Evaluation of in vitro methodology to determine protein digestibility and quality of plant-based proteins

Protein quality evaluations currently require that an animal bioassay be performed to determine true protein digestibility (TPD). This measure is used to calculate the protein digestibility corrected amino acid score (PDCAAS) prior to qualifying for a protein content claim. Several in vitro assays evaluating protein digestibility that currently reside in literature have not been used to assess protein quality, hence this thesis was undertaken to evaluate the pH-drop (PHD) and two-step digestion (TSD) method to determine PDCAAS in vitro on 65 plant-based proteins composed of different species, variety and heat treatment. Strong significant correlations were indicated by both in vitro protein quality calculations for the PHD (R = 0.91; P ≥ 0.0001) and the TSD (R = 0.92; P ≥ 0.0001) with the PDCAAS. This relationship suggests that either method to evaluate protein digestibility may be reliable to calculate PDCAAS in vitro, thus reducing the time, expense and ethical quandaries that currently apply to evaluating protein quality content claims.