Properties of biomacromolecules in African-grown rice species

Oryza glaberrima, commonly known as African rice, is the native African domesticated rice and has interesting properties from the sustainability and nutritional standpoints. O. glaberrima is an entirely different species from the more common Asian rice (Oryza sativa). The lower crop yield and some transformability issues make O. glaberrima less popular among rice farmers than O. sativa. The aim of this study was to compare the properties of starch and proteins in O. glaberrima with those of O. sativa cultivars grown in Africa, in order to identify the molecular basis of their possible use in specific food products. These products may include pasta, pasta-like products, and a large variety of ready-to-eat rice-based foods. Starch properties and protein content in individual samples were characterized by standard chemical methods. The structural organization of starch was investigated by measuring susceptibility to selective enzymatic activities [1]. Viscoamilography was used to investigate the possible relationships between structural features and the pasting behavior of starch [2]. The potential glycemic impact was estimated by using an in vitro method and a predictive equation [3]. O. glaberrima showed different pasting properties and a different fragmentation pattern by amylolytic enzymes with respect to O. sativa, suggesting that O. glaberrima may be best suited for instant food. Information on the protein pattern in was gathered by electrophoresis, and the accessibility of specific residues and of specific regions involved in determining the properties of products was addressed by appropriate chemical and spectroscopic approaches [4]. The overall protein structural organization in O. glaberrima is quite different from the one in O. sativa. In O. glaberrima the proteins are organized in highly polymeric form, generating a compact structure mainly stabilized by disulphide bonds. Moreover, the estimated glycemic index in O. glaberrima resulted slightly lower than that estimated for O. sativa. The approaches presented here seem able to provide useful insights as for the intrinsic structural and nutritional characteristics of starch and proteins in this two African rice species. This work was supported by the “New Products“ Project from the Global Rice Science Partnership (GRiSP). References [1] Barbiroli A, Bonomi F, Casiraghi MC, Iametti S, Pagani MA, Marti A (2013). Process conditions affect starch structure and its interactions with proteins in rice pasta. Carbohyd. Polym. 92, 1865–1872. [2] Marti A, Seetharaman K, Pagani MA (2010). Rice-based pasta: a comparison between conventional pasta-making and extrusion- cooking. J. Cereal Sci., 52, 3, 404-409. [3] Englyst KN, Hudson GJ, Englyst HN (2000). Starch Analysis in Food. Encyclopedia of Analytical Chemistry. pp. 4246-4262. [4] Bonomi F, D’Egidio M G Iametti S, Marengo M, Marti A, Pagani MA, Ragg EM (2012). Structure–quality relationship in commercial pasta: A molecular glimpse. Food Chem. 135, 348–355.