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Fi-Kje-Te rapporter

Fi-Kje-Te rapporter

The effect of gamma radiation on cod fillets was studied. Cod caught off the west coast of Norway were immediately filleted after slaying, packed in plastic bags and irradiated at the Institute of Atomic Energy, Kjeller. The doses were 25, 50, 90 and 180 krad. Irradiated and nonirradiated fillets were stored at 0 °C and analysed at intervals with respect to proteolytic activity, total bacterial count, trimethylamine (TMA), total volatile base (TVB), volatile acids (VA), hypoxanthine and glutamate-oxalacetate-transaminase (GOT). In irradiated cod fillets the proteolytic activity was considerably lower than in nonirradiated fillets. The proteolytic activity is correlated with the bacterial count, which was significantly decreased by irradiation. Correspondingly, TMA, TVB, VA and hypoxanthine formation were retarded by irradiation. The GOT concentration was lower in irradiated fillets than in nonirradiated. During the first days after irradiation a crab-like odour could be registered in fillets receiving 90 and 180 krad. This special odour disappeared gradually and irradiated fillets were found to be organoleptically acceptable after 27 days storage at 0°C, compared to 14 days for nonirradiated fillets.

Fi-Kje-Te rapporter

For å få et innblikk i om man ved kjemiske undersøkelser kan slutte seg til om et sildemel har vært for sterkt påkjent under tørkingen, er det gjort en del analyser av presskake og mel umiddelbart etter framstillingen og av melet også etter lagring i 3 og 12 måneder ved vanlig romtemperatur. Sildemelprøvene representerer følgende tørkeprosesser: (1) fyrgasstørke, (2) vannluft-tørke (Huse), (3) damptørke og (4) vakuumtørke. I det ferske mel fra fyrgasstørkene var vitamin A fullstendig destruert (Carr Price Test), mens tilsvarende mel fra varmlufttørken hadde tapt over halvparten av sin opprinnelige vitamin A-verdi. Melet fra sistnevnte tørke inneholdt ikke vitamin A etter 3 måneders lagring. I mel fra damptørke var vitamin A bevart selv etter 3 måneders lagring. En dyprød farge forstyrret antimontrikloridreaksjonen ved bestemmelse av vitamin A i vacuumtørket sildemel. Harskheten i melfettet ble bestemt etter en modifisert KREIS-metode og med SCHIBSTEDS aldehydreagens. Det nyproduserte mel fra fyrgass- og varmluft-tørkene var meget harskt. Tilsvarende mel fra damp og vacuum-tørkene viste betydelig lavere harskhetstall. Harskhetsanalysen etter ovennevnte metoder sviktet for lagret sildemel. Melfettets innhold av frie fettsyrer steg ikke hverken under selve tørkeprosessen eller under lagring av melet, og skulle således være et godt mål for kvaliteten av det opparbeidete silderåstoff. Den største tilbakegang i eterekstraherbart fett under lagringen fant en i de mel som ble mest oksydert ved tørkeprosessen. Melets cholininnhold var lite influert både av tørkebetingelser og lagringstid. Omkring 40-50 % av det »lett avspaltbare kvelstoff« (ammoniakk) forsvant under tørkeprosessen. Den anvendte metode for bestemmelse av proteinets lettfordøyelighet med pepsin--saltsyre ga ikke verdier som sto i noen tydelig relasjon til tørkebetingelsene. ENGLISH The intention of these investigations was, by chemical methods, to determine the influence of various drying processes upon the quality of herring meals. The herring meal from four types of dryers - (1) flame-dryers, (2) hot air dryers, (3) steam dryers, (4) vacuum dryers - and the corresponding presscakes were analysed immediately after processing and the meals also after storage for three and twelve months at ordinary room temperature. The vitamin A, determined by a special procedure, using antimony trichloride as reagent (CARR-PRICE test), was very susceptible to destruction in dryer (1) and (2) (see above). In herring meal from dryer (3) the vitamin A content was intact for a storing period of at least three months at ordinary room temperature. A deep red colour interfered with the vitamin A determination in the vacuum dried meal. The rancidity of the fats extracted from newly prepared meals, as determined by KREIS-value (a modified method) and by SCHIBSTED'S reagent for aldehydes, gave high figures for dryer (1) and (2). The corresponding figures for dryer (3) and (4) were considerably lower. The above mentioned rancidity reactions proved unfit for stored herring meals. The free fatty acid content of the meal-fat did not rise neither during the drying process nor during storage of the meals for a period of twelve months at room temperature. The percentage of fatty acids in the meal-fat is therefore a fairly good indication of the quality of the herring raw materials entering the dryer. The largest decrease in ether-extractible fat after storage was found for those herring meals which had become most rancid during the drying process. The cholin content of the meals was rather constant, and little influenced by either drying conditions or storing time. About 40 to 50 per cent of the volatile nitrogen disappeared during the drying process. With the analytical method used no definite relation was found between the content of easy digestible proteins in the meals and the drying conditions.

Fi-Kje-Te rapporter. Virkningen av en eller flere timers forsinket filetering av fisk uten forutgående bløgging. En sammenlikning mellom effekten av umiddelbar bløgging og direkte sløying på mengde avgitt blod av fisken og det resterende blodinnhold i fileten

Fi-Kje-Te rapporter

Saithe, caught on the western coast of Norway, was filleted immediately after killing, packed in plastic bags and irradiated using a cobalt- 60 source at the Institute of Atomic Energy, Kjeller. The doses were 50, 100, 150, 50 + 50 and 50 + 100 krad. All samples were analysed for their total bacterial count, proteolytic activity, ammonia, total volatile acids, trimethylamine oxide, tri- and dimethylamine and formaldehyde. The organoleptic quality was evaluated by a panel of tasters. Double doses were more effective in reducing the total bacterial count than an equivalent single dose. A close relation was found between the bacterial count and the proteolytic activity. The trimethylamine oxide concentration was found to vary between 33 and 44 mg/100 g muscle, decreasing rapidly in non-irradiated fillets to 3 mg/100 g. In non-irradiated fillets trimethylamine oxide was mainly reduced to trimethylamine and in irradiated fillets to dimethylamine and formaldehyde. A split dose of 50 + 50 krad may have a favourable effect on the total bacterial number, but the analyses of proteolytic activity, the volatile acids and the trimethylamine indicated that a higher proportion of spoilage bacteria survive. The low proteolytic activity and the high content of DMA/FA prove that split doses of 50 + 100 krad as compared with single dose of 150 krad, are particularly favourable in the case of saithe.