Food Comm- Fish and Shellfish
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how large is the world fish catch?
>90 million tons
what is the distinct feature that distinguishes fish?
they respire via gills
what are aquatic environments?
- marine (ocean)
- brackish (lagoon)
- fresh water (lakes/rivers)
what are the current marine fishing capacities vs. the prediction for 2030?
85x106 now, 85x106 in 2030
what are the current inland waters fishing capacities vs. the prediction for 2030?
9x106 now, 6x106 in 2030
what are the current aquaculture fishing capacities vs. the prediction for 2030?
35x106 now, 80x106 in 2030
how many tons of fish per year are used as food production?
what are the reasons why fish production is increasing?
- growing population
- fish is a major source of animal proteins in developing countries
- perceived health benefit vs. red meat
what are the world major producers of fish, starting with the largest?
- China (increasing due to improved technology, fish farming, less conservation)
- Peru (decreasing)
- Japan (decreasing)
- US (decreasing)
- Chile (decreasing)
- Denmark (decreasing)
- Norway (decreasing)
- Iceland (decreasing)
- Thailand (stable)
- Indonesia (stable)
what is the current percentage of fish used as food, and what is the prediction?
~75%, expected to increase to 85%
what is the percentage of fish eaten fresh?
what is the percentage of fish eaten frozen?
what is the percentage of fish eaten canned?
what is the percentage of fish eaten smoked/salted/dried/marinated??
what are some examples of non-food uses of fish?
fish meal, fish oil, fertilizer, bait, paints, cosmetic products
how many species of fish are known?
what percentage of species of fish are consumed?
which are the most harvested species of fish?
anchovies most, then Alaskan pollock, then herring, tuna, mackerel
what types of fish does Canada produce a lot of?
herring and mackerel (but Quebec considers then "trash fish")
what are the vitamins that fish are good sources of?
B2, B6, B12, C, A, D
what are the minerals that fish are good sources of?
Ca, P, Mg, Fe, Zn, Se, I
what are the essential oils that fish are good sources of?
what does the term "fish" refer to?
- true bony fish (bony, cartilaginous)
- shellfish (crustaceans, mollusks)
what are crustacea?
shrimp, crab, lobster, crayfish
what are mollusks?
gastropods, cephalopods, bivalves
what are poikilotherms?
- cold blooded fish
- body temp is within 1°C of the ambient water temp
what are endotherms?
have a body temp that can be much higher (~20°C) than ambient temp
what are some examples of endotherms?
white shark, tuna, sturgeon
what are some examples of soft or delicate textured fish?
anchovies, bass, herring, sea urchins
what are some examples of medium textured fish?
cod, salmon, tilapia, snapper, shrimp
what are some examples of firm textured fish?
catfish, dogfish, sturgeon, tuna, scallops, lobster
what are some examples of mild flavored fish?
sole, flounder, hoki, hake, halibut
what are some examples of moderate flavored fish?
cod, lobster, scallop, oysters
what are some examples of intense flavored fish?
salmon, tuna, mackerel
what is DHA?
docosahexenoic acid, a brain lipid that's useful for brain development and function, the cardiovascular system, lowering blood cholesterol levels, also good for platelet aggregation and related cardiovascular diseases
what are some heavy metals risks in fish?
heavy metals like Pb, Hg, Cd, As can cause problems like headache, nausea, metallic taste in the mouth, renal degeneration, and a variety of cancers
what is the major allergenic fish protein?
what should we associate "urchendontia" with?
puffer fish and toxins
why are histidine and tyrosine amino acids of concern?
- decarboxylation of these amino acids will lead to the formation of their corresponding amines
- histidine → (histidine decarboxylase, lose CO2) → histamine
what are scombroid fishes?
fishes such as tuna, mackerel, or herring, which tend to have high levels of the amino acids histidine and tyrosine, and what's even worse is they have microorganisms that produce the enzymes for decarboxylation
what are histamine and tyrosine known as?
harmful biogenic amines
why is domoic acid concerning?
- micro-algae release various metabolites, one example being domoic acid, which are absorbed by shellfish
- when such shellfish are consumed they cause health hazards
can fish also be infected by parasites?
what are some examples of bony fish?
cod, tilapia, salmon
what are some examples of cartilaginous fish?
sharks, rays, skates
what are shellfish?
- mollusks (cephalopods, gastropods, bivalves)
what are some examples of crustacea?
crabs, lobster, shrimp, crayfish
what are some examples of gatropods?
abalone, sea snails
what are some examples of cephalopods?
squids, octopus, cuttlefish
what are some examples of bivalves?
oysters, clams, scallops, mussels
what are some examples of echinoderms?
sea urchin, starfish, sea cucumber
what is the amount of moisture in fish?
66-88% (compared to 75% in mammals)
what is the amount of protein in fish?
16-21% (compared to 20% in mammals)
what is the amount of fat in fish?
3-25% (compared to 3% in mammals)
what is the amount of carbohydrates in fish?
<0.5% (compared to 1% in mammals)
what is the amount of ash in fish?
1.2-1.5% (compared to 1% in mammals)
what can variations in proximate composition in fish be due to?
- species differences
- season of harvest
- diet/nutritional status
- age, sex, etc.
what are high protein fish?
have a protein content of about 28%
what are some examples of high protein fish?
anchovies, cod, tilapia, salmon, snapper, trout
what are low protein fish?
have a protein content around 6%
what are some examples of low protein fish?
catfish, mussels, oysters, flounder
*true or false: in fish, the unsaturated fatty acid levels exceed the saturated fatty acid levels.
*what are the nitrogen containing extractives in fish flesh?
- volatile bases (like TMAO, and NH3)
- free amino acids
- nucleotides and purine bases
- urea (in cartilaginous fish)
*what are the major components of the sarcomere?
- the Z-disks that define the boundaries of the sarcomere
- thin filaments, which are anchored at the Z-disk
- thick filaments in the central region of the sarcomere that partially overlap with the thin filaments
- titin filaments that span from the Z-disk to the M-line
what are the seasonal nutritive variations for herring?
protein concentration tends to be uniform throughout the year. however, during the summer active feeding season, the fat content gets much higher
what are the seasonal nutritive variations for mackerel?
protein content stays almost uniform throughout the different seasons. however, like many fishes, in the spawning season fat content declines because the reserves are used up for energy generation
what are high fat fish?
- fish that have a higher fat content throughout their bodies
- fat tends to be deposited in muscle tissues and around the belly cavity
- these species are said to be the pelagic species and swim closer to the surface
what does pelagic mean?
- fish that live near the surface of the water
- tend to be the high fat fish
what are some examples of pelagic fish?
high fat: mackerel, herring, sardines, salmon
what are low fat fish?
- fish with a lower fat content throughout their body
- fat tends to be stored in the liver and not in muscle nor around the belly
- these species are said to be demersal fishes, and tend to swim closer to the bottom of the ocean
what does demersal mean?
- fish that live near the bottom of the ocean
- tend to be low fat fishes
what are some examples of demersal fish?
low fat: cod, halibut, bass, porgy
how many layers does fish skin have, and what are they?
2 → outer and inner
what is the outer skin layer?
epidermic, made up of phospholipids with several mucosal cells that produce surface slime on the fish skin
what is slime made up of?
what is the purpose of slime?
slime is for defense against bacteria and predators
what is the inner skin layer?
- derma, made up of connective tissue material (mainly collagen) and blood vessels
- there are grooves in the derma from which emanate the scales (in the case of bony fish)
what is the main connective tissue material in the inner fish skin layer?
what are scales made up of?
calcium salts, carbonates, and hydroxyapatite
what is the purpose of scales?
defense for the animal
do cartilaginous fish have scales?
not true scales, but a much reduced form
what are the shells of crustacea made of?
chitin, calcium carbonate, lipoproteins
what are the shells of mollusks made of?
calcium carbonate, hydroxyapatite, collagen
what liquid are myomeres bathed in?
sarcolemma (similar to cytoplasm)
what is the light zone in the fish filet drawing?
the I-band, mostly thin actin filaments
how are myosepta connected to each other?
what is the dark zone in the fish filet drawing?
the A-band, thin filaments overlapping each other
what does I-band mean?
isotropic band, means the effect on light panned through it is some in all directions
what does A-band mean?
anisotropic band, means the effect of light through it changes with the direction
what is the Z-disk?
thin band within the I-band, anchors the thin filaments
what is the distance between 2 Z-disks known as?
what is the protein that goes through the heavy band and is anchored by the Z-disk in the fish filet?
what is the purpose of the titin in fish muscle?
hold heavy filaments in place, but it is also very elastic so it allows the sliding motion between the actin and myosin
what is the H-zone?
the space between 2 filaments of the light zone, it is even lighter
what is the bump on the A-band?
known as the M-line, protein filament from which the protein filaments extend
what constitutes one unit of muscle fiber?
adjacent myosepta, their myomeres, and sarcolemma
what are the 3 type of fish muscle proteins?
- connective tissue/structural/stromal
what are myofibrillar proteins responsible for?
contractile proteins: comprise the proteins that participate in contraction and relaxation of the muscle
what is the solubility of myofibrillar proteins?
- salt soluble in concentration of 4-8%
- not water soluble
what percentage of fish proteins are myofibrillar?
which is the most abundant myofibrillar fish protein?
what are some other myofibrillar proteins?
- actin, tropomyosin, titin
- these make up 40-45% of myofibrillar proteins
what is myosin like structurally, and why is this important
- large molecular weight (~200kDa)
- made up several polar and charged amino acids
- this is important because it makes myosin most able to uptake moisture and fat. this capacity is exploited in emulsion and batter formation, as it coagulates and gels readily under heat treatment, so plays a useful role in the formation of heat induced gels.
what is the amount of connective tissue protein in fish?
3-10%, which is less than in mammalian and avian tissues
what are the main connective tissue proteins?
collagen (90%), rest is elastin
what is the solubility of collagen?
neither water nor salt soluble
what is the amino acid composition of collagen?
33% glycine, 10% hydroxyproline, then lysine, proline, hydroxylysine make up the rest
what does hydroxyproline do to the collagen molecule?
makes it mostly non-polar because these amino acids are not charged, so the molecules tend to be tough and function by transmitting force or holding components together.
what is used as a measure of collagen content?
what are sarcoplasmic proteins?
globular, water soluble proteins
what percentage of fish proteins are sarcoplasmic?
what are most of the sarcoplasmic proteins?
what are calpains?
- enzymes, sarcoplasmic proteins
- play a role in muscle contraction/relaxation and meat or flesh tenderization
what are some examples of sarcoplasmic proteins?
calpains, glycolytic enzymes, proteases, lipases, myoglobin, hemocyanin
what are the dangers of proteases and lipases in fish tissue?
play a useful role in postmortem flavor development, but can also adversely impact texture and cause off-flavors if not controlled
what does myoglobin do in fish tissue?
- heme part: responsible for color, binds oxygen
- protein part: mostly colorless
where is hemocyanin found? what is it?
- in shellfish, it is like myoglobin but in shellfish
- Cu is the central atom, so shellfish have "blue blood"
what effect does the smaller degree of connective tissue proteins in fish have?
- degree of cross-linking by the collagen is lesser in fish tissue than in mammalian or avian muscle
- because of this, fish tissue proteins are much more easily digestible, and much more heat labile
what are the major lipids found in fish?
phospholipids and triglycerides
what is the key thing to note when comparing fish lipids with lipids from other animal sources?
- tend to be a better source of PUFAs (20:4, 20:5, 22:5, 22:6 are found in fish but not as much in the other sources)
- although these PUFAs have beneficial health effects, they also tend to be highly prone to oxidation, causing fish spoilage
what is the main carbohydrate found in fish muscle?
what is the amount of carbs in fish compared to other meat?
- lower than in other meats
- serves as source of energy for muscle tissue during relaxation/contraction
what is NPN?
non-protein nitrogenous material
what is TMAO?
trimethylamine oxide, volatile NPN material
what are some NPN volatiles?
what is responsible for "fishy odor"?
when TMAO undergoes reduction to form TMA (trimethylamine) catalyzed by trimethlamine oxidase. TMA is responsible for this odor
besides causing undesirable "fishy odor", what else can TMA do?
can undergo demethylation (lose a methyl CH3 group) catalyzed by TMA demethylase for form DMA (dimethylamine, bad smell) and FA (formaldehyde, which causes cross-linking to form between proteins in fish tissue, causing a tougher texture)
what is creatine phosphate and why is it important?
- high energy phosphate compound
- transfers its P to ADP to form ATP
- the creatine left has objectionable odor
when is NH3 produced in fish?
when amino acids undergo deamination, NH3 is produced and causes off-odors
why are nucleotides, purine, and pyrimidines important?
- degradation products of these such as hypoxanthine and xanthine adversely affec flavor
what percentage of fish is waste?
10-50% depending on where fish are caught
what percentage of shellfish is considered waste?
up to 75-80% of the animal
how can viscera be processed? (STEP-BY-STEP)
can be processed to get enzymes (digestive enzymes). First homogenize with appropriate buffer (acid pH for stomach enzymes; alkaline pH for intestinal enzymes), then centrifuge, discard insoluble material, and precipitate out enzymes from the supernatant, either with neutral salt (like (NH4)2, SO4), or cold ethanol.
how can skins and heads be processed? (STEP-BY-STEP)
crush into small pieces, get a powder. Then, de-fat the powder to get the defatted material. De-mineralize the defatted material to remove minerals. What you are left with is predominantly protein, treat this de-fatted/de mineralized material with an enzyme (use NaOH or an enzyme like trypsin (protease) to remove non-collagenous material). What you are left with is essentially collagen. You can either heat treat or use heat in combination with another enzyme like pepsin, to obtain gelatin.
which parts of shellfish are mostly discarded in North America?
- head, carapae, legs
- these make up about 80%
what is shellfish waste high in?
protein, fat, pigments, chitin
what can you use chitin for?
make chitosan to make edible films
how can you process shellfish waste? (STEP-BY-STEP)
- Hydrolyze the shells, filter this hydrolysate, the filtrate is high in taste-active compounds like amino acids and sugars, concentrate this filtrate to get crustacean flavoring. The residue left after filtering still has useful compounds (residual protein, pigments, chitin, ash). First, de-mineralize, then de-proteinize with protease, get your hydrolysate. You centrifuge/filter to get the supernatant or filtrate, dry this (freeze drying, tray drying) and get a powder, which is protein and pigment complex (carotenoprotein)
- CAROTENOPROTEIN → feed to fish to give them nutrients and also to impart color, or just use as colorant for imitation products and soups. The insoluble residue left after centrifugation/filtration is depleted of pigment, ash, and protein. This is essentially your ash, but it is not totally pure or de-colorized. Decolorize with hydrogen peroxide or acetone to get pure chitin. De-acetylation to form chitosan. The structure is similar to cellulose, except around the C2 position, which you lose when you add NaOH, what you’re left with is glucosamine.
saltwater fish have a high content of what?
what amount of glycogen is found in fish muscle tissue and how does this compare to mammalian tissue?
- up to 0.3%
- generally lower than in mammalian muscle tissue
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