Nutritional Properties of Proteins Protein digestibility The quality of a protein is related mainly to its essential amino acid composition and digestibility. Animal proteins are better quality than plant proteins. Proteins of major cereals and legumes are often deficient in at least one of the essential amino acids. While proteins of cereals, such as rice, wheat, barley and maize are very low in lysine & rich in methionine, those of legumes and oilseeds are deficient in methionine and rich or adequate in lysine. • The process of digestion is defined as the ‘process by which macromolecules in food are broken down into their component small molecule subunits’. • Protein digestion takes place in two different phases: ¤ In the stomach ¤ In the small intestine • Both of these phases of digestion are based on several types of enzymes that are called proteinases and proteases Several factors affect digestibility of proteins Protein conformation: The structural state of a protein influences its hydrolysis by proteases. Native proteins are generally less completely hydrolyzed than partially denatured ones. Antinutritional factors: Most plant protein isolates & concentrates contain trysin & chymotrypsin inhibitors & lectins. These inhibitors impair complete hydrolysis of legume & oilseed protein by pancreatic proteases. Lectins, which are glycoproteins, bind to intestinal mucosa cells & interfere with absorption of amino acids. Binding: Interaction of proteins with polysaccharides and dietary fibre also reduces the rate and completeness of hydrolysis. Processing: Proteins undergo several alterations involving lysyl residues when exposed to high temperature and alkaline pH. Such alterations reduce their digestibility, reaction of reducing sugars with α amino group also decrease digestibility of lysine

1. https://www.sciencemag.org/news/2020/11/game-has-changed-ai-triumphs-solving-protein-structures
NUTRITIONAL
PROPERTIES
OF PROTEIN
Presented by- Kirti Gautam

2. PROTEIN
• Proteins function as building blocks for
bones, muscles, cartilage, skin, and blood.
They are also building blocks for enzymes,
hormones, and vitamins. Proteins are one of
three nutrients that
provide calories. Nutrients provided by
various protein foods can differ.
•

3. NUTRITIONAL VALUE OF PROTEIN
PDCAAS
PER
PROTEIN DIGESTIBILITY
TOTAL ASSIMILABLE NITROGEN

4. PDCAAS
(PROTEIN
DIGESTIBILITY
CORRECTED
AMINO ACID
SCORE)
• It is a method of evaluating the quality of
protein based on both the amino
acid requirements of humans and their ability
to digest it.

5. CONT…
• It is the amino acid score corrected for the digestibility
of the protein
• It is a method of evaluating the protein quality based
on both the amino acid requirements of humans and
their ability to digest it.
• The PDCAAS rating was adopted by the US Food and
Drug Administration (FDA) and the Food and
Agricultural Organization of the United Nations/World
health Organization (FAO/WHO) in 1993 as "the
preferred 'best'" method to determine protein quality.

6. THE FORMULA
FOR
CALCULATING
THE PDCAAS
PERCENTAGE
IS:
• (mg of limiting amino acid in 1 g of test protein
/ mg of same amino acid in 1 g of reference
protein) x faecal true digestibility percentage.
• PDCAAS = Protein digestibility x Amino
acid score

7. PROTEIN
EFFICIENCY
RATIO
• Protein efficiency ratio (PER) is based on the
weight gain of a test subject divided by its intake
of a particular food protein during the test period.
With this method no allowance is made for
maintenance: i.e. method assumes that all protein is
used for growth

8. PROTEIN
DIGESTIBILITY
•‘The process by which macromolecules in food
are broken down into their component small
molecule subunits’.

9. • Protein digestion takes place in two different
phases:
In the stomach
In the small intestine
• Both of these phases of digestion are based
on several types of
enzymes that are called proteinases and
proteases
Cont…

10. • Protein Conformation
• Anti nutritional Factors
• Binding
• Processing
SEVERAL
FACTORS
AFFECTING THE
DIGESTIBILITY OF
PROTEINS

11. NPU takes into account the digestibility factor.
Net protein utilization can be calculated as
Nitrogen Retained
NPU = X 100
Nitrogen Ingested
NET PROTEIN
UTILIZATION
(NPU)

12. • Total Assimilable Nitrogen (TAN) or Yeast
Assimilable Nitrogen (YAN) is an essential
nutrient for yeast growth and metabolism during
fermentation.
•YAN is composed of ammonium ions and Free
Amino Nitrogen (FAN).
• Yeast metabolism is also influenced by the
interaction between yeast strain and the
chemical composition of YAN.
Total
Assimilable
Nitrogen
(TAN)

13. • The biological value of protein is defind as the
percentage of absorbed nitrogen retained by the
body.
Nitrogen Retained
BV = X 100
Nitrogen Absorbed
Biological
Value