Fish and Shellfish Flashcards
What is seafood?
aquatic animals for human consumption
true fish + shellfish
What are the commonly marketed fish products? (6)
Fresh Frozen Smoked/salted/marinated Canned Fish Meal Fish Oil
The top fish producing country is:
China
What are the various animal types harvested for seafood?
vertebrates: - bony fish - cartilagenous fish (shark, skate) invertebrates: - mollusc - crustacean - echinoderms
What are the flavor classifications of fish? give some examples
Mild: Cod, Halibut, Porgie
Medium: Shrimp, Lobster, Skate
Strong: Salmon, Mackerel, Sardines
What are the factors that affect fish composition? (8)
- species
- diet
- season
- age
- sex
- habitat
- population density
- migratory or spawning behaviour
Most fish sold as food is in ____ form, followed by _____.
frozen (24%); fresh (22%)
Wild harvest of fish was increasing, but now has stabilized around ___. Why?
What source of fish in increasing?
95 tonnes
- Regulations (government limit)
- Depletion of stocks (overfished, few left)
Aquaculture (farmed fish) is increasing
What are some non-food uses of fish? (5)
Fertilizer Feed Supplements Gelatin (glue) Cosmetics
Name the fins on a teleost fish:
on back: Dorsal, Adipose (near tail)
Tail: Caudal
Belly: Pectoral (front), Pelvic, Anal
How does fat distribution differ in fatty and lean fish? What types of lipid predominate?
fatty: fat throughout flesh
lean: fat accumulates in liver/gut
mostly TG, also PL in skin and membranes
fish is about ___% protein, which is comparable to ____.
16-21%
beef
What component shows the most variation in fish? What other component will also vary, and what causes these variations?
Lipids, also protein
spawning/migration -> use energy, lower lipid/protein
increase in period of heavy feeding
Describe the 2 layers of fish skin:
outer layer: epidermis - high moisture - glands make mucus (MUCOPOLYSACCARIDES) inner layer: dermis - scales - conn tissue fibres - pigment cells (GUANOPHORES)
The main sugars of mucopolysaccharides that form the fish slime layer are: (2)
glucosamine, galactosamine
Fish oil is an excellent source of ____ PUFAs, but what problem does this cause?
omega 3 (good for health!) prone to oxidative rancidity
What is the main cause for the rapid bacterial decay of fish?
The microflora present on scales/skin, resistant to low temperatures
Name the 3 protein types in fish, and their proportions.
Sarcoplasmic (dissolved) - 20-30%
Myofibrillar (muscle, salt-soluble): 65-75%
Stromal (insoluble) : 3-10%
actin, myosin, and troponin are all ____ proteins, while collagen is a ____ protein.
myofibrillar
stromal
how do the proportions of fish protein types compare to that in mammals?
How does this affect the fish meat?
Less stromal: don’t need as much connective tissue since water can support weight
More myofibrillar: need strong muscle for swimming
sarcoplasmic stays the same (enzymes, etc)
fish is more tender than meat, since less sarcoplasmic
What type of protein is Mb?
sarcoplasmic
How do fish myofibrillar proteins compare to mammalian counterparts?
more myofibrillar, but individual proteins in same proportion
More easily denatured by heat
Fast hydrolysis
(easy digestibility)
True/False: the sarcoplasmic protein proportions and types remain fairly constant among all fish.
False: different patterns can be seen, and used to identify fish
What sarcoplasmic fish protein is different from the mammal version? This protein is concentrated in ______.
Mb - fish has cysteine, mammal does not
concentrated in dark muscle
Fish protein generally has higher levels of what AAs, compared to mammals? This means that it would pair well with:
lysine, cysteine, methionine
cereals (low in those AAs)
___, a very basic non-protein AA, is found in fish and has antimicrobial properties
protamine
The main connective tissue proteins in fish are:
collagen (90%), elastin
How does the final meat yield from fish compare to mammals?
lower yield after removal of head, guts, tail, etc (lose up to 50%)
mollusc/crustacea lose even more (over 50%)
but less losses during cooking
True/False: fish contain all the essential AAs.
True (like all animal protein)
What are the major NPNs found in fish? (6)
N containing extractives:
- volatile bases (TMAO, NH3)
- urea (cartilagenous fish)
- nucleotides/purines
- free AA
- creatine
Fish are a good source of what vitamins and minerals?
vitamins: B (multiple), D and A (fatty fish)
minerals: Na, K, Mg, Fe, I (saltwater), Se, Cu, Ca, P
What are some non protein AA found in fish? (4)
betaine, carnosine, anserine, protamine
TMAO is naturally present in fish for what purpose? What happens after harvest?
trimethylamineoxide - help fish stay afloat (osmolyte)
TMAO reduced (lose H2) -> TMA -> (dehydrogenase) -> DMA + formaldehyde
TMA has fishy odor (bad)
formaldehyde will cross link proteins -> tougher texture
_____ fish contain some urea content
cartilagenous
What are the various nucleotides? (5)
ATP, CTP, UTP, TTP, GTP
breakdown of ___ yields IMP, which is (good/bad). Why?
ATP; good (enhance flavor, indicates freshness)
___ is produced from AA catabolism, its presence in fish indicates poor quality
urea
How would continued breakdown of ATP produce unwanted compounds? Describe the process
ATP -> ADP -> AMP -> adenosine + IMP (good, enhance flavor)
IMP -> hypoxanthine -> xanthin -> uric acid/urea
hypoxanthine, xanthin, urea will cause off taste, quality loss
What are the carbohydrate sources in fish? (2)
glycogen in muscle
polysaccharides in slime layer
Fish contains (more/less) glycogen than mammals.
less; need lot of energy for swimming so less is stored
What is the “lateral line”
horizontal row of scales down fish body - can use to sense changes in surroundings/movement
Describe the process of bringing wild fish to market (8)
- catch
- hold (store live in tanks, since long time at sea)
(can use tranquilizer to slow - Aqui-S) - sort (remove bycatch, too small fish)
- bleed/gut - remove head/guts/blood
- clean/wash - remove pigments and gut residue (contamination)
- ice/chill
- storage
- market
What are the grades of fish? What are some factors it is based on, and what 2 factors do not affect grade?
Premium, A, B, C
color of eyes/gills, state of fins/skin/body, odor, if it has been bled/chilled
does not depend on flesh color, or skin color (varies with species and feed)
What problems can occur with evisceration? (3)
blood pigments will discolor fish
gut bacteria cause contamination
proteases/lipases cause degradation
What are some uses for undesirable fish? (2)
Mild fish (pollock, carcasses, etc) -> surimi strong fish (mackerel, herring) -> fish oil
What is surimi? How is surimi produced?
nutrient dense fish paste
take mild fish -> gut/bleed/clean -> debone -> leach -> strain -> mix with CRYOPROTECTANTS (preserve texture) -> pack in frozen storage
How is fish oil obtained?
cook fatty fish -> press to remove liquid -> separate liquor into water and CRUDE OIL -> water wash + C to remove odors/pigment -> fish oil
What is the lipid composition of fish oil? What are its uses (5)?
PUFAs: 40%
MUFAs: 30%
SFAs: 30%
health: PUFAs prevent cardiovasc disease, important for growing brain cosmetics fuel plant protective coatings paint
What are two compounds in crustacean waste that can be repurposed?
carotenoproteins - coloring - as additive or for salmon feed
chitosan/chitin - films, plastics, thickeners, etc
How is chitosan obtained?
crush -> demineralize (chelator) -> proteolysis (protease) -> centrifuge
dry the residue: and repeat previous steps to purify -> decolorize with acetone, HClO2, or peroxide -> CHITIN -> remove acetyl group -> CHITOSAN
Fish gelatin is in ___ form, so it is easy to work with, and acts as a ____ or _____. What are some non food uses?
liquid; stabilizer; thickener
can use for pharmaceuticals, glue, films
Describe the process of fish skin gelatin production
remove oil for other uses, then dry with mild heat to not damage protein
solvent extraction to completely defat
Use NaOH and Trypsin to destroy non-collagen protein
Use chelator (citric acid) to remove minerals
hydrolyze collagen with pepsin or other protease
gelatin
Describe the process of fish skin gelatin production
remove oil for other uses, then dry with mild heat to not damage protein
solvent extraction to completely defat
Use NaOH and Trypsin to destroy non-collagen protein
Use chelator (citric acid) to remove minerals
hydrolyze collagen with pepsin or other protease
gelatin
How are carotenoproteins extracted from crustacean shells?
take supernatant (liquid) after chitin removal, then dry
What is the difference between chitosan and chitin?
Chitin has acetyl group, insoluble white powder.
convert to chitosan to make soluble in dilute mineral acid.
