The nutritional quality of pulse protein for human diet

International audience

English. Pulses are crops harvested for dry grain that include grains such as dry beans, lentils, chickpeas or peas, often classified as protein-rich food products. Pulses are traditionally used in human diets and can significantly contribute to different nutritional requirements, and particularly to the supply of protein. Dietary proteins provide nitrogen and amino acids that according to the metabolic needs and physiological state and activities are used as precursors of body protein synthesis for maintenance and growth of body tissues or are converted into various biochemical intermediates involved in different cellular and physiological activities and functions. Protein needs derived from nitrogen balance and by a factorial approach indicate a requirement of 0.66 g protein per kg body weight by day for adult, and of 0.82 g/kg body weight /day in 1 to 3 years infants, respectively. Pulses contain in average 20-25 g of protein per 100 g dry matter, providing for 100 g cooked pulse 8.6¬ g of protein that account for about 15-20 % of these daily protein needs. Not only the amount but also the quality of protein is considered based on the capacity to fulfil indispensable amino acid needs evaluated by the scoring approach that compare the amino acid profile of pulse proteins corrected for digestibility to a reference amino acid profile. Pulse proteins are relatively high in lysine and threonine and moderately low in sulphur amino acid (methionine, cysteine) and tryptophan. Pulse protein and amino acid digestibility is an important issue that has been assessed by different approach leading to values of digestibility in the range 75-90%, depending on the form of the ingested products (purified protein, complex flour or whole grain). These characteristics lead to a protein quality score of pulse protein of about 80-90%, below most animal protein but above other plant proteins such as cereals, and their nutritional quality can be improved by methionine fortification, or by a combination in the diet with other protein sources to compensate for the sulphur amino acid (methionine, cysteine) moderate deficiency. Other results also indicate a benefit of plant protein in substitution for animal protein for the prevention of different metabolic diseases. These crop proteins could represent a promising source of protein in the strategy aiming at the increase of plant-derived food products in human diets.