Berg, Eric P., and Hans H. Stein. 2021. A Salute to PVT TIM HiLL: Indispensable Amino Acids and Global Human Health. Meat and Muscle Biology 2021.5(3): 4, 1–10. doi:10.22175/mmb.12925. Link to full text.

In the U.S. and most other developed countries, animal-based proteins provide a significant portion of the human diet. However, predictions for animal protein consumption indicates that consumption in Europe and North America will begin to decline by 2035 because plant-based proteins have become accepted as having an appearance, texture, and taste that is close to that of animal products. Examples of plant based proteins that are already on the market are plant-based burgers such as the Impossible Burger and the Beyond Burger, which are produced primarily from soy and pea protein, respectively. The digestible indispensable amino acid score (DIAAS) is recommended by FAO as the best method to determine protein quality in human foods. This method allows for calculation of the protein value of both individual ingredients and combined meals consisting of several proteins. Previous research in our laboratory demonstrated that values for DIAAS obtained in milk and breakfast cereals are additive in mixed meals, and the principle of additivity is believed to be applicable to all types of combined meals, but additional research to demonstrate this is needed. Therefore, the objectives of this experiment were to determine DIAAS values for animal and plant-based burgers and test the hypothesis that DIAAS calculated for a burger and a burger bun are additive in a combined meal.

Breakfast cereals are usually consumed with milk as a breakfast meal. To meet requirements for amino acids (AA), higher quality proteins are needed to complement the protein in cereals to provide a meal that is adequate in all indispensable AA. The digestible indispensable amino acid score (DIAAS) method used to determine protein quality allows for calculation of the protein value of individual ingredients and mixed meals consisting of several proteins. Values for DIAAS are based on values for apparent ileal digestibility (AID) of AA that are corrected for the basal endogenous loss of each individual AA, resulting in values defined as standardized ileal digestibility (SID). Values for SID of AA are additive in mixed meals because these values are independent of basal endogenous losses. Consequently, it is expected that DIAAS obtained for individual food ingredients are additive in a mixed meal, but data to demonstrate this have not been reported. Therefore, the objective of this experiment was to test the hypothesis that AA in milk complement AA in breakfast cereals to provide a balanced meal and that DIAAS in individual foods are additive in a combined meal.  

Bailey, Hannah M., John K. Mathai, Eric P. Berg, and Hans H. Stein. 2020. Pork Products Have Digestible Indispensable Amino Acid Scores (DIAAS) That Are Greater Than 100 When Determined in Pigs, but Processing Does Not Always Increase DIAAS. The Journal of Nutrition. Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions. doi: https://doi.org/10.1093/jn/nxz284.

Mathai, J. K., Y. Liu, and H. H. Stein. 2017. Values for digestible indispensable amino acid scores (DIAAS) for some dairy and plant proteins may better describe protein quality than values calculated using the concept for protein digestibility-corrected amino acid scores (PDCAAS). Brit. J. Nutr. 117:490-499. Link to full text (.pdf)

Stein, H. H. 2016. Evaluating protein quality of human foods using the pig as a model. J. Anim. Sci. 94(Suppl. 2):20 (Abstr.) Link to abstract (.pdf)