Table 1.

Factors influencing the digestibility of gluten.

	Factors	Digestibility of Gluten	Mechanism of Influence	References
Internal	The amino acid sequence of the proteins	The higher the proline content, the lower the digestibility	Gluten is rich in proline, making it difficult for enzymes to break down.	[73]
	Protein folding and cross-linking	Reduce digestion	Tight protein folding or protein aggregation limits enzyme cleavage sites and affects gluten digestibility.	[74]
External	Protease inhibitors	Reduce digestion	Protease inhibitors decrease protein digestibility by inactivating digestive proteases.	[75]
	Starch	Improve digestion	Starch protects gluten from aggregation in water, disrupts the spatial structure of gluten, exposes more cleavage sites, and facilitates gluten digestion.	[76]
	Tannin	Reduce digestion	Tannins reduce gluten digestibility by denaturizing proteases, inhibiting intestinal amino acid transporters, and complex glutens.	[77]
	Dietary fiber	Reduce digestion	Dietary fiber surrounds gluten, creates a steric hindrance between gluten and proteases, and compresses gluten conformation, inhibiting proteolysis by proteases.	[78]
	Low pH	Improve digestion	Acidic deamidation of gluten occurs at low pH and is accompanied by partial hydrolysis of peptide bonds.	[79]
Processing	Grind	Improve digestion	Cellular structures are split in grinding and the gluten matrix is exposed to the environment and hydrolases.	[68]
	Shear	Unchanged	-	[80]
	Heat	Reduce digestion	Heating changes the degree of network interconnection within the thiol-rich gliadin and thus the structure of gluten in bread.	[81]
	Extrusion	Improve digestion	Extrusion treatment increases the structural flexibility of wheat proteins and exposes more restriction sites.	[82]
	Fermentation	Improve digestion	Gas production and capture during fermentation maximize the separation of parallel protein chains and limit gluten cross-linking during baking.	[83]
	Cold atmospheric plasma	Improve digestion	Generating numerous high-energy excited atoms, photons, electrons, and reactive oxygen and nitrogen species modifies gluten to depolymerize gluten proteins, reducing the amount of large-sized protein polymers and decreasing immunoreactivity.	[84]