ZEJP.htm

NR ZEJP

AU Leupold,G.

TI Lebensmittelhygienische Untersuchungen an Regenbogenforellen (Oncorhynchus mykiss) nach Anwendung verschiedener Betäubungsverfahren

QU Vet.med. Dissertation Leipzig, 1997

PT Dissertation

AB According to section 13 of the animal protection bill (draft from 16.3.1995) fish has to be stunned immediately before killing. Electric shock, head blow and C=2 administration are to be licensed for this means. There are so far no definite guidelines concerning the appliances, duration of stunning, nor are the criteria defined by which to ascertain a sufficient effect of stunning. Therefore the parameters for alternating current, direct current and pulsed current had to be determined at large which assure a secure and yet mild stunning of trout. A stunning method is only applied on a large scale if it satisfies the quality needs of the processing industry. The main part of the experimental work consisted of stunning in total of 420 trout by alternating current, direct current, pulsed direct current, head blow and carbon dioxide and processing it to fresh fish on ice, frozen fish and smoked filleted trout. The this way produced food was examined after different storage times by physical, bacteriological and sensory methods. The results in summary are: 1. Alternating current: it was possible to stun trout sufficiently according to the described conditions (200 V, 50 Hz, 5s administration time) without occurrence of fractures and bleeding which had been previously described. The duration of stunning is mainly determined by the length of the administration time. the obtained food had good bacteriological and sensory characteristics. 2. Direct current: Direct current devices should administer a slowly increasing current. It is impossible to distinguish stunning from killing reliably. However, direct current is a method to kill trout safely without inflicting pain (320 V, 30 s). The thus obtained fish products had the highest germ concentration in raw, frosted and smoked forms and there were some sensory deviations following prolonged storage in frozen form. Fish which has been stunned by direct current is not suitable for processing or prolonged freezing. 3. Pulsed direct current: Using the described conditions (530 V, 1ms length of pulse, 1 s administration time) pulsed direct current is a mild method to stun the animals. Their flesh is well suited for processing and achieved the best results in most examinations. Stunning by pulsed direct current should be examined for further development according to the conditions of the fish processing industry. However, the cost are much higher than the reminder of the examined methods. 4. Head blow: This most frequently applied method is simple and yet mild to fish. The obtained food is of good hygienic quality. However, this method is unsuitable for large amounts of fish. 5. Carbon dioxide: The carbonic acid, which is generated by carbon dioxide insufflation, alters the acid-base-balance and causes extreme stress to fish. The animals suffer until stunning occurs (very late, after 12 min). Stunning of trout by carbon dioxide is not reconciable with the concept of animal protection. The sour taste impairs the sensory quality (taste and consistency) of the flesh even after prolonged freezing. This fish is only partially technologically useful.

SP deutsch

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