Formulation of a low-phenylalanine flatbread from isolated millet starch and hydrocolloids for phenylketonuria

Phenylketonuria (PKU) is an inherited metabolic disorder characterised by impaired catabolism of the amino acid phenylalanine (Phe), necessitating lifelong adherence to a Phe-restricted diet. Access to palatable, low-Phe staple foods remains limited in many low-resource settings, including sub-Saharan Africa, where millet serves as a primary cereal grain. The present research aimed to formulate a low-Phe flatbread by exploiting the near-complete removal of protein that occurs during alkaline wet-milling of finger millet (Eleusine coracana) grain into isolated starch, combined with the textural reinforcement provided by food-grade hydrocolloids. Finger millet starch was isolated through soaking in dilute sodium hydroxide, wet milling, repeated centrifugal washing and oven drying at 40 degrees Celsius, yielding a powder with residual protein below 0.4 g per 100 g and Phe below 30 mg per 100 g. Five flatbread formulations were prepared by blending the isolated starch with xanthan gum (0.5, 1.0 or 1.5 per cent w/w), guar gum (1.0 per cent) or hydroxypropylmethylcellulose (HPMC, 1.0 per cent), together with salt and water, followed by sheeting and griddle baking at 200 degrees Celsius. Proximate composition, Phe content, instrumental texture (hardness, extensibility, cohesiveness) and consumer acceptability were evaluated. All millet-starch flatbreads contained fewer than 32 mg Phe per 100 g, representing a 94 per cent reduction relative to a conventional wheat control (483 mg per 100 g). Xanthan gum at 1.0 per cent produced the highest extensibility (26.3 mm) and overall acceptability score (7.4 on a nine-point hedonic scale), while HPMC yielded the lowest Phe value (26.8 mg per 100 g). These findings indicate that isolated finger millet starch, when combined with an appropriate hydrocolloid, can yield a flatbread that meets the stringent Phe limits for PKU dietary management and is well accepted by consumers.