in the extractable proteins. Comparative tests showed that, in the concentrations normally encountered in deteriorating frozen gadoid fillets, formaldehyde was a much more active protein-insolubilizing agent than free fatty acid. It is evident that in these protein changes more than one mechanism is involved. Observed species-differences in the extent to which fish proteins became insolubilized during storage appeared to be related to presence or absence of these different mechanisms. The more rapid and more extensive denaturation of most gadoid fillets in frozen storage than of fillets of nongadoid species appears to be directly related to the presence of muscle enzyme of the former group that is capable of producing formaldehyde from trimethylamine oxide, which is absent in the muscle of the nongadoid species so far tested.

Commercial fish meals have been examined for their net protein utilization by rats and have been found to be of poorer nutritive value than laboratory fish preparations, which have a net protein utilization of about 80%. The factors responsible are chiefly the conditions of drying and consequent occurrence of the Maillard reaction. No damage was detectable in the dried product after storing for 3 months at room temperature. It is shown that water as well as sugar and protein, is an essential for the Maillard reaction, and it is suggested that anti-Maillard reagents may offer some hope for the prevention of damage during drying. For rats, methionine is the limiting amino-acid in the damaged meals and might be added with advantage to these products.

It is well recognized that the amines, as well as ammonia, are products of protein decomposition. Allen’ quotes several authors who report finding one or .more of the alkylamines in decomposed protein products. Thus Bocklisch2 frequently found methylamine in spoiled fish. He suggests that it is formed in such material by the loss of carbon dioxide from glycine and also from trimethyl- amine. Dimethylamine was found in herring brine by Bocklisch, in putrid gelatin and yeast by Brieger, and in poisonous sausage by Ehrenberg.3 In the bacterial cultures from this sausage Ehrenberg reports finding diethylamine. Allen also states that ethylamine has been obtained from putrid yeast and flour, and that trimethylamine is a common putre- factive product found in herring brine and in extract of ergot. It is known that various forms of amines occur in the tissues of fish. In the preparation of salt-cured fish, amines are extracted or formed from the fish proteins, herring brine, for example, fur- nishing a commercial source for trimethylamine. In the determination of ammonia in biological fluids and in food products by Nesslerizing4 the volatilized base, obtained by aera

On the evaluation of the nutritive value of food protein, the availability of amino acids in them is an important factor to be duly considered. Most of the lysine resources in Japanese foods are fish proteins. So, in this report, the available lysine in the proteins of several species of marine aniamals, along with that of algae such as Chlorella and Scenedesmus, which are being remarked as new protein resources, was determined as well as chages of it by heating, browning reaction with glucose and reaction with acetaldehyde were studied. The available lysine was estimated by the Carpenter's method, based on the determination of free e-amino group of lysine in the protein, and the results obtained are shown in Table 1, 2, and 3. As seen in these Tables, available lysine value of fish protein was about 8 and that of shellfish was a little lower than that. The value of the algae was ranged from 3 to 4. These values of fish and shellfish lost about 10% by heating, and more than half by reactions with glucose and acetaldehyde.

SUMMARY— It is known that even small concentrations of sodium chloride cause a loss in the solubility of actomyosin in fillets of Baltic herring. This change is prevented by the simultaneous presence of a sufficient amount of phosphates. To date, the mode of action of phosphates is unsettled. This problem has here been studied by the aid of radioactive pyrophosphate. The fillets were kept in solutions containing sodium chloride, pyrophosphate, or both, at +4°C. The migration of tracer pyrophosphate was followed by application of the auto-radiographic method; at the same time, changes in the solubility of actomyosin were checked. To avoid losses of soluble compounds, the sections for autoradiogaphy were prepared by freeze-drying and paraffin impregnation techniques. It was found that the migration was very rapid: in 24 hr the fillets were completely marked. The rate of migration was also estimated by counting of the sections. Studies were also made of the changes in the phosphorus fractions of the fillets during the course of standing using 1% pyrophosphate and maximal standing time of 5 days. Initially, there occurred a rapid loss of phosphorus compounds from the fillets; this related to the lipid and nucleic acid phosphorus. The tracer migrated rapidly into the fillets during the first day, and more slowly after this. The bulk of the tracer was in the acid-soluble fraction. Apparently, there also occurred some incorporation into the lipids and nucleic acids.

SUMMARY– Comparisons were made on the availability (enzyme digestion) of 4 amino acids (lysine, methionine, tryptophan, and threonine) in sarcoplasmic fish proteins and sarcoplasmic fish proteins complexed with sodium hexametaphosphate. The protein complexes were formed by reacting 1% solutions of sarcoplasmic fish proteins at pH values ranging from 2–4 and at phosphate concentrations ranging from 0.005–0.05 M. Uncomplexed sarcoplasmic protein was obtained by precipitation from 70% isopropanol. The samples were digested with the enzyme pronase and the available amino acids were measured with a bio-assay system. No significant differences in the availability (enzyme digestion) of amino acids were found between complexed and noncomplexed samples. Assays of samples dried at 75°C showed that nearly 100% of the methionine, threonine and tryptophan and 85% of the lysine were available. When the samples were subjected to moist heat (50% moisture, 100°C) for up to 24 hr, availability of lysine, methionine, tryptophan and threonine was reduced by 35, 22, 39 and 34%, respectively. Results of this study indicate that the nutritional characteristics of fish proteins are unimpaired when they are complexed with sodium hexametaphosphate.

Succeeding to the previous papers1-3), in which the amino acid composition of the proteins of fish and crustaceans was given, the present paper deals with the shell-fish proteins. The minced edible part of a hard clam (Meretrix meretrix lusoria GMELIN) and that of an abalone (Haliotis gigantea GMELIN) were thoroughly extracted with boiling water acidulated with acetic acid (pH 4.5), ethanol and ether in order. Amino acids in the proteins thus obtained were determined by the column chromatographic method using an ion-exchange resin and the results obtained are given in Table 3. Although the pattern of amino acid distribution in the proteins of these shell-fishes is relatively uniform, some slight differences are observed on several amino acids. The protein of abalone is rich in glycine, proline and arginine and poor in leucine, glutamic acid, tyrosine and lysine when compared with that of hard clam. It is also found that the tryptophan content of the hard clam protein is rather high. These shell-fish proteins show a lower value of valine, methionine, phenylalanine, lysine and histidine than the muscle proteins of fish1, 2) and crustaceans3) examined in our previous studies.

At the end of the last century, Miescher (66) made a careful study of fish protein in his series of classic investigations on protein metabolism in the Rhine salmon during milting. These experiments, their extension by Kossel (55), and the valuable contribution of Greene (39), Greene (40) and Weiss (106) constitute one of the most stimulating chapters in “dynamic” biochemistry. Except for this unique achievement, the literature related to the biochemistry of fish proteins unfortunately has very few highlights. For the most part, the work done is a recapitulation of mammalian biochemistry; some fish tissues have been analyzed for the presence or absence of compounds previously demonstrated in mammalian or avian tissues. Special investigation of the peculiarities of fish protein, studies of the physical and chemical properties which differentiate these particular substances as “fish proteins” have not yet been attempted.

THE PROBLEM of measuring the nutritive value of proteins involves not only the levels of the amino acids in the proteins, but also the availability of these amino acids to the animal. Therefore animal experiments continue to be necessary in the study of protein quality. The kind of animal experiment selected depends upon the investigator’s interpretation of “quality.” He may use the protein under study as the sole source of protein and measure its ability to meet the animal’s total requirements for nitrogen and essential amino acids. Results of such a study might or might not indicate the ability of the protein to supplement a cereal diet already containing some protein of relatively low quality. These and related problems have been discussed by Grau and Carroll (1958). Fish meals are commonly used at relatively low levels in poultry diets not only to supply an unidentified dietary factor, but also to…

AS INTEREST increases in the worldwide problem of malnutrition in infants and preschool children, it becomes ever more apparent that the basic problem is the lack of a proper substitute for human breast milk and that the age at which infants are weaned determines the type of malnutrition encountered.1If unlimited amounts of whole cow's milk could be made available in a safe form to the millions of undernourished children of the world, there would be little need to contemplate other substitutes. Unfortunately, the supply of this most valuable of foods is limited and difficult to increase; its cost of production places it beyond the reach of most impoverished people and the problems involved in protecting it from contamination remain an important barrier to its use in primitive environments. In recent years considerable effort is being devoted to the study of possible substitutes for milk protein, many of them

Free L-lysine. HCl, roller-dried skim milk, fish protein and soya bean protein were added to the dough of wheat bread and their supplementary values for the improvement of the protein value of the bread were compared. The growth rates and nitrogen efficiency ratios of young albino rats were used as indices of the improvements obtained. Within the concentration range studied, the supplementary values of the added substances were directly proportional to the amount of available lysine which they provided. No beneficial effect from the other essential amino acids supplied by the proteins tested as supplements was detected. The data also indicate that roller-dried skim milk suffered a considerably greater loss of lysine during the baking of wheat bread than did the other supplements.

IT is well known that frozen fish alter in character during storage at sub-zero temperatures, becoming progressively tougher to eat, and exuding much fluid or ‘drip’ on thawing. The change proceeds more slowly the lower the temperature. There is a real need for an accurate objective method of measuring this deterioration, from the point of view of product control and also as a tool for systematic research on methods of freezing and storage. Most of the observed phenomena have been attributed to changes in the proteins of the flesh1, and these changes have therefore been examined by a number of workers with the object of providing a successful method.