Contribution of the starch, protein and lipid fractions in the physical, termal and structural properties of Amaranth (Amaranth caudatus) flour films

TAPIA BLACIDO, D., MAURI, A.N., MENEGALLI, F., SOBRAL, P.J.A., AÑÓN, M.C.,

JOURNAL OF FOOD SCIENCE

Año: 2007 vol. 75 p. 293 - 300

0022-1147

ABSTRACT: Amaranth protein–lipid (PL) and protein (P) films were elaborated and compared with amaranth flour films in order to determine the contribution of the interactions between the biopolymer (starch and protein) and the lipids to the film properties. The films were made by the casting method, using the same glycerol concentration (0.9 g glycerol/100 g solution). A separation of the lipid fraction in the PL films and a polymorphic transformation ofthe corresponding fatty acidswere observed by differential scanning calorimetry (DSC) and verified by an analysis of themicrostructurebyscanningelectronmicroscopy (SEM).Theflour filmsshowednoseparation of the lipid fraction, evidence that the lipids were strongly associated with the proteins and homogenously distributed throughout the starch network, contributing to the good mechanical properties when compared to the PL films and to the excellentbarrier properties when compared to both the PL and P films. The protein-protein interactions also contributed to the mechanical properties of the flour films. The presence of proteins and lipids in the flour films had an important effecton film solubility, and alsoonthe color and opacity of the films. This study showed that the flour film properties depended on the interactions formed by their polymers (starches and proteins) and by the lipid, on the distribution of these interactions within the film matrix and on the concentrations of each component in the film.Keywords: amaranth flour, edible films, mechanical properties, microstructure, protein