2.5. Measurement of quality of bonito flesh
The deterioration in the quality of the bonito flesh was subject to assay in order to identify the meat level of volatile-based nitrogen (VBN), the peroxide value (PV),the concentration of 2-thiobarbituric acid-reactive substances (TBARS) and protein carbonyls. Fluorescence
and absorption spectrometry were also performed on the samples in order to investigate the relative quality of the contained protein. A 2.5 g sample of bonito meat from treated and untreated fillets were homogenized in a Polytron homogenizer with 20 ml 20 mM phosphate
buffer (pH¼6.86) at 25 C for a period of 2 min prior to the quality of the flesh being analyzed. The VBN value was determined using a microdiffusion method (Conway, 1950, pp. 157–159).