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Role proteins in nutrition. Parameters of good value proteins. 3. Protein efficiency ratio (per) > 2,5. 4. Net protein Utilization - NPU > 0,7
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ROLE PROTEINS IN NUTRITION
Proteins carry out many very important functions in an organism: structural - construction fabrics, protective (gamma - globulines etc. ), regulative (hormones, enzymes), transport (hemoglobin of blood), energy (14 % of daily calory).
Classification proteins by full value: high-grade and less high-grade.
Attributes of full value proteins:
1. Presence in protein irreplaceable amino acids in normal amount and in optimal ratio. By this criterion proteins settle down in the following order: eggs, milk, meat, a fish, a soya, sunflower.
2. Good comprehensibility of the protein in organism. 3 groups of proteins:
а) Good comprehensibility - milk, a fish,
b) Average comprehensibility - meat, eggs (after thermal processing),
c) Bad comprehensibility - leguminous, bread, mushrooms.
3. High biological value. After absorbtion the most part of irreplaceable amino acids should be used on the main functions of proteins, except for energy.
PARAMETERS OF GOOD VALUE PROTEINS
1. AMINOACIDIC NUMBER (AAN) in %%:
mg amino acid in 1 g of the given protein
AAN = --------------------------------------------------------- х 100 %
mg amino acid in 1 g of ideal protein
Composition ideal protein (by FАО/WHO) in 100g of protein must be: Valine - 5, Leucinum - 7, lysine - 5, 5, isoleucine - 4, methionine - 3, 5, threonine - 4, tryptophan - 1, phenylalanine – 6 g.
AAN of key products: a chicken ovum - 100 %, cow milk - 95 %, rice - 67 %, wheat - 53 %
2. INTERRELATION of irreplaceable and replaceable amino acids in protein:
The sum of irreplaceable amino acids
--------------------------------------------------- ~ 0, 4 (40 %)
The sum of replaceable amino acids
3. Protein Efficiency Ratio (PER) > 2, 5
W2 - W1 W2 - mass of a body animal in the end
PER = -------------- of Experiment
B W1 - initial mass of a body
В - quantity(amount) of protein in g, received by animal during experience
4. Net Protein Utilization - NPU > 0, 7
A - U - F A - quantity of nitrogen in meal, g
NPU = ------------- U - quantity of nitrogen, discharged
A with urine, g
F - quantity of nitrogen, discharged
with faecals, g
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Irreplaceable amino acids and it functions.
Irreplaceable amino acids - are not synthesized in an organism of the person and should be received from the outside with a food. Among 20 amino acids of all for the adult person it is 8 irreplaceable amino acids: Methyonin, lyzin, tryptofan, leuchin, izoleuchin, treonin, valin, phenylalanin.
Functions of some irreplaceable amino acids.
Methyonin. 2-3 g per day. Adjusts exchange of fats, phosphatides and cholesterol - the antisclerotic factor. Contains in milk, in cottage cheeses, eggs, leguminous, meat, fishes.
Lyzin. 3-5 g per day. Participates in synthesis of hemoglobin, supports nitrogenous balance, adjusts contents Са in blood. Consists in milk, meat, fish, soya. It is not enough - in cereals.
Tryptofan. 1, 6 g per day. Stimulates growth of fabrics, synthesis blood proteins and hemoglobin, participates in maintenance of nitrogenous balance. Consists gradually in different food proteins.
For children in addition there are 2 irreplaceable amino acids - аrgynin and gystidin. Conditionally irreplaceable – needs for development, metabolism, blood formation and are synthesized in an organism, but in insufficient amount for a growing organism since stimulate growth.
Protein norm and protein minimum.
Protein norm - necessary amount protein for the person per day for performance all functions of protein. It is a component of the norms of nutrition of the population. Depends on age, sex, degree of weight of work. For adults on the average it is 70-100 g per day. The optimum ratio of animal and vegetative proteins for adults 50: 50 %, for children 60: 40 %.
DIALY NEED PROTEIN (g / kg body mass)
| COUNTRY | MAN 18-59 years | WOMAN 18-59 years |
| FAO \ WHO | 0, 75 | 0, 75 |
| USA | 0, 80 | 0, 80 |
| Canada | 0, 77 | 0, 69 |
| England | 1, 15 | 1, 0 |
| Russia | 0, 93 – 1, 7* | 0, 96 – 1, 4* |
| Ukraine | 0, 83 – 1, 53* | 0, 83 – 1, 4* |
The notes: * - In dependence on age and gravity of work
The protein minimum - necessary amount protein for maintenance of nitrogen balance in organism – at it all protein goes on disintegration and allocation nitrogen. Calculation: per day from an organism it is lost 6-7g nitrogen, 1 gramm nitrogen is formed at disintegration 6, 25 grammes of protein (all about 40 gramm, that is less than 50 % protein norm). At nutrition at this level the basic functions of protein are not carried out, can arise acquired immunodeficity.
Protein problem and ways of its decision.
On a global scale now in the world it is made 50 % necessary amount proteins for a feed of all population of a planet. It is almost in all countries, especially with an insufficient level of economic development and a low standard of living of the population.
Traditional ways of the decision of protein problem:
а) Increase agricultural production by extensive and extensive ways (at it is necessary to use agrochemicals, which can collect in food products)
b) Increase preservation of a crop by chemicals
c) Wide use protein products of ocean (but it is very expensive, give allergic reactions, in sea products can collect pollutats from sea water).
d) Allocation protein concentrates from soya, sunflower and their addition in sausages up to 20-30 %.
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Nonconventional ways of the decision of an protein problem:
а) Use microbiological synthesis (growth some microbes at oil substrates, but it is very difficult to clean protein from substrate, and such protein can not use in food for man).
b) Search profitable ways synthesis of irreplaceable amino acids - while such chemical synthesis very expensive.
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