1. New approaches to the assessment of protein quality: Whey proteins
Paul Moughan
Riddet Institute, Massey University, New Zealand

2. See display copy at Elsevier stand.

3. “Not all proteins are created equal nutritionally”
Milk
Meat
Egg
Soya
Bean

4. In particular vegetable-based proteins are of lower quality than dairy based proteins
fibre
anti-nutritional factors
different structures

5. An accurate description of Dietary Protein Quality is of fundamental importance:
Dietary Assessment
Nutritional Planning
Regulatory Environment
Trade

6. How then should Protein Quality
be determined?

7. In the past PDCAAS (protein digestibility corrected amino acid score) has been the recommended scoring method (FAO 1989)
There are a number of shortcomings of PDCAAS.
New Recommendations (FAO, 2013)

8. Emphasis on individual digestible amino acid contents rather than a single score (ie treat each amino acid as an individual unit). This maximises the information on the nutritional (protein) value of food.
Amino acid digestibility is determined at the end of the small intestine (True ileal digestibility).
For processed foods ‘reactive lysine’ is determined in diet and ileal digesta rather than ‘total lysine’ to give lysine availability measures. 1.

9. How should ileal amino acid/ “reactive lysine” digestibility be determined?

10. In humans: Digesta can be collected using ileostomates
Ref: Wrong OM, Edmonds CJ and Chadwick VS (1981) Comparative anatomy and physiology In:
The Large Intestine, p 5, MTP Press Ltd, England.
Terminal ileum
In humans:
Digesta can be collected using ileostomates
Digesta can be collected using a naso-ileal tube
Both methods have drawbacks and are not routine
Need for an animal model. 10

11. Growing pig (a meal-eating omnivore) is preferred model:
Need to collect ileal digesta

12. True ileal AA digestibility in the adult human and growing pig
True N digestibility in human (%)
True N digestibility in pig (%)
(Moughan, unpublished)

13. Conventional digestible lysine can be higher than available lysine
Digestible reactive1 (available) lysine versus digestible total lysine (gKg-1 DM)
Lysine
Digestible Total
Available
Difference %
Shredded Wheat
1.8
1.6 11
Dried corn
2.6
1.9 27
Unleavened bread2
6.5
4.9 25
Puffed Rice
1.1
0.6 45
Rolled Oats
3.7
2.8 24
Wheat Bran
0.7 36
Corn
0.4
0.2 50
1Based on -methylisourea assay; 2P Pellett, N Scrimshaw and P Moughan (unpublished data).

14. But not so in dairy:
Ileal digestible total and “available” lysine contents (g/kg air-dry) for 12 dairy protein sources
Lysine
Digestible
Availablea
Whole milk protein
26.2
24.0
Infant formula A
8.3
8.6
Infant formula B
9.1
9.2
Infant formula C
11.1
11.7
Whey protein concentrate
79.9
77.5
UHT milk
31.7
31.4
Evaporated milk
23.4
20.5
Sports formula
20.4
19.1
Elderly formula
11.8
Hydrolysed lactose milk powder
27.2
25.1
aBioavailable lysine; minimal difference between total lysine and reactive lysine denotes minimal Maillard damage.
Adapted from Rutherfurd & Moughan (2005), with permission of the publisher. 14

15. Amino acids in whey proteins are generally highly digestible
Whey Protein Concentrate (n = 4)
Whey Protein Isolate (n = 1)
Whey Protein Hydrolysate (n = 1)
Lysine 98
100 94
Methionine 99 80
Cysteine
Leucine 96
Isoleucine
Valine
Tryptophan -
Histidine 93 90
Threonine

16. When a single score of Protein Quality is needed DIAAS replaces PDCAAS.
With DIAAS (FAO, 2013):
Ileal AA digestibility replaces faecal CP digestibility
Reactive lysine replaces total lysine (conventional AA analysis)
Scores are not truncated (unless diet or sole-source food)
AA Reference Pattern (for regulatory purposes):
Infants: AA composition human milk
All others: AA requirement pattern for child (6 months – 3 years) 2.

17. Non truncation is significant DIAAS
Milk Protein Whey Protein Whey Protein Red meat
Concentrate Isolate Concentrate
Non-truncated
Truncated
DIAAS

18. DIAAS and PDCAAS values1 are different
DIAAS and PDCAAS values1 are different. PDCAAS often overestimates for lower quality proteins
Milk Protein Concentrate
Whey Protein Isolate
Soya Protein Isolate
Pea Protein
Cooked Beans
Cooked Rolled Oats
Wheat Bran
Roasted Peanuts
Rice Protein
Cooked Peas
PDCAAS
1.00
0.89
0.65
0.67
0.53
0.51
0.42
0.60
DIAAS
1.18
1.10
0.97
0.82
0.58
0.54
0.41
0.43
0.37
1(Rutherfurd and Moughan, unpublished data). 18

19. But single scores omit much useful information: (eg leucine supply for optimal muscle function versus body protein maintenance).
Threonine
Met + Cys
Valine
Isoleucine
Leucine
Tyr + Phe
Histidine
Tryptophan
Lysine
Whey Protein Isolate
1.80
2.29
1.21
2.22
2.57
1.71
1.09
3.35
2.51
Whey Protein Concentrate
2.53
1.29
2.35
1.93
1.43
0.97
2.74
2.03
Soya
Protein
Isolate B
1.13
0.91
1.02
1.38
1.65
1.18
1.69
0.99
Milk Protein Concentrate
1.56
1.55
1.81
1.77
2.39
1.60
1.94
Isolate A
1.30
0.90
1.11
1.59
1.85
1.37
1.67
1.16 19

20. Conclusions
Considering amino acids as individual nutrients gives maximum information.
DIAAS incorporates recent scientific advances, and is an improvement over PDCAAS.
Before DIAAS can be implemented we need more data on the true ileal amino acid digestibility of foods.
Establishment of such a world food data-set is greatly needed.
This is an important step in the fight against malnutrition.

21. “Protein/Energy malnutrition affects every fourth child world-wide”
WHO/NHD (2000)