Fish Quality Flashcards
(63 cards)
sensory, microbial, and chemical quality indices
odour
appearance
texture
flavour
how many phases of deterioration are there for fish
4
describe phase 1
fresh
characteristic odour
delicate taste
how long does phase 1 last
almost 2 days
describe phase 2
loss of odour and taste
autolysis begins
what is autolysis
biochemical changes and degradation of proteins, nucleotides and molecules
days of phase 2
2-6
describe phase 3
‘fishy’ odour associated with
microbial spoilage
enzymatic reactions
days that phase 3 occur
6-12
describe phase 4
putrid odour, mushy/soft texture
advanced proteolysis
days that phase 4 occurs
> 12 days
what are cephalopods
squids etc
how does glycolysis occur in fish
-6C and 3C molecules are transformed to pyruvate
-pyruvate is used in TCA cycle and converted to lactate (except cephalopods)
what is pyruvate converted to in cephalopods
octopine
consequences of octopine conversion over lactate
results in a higher ultimate pH
why is the pH drop in fish less than terrestrial animals
less glycogen stored
typical pH fall in fish
6.8-7.2 intially
drops to 6.1-6.9
% of glycogen stores in land animals vs fish
2-1% in land
0.5% in fish
when does rigor develop in fish
2 hrs after death
when does rigor resolve in fish
1 day
what is the rate of onset of rigor determined by
temperature (cold or tropical fish)
condition
handling
size
is rigor desired in
-fish
-red meat
yes in fish
no in reed meat
why is rigor wanted to be preserved in fish
the firmness of fish makes it more difficult for bacteria to move to the surface
what ‘condition’ could result in low glycogen stores in fish
spawning
