Peak viscosity

In general, derivatization increases solution and gel clarity, reduces the tendency to gel, improves water binding, increases freeze—thaw stabiHty, reduces the gelatinization temperature, increases peak viscosity, and reduces the tendency to retrograde. Combinations of substitutions are used to obtain desiredproperti.es for specific appHcations. 

Process and product Peak viscosity B.U. Cold paste viscosity B.U. Degree of gelation % Gel colour... 

Potato starch shows the highest peak viscosity and the lowest pasting temperature with moderate final viscosity and lower setback (Liu et al., 2003), compared to other commercial starches. This indicates that potato starch gelatinizes rather easily compared to other starches, producing more viscous pastes that easily break. 

The semi-continuous latexes with relatively high MAA content were found to exhibit 5 orders of magnitude increase in viscosity at pH 8-9. Furthermore, visual observation of these latexes showed that the milky white color disappeared and the dispersion became slightly hazy at the pH of the peak viscosity. For the semi-continuous latexes with low MAA contents of 5 and 10%, no significant viscosity change with pH was observed. On the other hand, batch latexes, even with the highest MAA content, main-... 

Normal wheat starch has a higher pasting temperature (90.6°C) and produces a lower peak viscosity (96 RVU) than does normal maize starch (81.5°C and 159 RVU, respectively). In comparison, waxy wheat starch has a lower pasting temperature (62.5°C), but produces a higher peak viscosity (230 RVU) than does waxy maize starch (69.8°C and 200 RVU, respectively). The extraordinarily large differences between normal and waxy wheat starches (28.1°C and 134 RVU) are attributed to an amylose-phospholipid complex present in normal wheat starch.134... 

The concentration of lactic acid in the steep has been shown to affect both the yield of starch178 and the quality of the resulting starch.179 Starch yields increased with increasing lactic acid concentration up to —0.5%, and decreased when more than —2% lactic acid was used. Shandera and lackson179 tested starch quality when steeped at 57°C with either 0.2% or 1.5% lactic acid and 0.05% or 0.3% sulfur dioxide. The level of sulfur dioxide had a small effect on starch quality, but the level of lactic acid had a pronounced reduction effect on peak viscosity, shear thinning viscosity, set-back viscosity, pasting viscosity and starch water solubility. 

Oxidation of wheat starch using a concentration range of 0.4-2.4% available chlorine in sodium hypochlorite solution at pH 8 causes the amylograph peak viscosity to decrease at first, then to increase with increasing chlorine concentration used for oxidation. In addition, the temperature at peak viscosity and the final viscosity at 95°C decrease as the chlorine concentration is increased. 

The viscosity of a starch paste is mainly a function of the size of swollen granules. Waxy maize starch has smaller granules, so its swelling power is less than that of amylopectin potato starch. The peak viscosity of amylopectin potato starch, in comparison to potato starch and waxy maize starch, is shown in Figure 11.7. The gelatinization properties of amylopectin starch resemble those of potato starch. With reduced amylose content, the peak viscosity occurs as a lower temperature as swollen granules are weak and can be ruptured more easily with shear. 

Waxy com starch contains only amylopec-tin com starch contains both amylopectin and amylose. This results in a different viscosity profile (Figure 8-37). Com starch shows a lower peak viscosity and less breakdown during heating. After cooling, the viscosity continues to increase, probably because the amylose interlinks with the amylopectin. On further storage at 25°C, the slurry sets to a firm gel. Tapioca starch is intermediate between com and waxy com starch (Figure 8-37). This is explained by the... 

Starches can be substituted by nonionic or ionic groups. The latter can be made anionic by introduction of phosphate or succinate groups. These have lower gelatinization temperature, higher peak viscosity, and higher final cold viscosity than nonionic starches (Figure 8-38). 

Although all emulsions in this study were thick and peaked, viscosities decreased as the treatment temperature was increased... 

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