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Viscoelastic properties of amaranth starch gels and pastes. Creep compliance modeling with Maxwell model
Author(s) -
Villarreal Myriam E.,
Iturriaga Laura B.
Publication year - 2016
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.201600065
Subject(s) - amaranth , creep , viscoelasticity , starch , materials science , crystallinity , rheology , amaranthus hypochondriacus , amylose , composite material , amaranthus cruentus , chemistry , food science
In this work, the morphological, thermal, and crystalline properties of starches isolated from two amaranth cultivars, Amaranthus cruentus (ACr) and Amaranthus caudatus (ACa); the viscoelastic properties of their pastes and gels, through oscillatory and creep‐recovery tests and the adjustment to the Maxwell mechanical model, were studied. Both starches presented type A crystalline patterns with high crystallinity degree (CD), 41.84% for ACr and 40.70% for ACa, associated to their low apparent amylose content (AAM) (1.06 g/100 g for ACr and 7.39 g/100 g for ACa). The ACr starch showed the highest values for temperature of gelatinization ( T g ) (74.50°C) and Δ H (16.15 W/g). Amaranth gelatinized starches exhibited rheological behavior that corresponds to concentrated macromolecular solutions for ACr while ACa starches showed a gel‐type behavior. The ACa gels behaved as a viscoelastic solid with smaller values of instantaneous compliance (0.006 Pa −1 < J 0 < 0.0002 Pa −1 ), retarded compliances (0.0005 Pa −1 < J 1 < 0.6 Pa −1 ; 0.0016 Pa −1 < J 2 < 0.00008 Pa −1 ) and higher values of newtonian viscosities (33.4 × 10 5 Pa · s ≤ η 0 ≤ 357.1 × 10 5 Pa · s) than ACr, which facilitated their later structural recovery (75.8% ≤ final recovery ≤ 85.1%). The gels exhibited a small contribution of viscous flow's compliance ( t / η 0 ) brought about by the dashpot of the Maxwell's simple element, while in the ACr pastes, this element acquired importance. The Maxwell model of six‐parameters adjusted satisfactorily ( R 2 ≥ 0.986; RSS ≤ 3 × 10 −4 ) the results of creep curves.