Lecture 19/5 - fisk detariation

Question 1

Hur ser man på sensoriska kvalitetsaspekter?

Answer 1

Appearance (eyes, gills, skin, etc), QIM

Question 2

Vad är Quality index method. ?

vad får man ut?

Answer 2

With the qim method several quality parameters of fish get points from 0-3, the total qim value can be compared to a calibration curve. From this curve you can achieve information about the relative freshness with is equal to the number of day the fish has been stored on ice.

From the same curve you may also read out how long the fish can be stored on ice.
There is special soft wears developed for different fish species. Today the method is developed for 12 different fish species. Qim can be applied at any point in the trade chain.

Question 3

Nutritional quality i fisken

Answer 3

polyunsaturated fatty acids, DHA, EPA, AA
lipid content
antioxidants
proteins

Question 4

Vad beror shelflife till största delen på?

Answer 4

BACTERIA
formation of biogenic amines,
Oxidation and lipolysis of lipids,
rancidity

Question 5

Rancidity - oxidation - varför sker detta?

Answer 5

Mostly oxidative processes of pure chemical nature, but enzymatic degradation may also play a role.

Auto-oxidation, reaction of oxygen and PUFA

Results in rancid flavours and odours and discoloration

Question 6

Vad kan lipid oxidation ge

Answer 6

dålig smak, lukt, kan va giftig

Question 7

Vad beror Discoloration på?

Answer 7

Antioxidant asthaxantine in salmon is consumed during oxidation. During oxidative processes the color intensity of the muscle will decrease.
syns speciellt i lax

Question 8

Vilka antioxidanter kan tillsättas för att minska oxidationen? Hur är dessa lösliga?

Answer 8

Water soluble:
Vitamin C
Citric acid
Some sulphur compounds 
Antioxidants formed during smoking

Lipid soluble: 
Vitamin E
Carotenoids
asthaxantine
Some sulphur compounds

Question 9

Hur påverkar temperatur lipolys?

Answer 9

The speed of lipolysis is dependent on temperature.

At higher temperatures more FFA are formed

Question 10

Vad är aminer?

Vad orsakar de i fisk?

Answer 10

Amines are organic compounds related to
ammonia.

Största orsaken till dålig lukt i fisk

Question 11

The most important amines that may be present in fish and shellfish:
give examples

Answer 11

votile
Trimethylamine (TMA),
Dimethylamine (DMA),
Methylamine

non votile
Histamine (Hs), Tyramine (Tyr),
Tryptamine (Try), Agmatine (Agm), 
Putrescine (Put), Cadaverine (Cad), 
Spermine (Spm) and Spermidine (Spd)

Question 12

Hur bildas aminer?

Answer 12

Amines are formed from NPN. Non protein Kväve

Question 13

Amines

var kommer de ifrån

Answer 13

Undesirable products from autolytic or bacterial activity which accumulate in fish and shellfish muscle during the storage.

Question 14

Vilka är de mest common aminerna?

Hur bildas de

Answer 14

TMA and DMA

DMA are produced by endogenous enzymes in frozen fish.

TMA are formed by bacteria., often stored on ice where the bacteria can grow

Question 15

The enzyme responsible for DMA formation is

Var finns detta och när inaktiveras det?

Answer 15

TMAOase,
TMAoase exist in gadiform fish.
The enzyme is not active at -30 degrees or less.

Question 16

Formation of DMA and HCHO (formaldehyde) from

• vad gör det med fisken
• hur regueras det här compoundet
• I vilken typ av marint liv finns detta?

Answer 16

Formation of DMA and HCHO (formaldehyde) from TMAO are associated with off-flavors and toughness

Formaldehyde cause protein denaturation, changes in texture and loss of water

TMAO is an osmoregulatory compound

TMAO are present in all marine species and some freshwater species (1-7% of muscle tissue dry weight)

Question 17

TMA - vad gör detta, vilka är mest mottagliga.
VAd klassas som TMA - ge exempel
(vad är tma)

Answer 17

TMA is responsible for the fishy smell
Most of the amines in fish is TMA

By nature shell fish contain more Non Protein Nitrogen, therefore the highest levels of TMA are found in shellfish as there is more substrate to form TMA

Question 18

Non-volatile amines or Biogenic amines - exempel

Answer 18

Histamine (His), Tyramine (Tyr), Tryptamine (Try), Agmatine (Agm), Putrescine (Put), Cadaverine (Cad), Spermine (Spm) and Spermidine (Spd)

Question 19

Varför vill man inte ha histamin?

Answer 19

Food intoxication: histamine is potentially hazardous and is a causative agent in scombroid fish poisoning.

Main symptoms: headache, vomit, itch, numb mouth, face swelling and ardour.
Severe cases - anaphylactic chock

Question 20

Hur länge kan fisk förvaras innan det blir för dålig?

Answer 20

After 12 days of storage the fish reach an unacceptable limit for consumption.

Question 21

Vad har NPN för gemensamma faktorer?

Answer 21

In common for NPN:
compounds of non-protein nature,
soluble in water,
low molecular weight