Comparing nutritional and digestibility aspects of sustainable proteins using the infogest digestion protocol

Introduction: In vitro digestion models are valuable tools to study food digestion and are good candidates to complement or replace animal-based models when evaluating protein quality for human nutrition. Here we studied several sustainable alternative protein concentrates and a whey protein concentrate as reference, to determine their protein composition, digestibility and quality using the harmonized INFOGEST static digestion protocol.
Methods: The INFOGEST static digestion model for humans was performed in a pH-stat and expanded with a cross-flow filtration using a 5kDa cut off to separate the proteins, peptides and amino acids in the final digest sample in an absorbable filtrate fraction and a retentate fraction. The amino acid composition in digest, filtrate and retentate were fully analysed. The protein concentrates were analysed to determine their conversion factor, degree of hydrolysis, true ileal digestibility, in vitro digestible indispensable amino acid score (IVDIAAS) and total absorbable amino acids and total essential amino acids.
Results: Whey, blood plasma concentrate and yeast protein concentrate have a high mean true ileal indispensable amino acid in vitro digestibility (90.6-85.8%), closely followed by corn, pea, potato and proteins derived from lesser meal worms (ranging between 82.8-77.6 %). Whey, potato, blood plasma and yeast protein concentrates ranked highest in IVDIAAS (between 83.9-119), followed by lesser meal worm and pea (between 55.0-73.8) with corn protein concentrate having the lowest IVDIAAS due to underrepresentation of lysine. The results revealed that the two referent protein samples whey and pea show good correlation between the in vitro DIAAS values and in vivo DIAAS values from literature.
Discussion: Normally DIAAS are calculated on the remaining protein content in the ileum of animal based models. Our study describes an IVDIAAS that could be useful as replacement of animal studies. The method and data presented can form a start for further applying the INFOGEST in vitro digestion protocol to evaluate protein quality of sustainable and novel protein sources.