Storage experiments.
In fresh condition B. pterotum has firm flesh and a strong and very typical smell which is difficult to describe.
(i) No cooling, no draining.
A quantity of 10 kg caught 3/8 in the Gulf of Oman (trawl station 202, N 24°03' E 58°07') with an initial temperature of 25 C and a pH 6.6 was held in a container at ambient temperature. Changes during storage are seen in the table below. Samples were prepared during the experiment for later analysis in Tromsø: 40 grams minced fish was mixed with 40 ml of 10% TCA (trichloracetic acid) and subsequently frozen; also 1 kg was taken from the batch and frozen as well.
|
Day |
time |
temp. (°C) |
PH |
appearance and smell |
|
3/8 |
12.30 |
24.8 |
6.6 |
fresh |
|
14.30 |
31.0 |
6.6 |
fresh |
|
|
16.45 |
31.4 |
6.7 |
not fresh |
|
|
18.45 |
31.6 |
6.7 |
not fresh |
|
|
21.00 |
33.8 |
6.6 |
slightly spoiled |
|
|
4/8 |
03.00 |
30.2 |
6.5 |
spoiled |
|
2/8
|
23.00 |
25.0 |
6.6 |
fresh, bright, typical smell |
|
24.00 |
8.4 |
7.3 |
fresh; paler |
|
|
3/8 |
24.00 |
-1.0 |
7.4 |
fresh; pale |
|
4/8 |
|
0 |
7.2 |
|
|
5/8 |
|
1 |
7.0 |
|
|
7/8 |
|
8 |
7.3 |
fresh; pale |
|
8/8 |
|
5 |
7.8 |
|
|
9/8 |
|
6 |
7.0 |
not fresh; paler; softening; sweet smell |
|
10/8 |
|
3 |
7.4 |
|
|
11/8 |
|
|
|
|
|
12/3 |
|
|
|
slightly spoiled |
|
13/8 |
|
|
|
spoiled |
Silage was prepared from 5 liters minced fish and 85 ml of a mixture of propionic and formic acid (1:1) both of 85% concentration. After mixing the pH was 4.5. The fish had been caught 3/8 at trawl station 202 (N 24°03' E 58°07') in the Gulf of Oman. The initial temperature was 24.8°C. Daily samples were taken for analysis in Tromsø.
Autolysis.
A quantity of 10 liters fish caught 3/8 in the Gulf of Oman at trawl station 202 was stored at 45°C in the engine room of the ship. After 6 hours the fish was spoiled. It appears that the initial temperature of 25°C is too low and warming up too slow to obtain any positive preserving effects of the high ambient temperature.
(ii) Cooling with freshwater ice, no draining
A quality of 20 liters of fish caught 2/8 in the Gulf of Oman at trawl station 199 (N 24°03' E 58°07') was mixed with 10 liters crushed freshwater ice and stored in the chill room of the ship which is normally kept at -1°C. Changes are seen in the table below. Samples were taken during the experiment for further analysis in Trømsø.
Fig. 1. Cruise tracks in the Gulf of Oman.
Fig. 2. Cruise tracks in the Gulf of Aden.
Fig. 5. Hydrographical sections in the Gulf of Oman.
Fig. 6. Hydrographical sections in the Gulf of Aden.
Fig. 7. Hydrographical sections in the Gulf of Oman.
Fig. 8. Estimated abundance of mesopelagic fish in the Gulf of Oman and in the Gulf of Aden 1975-79.
Fig. 9. Length distribution of Benthosema pterotum caught in Harstad trawl and Krill trawl.
