3. Fish and Shellfish Flashcards
fish are broken down into two main groups, which are…
- true fish: have bones and exoskeleton
2. shellfish: have vertebrates
vertebrates are further broken down into two groups, which are…
- fish with bones (eg. tilapia, cod, salmon)
2. fish with cartilage (eg. sharks)
invertebrates are broken down into 3 groups, which are..
- mollusces
- crustaceans (eg. lobster, crab, shrimp)
- echinoderms (eg. starfish, seacucumber, sea urchin)
what are non-food uses of fish?
health products, cosmetics, glue (using gelatin from fish), photographic films
what fish has mild, medium or strongflavours?
mild: cod, perch, haddock
medium flavours: shrimp, lobster
strong flavors: salmon, mackerel, tuna
compare the blood of fish and mammals
fish:
- cold blooded (body temp fluctuates +/- 1 deg from ambient temp)
- poikilotherms or endotherms
mammals
- warm blooded (maintains fairly constant body temp regardless of ambient temp)
- ectotherms
what are some fish that are warm blooded?
tuna
sturgeon
white shark
what factors affect composition of the fish?
- where they are harvesting, age, sex, environment, activity levels
- feed intake
- migratory swimming
- sexual changes in connection with spawning
why is it important to know the composition of fish?
- useful for cooks/chef to select types of fish
- helps determine the type of processing used for that type of fish (eg. freezing, chilling, cooking)
- useful for health professionals + nutritionists (knowing the FA profile of a fish to make recommendations to individuals)
- composition affects flavor
- helps producer know which parts of the fish to use for what
what is the min and max levels for protein and moisture content of fish?
what is the range for fat?
protein and moisture content is 1:3
fat is 1 to several hundreds
what does spawning and migration of fish allow for?
- high use of energy
- low levels of lipid and protein
what is spawning
external reproduction (releasing unfertilized eggs by mother)
during periods of heavy feeding, which components of fish muscles increase the most?
- mostly lipids, which shows the most variation
- also, proteins
what are the 2 layers of skin in fish?
outer epidermis
inner derma
describe the outer epidermis of fish
high moisture content and numerous gland cells that produce the mucous responsible for the slimy surface
describe the inner derma of fish
- permeated with connective tissue fibers, various pigment cells, including guanophores which contain silvery white glistening guanine crystals
- scales protrude from the derma.
where do scales protrude from? how does this vary from species to species? why is this important for processing?
- the derma
- their number, size and kind differ from species to species
- important since it determines whether a fish can be processed without removing the skin
the skin of fish has ____ that are resistant to low temp
spores
what is the main cause of the rapid decay of fish?
spreading of skin microflora after death
what is the major component of mucous?
what main sugars does this contain?
mucopolysaccharides
main CHOs: galactosamine and glucosamine
what are the two main types of fish lipids?
phospholipids and TGs
what are the uses of phospholipids and TGs in fish?
PL: integral structural units of membrane (but membranes also contain some cholesterol)
TGs: storage lipids in fat depots
how are fish classified based on their lipid content?
classified as lean of fatty depending on where the lipids are stored
where can fat be deposited in fish?
muscle tissue, liver or intestines
in lean fish, where are lipids stored?
liver
in fatty fish, where are lipids stored?
stored in fat cells throughout the body (typically in the subcutaneous tissues, in the belly flap muscle and in muscles moving the fins and tail)
which PUFAs are fish high in?
n-3 PUFAs with 5 and 6 double bonds
what is the high amount of unsat lipids in fish prone to?
oxidation and rapid quality deterioration
what are 3 main types of fish proteins?
structural (or myofibrillar)
sarcoplasmic
stromal (or connective tissue)
describe the solubility of myofibrillar proteins
salt soluble
what is the main function of myofibrillar proteins?
metabolic functions
compare myofibrillar proteins in fish vs mammals
- proportion of myofibrillar proteins in fish total protein is higher than in mammalian total protein (proportions of individual proteins are similar to those in mammalian muscle tissue
- more heat stable in fish than myofibrillar proteins in mammals
- hydrolysis of fish myofibrillar proteins by proteases is faster than for terrestrial mammals
- these features account for high digestibility of fish proteins
what are examples of myofibrillar proteins?
Actin, myosin, tropomyosin and actomyosin
describe the solubility of sarcoplasmic proteins
H2O soluble
what are examples of sarcoplasmic proteins?
- myoglobin
- albumin
- mostly enzymes
what is the main function of sarcoplasmic proteins?
mechanical (eg. locomotion)
compare sarcoplasmic proteins in fish vs mammals
- when fish SPs are separated by electrophoresis, specific patterns are obtained for each fish species (useful for taxonomy)
- fish myoglobin has a cysteine residue that is absent in mammalian myoglobin
- fish Mb is concentrated in dark muscle, but Hb is absent in some mollusks and in antartic fish with colorless blood
- in highly pigmented fish (eg. tuna), pigment degradation reactions can induce meat discoloration
describe the solubility of connective tissue proteins
H2O and salt insoluble
what is the main component of connective tissue proteins?
what is the remainder component?
collagen (90%)
remainder is elastin
compare connective tissue proteins in fish vs mammals
- fish CTP is much lower than in mammals
- lower content of CTP and lower shrinkage temp make fish meat more tender than mammalian meat. Thus, fish meat is easier to hydrolyze and easy to digest
which has a higher portion of total body wt that is edible?
A) fish
B) mammals
mammals
which type of proteins are digested faster?
A) fish
B) terrestrial mammals
fish
describe the AA profile of fish proteins
- high in lysine and sulphur containing AA (methionine and cysteine)
- high in basic proteins (protamine), which has antimicrobial properties
- contains all essential AAs
what vitamins are fish especially high in?
- B vits
- vit A and D (in fatty fish)
which minerals are fish especially high in?
- Ca and P
- iron, copper, selenium
- Iodine (for saltwater fish)
what are 5 N-containing extractives in fish muscles?
- volatile bases (TMAO and NH3)
- creatine
- unusual free AAs
- nucleotides and purine bases
- urea
what is TMAO?
trimethylamine N-oxide
what is TMA?
trimethyl-amine
what is DMA?
dimethyl amine
what volatile bases are present in fish muscles?
TMAO and NH3
where is TMAO naturally present? what is its function?
- naturally present in the liver
- helps the animal with floatation
what reaction does TMAO undergo?
TMAO (trimethylamine N-oxide) + H2 –> TMA (trimethyl-amine) –> DMA (dimethyl-amine) + formaldehyde
what does the presence of TMAO indicate? what does the presence of TMA indicate?
TMAO: fish freshness and higher quality
TMA: associated with “fishy odors”. TMA is present when TMAO is broken down
in the reaction of TMAO to fomaldehyde, what causes texture toughness?
formaldehyde forming cross linkages
what happens to the texture of fish when you leave it in the freezer for a long time?
texture becomes tougher due to formaldehyde formation and dehydration
what reaction is catalyzed by creatine kinase?
creatine-P –> (ADP to ATP) –> creatine
which is the high energy compound? which is the precursor?
A) creatine-P
B) creatine
creatine-P is high energy
creatine is the precursor
what are unusual free AAs found in fish muscles?
betaine anserine carnosine urea osmolytes
what is GMP and IMP also used for?
flavor enhancers
what is the k-value derived from?
what is the k-value used for?
from ATP breakdown
used as index of fish freshness and quality
what breakdowns of ATP indicates decreased quality of fish?
hypoxanthin and xanthin
in fish muscles, what products does ATP break down into?
- ATP –> ADP –> AMP
- adenosine and IMP
- inosine
- hypoxanthine
- xanthine
- uric acid
free AAs present as building blocks of protein breakdown products of proteins contribute to ______
flavour characteristics
what is the principle CHO in fish muscle tissue?
glycogen
which has HIGHER glycogen content?
A) fish
B) mammals
mammals
in fish skin, what produces the mucous material?
slime cells
what is the function of mucous material in fish skin?
imparts slime to the surface of the skin, which provides protection from parasites and predators
what does the lower amount of glycogen stores in fish indicates? why?
- less stored energy
- b/c they are always moving and it is easier for them to get food
what shape are fish usuall?
“torpedo” shape
what type of cells does the epidermis (outer layer) of the fish contain?
epithelial cells, b/c they don’t have blood vessels
how do fish obtain nutrients through the epidermis?
by osmosis
where are slime cells found?
in between epidermis and dermis
what does the dermis mostly consist of?
connective tissue material
where do scales start forming?
from the base of the dermis
what is the function of scales?
- provides protection from the environment
- provides indicators on the age of the fish
what is the function of fins?
provides stability, steering and locomotion
what is the function of the lateral line?
enables fish to sense changes in its surrounding
what are the fish grades? what are they based on?
grades: premium, grade A, B, C
based on features of the fish (ie. whether the fish was bled, integrity of the skin/flesh/gills, if the fish was chilled, odors, eye color)
what is surimi?
what is it used for?
what fish is surimi used with?
- high protein and nutrient dense paste
- used for fish cubes, imitation crab cakes, fish balls
- used with baby cod fish or alaskan pollock (which are very soft b/c of high breakdown of proteins in the flesh)
what is surimi mixed with to maintain moisture content?
cyroprotectants
which PUFAs are mostly found in fish oil?
EPA and DHA
what is the ratio of EPA to DHA in fish oil?
3:1
what are the steps of fish oil production?
- take fresh fish or discards
- cook to release fat from association with other biomolecules
- pressing
what are the two methods of pressing used to produce fish oil?
A) pressing liquids to produce water and crude fish oil. Crude fish oil undergoes water washing and carbon treatment (to remove pigments and odor)
B) solid residues are pressed. Used as feed or fertilizer
what are non-food uses of fish oil?
cosmetics, fuel for street lamps, paints, protein material, coating material for plants (to control pests)
what are the steps of gelatin production?
- drying step: freeze drying or low temp vacuum drying
- defatting: use hot water (in commercial setting), use solvent (in lab setting)
- remove non-collagenous proteins: NaOH (commercially), proteinase eg. trypsin (in lab) which results in collagenous material
- demineralization: HCl, EDTA, citric acid, which results in collagen
- depolymerize or hydrolyze (using protease, heat, pH) to result in gelatin
what are food and non-food uses of gelatin?
food uses of gelatin: candies
non-food uses: biodegradable plastic films and producing glues
what is carotenoprotein? what is it used for?
- bright orange powder produced by crustacean by-products
- used for fish feed supplement for farmed fish and adding to products (soups, crabsticks and pizzas) for color/flavor
what two products can be produced from crustacean-by-products?
carotenoprotein
chitosan
