CONTENTS 



Page 



Introduction 1 



The general problem 2 



Quality in tuna 2 



Refrigeration of tuna: chilling and freezing 4 



Relation of refrigeration experiments to present practices 6 



Effect of refrigeration on yield 8 



Chemistry of raw and canned tuna 8 



Heme pigments, the principal color factors in tuna 8 



Sugars, the secondary color factors in tuna 10 



Purine compounds 11 



Other factors 12 



The effects of premortem stress and postmortem biochemical changes on the 



quality of canned skipjack tuna 12 



Materials and methods 13 



Materials 13 



Sampling 14 



Chemical analyses 14 



Organoleptic evaluation 15 



Results and discussion 15 



Glycolytic degradation products (Table 2) 15 



Total reducing sugars, fiu/g 15 



Glucose (free) , /uM/g 16 



Glucose phosphate, (lU/g 16 



Fructose phosphate, fiM/g 17 



Free fructose, fj.u/g 17 



Free ribose, /iM/g 18 



Pyruvate and lactate, fiU/g 18 



Purines and purine derivatives (Table 3) 18 



Inosinemonophosphate, juM/g 18 



Inosine and hypoxanthine, /j.M/g 18 



Organoleptic analysis (Table 4) 19 



Scorch and color 19 



Firmness, fiakiness 19 



Fibers 20 



Off odor and flavor 20 



Conclusions 21 



Bibliography 22 



lU 



