30C-26 |
Hydration functional properties of amaranth protein isolates |
L. E. ABUGOCH, Facultad de Ciencias Quimicas y Farmaceuticas, Universidad de Chile, Vicuña Mackenna 20, Santiago de Chile, Chile, E. N. Martinez, Centro de Investigación y Desarrollo en Criotecnología de Alimentos, Universidad Nacional de La Plata - CONICET, 47 y 116, La Plata, 1900, Argentina, and M. C. Añón, Centro de Investigación y Desarrollo en Critecnología de Alimentos, Universidad Nacional de La Plata - CONICET, 47 y 116, La Plata, 1900, Argentina. Protein isolates must have high nutritional value and appropriate functional properties to be used as food ingredients. Amaranth proteins are of high quality but their functionality is still under study. Two amaranth isolates (A9 and A11) with different protein composition were prepared. They might present diverse structural and functional properties. The aim of this work was to determine the water holding capacity (WHC) and water imbibition capacity (WIC) of the isolates: and relate these properties with the stability of the proteins. We also explored the influence of thermal and pH treatments upon the functional properties. We submitted the isolates to 60, 80 and 90 °C, or to pH 3, 5, 7, 9 and 10. The WHC and WIC of the original and heated isolates and of the protein insoluble at every pH were determined. Protein folding state was analyzed by differential scanning calorimetry (DSC). A9 and A11 showed a high WHC (1.2 and 2.0 ml water/g isolate, respectively), similar to a native soybean isolate, and the thermal treatment increased this capacity. The insoluble isolates also presented a better WHC than the nontreated isolates. The highest WHC was achieved by the A11 heated at 90 °C (4 ml water/g isolate). The WIC of A9 and A11 - 1.8 and 2.6 ml water/g isolate respectively - were low compared with a native soybean isolate and their heating slightly improved this functionality. The WIC of the pH insoluble isolates were similar to those of the non-treated isolates. DSC results showed that better WHC was attained with the less folded proteins whereas there was not a direct relationship between the WIC and the folding state of the proteins. A11 isolate presented better functionality for both properties than A9 isolate and the treatments improved the properties of both isolates. These isolates may present different aplications in the food industry.
Session 30C, Food Chemistry: Proteins
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