Protein quality is the digestibility and quantity of essential amino acids for providing the proteins in correct ratios for human consumption. There are various methods that rank the quality of different types of protein, some of which are now considered outdated, others are no longer in use. The Protein Digestibility Corrected Amino Acid Score (PDCAAS), which was recommended by the Food and Agriculture Organization of the United Nations (FAO), became the industry standard in 1993. FAO has recently recommended the newer Digestible Indispensable Amino Acid Score (DIAAS) to supersede PDCAAS. The dairy industry is in favor of this, because while PDCAAS truncates all protein types that exceed the essential amino acid (EAA) requirements to 1.0, DIAAS allows a higher than 1.0 ranking, and as such, while for example both soy protein isolate and whey isolate are ranked 1.0 according to PDCAAS, in the DIAAS system, whey has a higher score than soy.
Video Protein quality
PDCAAS versus DIAAS
The main limitations of PDCAAS is that it doesn't take into account anti-nutrient factors like phytic acid and trypsin inhibitors, which limit the absorption of protein among other nutrients. For this reason, DIAAS is promoted as the superior method and preferable over the PDCAAS. Other older methods like BV, PER, NPU and nitrogen balance may not reveal much about the amino acid profile and digestibility of the protein source in question, but can still be considered useful in that they determine other aspects of protein quality not taken into account by PDCAAS and DIAAS.
Maps Protein quality
Protein ranking
Below follows a table that compares various proteins based on their rankings. Some of these results may differ and vary significantly depending on if it is soybeans or soy protein isolate, and so on. For example, while soybeans have a PDCAAS score of 0.91, many soy protein isolates (though not all) typically get a PDCAAS score of 1.0. Likewise, the amino acid profile may differ from crop to crop depending on the soil, and between different breeds of soy. Generally speaking, however, soybeans rarely outperform whey protein isolate in PDCAAS rankings.
Amino acid profile
The table below compares the amino acid profiles of various proteins and a suggested target for how much of each amino acid would be desirable per 100g. If a protein falls short in one of the amino acids, more of that protein would be required. For example, soy has only 87% of the suggested target for methionine, so 114g of soy protein would have to be eaten to meet the suggested target. It should also be noted that essential amino acids are stored in the liver which can release the necessary amino acid into the blood if protein is needed and a meal was deficient in a certain amino acid. The risk of a deficiency is for a subject consuming only one type of protein over a long period (e.g. nothing but soy beans, no nuts, no grains, no vegetables, etc.). PDCAAS scores do not take into account the quantity of the non-essential amino acids.
*Semi-essential, under certain conditions
**Branched-chain amino acid (BCAA)
References
Source of the article : Wikipedia
0 Comments