Production and characterization of enriched pasta based on African rice

The development of innovative enriched rice products is a promising way to exploit low-grade African rice varieties. In particular, this project aimed at addressing the properties of rice-based pasta, enriched with common ingredients in the African tradition, such as flours from soybean and orange-fleshed sweet potato. Four different formulations based on pregelatinized rice flour and liquid egg albumen, and containing soybean and/or sweet potato (up to 20%) were prepared and characterized via a multidisciplinary approach. Soybean and sweet potato enrichment leads to a decrease in the pasta consistency and in significant changes in the color of the resulting samples. In particular, soybean clearly affected pasta yellowness, whereas the addition of sweet potato resulted in a significant decrease in lightness and an increase of redness, most likely as a result of browning Maillard-type reactions. E-sensing approaches indicated that the sensory profile of the various pasta products strongly depends on the peculiar enrichment. Sweet potato increased the pasta astringency, whereas soybean enrichment resulted in a typical umami taste and a specific electronic nose response. As for the pasting properties, addressed by vicroviscoamylograph, the lower viscosity of enriched samples indicates that both soybean and sweet potato compete with rice for water needed for starch granule hydration and subsequent gelatinization. This also resulted in differences in the optimum cooking time of the various products. Structural characterization of proteins - performed by differential solubility indices, and by measuring thiols reactivity - clearly indicates the presence of protein aggregates stabilized by hydrophobic interactions and disulphide bonds in all pasta samples, and a higher network-forming ability in soybean-enriched pasta, that may explain the lower cooking losses of this specific sample. The application of a multidisciplinary approach to the characterization of differently enriched rice-based pasta allowed to identify quality parameters and differences among samples, that can be related to specific ingredient combinations. This information can offer some guidelines as for designing and producing pasta fit to the consumers’ expectations, that can also add value to local African raw materials.