Changes in protein structural characteristics upon processing of gluten-free millet pasta

Proso millet exhibits favorable agronomic and nutritional properties but is currently under-utilized in the northern hemisphere. This study compared processing-induced changes in protein characteristics of commercial pasta to fresh gluten-free pasta from proso millet varieties differing in prolamin profile. Protein solubility, accessible thiols and secondary structures were measured in dough, sheeted and cooked pasta. Relationships between protein conformation and characteristics related to pasta quality were determined. Cooking significantly lowered protein solubility and induced exposure of thiol groups as well as a shift in secondary structure distribution, while sheeting only had a minor effect. Random structures positively and significantly (P < 0.05) correlated with solubility, cooking loss and protein digestibility. In contrast, β-sheets, the main secondary structure in cooked pasta, negatively correlated with these properties. The utilization of proso millet in gluten-free pasta is promising, however, processing optimization to elicit targeted protein modifications to balance quality and nutritional attributes requires further investigation.