Non-invasive measurement of fillet composition of four freshwater fish species by computer tomography

Abstract

Thecrude fat and crude protein content of fillets was predicted by X-ray computertomography (CT) and determined by chemical analyses. Between 20 to 40 serialscans were taken of 48 freshwater fish and samples from the ground fillet withskin were prepared for chemical analyses. Fish species investigated were asfollows: common carp (n = 18), grass carp (n = 10), silver carp (n = 10) andpike-perch (n = 10), all collected directly from fishponds and processedimmediately. The variables of the prediction equations were taken from thedensity values of the Hounsfield scale, on a range between −90 and+150, by summing the frequencies within each interval of 10 values. Withprincipal component analysis fillet fat and crude protein content could beestimated with R2 = 0.88 and R2 = 0.87 accuracy,respectively. Three dimensional"volumetric" estimation of fat tissue was also carried out on the basis of fatindices developed at our lab. The fillet composition of the Cyprinid speciescould be evaluated well with the applied methods, but not that of pike-perchwhich had an extremely low fillet and body fat content.