Plant proteins are gaining prominence in the transition toward more sustainable, plant-based diets due to their environmental and health advantages compared to animal-derived proteins. However, their nutritional quality is often constrained by suboptimal essential amino acid profiles and limited protein digestibility, influenced by the complexity of the food matrix (including the presence of antinutrients) and the effects of food processing. Processing plays a central role in modulating the nutritional quality of plant proteins, as certain methods, such as soaking, germination, cooking, and extrusion, can reduce antinutrients and improve protein digestibility. However, these processes may also induce undesirable changes, including protein denaturation, chemical modifications, and losses of essential amino acids. This highlights a key paradox: while processing can enhance functionality and sustainability, it may simultaneously compromise aspects of nutritional quality. This presentation will examine how in vitro digestion models can be used to investigate plant protein digestibility and amino acid availability, with a focus on their ability to capture the effects of processing and food matrix interactions. Emphasis will be placed on how these models contribute to mechanistic understanding and how well they reflect in vivo outcomes.