Kinesiology 3339A/B Lecture Notes - Lecture 23: Protein Digestibility Corrected Amino Acid Score, Soy Protein, Histidine

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Lecture 23!
Kinesiology 3339: Exercise Nutrition !
Protein Part 3
Protein Quality Method
4. Protein Digestibility - Corrected AA Score*
-* Score based on AA profile, AA content, and digestibility of food
-Likely best for humans because based on human AA requirement
Suggested pattern of amino acid - table
-As you get older, adult values for protein requirement are lower because growth is reduced as
you get older
-Amino acid score is based on the needs of 2-5 year old, which is actually an overestimate
because adults do not need as much
How to calculate the PDCAAS of a food protein - table
-1. Analyze for proximate nitrogen (N) composition of the food
-Easy to measure nitrogen, and that nitrogen is found in the protein - simple relational
calculation
-2. Calculate protein content (N x 6.25 (100/16 because the average nitrogen composition is
16%) or specific AOAC conversion factor)
-Some proteins have slightly more or less than 16%, but it most cases it is 16%
-3. Analyze for essential amino acids (EAA) profile
-4. Determine the amino acid score (uncorrected):
-uncorrected amino acid score = mg of EAA in 1g of test protein!
mg of EAA in 1g reference protein
-Reference protein EEA profile = 1985 FAO/WHO 2-5 year old requirement pattern
-If ratio is greater than 1, protein is greater than reference
-If what is protein is less that reference, ratio less than 1
-5. Analyze for digestibility
-PDCAAS: lowest uncorrected amino acid score x protein digestibility (correct for
digestibility)
-6. Calculate the PDCAAS:
-PDCAAS: lowest uncorrected amino acid score after correcting for digestibility when
compared to all other amino acids
Calculation of PDCAAS of an Isolated Soy Protein
If you analyze a gram of soy, the amount of indispensable (essential) amino acids (EAA) are present on
the left column of the chart
-E.g., Per gram of soy, get 26 mg/g of histidine
Then look at what is needed by 2-5 year old child, only need 19 mg/g of histidine per gram of soy
-Uncorrected amino acid score: take 26 mg/g / 19 mg/g = 1.37 (a number greater than 1)
Then multiple the uncorrected amino acid score by the digestibility of soy protein (true digestibility
which is very high and close to 100% = it is 97%)
-PDCAAS = 1.37 x 97% (0.97) = 1.33
-This number is above 1, meaning soy protein is a good provider of histidine
As you go down the rest of the EAA list, calculate PDCAAS for all EAA
-Then look for the lowest value (methionine + cystine) of corrected amino acid score
-From the lowest EAA score, can determine the PDAAS score for the whole soy protein
-Since the lowest PDCAAS is 1.00 = good quality protein and is providing the amount of amino
acids that is needed
Calculation of PDCAAS of Beef
If you analyze a gram of beef, the amount of indispensable (essential) amino acids (EAA) are present
on the left column of the chart
-E.g., Per gram of beef, get 34 mg/g of histidine
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Document Summary

* score based on aa profile, aa content, and digestibility of food. Likely best for humans because based on human aa requirement: suggested pattern of amino acid - table. As you get older, adult values for protein requirement are lower because growth is reduced as you get older. Amino acid score is based on the needs of 2-5 year old, which is actually an overestimate because adults do not need as much: how to calculate the pdcaas of a food protein - table. Analyze for proximate nitrogen (n) composition of the food. Easy to measure nitrogen, and that nitrogen is found in the protein - simple relational calculation. Calculate protein content (n x 6. 25 (100/16 because the average nitrogen composition is. Some proteins have slightly more or less than 16%, but it most cases it is 16% Uncorrected amino acid score = mg of eaa in 1g of test protein mg of eaa in 1g reference protein.

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