CONICET | Buscador de Institutos y Recursos Humanos

Amaranth is a pseudo cereal of rapid growth, with high tolerance to arid conditions and poor soils where traditional cereals cannot be grown. Besides the social and economical benefits of employing non-productive soils, amaranth seeds contain a significant proportion of starch, high quality proteins and essential lipids, which make the different fractions promising materials for several and innovative food applications. In order to widen the use of this valuable resourse, several characterizations should be performed, which require the use of non-destructive, rapid and reliable methods. The FT-IR spectra of amaranth flour, starch or lipid-protein enriched fractions and purified starch, obtained by different milling processes, were studied. The changes of starch, protein and lipids relative content as so as their conformational or structural modifications were analyzed. The objectives of this study were: a) to identify FT-IR peaks of main grain components; b) to analyze 6 month-aging effect and starch crystallinity loss, associated to milling severity, based on intensity ratio of characteristics FT-IR bands. Several fractions were obtained from amaranth seeds using a laboratory mill for rice pearling. Amaranth starch was isolated by wet-milling procedure and flour samples were obtained from a cutting mill (control) and a planetary ball mill (ball milling). The FT-IR spectra were recorded within the range of 4000-600 cm-1 employing an ATR accessory. Characteristics FT-IR bands were identified for the main components at the following wave numbers: a) starch: 996, 1014 and 1039 cm-1, associated to C-O-C glycosidic starch bond ; b) lipids: 2923, 2853 and 1740, and 1240 cm-1, corresponding to the C-H and OH vibrations, respectively; c) proteins: 1640 and 1540 cm-1, related to amide I and II vibrations. Aged flour has shown a 34.4% decrease in the height ratio of the 2923 and 996 cm-1 bands (2923/996), attributed to its higher rancidity in comparison with control. A significant increase from 0.76 to 1.07 in ratio of the height ratio 1640/996 and from 0.46 to 0.69 in the height ratio 1540/996 was observed for lipid-protein enriched fraction according to its higher protein proportion in relation to the control samples. In the same way, the increase from 0.27 to 0.48 of the 2923/996 height ratio has reflected the major proportion of lipid in such enriched fraction. The analysis also showed that ball milling significantly decreased the ratio of 1039/1014 cm-1 and 996/1014 cm-1 corresponding to the crystalline/amorphous part of starch structure. FT-IR analysis was a useful tool to determine the relative proportion of grain components within amaranth milling fractions as well as to investigate starch modifications provoked by ball milling.

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