2. 2
QUALITY OF PROTEINS
Proteins supply different proportions of
essential amino acids
General - animal proteins of better quality
than vegetable proteins.
"Good quality“ - that approach ideal (well-
balanced) proportion corresponding to
human requirements when eaten alone,
readily digestible
3. 3
QUALITY OF PROTEINS
Nutritional value of protein
depends on relation of amino acids to those
required for building new tissues
Limiting amino acid - furthest below standard
Tryptophan in maize
Lysine in wheat
Methionine and cystein (sulphur containing)
in beef proteins.
4. 4
QUALITY OF PROTEINS
Determination of Protein Quality
By biological tests
1. Biological value (BV)
2. Protein efficiency ratio (PER)
3. Net protein utilisation (NPU).
5. 5
Biological value (BV)
Definition
Amount of absorbed protein retained in the
body and expressed as the coefficient of
protein nitrogen retention.
When amino acids contained in ingested
protein correspond to complete protein
requirements of body, almost all nitrogen is
retained and BV is close to 1.0.
6. 6
Biological value (BV)
Previously expressed as percentage
Now stated as ratio
When nutritional value of protein decreases
BV lowered because less protein nitrogen
retained
Calculated as follows:
• Retained Nitrogen
BV = —————————
• Absorbed Nitrogen
7. 7
Biological value of some foods
Food BV
Whole egg 0.95
Milk whey 0.95
Milk 0.80
Meat (muscle) 0.75
Fish 0.75
Rice 0.55
Bread, leavened 0.50
Groundnut 0.45
Wheat gluten 0.40
Gelatin 0.00
8. 8
Net Protein Utilisation (NPU)
In vivo method of determining amount of
protein in food retained by body for growth and
development of body tissues
Evaluation carried out in rats:
Compare protein content of body carcass in
groups fed for 10 days
On a diet containing 10% protein with that of
a similar group fed on a non-protein diet
Over the same period.
9. 9
Net Protein Utilisation (NPU)
Calculated as follows:
Retained nitrogen
NPU = ————————— x 100 OR
Intake of nitrogen
NPU = BV x Digestibility
10. 10
Protein Efficiency Ratio (PER)
Biological measure for determining nutritive
quality of proteins
Animals fed on ad lib ration containing 8 or
10% of protein under test for 28 days
Weight gains and amount eaten carefully
recorded
PER ratio between weight gain and protein
consumed.
11. 11
PER of some common foods
Proteins PER
Hen's egg 3.92
Fish 3.55
Cow's milk 3.09
Soybeans 2.32
Beef 2.30
Rice 2.18
Peanuts 1.65
Beans, pulses 1.48
Maize 1.18
Whole wheat bread 1.10
White bread 0.90
12. 12
CONTENT IN FOOD
High quality proteins
Meat
Poultry
Fish
Milk
Cheese
Eggs
Soybean protein good protein
Other legumes - good quantity protein, lack
certain essential amino acids
13. 13
CONTENT IN FOOD
Grain products
Low in proteins
Consumed in large amounts
Contribute significant proportion
Wheat grains deficient in lysine
Fruits and vegetables little protein
Sugars, syrups, pure fats and oils have none.
14. 14
Average protein content of some selected
foods (g/100g)
Food Protein
Cereals and cereal products
Corn flour, whole 9.6
Corn flakes 7.5
Rice, polished 6.7
Wheat, whole grain flour 10.9
Wheat bran 12.4
Wheat bread (chapati) 8.8
Wheat bread (raised) 8.3
15. 15
Average protein content of some selected
foods (g/100g)
Legumes and Pulses
Chickpea, cooked 12.4
Lentil, cooked 13.2
Mung bean, cooked 9.3
Vegetables
Bottle gourd 1.0
Bitter gourd 1.4
Cauliflower 2.2
Cucumber 0.8
Spinach 2.3
Tomato 1.3
16. 16
Average protein content of some selected
foods (g/100g)
Roots and Tubers
Carrots 0.9
Potato 1.8
Turnip 1.2
Fruits
Apple 0.4
Apricot 0.9
Banana 1.2
Guava, whole 1.0
Mango, ripe 0.8
Orange, sweet 0.8
17. 17
Average protein content of some selected
foods (g/100g)
Nuts and Dry Fruit
Almond 17.0
Walnut 16.4
Pistachio 21.5
Peanut, roasted 24.6
Dairy Products
Butter milk (lassi) 0.8
Curd 2.8
Milk, buffalo 4.1
Milk, cow 3.4
18. 18
Average protein content of some
selected foods (g/100g)
Meat
Beef 16.6
Chicken meat 20.1
Goat meat 18.1
Fish
Fish, shanghara 21.2
Fish, soal 18.8
Eggs
Eggs, hen, raw 11.8
Eggs, hen, boiled 12.6
19. 19
Average protein content of some
selected foods (g/100g)
Fats and Edible Oils
Butter 0.9
Ghee, buffalo 0.2
Soybean oil 0.0
Sugar and Sweets
Sugar, white 0.0
Gur 0.2
Honey 0.3
Jalebi 0.8
Halwa, suji 0.6
Halwa, gajar 4.3
