Until now freezing has been one of the most important means of storing fish. Several investigators have tried to solve the problems connected with the changes in the fish protein during frozen storage (Cowie et al. 1966, Olley et al. 1967).Changes in the lipid fraction of the fish may be of equal importance in lowering the quality of the fish, especially fatty fish, during frozen storage. The purpose of this study was to examine the effect of two different storage temperatures and two different means of packaging upon the organoleptic quality and the fatty acid composition of frozen rainbow trout. Material and methodsThe experiments were carried out with second-summer rainbow trout fed with Clark dry food for rainbow trout. The average weight of the fishes was 130 grams (from 85 to 201 grams) and the control fishes were transported to the laboratory alive. The rest of the fishes were killed and gutted and frozen rapidly at -40°C. One half of the fishes were glazed with water while the second half was individually packed in vacuum sealed polyethylene bags. The fishes were then transported to the laboratory in styrox containers into which CO a-ice had been added. The fish arrived at the laboratory 18 hours after gutting. At the laboratory the samples were divided again into two halves with storage temperatures of 18 and 32°C. For the organoleptic evaluation samples were taken from the control fish after 1 day, 1 week, 1 month and 3 months, and for the fatty acid analyses from the control fish after 1 day, 1 week, 1 month and 7 months.The organoleptic evaluation was performed according to Niinivaara et ai. 1966, and the fatty acid analyses in accordance with the methods used in the previous study (Varesmaa et al. 1968).
Das Ziel der vorliegenden Arbeit ist es gewesen, die eventuellen jahreszeitlichen Variationen in dem Nährstoffgehalt der Leber festzustellen. Die Lebern wurden im Juni, September, Januar und April analysiert. Insgesamt wurden 4 zusammengesetzte Rinder- und 4 Schweineleberproben untersucht. Jede Probe enthielt die Lebern von 5 verschiedenen Tieren. Aus den Proben wurde die chemische Zusammensetzung, der Vitamin-A-, Thiamin-, Eisen- und Kupfergehalt bestimmt. Die Fettsäurenzusammensetzung des Fettes wurde aus Proben bestimmt, die im Herbst, Winter und Frühjahr entnommen worden waren. Von den untersuchten Nährstoffen zeigten nur die Vitamin-A-Werte deutliche jahreszeitliche Variationen. Am Ende der Weideperiode war der Vitamin-A-Gehalt der Rinderleber mit 68.000 i.E./100 g über 7-fach höher als zu Beginn der Weideperiode mit 9000 i.E./100 g. Die grössten Unterschiede in den Vitamin-A-Werten der Rinder- und Schweineleber traten in den im Herbst untersuchten Proben auf, als der Vitamin-A-Gehalt der Schweineleber fast nur halb so gross war als derjenige der Rinderleber.
The transportation of fresh rainbow trout in good condition from the fisher to the consumer or to the fish industry presents a difficult problem. The fat of rainbow trout, like the fat in fish in general, contains plenty of unsaturated fatty acids and turns for that reason very easily rancid. According to Hansen (1964), the season and the sex of the fish influence the keeping quality of rainbow trout. Treatments that prevent the fish from coming into contact with the air (vacuum, glazing, dipping) The purpose of this study was to test BHA as an antioxidant in the storage of fresh rainbow trout. Ascorbic acid, the synergist of BHA, was also tested in the experiment. Material and methodsThe tested fish consisted of two-year-old male rainbow trouts weighing 300 grams. With the exception of the first experiment, the fish were brought alive to the laboratory, where they were killed, rinsed and filleted. They were then divided into four groups: 1) Control group, 2) 0.02 % BHA, 3) 0.01 % BHA, and 4) ascorbic acid.The fish fillets were packed in polyethylene bags. BHA, mixed in sunflower oil, was added to the bags. In the fourth group the fish fillets were dipped before packing for 2 minutes in 0.2 per cent ascorbic acid solution. The fish were stored at -f 4°C in ice which was changed daily.
Seasonal variations in rainbow trout were studied in four geographically different places of growth. Experiments were carried out in May, July, September and February. The fish was weighed and tested for approximate chemical composition, total and coliform bacteria, and organoleptic quality. Besides chemical and microbiological analyses, tests were made from the cultivating waters. The results indicated that the fish varied according to the season and place of growth. In chemical analyses the greatest differences occurred in the amounts of water and fat. The organoleptic quality of trout seemed, however, to be mostly influenced by the places of growth.
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