The use of ESR spectroscopy for the detection of irradiated crustacea with particular reference to Nephrops norvegicus (Norway lobster)

  • Eileen Stewart

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

The potential of ESR spectroscopy for the identification of irradiated Crustacea, in particular the Norway lobster, has been investigated.

The ESR signal induced in the cuticle of different exoskeleton components of irradiated Norway lobster consisted of the characteristic Mn 2+ spectrum with an additional peak in the centre at 349.5 mT. This peak was radiation-specific as it was not generated by other
processing treatments such as drying, grinding, chilling, freezing or cooking.

Several variables which could potentially affect signal intensity were evaluated. Signal strength increased linearly over the dose range 1 to 5 kGy except in samples cooked prior to irradiation where linearity was lost after 4 kGy. During storage signal intensity decreased, the reduction being significant in samples given 2 to 5 kGy. There was also a greater decline in signal strength in samples stored at +5 c than those kept at -20°c.
Samples cooked before irradiation showed a dramatic increase in the intensity of the radiation-induced peak while cooking after irradiation reduced signal strength.
ESR signal intensity differed in irradiated exoskeleton components being the most intense in the claws.

The usefulness of the method not only for qualitative identification of irradiated Norway lobster but also for estimation of the dose received was provided by the results of an in-house blind trial. All samples were correctly identified and using a re-irradiation procedure dose estimates were within 1 kGy of the applied dose.

The methodology was also extended to other Crustacea, namely pink shrimp, tiger prawn, king prawn and Mediterranean crevette. The shape of the ESR signals induced in the cuticle of these species by ionising irradiation was more complex than that of Norway lobster. Signal intensity was significantly affected by irradiation dose and storage, the signals being less stable than that present in irradiated Norway lobster.
Date of AwardJul 1993
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorM. HILARY STEVENSON (Supervisor)

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