This document summarizes the biochemical composition and nutritional value of raw fish. It notes that fish are primarily composed of protein (15-28%), fat (1-8%), and water (55-83%). Fish protein provides essential amino acids and minerals like calcium, magnesium, and iron. While cooking, canning, and preserving methods can impact vitamin and mineral content, fish overall provide a nutrient-dense food that is higher in protein and lower in fat than meat. The document also outlines several fish byproducts used for human consumption or other purposes, including fish protein concentrate, fish maws, isinglass, fish body oil, fish liver oil, chitosan, and shark fin rays.

1. Fish as food
TYBSc Semester VI
(Applied component: Marine science)
Biren Daftary

2. Biochemical composition of Raw Fish
• Principal contents: protein, fat and water
• Protein = 20%
• Variation in fat and water
• Minerals, vitamins and enzymes
• No carbohydrate except glycogen in liver
• Water = 55 - 83%

3. Proteins
• Normal 15 - 20%
• In some species < 15% or as high as 28%
• Chains of chemical units linked together to make
a long molecule
• Each unit = amino acid (20)
• Essential in human diet for maintenance of good
health
• Lysine & Methionine are found in high
concentrations in fish proteins
• Skeletal protein = 50 – 60% of total weight of fish

4. • Protein content classified into following
groups:
a) Albumin fraction: 16 – 22%
b) Protein fraction: 75%
c) Stroma: 3%

5. Non-protein N2 components
• Peptides (Flavour)
• Free AA, Histidine (Richer in red muscle than
white)
• Bases like ammonia, trimethylamines
• Creatine, taurine, betaine, histamine, glycine,
uric acid, carnosine, etc.
• Nucleic acids

6. Fat
• Average fat content between 1-8%
• If fat > 8% fish classified as oily or fat
• Depot fats
• Brain shows highest concentration of fat
• Heart shows lowest
• Fat content determines the quality of fish and
hence its price

7. • Fatty substances: glyceride group or lipid
group of fatty acids
• Fatty acids: Straight chain monocarboxylic
forms having even no of C atoms (12-28)
• Glyceride group: Fatty acids occur on three
-OH groups of glycerol molecule

8. Fish Oil
• Marine fish oil contains larger quantities of
C18, C20 and C22
• Fresh water fish oil contains larger quantities
of C16 and C18 but less of C20 and C22
• Large applications in industries
• Shark oil rich in unsaponifiable substances

9. Minerals
• 1-2% of fish flesh composition
• Concentrated in fish bones
• Principal minerals: Ca, Mg, K, Na, P, S, Fe, Cl,
Cu, Mn, I, Br
• Trace minerals: Sr, Zn, Ba, Al, Pb, Mo, Co, Ni,
Hg, Cd

10. Vitamins
• Liver rich in B12 and B complex, A and D
• A and D: inner organs of the body
• B: liver, eyes, skin, kidney, spleen and
intestines and roe
• Eels are rich in vitamin A, mackerel in vitamin
D
• Vitamin A, D and E: Fat soluble
• Vitamins of B group: water soluble

11. Nutritional value of Raw Fish
• Nutritional value of fish meat > meat of cattle
• Less stroma protein in fish
• Excellent source of all essential AA needed in diet
• 300g of fish = ½ of total protein & fat
requirement and 1/4th of calories needed in
balanced daily diet
• This amount also provides 50% P, 30% Fe, 100%
vit A, 30% vit B1 & B2 and 50-100% of niacin req.

12. Nutritional value of preserved and
processed fish
• Exudation causes 4% loss in proteins, water soluble
vitamins are also lost
• Cooking at 60˚C causes loss in weight due to water loss
• Frying causes heavy loss of essential AA
• Steam/pressure cooking causes loss in proteins and
minerals
• Canning doesn’t affect protein and fat and heat stable
vitamins
• Canning causes considerable losses in vit B1, C,
pantothenic acid & pteroylglutamic acid
• Salting: 1-5% loss in proteins
• Smoking: 8-30% loss in proteins

13. Freezing & lyophilizing:
• Only vitamin E is destroyed
• Encourage rancidity of fat & denaturation of
proteins
• Undesired look reduces acceptability of the
product, although there is no actual loss of
proteins

14. FISH BY-PRODUCTS

15. Fish Protein Concentrate
• FPC is prepared from whole fish or its parts
• Concentration is increased by removal of water,
oil, bones and other materials
• FPC does not bear resemblance to the original
nutritive values of raw fish
• It is a gritty odourless, colourless & tasteless
powder
• Stable at room temperature for 3-4 years
• Components: Highly digestible protein + lysine +
minerals

16. • Highly nutritious
• For human consumption but not direct
• 5-10% added in bread and biscuits
• 35g/day is recommended level of use of FPC

17. Fish maws
• Fish maws is the internal gas filled organ that
helps to maintain the buoyancy of fish
• Also called swim bladder/air bladder
• In some Asian cultures fish maws are considered
a food delicacy (China)
• Served in soups or stews
• Used in the food industry as a source of collagen
• Can be made into a strong water resistant glue
• Making isinglass for the clarification of beer

19. Isinglass
• It’s a collagen derived from thin, inner shiny
silvery layer of airbladder of some fishes
• Airbladders are washed thoroughly, outer thick
fibrous layer is separated from inner layer which
is isinglass raw material
• This raw material is then purified
• Russian isinglass from sturgeons is considered as
a very high quality product
• Good substitute for gelatin in confectionary
• Swells in cold water without dissolving

20. • At high temp it produces strongly adhesive
gelatin
• Chief use is clarification of beer, vinegar, etc.
• Also used as an adhesive in the form of
cements and court plaster

22. Fish Body Oil
• Obtained from entire body of fish along with
liver
• Generated from oil sardines / less edible
varieties of fish or from wastes discarded from
canneries
• 5kg of fish = ½ kg fish body oil
• Lesser Vit A and D, less unsaponifiable matter
when compared to liver oil

23. Uses:
• Source of vit A and D for medicinal purpose
• Manufacture of paints & varnishes
• Leather and tanning industry
• Manufacture of cheap soaps
• Iron and steel industry as a tempering agent
• Manufacture of chemicals, cosmetics and candles
• Fungicides for citrus group of trees

25. Fish Liver Oil
• Rich source of vit A and D
• Fat of liver is the source of fish liver oil
Uses:
• Prophylactic & curative agent
• High vit A & D enables it to cure rickets, eye
disorders, abnormalities of skin and vertebrae
• Good growth of bone and teeth
• More resistance to counter bacterial attack

26. Methods of extraction:
• Auto fermentation
• Boiling
• Steaming (85-90˚C under 2kg/sq-cm pressure)
• Chemical digestion
• Solvent extraction
• Refinement of oil

28. Chitosan
• It is a linear polysaccharide
• Made by treating shrimp and other crustacean shells with
NaOH
• No of commercial and biomedical uses
• Used in agriculture as seed treatment & bio pesticide
• Used in wine making industry, helps to prevent spoilage
• Rapidly clots blood and hence used in bandages and
haemostatic agents
• Research going on for study which shows it limits fat
absorption in the body
• Also used in water filtration

30. Shark Fin Rays
• Valuable by-product of shark
• Shark fins are dried & soaked overnight in 10%
Acetic acid
• The scale and softened muscles are scraped
off and the rays are separated individually
• Then thoroughly washed and dried
• Essential ingredient in some exotic soups