The nutritional quality of raw, precooked and canned tuna was assessed by determining the total amino acids, in-vitro protein digestibility, Computed Protein Efficiency Ratio (C-PER), Tetrahymena Relative Protein Value (RPV), and fluorodinitrobenzene reactive lysine, together with selected vitamin and mineral assays. Amino acid composition, in-vitro protein digestibility, C-PER and Tetrahymena RPV remained almost the same for the raw, precooked and canned tuna. The percent retention of FDNB-reactive lysine was 91% for the precooked tuna and 80-85% for canned tuna. Thiamin retention for the canned tuna was about 5%, while niacin and riboflavin ranged from 71-73% and 49-50% respectively. The values for Cu, Fe, K, and Ca were significantly lower in canned tuna.

A preliminary study of the potential of high vacuum flame sterilizing canned diced tuna was carried out. The investigation included inoculated experimental sighting packs study at five process levels, and comparative assessment of the physical, chemical and nutritional property of the raw, precooked, high vacuum flame sterilized (HVFS) and still-retorted canned tuna. The vacuum achieved in the HVFS packs was significantly higher (P < 0.05) than the control packs. Fatty acid and amino acid composition, in-vitro protein digestibility, and the Computed Protein Efficiency Ratio (C-PER) were similar for the raw, precooked and canned tuna. Available lysine was marginally decreased by precooking, and HVFS processing caused no measurable change. However, available lysine, thiamin, riboflavin, niacin and mineral concentrations were generally lower in the retort process control canned tuna.