Evaluation of protein quantity and protein nutritional quality of protein bars with different protein sources.

A comprehensive overview of commercially available protein bars, focusing on their protein content, protein source(s) and nutritional composition. Four protein bars were selected based on the quality of their protein sources; (i) plant only (pea and rice); (ii) animal only (milk proteins); (iii) mix of animal (milk and egg) and plant (soy); (iv) mix of animal (milk and collagen) and plant (soy) to assess the relationship between protein sources and protein nutritional quality. Data analysis was conducted on data from an online consumer-generated database (OpenFoodFacts.org). Indeces of protein nutritional quality, DIAAS and PDCAAS, were determined after in vitro digestion simulation using the Infogest method. Of the 1641 bars, 81% had sufficient protein to be classified as "high in protein" (protein content > 20E%). However, the results show that lower protein digestibility values (between 47 and 81%) were measured when the proteins were included as a component of the protein bar matrix than when the digestibility of the same proteins was evaluated in a pure format. All measured in vitro-DIAAS and PDCAAS values were relatively low with the highest DIAAS = 61(Trp) and PDCAAS = 62(Trp) obtained for a protein bar containing only milk proteins (WPC, MPC). Although most protein bars are labelled 'high in protein', their protein nutritional quality could be very low based on DIAAS. The low numbers are most probably due to application of lower-nutritional-quality proteins (such as collagen) and of other ingredients such as carbohydrates, fats and fibres, that might deteriorate the bioaccessibility of essential amino acids.