Effect of puroindolines on protein characteristics in flour and dough

Puroindolines are wheat endosperm proteins that account for most differences in kernel texture among soft, hard, and durum wheat. Puroindolines expression results in soft kernel texture, whereas mutations in one or both genes controlling their expression results in a hard texture. This study aimed at investigating the effect of puroindolines on some features of wheat proteins in both flour and dough. Flours and related doughs were characterized for 1% SDS protein solubility, 1% SDS-accessible thiols content, surface hydrophobicity, and conformation, using durum wheat (Svevo cv, S), soft-textured durum wheat (Soft Svevo, SS), soft wheat (Alpowa cv, A) and hard-textured wheat (Alpowa with 5DS distal end deletion, AD). Puroindolines expression resulted in a significant (p<0.05) decrease in soluble proteins (S: 867; SS: 504 mg/g protein) and in SDS-accessible thiols (S: 12.4; SS: 8.2 micromol/g protein) in flours. On the other hand, 5DS distal end deletion resulted in a significant (p<0.05) increase in the amount of soluble protein (A: 537; AD: 816 mg/g protein) and of SDS-accessible thiols (A: 5.6; AD: 7.0 micromol/g protein) in flours. No significant (p<0.05) differences related to puroindolines expression were found in either protein solubility or thiol content in dough, if not for 5DS distal end deletion affecting the thiols content (A: 5.9; AD: 7.2 micromol/g protein). Puroindolines expression (S vs SS) resulted in a decrease in protein surface hydrophobicity, whereas the 5DS distal end deletion (AD vs A) did not change protein hydrophobicity. Both expression and deletion caused an increase in beta-turn structures (S: 40.1%; SS: 46.8%; A: 35.4%; AD: 40.3%). In conclusion, puroindolines seem to affect some gluten proteins overall characteristics, but specific effects seem to be species-dependent.