Thixotropic properties of normal potato starch depending on the degree of the granules pasting

Abstract

The aim of this paper was the study of the rheological instability (thixotropy and/or antithixotropy) of normal potato starch (NPS) pastes depending on their concentration (2-5%) and degree of pasting. Flow curves with hysteresis loops, apparent viscosity at constant shear rate and in-shear structural recovery tests were carried out. Granule size profiles, the pasting characteristic of corresponding starch suspensions and the transmittance of the pastes, the molecular weights and polydispersity of granular starch and its pastes prepared at 80, 95 and 121°C were also studied. The degree of pasting was dependent on the temperature and the concentration and influenced strongly the rheological behavior of the pastes. All pastes belonged to the non-Newtonian liquids thinned by shear and were rheologically unstable to the various extent. Thixotropic properties were connected to the size and the number of the starch granules in the pastes as well as depended on the measuring method used. In the 2 and 3% samples pasted at 80°C the swelling of the granules prevailed their destruction (thixotropy was observed). In the other samples the destruction predominated the swelling (antithixotropy observed).

Physico-chemical and rheological properties of gelatinized/freeze-dried cereal starches

“…Thixotropic behaviour of native cereal starch gels confirmed inhomogenity of these mixtures: they contained not only pasted granules but also swollen and partially pasted granules. As it was confirmed by Krystyjan et al (2016) and Sikora et al (2015), the pasting temperature of starch significantly influenced the rheological parameters of the resulted gels which may have thixotropic, antithixotropic or mixed thixotropic/ T a b l e 3. antithixotropic characteristics. The authors confirmed that at 95°C incomplete starch pasting took place.…”

“…The areas of thixo-and antithixotropy hysteresis loops were calculated according to Sikora et al (2015) by the summing-up of the areas of particular trapeziums formed between the curve 'up' and 'down'.…”

Binary mixtures of two anionic polysaccharides simulating the rheological properties of oxidised starch

“…The areas of the hysteresis loop were calculated by summation of the areas of trapeziums situated between ascending and descending curves. The power of thixotropy in the volume of the sample was calculated as a function of the shear rate (Sikora et al, 2015). Rheological properties were analysed by fitting the Ostwald -de Waele rheological model (1) to the flow curves taken at shear rate increasing from 0 to 300 s -1 :…”

“…In-shear structural recovery test with pre-shearing was carried out according to the procedures of Mezger (2002), Achayuthakan and Suphantharika (2008), Wang et al (2009;2010), modified by Sikora et al (2015), as follows: 1) preshearing -a constant shear rate of 100 s -1 for 30 s, 2) relaxation -a zero shear rate for 300 s, 3) a constant shear rate of 1 s -1 for 120 s, 4) a constant shear rate of 300 s -1 for 60 s, 5) a constant shear rate of 1 s -1 for 240 s. The results enabled calculations of the degree of structure recovery (DSR) of the pastes according to Wang et al (2009;2010) -the ratio of the average apparent viscosity in the fifth (obtained in the first 120 s) and the third step were considered.…”

“…Rheological and textural properties of pastes and gels of a given starch are determined by the pasting regime, eg concentration, time and temperature, all influencing the degree of pasting and accompanying degradation of amylose and amylopectin chains (Appelqvist and Debet, 1997;Sikora et al, 2015;Schilling, 1998a, 1998b). Also, the rheological properties of starch systems are dependent on the pH and temperature changes as well as on mechanical forces (Arocas et al, 2009;Kaur et al, 2012;Rutkowski et al, 2003).…”