Seafood Flashcards
Part 1
What are the 2 main ways in which we obtain fish?
- Wild caught
- Commercially farmed
Part 1
What are the main problems with catching fish in the wild? [2]
- Non-sustainable → supply will eventually run out and fish may take very long to reproduce etc
- Negative environmental and by-catch impacts
- when fishermen catch some seafood that they don’t want, these organisms are left on the trunk on the ship while sorting their catch → organisms may die → dead organisms thrown back into the sea
Part 1
What are the main types of fish based on their habitats? [3]
- Marine fish – spend their lives in salt water (sea water)
- Diadromous fish – partially spend live in seawater, partially in freshwater
- Freshwater fish – spend their lives in freshwater only
Part 1
Marine fish is the most commonly consumed type of fish. What are the 2 different kinds of marine fish?
- pelagic (fatty, store lipids in body tissue) → have higher % of dark muscle → dark meat
- demersal (lean, store lipids in liver only) → very low % of dark muscle, white muscle (surimi)
Part 1
What are crustaceans, and how are they characterized? Give some examples.
Crustaceans are arthropods characterized by a hard, close-fitting shell that is shed periodically. Examples include shrimp, lobsters, crabs, and crayfish.
Part 1
What are molluscan shellfish?
What are the different types of common molluscs? (not v impt)
Molluscan shellfish are aquatic invertebrates characterized by a shell that wholly or partly encloses the soft unsegmented body.
- Bivalves (2 shells) – oyster, clam
- gastropods (one shell) – abalone
- Cephalopods (shell inside body) – squid
Part 1
Why is fish such an important source of food?
Fish muscle is a valuable source of:
- proteins
2. micronutrients - polyunsaturated fatty acids.
Part 1
What are the differences between white and dark muscle in fish? [3]
White muscle is used for quick bursts of energy and has lower myoglobin levels. Gets energy from anaerobic respiration, using glycogen as a fuel.
Dark muscle has more myoglobin, capillaries for a more sustained source of energy and employs aerobic metabolism using* fat *as the main fuel.
Part 1
What are the 3 main types of proteins in fish?
- Structural proteins
- Sarcoplasmic proteins
- connective proteins
Part 1
What are the types of structural proteins found in fish muscle and what are their functions?
Structural proteins = myofibrillar proteins
- actin, myosin, tropomyosin, and actomyosin
- Function : mainly involved in muscle contraction
Part 1
Structural proteins make up ____% of total proteins in fish muscle.
70-80
Part 1
What are the types of sarcoplasmic proteins found in fish muscle and what are their functions?
Small moelcular weight proteins like myoalbumin, globulin, and consists of mostly enzymes
- sarcoplasm surrounds the myofibrils, it is the cytoplasm of fish muscle containing organelles (mitochondria, lysosome) and these organs contain enzymes
- Function: responsible for the metabolism of animal cells and are made up of oxidative enzymes, heme pigments, mitochondrial oxidative enzymes, lysosomal enzymes, and nucleoproteins.
Part 1
Sarcoplasmic proteins make up ____% of total proteins in fish muscle.
25-30
Part 1
What 3 processes mainly leads to spoilage of fish meat?
- Autolytic processes
- Chemical processes
- Bacteriological changes
Part 1
At different stages of storage, how does spoilage of fish change?
At first, when fish is freshly caught, spoilage is due to autolytic process (enzymes breaking down compounds). As storage time increases, spoilage is due to bacteria spoilage
Part 1
What are 2 autolytic processes that occur that causes fish spoilage?
- Enzymatic breakdown of ATP
- Enzymatic reduction of TMAO
Part 1
Normally when a fish is caught, post-mortem ATP metabolism is one of the intrinsic factors pertinent to the quality of fish.
Describe the steps of post-mortem ATP metabolism from “fish caught” to “changes in nucleotide metabolism”.
- After fish is caught, ATP is still being synthesised from creatine phosphate.
- During post-mortem, endogenous enzymes in the fish muscle tissue become active and contribute to the autolytic breakdown of ATP and formation of other compounds.
This autolytic process includes the activation of enzymes like ATPases and proteases.
[MUST KNOW]
- ATP → ADP → AMP → IMP (inosine monophosphate) → Ino (inosine) → Hx (Hypoxanthine) → Xa (xanthine) → Uric acid
- Breakdown products, such as inosine and hypoxanthine, can contribute to bitter off-flavours in fish
Part 1
In the metabolism of ATP, what compound is responsible for the fresh flavour of fish?
IMP, inosine monophosphate
Part 1
In the metabolism of ATP, inosine (Ino) and Hypoxanthine (Hx) contribute to ____ off-flavours
Bitter
Part 1
What is k value and its equation?
K-value : gives a relative freshness rating based primarily on autolytic changes that take place in muscle during fish storage
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Equation = [([Ino] + [Hx]) / everything] x 100%
- everything = [ATP] + [ADP] + [AMP] + [IMP] + [Ino] + [Hx] +
Part 1
The higher the k value, the fresher the fish. True or False?
False, since numerator is [ino] and [hx], which contribute to off-flavours
Part 1
Enzymatic reduction of Trimethylamine N-oxide is carried out by which enzyme and what volatile compounds are produced?
TMAO demethylase breaks down TMAO to give products like TMA (trimethyl amine) + DMA (dimethylamine) + .. + formaldehyde