Art. XXVIII.—The Composition of some New Zealand Foodstuffs.

By John Malcolm, M.D., Physiology Department, University of Otago.

bath for three hours; the glycogen was then precipitated with alcohol, washed, and converted into glucose, which was estimated by Fehling's method.

Fat was estimated by Rosenberg's method—i.e., extraction of the dried material with boiling absolute alcohol and chloroform alternately, with subsequent ether extraction of the material so obtained.

Protein was calculated from the amount of nitrogen on the assumption that the nitrogen formed 16 per cent. of the molecule. It was recognized, of course, that all the nitrogen present was not in the form of protein—in fact, oysters owe much of their value in dietetics to the presence of nitrogenous extractives; on the other hand, they contain much nucleo-protein, or a similar body rich in phosphorus, in which the nitrogen must be under 16 per cent.

Ash or mineral matter was estimated by incineration, aided by extraction with hot distilled water and subsequent evaporation of the extract.

The results are given in Tables I and II.

In the above table it may be observed that samples I, II, and III were obtained early in the season, sample IV at the end, and on comparing these it is evident that a marked deterioration of the oyster occurs by the end of the season: it becomes more watery, glycogen drops to one-seventh of its initial value, the fat diminishes to nearly half, and the extractives are relatively increased. It would be interesting scientifically, and would throw a valuable light on what ought to be the limits of the oyster season in New Zealand, if analyses were made at regular and frequent intervals throughout the year.

From Table II it will be seen that at their best the New Zealand oysters contain much less glycogen and relatively more fat than the average American oyster.

II. Frostfish (Lepidopus caudatus).

This peculiar - looking fish, known in other parts of the English-speaking world as “scabbard-fish,” is found in the Mediterranean and warmer parts of the Atlantic as well as around the Tasmanian and New Zealand coasts. It derives its popular name from the fact that it is thrown up by the sea in frosty weather, and is found dead or dying on the beach. According to one view, it comes ashore voluntarily, as if bent on self-immolation; it has seldom, if ever, been caught alive, and is generally believed to be a deep-water fish. In shape it is long and ribbon-like, and has a bright scaleless skin. Unlike many New Zealand food fishes, it has a distinctive flavour, and partly from this and partly no doubt, from its comparative rarity it is regarded as a delicacy, and sells at 1s. 6d. to 3s. per pound. For the purposes of sale and for cooking it is cut into slices across its long axis; all such cutlets include the vertebral column, and some also include the abdominal cavity. There is a considerable amount of waste matter in the cutlets; thus in an ordinary slice as bought only 85 grm. out of a total of 134 grm. consisted of edible flesh. The residue (36°5 per cent.) consisted of bone, skin, and tough intermuscular septa, although the latter would probably form gelatine during the process of cooking, and should not be considered altogether as waste.

Fat.—The flesh is obviously fatty, and an oily scum forms on the water in which it is boiled; but the fat is unequally distributed, there being much more in the tissues immediately surrounding the abdominal cavity than in the muscles of the sides. In the first sample examined the fat of the dorsal portion or sides of the fish amounted to 4°55 per cent., and that of the ventral to 16°77 per cent. In the second sample there was 7°36 per cent. fat in the sides, and 20 per cent. in the ventral portion. From the culinary point of view, therefore, the frostfish should be reckoned as a fatty fish somewhat akin to turbot. The fat extracted by ether is a yellow-coloured oil, half-fluid at room-temperature, and possessing a smell which recalls that of cod-liver oil. It contains 1 per cent. of nitrogen.

Protein.—Owing to the presence of a considerable amount of non-protein nitrogenous substance, it is not permissible in this case to use the total nitrogen as the basis for calculating the percentage of protein. The following procedure was therefore followed: The residue, after extraction of the fat, &c., by chloroform and alcohol, was weighed and sampled for nitrogen-estimation—thus 10°967 grm. partly dried “sides”