Fish pt. 3 Flashcards
list some components of fish that can cause adverse health effects
- heavy metals
- allergens
- biotoxins
- parasites
describe the effect of heavy metals from fish
Cd, As, Hg, Pb found to elicit health disorders including: - neurological - kidney - headaches - fatigue - coughing
what is the major allergen in fish
parvalbumin
what are some examples of biotoxins from fish
- scombroid: histamines from scombroid fish species (tuna, mackerel, herring)
- tetrodotoxin (pufferfish)
give an example of a parasite found in fish flesh
anisakis
list some non-protein nitrogenous compounds
- free amino acids
- trimethyl amine oxides
- betaine
- carnosine
- anserine
- creatine
- urea
what is TMAO?
trimethyl amine oxides: maintains osmotic balance in aquatic animals
- protects biological molecules from changes in environmental stresses like temperature and pressure
- assists animal in floating in aqueous environment
what are the breakdown products of TMAO?
TMA, which breaks down into DMA, and FA
expand TMA
trimethyl amine
expand DMA
dimethyl amine
expand FA
formaldehyde
what’s responsible for the fishy odors associated with bad quality fish?
TMA and DMA
what’s the role of FA in fish?
causes cross linkages between proteins in fish flesh which makes the texutre toughen
what is betaine?
- NPN
- osmolyte
- net neutral charge
- functions similar to TMAO
what is carnosine?
- dipeptide comprised of B-alanine and histidine
= acts as an antioxidant
what is anserine?
- dipeptide comprised of B-alanine and methyl histidine
- acts as an antioxidant
- more potent antioxidant than carnosine
why does having a methyl on the histidine make it a better radical scavenger?
inductive forces imparted by the methyl group increase the draw of electrons toward the molecule
what is creatine?
- NPN
- glycine + arginine
- can be converted to creatine-phosphate by dephosphorylating ATP to ADP
- serves as an energy reservoir
what is urea?
- NPN
- formed from the oxidation of amino acids, proteins, and breakdown of nucleic acid
- osmolyte (helps w/floatation)
- offers an unpleasant flavor except for in a few cultures
what are the steps of fish processing/handling?
1) catching
2) holding
3) sorting/grading
4) bleeding and gutting/evisceration
5) washing
6) icing/chilling
7) packaging and storage
8) distribution to markets
how are fish caught?
usually on large boats where they are continually caught until the boat is at capacity
what factors may influence the end quality of a fish?
- catching gear/technique
- method of holding the fish
- whether or not you remove the guts/blood
- level of cleanliness
- pressure of jets used to wash fish
why are fish gutted?
avoid “belly burst”: guts have a lot of digestive enzymes that can remain active and act on the stomach and intestine and degrade them and cause the stomach to burst, releasing a slew of microorganisms that can contaminate the meat
why is fish bled?
prevent discolorations
why is fish washed?
remove residues from the gutting/bleeding step
describe how fish are iced/chilled
alternate layers of flakes of ice and fish in insulated containers so there is not too much pressure on the fish
how is fish quality assessed?
breakdown of ATP after the animal dies
describe the breakdown products of ATP
ATP –> ADP –> AMP
what are the breakdown products of AMP?
- adenosine by losing another P
- inosine-monophosphate (IMP) by losing NH3
- IMP –> inosine by losing P
- inosine –> hypoxanthine –> xanthine –> uric acid
what molecule is responsible for the fresh, sweet taste that we associate with good quality fish?
IMP
what molecules are responsible for the unpleasant flavors that denotes fish as low quality?
Inosine, hypoxanthine
physically draw all the breakdown products of ATP as it pertains to fish quality
:)
what is used as an index of freshness for fish?
K value
K = ([ino]+[Hx])/([IMP]+[ino]+[Hx])
a higher K value indicates (higher/poorer) quality fish
poorer
