Promoting proso millet (Panicum miliaceum) for food use: Chemical characterisation and performance as ingredient in gluten-free pasta

Despite of favourable nutritional and agronomic properties, millet is currently underutilized in North America and Europe. Our aim was to demonstrate millet’s suitability as ingredient in gluten-free foods, with the ultimate goal that such an effort could promote millet cultivation by establishing a market for its products. In the project’s first phase, six proso millet (Panicum milliaceum) varieties grown as a double crop in two locations in the American Midwest were screened for chemical and nutritional parameters. In the second phase, four of the samples were selected as raw materials for glutenfree pasta, based on harvest yields, prolamin profile, and amylose content. The pasta was evaluated for nutritional aspects (starch and protein digestibility), quality markers (cooking loss, optimum cooking time, water absorption, firmness, yellowness and carotenoid content) and subjected to descriptive analysis by a trained sensory panel. To gain more insight into the role of prolamins on pasta attributes, we evaluated protein solubility and structural characteristics (accessible thiol groups and secondary structure) across processing stages, i.e. compared dough, raw pasta after sheeting, and cooked pasta. All analyses were also performed on two commercial controls, one wheat-based, one gluten-free. The millet samples were similar in protein, fat, fibre, starch, and ash content, and displayed similar protein and starch digestibility. However, varieties differed in amylose content, affecting pasting properties. Both amylose content and prolamin profile affected millet pasta properties, including cooking loss and instrumental firmness, as well as texture ratings by the sensory panel. Proso-millet based pasta displayed several superior characteristics to commercial glutenfree pasta, specifically, lower cooking loss, higher carotenoid levels, and less rapidly digestible starch. Results show that proso millet is a feasible ingredient for food product development, especially for the gluten-free market. The study also highlights characteristics that require improvements, and parameters that potentially distinguish millet from other grains.