Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Food Chemistry 1 > P6. Fish > Flashcards

P6. Fish Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Gourmet Food flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

are fish proteins digested faster than muscle proteins of land animals?

A

yes! substantially faster

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

which 3 aa are more abundant in fish vs beef muscle?

A
  • aspartic acid
  • cystine
  • lysine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

distribution of 3 types of protein in fish? (give percentage range)

A
  • 65-75% myofibrillar protein
  • 20-30% sarcoplasmic protein
  • 3-10% connective tissue proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

myofibrillar proteins
- 1 similarity + 1 difference compared to mammalian protein

A
  • similarity: relative proportions of individual proteins (myosin, actin G, tropomyosin, troponin…) are similar
  • difference: proportion of myofibrillar proteins in fish total protein is higher than in mammalian total protein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q
  1. heat stability of fish myofibrillar proteins is higher/lower than mammalian counterparts
  2. protein hydrolysis by trypsin is faster/slower –> especially which protein?
    - these properties underlie what?
A
  • lower
  • faster –> myosin! actin is similar
  • good digestibility of fish protein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

fish sarcoplasmic proteins
- mostly what? –> correspond to those of mammalian muscle tissue?
- when these proteins are separated electrophoretically, what happens? helpful for what?
- aa composition of what protein in fish is different from that of mammalian counterpart? how?

A
  • enzymes –> yes!
  • specific patterns are obtained for each fish species –> helpful chemical means of fish taxonomy
  • fish myoglobin = different than mammalian myoglobin –> fish contains cysteine residue
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

myoglobin and other pigments for fish are concentrated in _____ muscle

A
  • dark muscle! ish mackerel
    (vs light tissue has less myoglobin)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how much hemoglobin/myoglobin do light fish muscles contain?
vs dark muscle like mackerel?

A
  • light: 0.1 g/kg of both
  • dark: 3.9 g/kg of myoglobin, 5.8 g/kg of hemoglobin (and 0.13 g/kg of cytochrome c)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is absent in some mollusks and in antarctic fish with colorless blood?

A

hemoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

in strongly pigmented fish (ex.?), pigment degradation reactions can induce what?

A
  • tuna
  • induce meat discoloration –> observable greening in canned tuna meat
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

connective tissue protein same in fish than in mammalian muscle?
- main components? (2)

A
  • lower in fish (1.3%) than in mammalian muscle
  • collagen (up to 90%) and the rest is elastin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

shrinkage temp of fish collagen vs mammalian collagen

A

fish: 45°C
mammalian: 60-65°C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what makes fish meat more tender than mammalian meat? (2)

A
  1. lower content of connective tissue protein
  2. lower shrinkage temperature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why do some fish not freeze in -2°C water?

A

because they have antifreeze serum proteins –> congealing temp of blood serum for polar fish of Arctic or Antarctic regions is about -2°C –> significantly lower than that of other fish (-0.6 to -0.8°C)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what makes congealing temp of blood serum of polar fish so low?
- MW?
- structure?

A

antifreeze glycoproteins –> aa sequence of this class of proteins is characterized by high degree of periodicity
- 10.5-27 kDa
- several a-helical regions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

antifreeze glycoproteins:
- highly _______ in solution
- antifreezing effects attributed to what? (2)

A
  • hydrated
  • disaccharide residues as well as methyl side chains of peptide moiety
17
Q

what is a predominant free aa in fish with dark-colored flesh (tuna, mackerel)?
- content %?
- vs light colored flesh?

A

histidine!
- content in flesh is around 0.6-1.3% of fresh weight –> can even exceed 2%
- light color: 0.005-0.05% free histidine

18
Q

what happens to histidine during bacterial decay?

A
  • converted to histamine! can cause allergic reactions
19
Q

what free peptides other than histidine are present in fish muscle tissue? (3)

A
  • free l-methylhistidine
  • anserine (b-alanyl-L-methylhistidine)
  • carnosine (b-alanyl-L-histidine)
20
Q

fish muscle tissue has high content ( 500 units?) of _________ –> derived from _______
- is it an aa?

A
  • 500 mg/kg
  • taurine (2-aminoethanesulfonic acid)
  • derived from cysteine
  • sometimes referred to as an aa, but lacks a carboxyl group
21
Q

what is surimi?

A

concentrate of insoluble fish muscle proteins (20%) that forms a solid cohesive gel when warmed

22
Q

how to make raw surimi? (4 steps ish)

A

highly mechanized process
1. mechanical filleting and deboning of fresh, lean (white-muscle) fish (mostly Alaskan followed)
2. comminution at 5-10°C
3. minced fish is then extracted with water until only myosin, actin, actomyosin and small amounts of collagen remain –> purpose = remove strong flavor compounds and pigments + water-soluble proteins that can interfere in gelation of myofibrillar proteins
4. results in odorless and flavorless high-protein fish flesh (no lipid and almost no carbs) = raw surimi

23
Q

3 properties of raw surimi compared with original minced fish

A

enhanced:
- gel-forming
- water-holding
- fat-binding properties

24
Q

addition of what enhances gel-forming properties of raw surimi?

A

paramyosin (protein similar to myosin that is present in thick filaments of invertebrates)

25
Q

after elimination of excess water from surimi, what is added? why?

A
  • cryoprotectants (sugars or sugar alcohols) are added and surimi is then frozen
  • adding cryoprotectants = necessary to retard protein denaturation during frozen storage, which would result in loss of functionality
26
Q

apart from adding cryoprotectants, how can we further process surimi?
- 2 main + role
- can also add (2)

A

addition of salt (2-3%) + heating
- role of salt = solubilize myofibrillar proteins
- add starch (5%) and egg white

27
Q

2 stage gelation process of surimi

A
  1. setting of gel at 40-50°C: formation of a loose 3-dimensional network by partially denatured actin and myosin
  2. formation of kamaboko at 80-90°C: conversion of loose network to an ordered, non-transparent gel that is more cohesive and elastic

Food Chemistry 1 (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions