Tutkimus pakastuksen soveltuvuudesta muikun ja kirjolohen varastoinnissa

Abstract

Abstract. The purpose of the study was to examine the microbiological, physical, chemical and organoleptical changes occurring in muikku (Coregonus albula L.) and rainbow trout (Salmo gairdneri) during frozen storage at -3s°C. The effects of various treatments, gutting and filleting, glazing and vacuum packing and of two different freezing seasons, winter and summer, on the keeping quality were compared. Two series of experiments were performed and the fishes in the first series were kept 6 months and in the second 3 months in frozen storage.All the muikkus and rainbow trouts treated and packed in different ways were acceptable after 3 months at -3s°C. Even after 6 months' frozen storage both the glazed and the vacuum packed rainbow trouts, gutted muikkus and fillets of muikku were judged to be acceptable, whereas the quality of the ungutted muikkus was clearly reduced.The total bacterial counts were generally low and no coliforms were found.The pH values, the liberation of drip from thawed fish muscle and the amount of free fatty acids increased during frozen storage. A correlation was found between the loss of protein solubility and the storage time. The differences between the glazed and the vacuum packed fishes were not significant and the freezing season did not affect the keeping quality. JohdantoSuomen sisävesien ja Perämeren pohjoisosan kalansaaliista noin 25 % on muikkua (Coregonus albula L.). Sitä pyydetään vuosittain noin 4. 1-5.7 milj. kg, mutta arvioiden mukaan pyynti voitaisiin kalavesien tuotantokyvyn rajoissa nostaa kaksinkertaiseksi (Anon. 1965). Muikku on herkästi pilaantuva kala ja suurin osa siitä käytetään tuoreena.