In vitro protein digestibility of gluten-free climate-smart cowpea-based pasta

Nutritional optimisation of staple food such as pasta with flours from climate-smart crops (i.e. resilient to climatic hazards and requiring minimal inputs) is in line with actual environmental and nutritional challenges. Although the quantity of protein is important, the quality through protein digestibility is essential. The aim of this work was to assess the protein digestibility of four gluten-free climate-smart pasta all based on cowpea flour with or without the addition of teff and/or amaranth leaf flour(s) using two static in vitro methods: static Infogest digestion protocol and Megazyme® enzymatic kit. The effect of both gluten absence and the high fiber content on the in vitro protein digestibility was investigated through the use of three durum wheat semolina pasta controls with increasing fiber content. Statistical analysis were made through ANOVA with p < 0.05. Despite structural differences, induced by protein origin and the disruption of the protein network by fibers, there was no significant difference in in vitro protein digestibility between cowpea-based and traditional durum wheat semolina pasta. Protein quality was then approached with the measurement of the in vitro Protein Digestibility Corrected Amino Acid Score (i-PDCAAS) for the two methodologies. Thanks to their balanced essential amino acid profile, cowpea-based pasta demonstrated i-PDCAAS that was twice as high as that of wheat-based pasta, as determined by both by the Infogest (68-86 versus 35-44) and enzymatic kit (99-104 versus 49-56) methods. In addition, for the first time both methodologies were compared and Infogest protocol appeared more suitable for more detailed studies.