Nutritional value in sustainability assessment of protein-rich ingredients and foods: A ‘farm-to-faeces’ approach

The environmental impact of ingredients and foods is often assessed from production of the raw materials up to consumption (‘farm-to-fork’ system boundaries). Comparing animal-to plant-based protein ingredients and foods points to plant proteins as being more sustainable than animal-sourced ingredients. However, the nutritive quality of plant proteins is often less than that of animal proteins, while processing also affects the nutritional value of proteins. Incorporating the protein digestibility as a functional unit into the life cycle assessment, a ‘farm-to-faeces’ approach, provides a more actionable measurement to compare a set of ingredients, processes or final products. Conventionally and mildly fractionated pea protein ingredients were compared to a whey protein isolate acting as a reference of animal-sourced proteins. Processing influences both the digestibility and the overall environmental impact of the food. In some cases, processing might improve protein digestibility while different processes or conditions could reduce it. The digestibility of conventional ingredients such as a protein isolate (pea and whey) is reduced more strongly by processing than the mildly fractionated ingredients. Mild fractions always provide a more environmentally sustainable alternative to whey and pea protein isolates, in relation to both ingredient production and protein digestibility, demonstrating the usefulness of mild processing. In general, this study clearly demonstrates that processing and digestion should be included in a life cycle assessment study, to obtain a correct view of the impact of fulfilling our nutritional needs.