Use of autoclaving in the preparation of homogenates for determining the proximate chemical and fatty acid composition of fish

Abstract

Abstract A comparative study was made of the proximate chemical and fatty acid composition of barramundi fish (Lates calcarifer, Bloch) processed by repeated mincing either without (M) or with autoclaving for 4 h at 126°C (M + A). M + A processing caused complete disintegration of the tissue, enabling easy homogenisation by blending. The eviscerated carcase and pooled gill/gut of 12 plate‐sized barramundi were individually processed by M or M + A procedures and the resultant freeze‐dried product analysed. Processing method did not alter ( P > 0.05) the analysed ash, nitrogen or fat content of the sample. An additional two samples of pooled gill/gut were M or M + A processed and analyzed both before or after freeze‐drying. Freeze‐drying caused a 16 and 19% depression ( P < 0.05) of eicosapentaenoic acid (C20: 5ω3) and docosa‐hexaenoic acid (C22: 6ω3) respectively for samples processed by M but not by M + A. It is speculated that M + A processing inactivates endogenous lipolytic enzymes which otherwise cause fatty acid losses during freeze‐drying. The present study demonstrates the suitability of autoclave processing for determining the proximate chemical or fatty acid composition of fish tissue.