The authors propose in this papar a procedure to apply some sorts of antioxidant to salting of salmon. The fish processed thus along a definite direction were examined organoleptically after storage for 3 to 6 months. Some chemical properties of the oil extracted from the processed fish were also examined.
The salt for the processing was prepared as follows: antioxidants such as butylated hydroxy-anisole (B. H. A), ethyl protocatechuate (E. P.), and propyl gallate (P. G.) were diluted with common salt respectively up to various concentrations properly specified after the previous studies¹⁾²⁾.
With the case of B. H. A., the results of preservation experiment were found to be almost satisfactory. However, E. P. and P. G. being less effective as compared with B. H. A., developed a reddish brown off-colour especially in the abdominal part of the products.

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To obtain a method suitable for determining the BHA added to marine products, three colorimetric methods were compared with one another: 2, 2'-dipyridyl (2, 2'-DP) method³⁾, 2, 6-dichloroquinonechloroimide (2, 6-D) method ⁴⁾, and potassium ferricyanide (K₃(CN)₆) method⁶⁾.
The antioxidant was drawn from the products together with crude oil by the Soxhlet extraction extended over 16 hrs., using peroxide-free ethys ether. After evaporating-off the solvent under reduced pressure, BHA was extracted by a modified method (see Table 1), and subjected to each colorimetric estimation mentioned above.
From the results obtained, only the 2, 6-D reagent towards BHA. In the case of the other two methods, the reagents reacted with some other materials coming dissolved in alcoholic extracts of crude oil. It is possible, therefore, when the estimation is made with any of the latter methods, that the results become too large and misrepresent spurious substance as BHA. Consequently, the said two methods should be regarded as inapplicable to the case of marine products.

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In the present work antioxigenic and synergistic effect of Na-erythorbate on BHA which is applied to salt-dried fishes (salmon, saury pike, and horse mackerel) are examined.
The antioxidative effect of Na-erythorbate on salt-dried fishes was evaluated both by organoleptic test and by measurement peroxide value. The available period was decided within 15 days, and better result was obtained at the concentration of 0.5% Na-erythorbate to dry salt than at 1%. But fishes are kept in better quality when they were treated with 0.5% Na-erythorbate solution before salting.
Antioxidative effect of BHA is larger when it was applied with Na-erythorbate than was applied it alone.
As Na-erythorbate is very soluble in water and easily penetrates into fishes, fish oil may be protected from oxidation by the antioxigenic ability of Na-erythorbate until BHA penetrates into fish oil to such quantity as it demonstrates its ability. Thus, the main cause of the synergistic ability of Na-erythorbate may be attributable to the water soluble property of this chemical.

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ROSENWALD reported that 3, 5-di-tert-butyl-4-hydroxyanisole was more effective antioxidant than BHA²⁾. The authors have applied this antioxidant in a variety of marine products to prevent oil autoxidation. In the preliminary experiments they confirmed that this compound exerts a strong antioxidant effect on saurel oil subjected to sun light (Table 2) and saury oil stored at 30±1°C (Table 3). However, this antioxidant was rather ineffective in salted-and-dried saury (Tables 4 and 5) and boiled-and-dried sardine (Table 6) as compared with BHA, and was almost equal in salted saury as with BHT (Table 7). This may be due to the low solubility of the antioxidant (c. a. 4.9% at 20°C in saury oil) and high melting point (104.0-105.0°C). In order to use 3, 5-di-BHA effectively in the protection of marine products, the usual method of application has to be modified.

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Recently, several antioxidant preparations containing some surface active agents have commercially been developed in Japan, which are to be used in fish manufacturing process for keeping the antioxidant as homogenized in curing solution. In the application of these preparations to the protection of marine products from oil oxidation, the authors have devised a practical method they have named “moment dipping method”. This method is very simple, labor-saving and needs no special apparatous. Thus, merely dipping the raw fish in a solution of a comparatively high antioxidant concentration, 0.05 to 0.10%, made by using said antioxidant preparations is effective enough to cause a considerable amount of antioxidant to be fixed on the fish body.
In this paper is presented the effect of “moment dipping method” obtained for salted-and-dried fish (saury), the results being as follows:
1) With dried fish having high moisture contents, BHA-preparations were found to be more effective than BHT-preparations, but the difference in efficacy between these two antioxidant preparations was quite small. So, application of the latter preparation, less expensive, is thought to be preferable.
2) On the other hand, with dried fish having low moisture contents, BHA-preparations are far superior to BHT-preparations. So, application of the former preparation seems to be desirable. Since 20% addition of BHT-preparation to BHA-preparation brought no appreciable reduction in efficacy thus in treating well dried fish, the cost of antioxidant addition will slightly but certainly be curtailed by such addition.
3) With dried fish having moisture content whether high or low, the efficacy of “moment dipping method” was found in either case to be slightly inferior to that of the long-time immersing method usually adopted in Japan. The difference may be attributed to the rather small fixation of antioxidant on fish body realized by said new method. So, if an increased amount of antioxidant in immersing solution up to above 0.10% or by increasing the viscosity of the solution by means of some material as, for instance, CMC, a much greater effect is expected to be attained.
4) The amount of antioxidant fixed on fish body calculated from the weight increase taking place in the moment dipping process showed that there is no danger in the “moment dipping method” even when an amount over the usage limit fixed by Japanese Welfare Ministry is used insofar as it is in the range here tested (0.05 to 0.10% as antioxidant concentration).

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In this paper, the authors examined the digestibility of fish meal by a physiological method (with rainbow trout) and an artificial method (the pepsin method). Samples of white fish meal (flatfish) and brown fish meal (saury) were treated with or without several kinds of solvents (ether, petrolum ether, acetone, and benzene) separately, and stored in an oven thermostatically controlled at 30±1°C. before the test. The results obtained are as follows:
1) The digestibility of white fish meal for feeding on rainbow trout, as estimated physiologically is so high as about 80 to 85%, while the same of brown meal is about 50%, So, this may be one of reasons for low feed efficiency of the latter meal. Hence this type of meal contains some indigestible state of protein.
2) The digestibility estimated both by the pepsin method and the physiological method differs a little for white meal, having high digestibility, whereas, the corresponding difference is large in case of a brown meal, having low digestibility.
3) Whether in the pepsin method or in the physiological method, digestibility of white fish meal is hardly affected by subjecting it to the solvent extraction, while that of brown meal is somewhat increased by the same treatment.

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Phosphorus is supposed to play an important role in fat metabolism as well as in carbohydrate metabolism. In this experiment, the behaviors of the phosphorus and fat contents of rainbow trout, Salmo irideus, during its growth were observed. Fat content was reduced during the development from fertilization to hatching and began to increase after 2 months feeding. The following samples showed a maximum content of phosphorus in each type: (1) 1 month fed fry-insoluble and ether soluble phosphorus, (2) 3 month fed fry-water soluble phosphorus. Total phosphorus reached its maximum content in 1 month fed fry.
It is considered that the most parts of phosphorus, in the early stage of growth, are utilized for construction of tissues and movement of fish.

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As an effective method for protecting some marine products from their oil oxidation, the authors have previously presented a novel technique“moment dipping method” so they called.¹⁾ In the present part of work, wherein salted saury was used as sample, this method was investigated in its aspect of cleaver usage, results being summerized as follows:
1) After long storage, the samples treated with BHT-preparations proved to have been far better preserved than those treated with BHA-preparations in agreement with the results previously obtained for alamaki (a sort of mildly salted salmon)⁴⁾.
2) BHA- and BHT-preparations exhibited their efficacy more strongly when used in combination than separately.
3) BHT was found more effective when used as an emulsion of high concentration than used as powder mixed with salt. This difference may have arisen likely from a better contact of antioxidant.
4) As to the amount of antioxidant the fish acquire in treating them by the moment dipping method, chemical estimation indicated that, while it varied truly in according to the concentration of the antioxidant bath employed, a sufficiently effective fixation is generally secured with ease.

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