Transactions and Proceedings of the New Zealand Institute, 1921 [electronic resource]

Art. LI.—The Food Values of New Zealand Fish: Part II.

By (Mrs.) Dorothy E. Johnson, B.Sc. in Home Science.
Communicated by Professor J. Malcolm.

[Read before the Otago Institute, 7th December, 1920; received by Editor, 31st December, 1920; issued separately, 12th August, 1921.]

The investigations described in Part I (Trans. N.Z. Inst., vol. 52, p. 20, 1920) have been continued along similar lines and by use of the same methods of analysis. An attempt was made to follow the seasonal variation of composition in groper and kingfish; some new varieties were examined (whitebait, red cod, &c.); and some further analyses were made of fish already reported on in Part I. The results are shown in the following tables.

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Table I—General Table showing Peroentage Composition of Fish Analysed.
Common Name of Fish.	Speonmen.	Scientific Name	Date received.	Water.	Solids, by difference.	Fat.	Protein.	Ash.	Total.
Silver-fish	1	Coillorhychus antaricticus	1/3/20	73.71	26.29	0.61	23.71	3.37	99.46
Ling	1	Genypterus blacodes	9/3/20	80.26	19.74	0.16	17.61	0.98	99.10
"	2	"	2/7/20	81.08	18.92	0.11	17.58	1.23	100.00
Red cod.	1	Lotella bacchus	12/3/20	81.96	18.04	0.46	15.58	1.15	99.55
"	2	"	21/5/20	79.87	20.13	0.48	17.48	1.18	99.01
Blue cod (pakirkiri)	2	Percis colias	16/7/20	73.88	26.12	6.13	18.46	1.29	99.76
"	1	"	16/10/19	79.70	20.30	0.90	18.79	1.05	100.44
Roe of groper	1		5/8/20	59.77	40.23	10.94	23.95	3.26	97.92
"	2		20/8/20	61.30	38.97	9.35	24.65	1.35	96.38
Flunder (patiki)	1	Rhombosolea monopus	13/8/20	78.74	21.26	1.97	17.28	1.16	99.6
Roe of flounder	1	"	13/8/2	67.24	32.76	4.39	24.28	1.76	98.27
Whitebait	1	Galaxias attenuatus	9/9/20	79.70	20.30	1.79	16.27	1.41	99.17
"	2	"	24/9/20	79.70	20.30	1.82	16.32	1.59	99.43

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Table II.
	Name of Fish, &c.	Kind of Sample	Price (Pence).	Weight. (Grammes).	Edible. (Percentage.)	Waste. (Percentage.)
Silver-fish	1	Slice	9	540	86.30	13.70
Ling	1	"	6	680	70.58	29.42
"	2	"	9	750	76.51	23.49
Red cod	1	"	4	595	69.42	30.58
"	2	"	10	654	80.58	19.42
Blue cod	1	"	21	744	47.44	52.56
"	2	Whole	36	1, 368	50.00	50.00
Roe of groper	1	"	15	808	94.19	5.81
"	2	"	12	822	93.31	6.69
Flounder	1	"	24	509	54.81	45.19
Roe of flounder	1	"	24	47	100.00
Whitebait	1	Large number	24	160	100.00
"	2	Ditto	54	423	100.00

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Table III.
	Name of Fish, &c.	Calories per 100 Grammes of Undried Edible Material.	Cost of 100 Grammes Protein. (Pence.)	Cost of 1,000 Calories (Pence)
Silver-fish	1	103.18	8.12	18.72
Ling	1	73.69	7.10	16.96
"	2	73.10	8.92	21.45
Red cod	1	69.81	6.06	13.91
"	2	76.16	10.85	24.92
Blue cod	1	85.40	31.70	69.70
"	2	132.71	28.51	39.66
Roe of groper	1	199.99	8.23	9.86
"	2	188.02	6.35	8.32
Flounder	1	91.22
Roe of flounder	1	142.86	39.16	74.63
Whitebait	1	83.31	92.19	108.06
"	2	83.85	78.24	152.23

In compiling Tables IV, V, and VI the results of analyses given in Part I have been included.

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Table IV.—Showing Fish in Order of Fat Content.
		Per Cent.
Roe of groper	1	10 94
Tarakihi	1	10 30
Mullet	1	10 09
Roe of groper	2	9 35
Blue cod	2	6.13
Roe of flounder	1	4 39
Kingfish	1	4 32
Sea-bream	1	4 25
Kingfish	2	4 10
Groper	3	3.40
Trumpeter	1	3.31
Moki	2	3.21
Tarakihi	2	3 05
Groper	4	2.93
Baby groper		2.32
Flounder	1	197
Groper	2	1.90
Whitebait	2	1.82
Whitebait	1	1.79
Crayfish	3	1.30
Moki	1	1.63
Blue cod	1	0 90
Crayfish	1	0.72
Silver-fish	1	0.61
Snapper	1	0.60
Crayfish	2	0.52
Red cod	2	0 48
"	1	0 46
Snapper	2	0 42
Ling	1	0.16
"	2	0.11
Eggs		10 50
Meat (beef)		5 50
Milk		4 00

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Table V.—Showing Fish in Order of Caloric Values.
		Calories.
Roe of groper	1	200 00
"	2	188.02
Mullet	1	172 89
Tarakihi	1	167 45
Roe of flounder	1	142 86
Blue cod	2	132 71
Sea-bream	1	119.51
Kingfish	2	119 47
"	1	116.93
Tarakihi	2	111.64
Groper	3	110 92
Trumpeter	1	110
Moki	2	104.96
Crayfish	3	103.73
Silver-fish	1	103 18
Groper	4	102.78
Baby groper		102.56
Crayfish	1	100 59
Groper	3	96.39
Moki	1	93.56
Flounder	1	91.22
Snapper	1	09.38
Crayfish	2	85.96
Blue cod	1	85.40
Whitebait	2	83.85
"	1	83.31
Snapper	2	81.51
Red cod	2	76.16
Ling	1	73 69
"	2	73 10
Red cod	1	69.81
Eggs		158.33
Beef		137.25
Milk		70.00

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Table VI.—Showing Fish in Order of Cost of 100 Grammes Protein.
		Pence.
Red cod	1	6 06
Roe of groper	2	6 35
Ling	1	7 10
Groper	1	7.31
Silver-fish	1	8.12
Roe of groper	1	8 23
Ling	2	8.92
Mullet	1	8.96
Groper	2	10 45
Red cod	2	10 85
Groper	3	11.80
Crayfish	1	11 49
Snapper	1	12.35
Crayfish	2	1266
Snapper	2	14 64
Tarakihi	1	15 61
"	2	15.95
Sea-bream	1	15.99
Moki	1	16.21
Kingfish	1	17.22
"	2	17.56
Moki	2	18.27
Groper	4	19.78
Trumpeter	1	20.11
Crayfish	2	22.98
Blue cod	2	28 51
"	1	31.70
Flounder	1	39.16
Whitebait	2	78.24
"	1	92.19
Beef		12.60
Milk		14.62
Eggs		32.94

Discussion.

The deductions of Part I are true for the further twelve samples analysed this year, though it may be noted that in the two samples of red cod the fat-percentage is practically the same (0–47), and the sample with 82 per cent. water has 16 per cent. protein, while the other with 80 per cent. water has 18 per cent. protein.

The following points are worthy of notice:—

1. The analyses of two samples of whitebait are almost identical.

Sample.	Water.	Solids.	Fat.	Protein.	Ash.
1	79.7	20.3	1.8	16.3	1.4
2	79.7	20.3	1.8	16.3	1.6

In these analyses a large number of the fish was used, giving as a result the average composition of that particular species. This eliminates to a large extent the variations noticeable in different samples of the same species of fish even when bought at short intervals. It indicates that in order to obtain the average analysis of any species a sample should be taken from the well-mixed muscle of as many fish as possible. That method would eliminate (1) the difference due to the different metabolism of the specimens taken, and (2), to some extent, the difference due to varying richness of feeding-grounds.

2. The analyses of the roes of groper and flounder show differences from the general analyses of fish-roe given in various books: e.g.—

—	Water.	Protein.	Fat.	Other Nitrogenous Matter.	Ash
(1.) Caviare and approximately all fish-roe (Hutchison)	38.10	30.00	19.70	7.60	4.60
(2.) Garfish-roe (German authority)	55.00	15 to 28	16 to 28	1.50	0.36
(3.) Groper-roe	59.80	23.95	10.94		3.26
(4.) Flounder-roe	67.24	24.88	4.39		1.76

The figures 23.95 and 24.88 in (3) and (4) include all nitrogenous matter. In the case of the roe, the method of extracting the fat with ether alone is not entirely satisfactory, and in future analysis of this class of material it is intended to use Rosenfeldt's method (alternate extraction with boiling absolute alcohol and chloroform).

Some Experiments on the Seasonal Variation of Composition of Groper and Kingfish.

In Part I of this paper reference was made to the variation in fat content in different samples of the same variety of fish. It was suggested that it was a matter, say, of metabolism or of seasonal variation. Further work was done in this connection with the object of ascertaining what

variation there was to the consumer in the food value of groper and Kingfish at different times of the year. Eleven samples of groper and seven of Kingfish were analysed. Table VII gives the results both of the variation in the composition and also in the price.

The graph shows the seasonal variation of the fat content of the two varieties of fish.

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Table VII.—General Analyses showing Seasonal Variation of Groper and Kingfish.
Specimen.	Date received.	Weste. (Percentage)	Water. (Percentage)	Solid (by difference).	Fat. (Percentage)	Protein. (Percentage)	Ash. (Percentage)	Calories per 100 Grammes Edible Material (calculated).	Market Price per Found. (Pence.)	Cost of 1,000 Calories. (Pence.)
					Groper.
1	23/2/20	15.91	76.86	23.14	3.17	18.37	1.08	95.08	8	22.14
2	24/2/20	24.52	76.38	23.62	3.58	18.70	1.09	109.95	8	16.43
3	17/3/20	16.48	73.89	26.11	6.16	18.91	1.10	134.87	8	13.16
4	17/6/20	14.84	74.36	25.64	5.07	19.10	1.20	125.45	15	23.35
5	6/7/20	23.88	74.99	25.01	4.88	18.94	0.98	123.06	12	19.86
6	10/7/20	4.16	75.57	24.13	5.26	17.98	1.03	122.66	15	23.12
7	30/7/19	5.38	76.00	24.00	1.90	19.20	1.27	96.39	6	20.80
8	11/8/19	2.95	76.10	23.90	3.40	19.34	1.08	110.92	6	20.60
9	28/8/19	12.68	77.03	22.97	2.93	18.42	1.08	102.78	9	34.40
10	11/9/19	60.69	76.41	23.59	2.32	19.75	1.10	102.56
11	1/11/20	13.08	72.14	27.86	7.63	19.84	1.09	152.30	15	23.03

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Table VII.—General Analyses showing Seasonal Variation of Groper and Kingfish—*continued.*
Specimen.	Date received.	Weste. (Percentage)	Water. (Percentage)	Solid (by difference).	Fat. (Percentage)	Protein. (Percentage)	Ash. (Percentage)	Calories per 100 Grammes Edible Material (calculated).	Market Price per Found. (Pence.)	Cost of 1,000 Calories. (Pence.)
					Groper.
1	3/3/20	27.84	78.25	21.75	1.31	18.52	1.19	88.11	11	37.05
2	8/3/20	20.23	80.04	19.96	0.54	17.49	1.22	76.75	10	37.12
3	12/5/20	21.57	73.20	26.80	6.79	19.49	1.19	159.44	12	14.99
4	17/6/20	24.07	72.63	27.37	5.57	19.54	1.26	131.92	15	24.34
5	1/11/20	22.20	74.99	25.01		18.46	1.02		15
6	3/11/19	26.70	75.65	24.35	4.32	18.72	0.93	116.93	12	28.10
7	11/11/19	21.75	74.37	25.63	4.10	19.84	1.14	119.47	15	28.60

Discussion.

It will be seen that the fat content of groper varies during the year from 1.90 to 7.63 per cent., while that of Iringfish varies from 0.54 to 6.79, so there is considerable variation in the nutritive value. This is well shown by comparing the total calories per 100 grammes of fresh material:-

Fish.	Fat. (Percentage.)	Calories. (Percentage.)
Groper	1.90	96.39
"	7.63	152.30
Kingfish	0.54	76.75
"	6.79	159.44

The nutritive value of a fish at its best is double that of the fish in pool-condition. When the high nutritive value of the roe is considered (calories per cent. of roe = 200), the low food value of fish after spawning is not remarkable.

Groper came into the market heavy with roe in July and August, but kingfish was hardly procurable in those months. The analyses give point to the probability of the spawning season for kingfish being in February or March.

The variations noted may be due to differences in age, sex, metabolism, richness of feeding-ground, or other causes, so that more must be known before the differences can be taken to represent seasonal variation alone. Were a sample taken from the mixed muscle of a number of fish, as in the case of whitebait, discussed above, some of these variations would be eliminated. The market, too, presents difficulties. The fish are not procurable at definite stated intervals. The results, however, embody the variation in the value that the consumer is obtaining when buying the same variety of fish at different seasons of the year.

All the expenses incurred in these investigations have been defrayed by a grant from the New Zealand Government, through the New Zealand Institute, and I have to thank the University of Otago for the use of laboratory-space and apparatus.