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Tesi etd-07172019-141456

Thesis type
Tesi di laurea magistrale LM5
Frodi per sostituzione in prodotti della pesca: selezione di parametri istologici per la discriminazione di polpo (Octopus vulgaris) fresco e decongelato.
Corso di studi
relatore Prof. Armani, Andrea
controrelatore Prof.ssa Abramo, Francesca
correlatore Dott.ssa Tinacci, Lara
Parole chiave
  • polpo
  • istologia
  • congelamento
  • frodi sostituzione
  • comparto ittico
Data inizio appello
Secretata d'ufficio
Data di rilascio
Riassunto analitico
The application of appropriate analytical techniques represents an important tool to prevent deliberate substitutions of fresh with thawed seafood. The histological method has already been validated to discriminate fresh from thawed fish [1,2], while it has never been applied to cephalopods [4]. The present study aimed at selecting histological parameters of freezing-induced structural alteration on Octopus (O. vulgaris), to be further used in the setting up of an operational grid for the discrimination of fresh and frozen-thawed samples. Ten whole fresh exemplars (F), maintained at 0-2°C, were sampled at different time (24h, 72h, 144h and 192h) within octopus shelf life [3] obtaining 10 longitudinal and transversal mantle samples at each sampling. Samples were fixed in 10% formalin, embedded in paraffin and sections stained with H&E were observed to define fresh tissue morphological pattern and to highlight possible histological spoilage-related alterations. Then, 85 mantle tissue sections belonging to 20 fresh (F), 20 conventionally frozen in a laboratory freezer at -20 °C for 15 days (CF), 25 industrially frozen in bulk blocks at -80°C (IFB) and 20 curled and Individually Quick Frozen (IQF) exemplars, were analogously processed and screened to select histological parameters descriptive of freezing-thawing process. Overall tissue structural organization (4x magnification), gaping among muscle fiber bundles and white round-oval-saccular spaces or clefts between and within the muscle bundles (10x magnification) were assessed on the central area of the longitudinal section, including radial, circular muscle bundles and a central connective tissue layer. Moreover, white spaces between and within muscles bundles were measured by morphometry and results expressed as percentage. Focal myofiber degeneration, shrinkage and swelling were histological modifications related to shelf-life. The increase of the overall tissue structure alteration, myofiber gaps and the presence of white spaces between and within muscle bundles were all statistically confirmed to be related to freezing as plausibly induced by the effects of water crystallization phenomena [4].The mean white space percentages recorded in F (22.97%), CF (43.09%), IF (46.57%), IQF (59.69%) highlighted significant differences between fresh and frozen tissue types. Thus, the study confirmed the suitability of all the aforesaid histological parameters as analytical indicators for the discrimination of fresh and frozen cephalopods. [