Postmortem Changes in Fish on Storage

Question 1

What are the postmortem changes in fish on storage?

Answer 1

Hyperaemia
Rigor Mortis
Autolysis
Microbial Putrefaction or Decomposition
Lipid Oxidation or Autoxidation
Discoloration

Question 2

Define Hyperaemia.

Answer 2

The skin of fish releases large quantity of mucus to the body surface.

Question 3

Define Autolysis.

Answer 3

Complex tissue components present in fish such as proteins, lipids, and nucleic acids are broken down into simple building blocks by the enzymes. It leads to the softening of fish. The resulting product is nutrient-rich medium for the growth of microbes.

Question 4

Define Rigor Mortis.

Answer 4

Rigor means Stiffening; Mortis means Death. It refers to the stiffening of fish for a certain period of time after death.

Question 5

Define Microbial Putrefaction of Decomposition.

Answer 5

The tissue components of fish are decomposed by microorganisms producing off-odor and off-flavor substances accumulation of which distracts the consumer which leads to spoilage of fish.

Question 6

Define Lipid Oxidation or Autoxidation

Answer 6

The unsaturated lipids of fish tissue are oxidized by the atmospheric oxygen which leads to the development of rancid flavor in the fish tissue.

Question 7

Define Discoloration.

Answer 7

Microbial spoilage or chemical changes results to autoxidation leading to undesirable flavor.

Question 8

How long will you incubate the Conway disc? At what temperature?

Answer 8

1hr at 37C

Question 9

It is the main substance that causes the off-flavor in fish.

Answer 9

Trimethylamine

Question 10

It is the method of analysis that quantitates the nitrogenous compounds (ammonia, dimethylamine, trimethylamine) present in fish that reveals the degree of freshness.

Answer 10

TVBN or Total Volatile Basic Nitrogen

Question 11

It is an osmosis-regulating substance that produces the trimethylamine compound.

Answer 11

Trimethylamine oxide

Question 12

What compound is placed in the inner chamber of the Conway disc when determining the TVBN?

Answer 12

2 ml of boric acid

Question 13

What compounds are placed in the outer chamber of the Conway disc when determining the TVBN?

Answer 13

1ml of the filtrate of homogenized fish and trichloroacetic acid + 1ml saturated potassium carbonate

Question 14

What is further added in the outer chamber when TMA is being determined?

Answer 14

0.5ml of formaldehyde

Question 15

What is the titrant used in TVBN and TMA?

Answer 15

0.02N sulfuric acid

Question 16

What is the expected color change during titration in determining the TVBN and TMA?

Answer 16

from green to pink

Question 17

What is the major component of fish that can produce amine?

Answer 17

Protein

Question 18

What forms the basic nitrogen in TVBN?

Answer 18

The degradation of proteins caused by the action of bacteria present in fish

Question 19

It is an important indicator of microbial spoilage of fish

Answer 19

TVBN

Question 20

As the time of refrigerated or chilled storage of fishes increases, TVBN also increases. True or False?

Answer 20

True