Molecular and sensory approaches to the characterization of soybean-enriched rice-based snacks

Rice in West Africa serves as a convenience food for urban consumers, and has recently become an attractive ingredient for the production of snacks as a result of its bland taste and digestibility. However, the development of nutritious snacks of high protein and energy value requires the combination of rice with other protein sources. Soybean is an excellent source of proteins and its blending with rice should provide a good and well-balanced protein intake. Soybean-enriched rice-based snacks were produced by extruding a mixture containing flours obtained from milled or parboiled African rice varieties and 10-40% of defatted soybean flour. Consumer preference tests identified five snacks (out of 20) as the most preferred ones. These samples were prepared with Togo Marshall rice and 10-25% soybean flour. The properties of the selected snacks were addressed by instrumental sensory analysis and by molecular approaches. Electronic tongue measurements allowed a clear separation of the samples according to saltiness, astringency, sourness, bitterness, and umami taste. Samples containing 25% of soybean present a better taste defined by umami taste and saltiness regardless of previous parboiling of rice. The electronic nose clearly indicates that all samples have a peculiar aromatic profile that may be ascribed to both their different soybean content and the different treatment of rice. Structural characterization of proteins - performed by differential solubility and protease susceptibility indices, and by measuring thiols reactivity - clearly indicates that soybean has a main role in defining the overall properties of the protein network, that in turn appear to be related to the different sensory properties. This work was supported in part by grants from the Global Rice Science Partnership (GRiSP) "New Products" Project.