In vitro protein digestibility of plant-based foods and ingredients vs standardized values in growing pigs

In vitro methods for protein quality assessment have great potential, but to represent a real alternative, they need validation against in vivo data. In particular, there is a lack of data on plant protein sources, which are increasingly demanded as environmentally and ethically alternative to animal-based proteins. This study evaluated the digestibility and digestible indispensable amino acid score (DIAAS) of 17 plant-based substrates using an in vitro method based on an internationally harmonized protocol, and the results were compared with standardized ileal digestibility determined in pigs on the same substrates. Except for corn flakes, the in vitro protocol predicted the crude protein and amino acid digestibility, with absolute percent errors below 20 %. The effect of heat treatment on the rapeseed protein digestibility was also evidenced by the peptide profile of ileal contents, pointing to napin as the main contributor to the protein resistance. The presence of trypsin inhibitors in the sample could limit the use of in vitro methods; however, methodological adjustments such as the optimization of the substrate load can overcome this issue. These findings provide evidence of the applicability of in vitro digestion protocols for evaluating protein nutritional quality, advancing efforts to reduce the use of animals in nutrition science.