Effect of ball milling energy on rheological and thermal properties of amaranth flour

Abstract

Pearled amaranth grains obtained by abrasivemilling were processed by planetary ball milling to produceamaranth flours. The influence of milling energy on rheologicaland thermal behavior of amaranth flour dispersionsand stability during 24 h storage at 4 °C were investigatedbased on a factorial design. The rheological behavior offlour dispersions (4 % and 8 % w/v) was determined usinga rotational viscometer, while gelatinization degree was determinedby differential scanning calorimetry as a measureof structural changes.The power law model was found tobe suitable in expressing the relationship between shearstress and shear rate. Flour dispersions showed apseudoplastic behavior. However this character decreasedwith the storage being dependent on flour concentrationand milling energy. A decrease of the consistency indexand an increase of the flow behavior index were observedas a result of the increasing milling energy. Gelatinizationenthalpy decrease showed the loss of crystalline structuredue to ball milling. Amaranth flour dispersions presentedincreasing stability during storage. It was observed, that thestability changed with the concentration of amaranthflours.Thus, more stable dispersions were obtained as theflour concentration increased. The highly milled samplewas the most stable sample during the storage