Rheological and structural properties of starches from different Indian wheat cultivars and their relationships

ABSTRACT

The structural, pasting, and dynamic rheological properties of starches isolated from six Indian wheat (Triticum aestivum L.) cultivars were evaluated. The amylose content of starches ranged between 18.35–20.58%; subsequently, these were normal-type starches. The light transmittance of gelatinized starch pastes decreased with increase in storage periods at 4°C. Scanning electron micrographs revealed bimodal size distribution of starch granules, with smaller B- and larger A-type. X-ray diffraction (XRD) pattern revealed typical A-type crystalline starch, with the highest crystalline index (CI) for cv.C-306. Fourier transform infrared (FTIR) spectroscopy was performed to understand the chemical bonding and short-range molecular order of starches. The highest 1047/1022 absorbance ratio (0.8666) for cv.C-306 justified its more crystalline nature. Peak viscosity (PV), trough viscosity (TV), and final viscosity (FV) were the highest for cv.WH-147 starch (1602, 1542, and 2123 cP, respectively). Peak G’, peak G”, and breakdown in G’ during heating were in the range of 5052–9067, 563–1463, and 909–3567 Pa, respectively. The power law model agreed well with the steady shear properties of starch pastes. Non-Newtonian fluid behaviour of starch was observed with n value ranging between 0.22 and 0.32. PV, FV, TV, and setback viscosity (SV) were significantly correlated to each other. Peak G’ exhibited negative correlation with TG’ (temperature at peak G’), light transmittance after 96 and 120h storage periods, and positively correlated with breakdown in G’. A significant positive correlation was observed between peak G” and tanδ during heating. Complex viscosity (η*) was also found positively correlated to G’.

KEYWORDS:

• Wheat starch
• Pasting and rheology
• Granule morphology
• Light transmittance
• Crystallinity
• Correlations