Potato starch temperatures

Com and rice starches have been oxidized and subsequently cyanoethylated (97). As molecular size decreases due to degradation during oxidation, the degree of cyanoethylation increases. The derivatized starch shows pseudoplastic flow in water dispersion at higher levels of cyanoethylation the flow is thixotropic. Com and rice starches have been oxidized and subsequently carboxymethylated (98). Such derivatives are superior in the production of textile sizes. Potato starch has been oxidized with neutral aqueous bromine and fully chemically (99) and physically (100) characterized. Amylose is more sensitive to bromine oxidation than amylopectin and oxidation causes a decrease in both gelatinization temperature range and gelatinization enthalpy. 

Compared to native starches, monophosphate esters have a decreased gelatinization temperature range and swell in cold water at a DS of 0.07. Starch phosphates have increased paste viscosity and clarity and decreased retrogradation. Their properties are in many ways similar to those of potato starch, which naturally contains phosphate groups. 

One of the commercial methods for production of lysine consists of a two-stage process using two species of bacteria. The carbon sources for production of amino acids are corn, potato starch, molasses, and whey. If starch is used, it must be hydrolysed to glucose to achieve higher yield. Escherichia coli is grown in a medium consisting of glycerol, corn-steep liquor and di-ammonium phosphate under aerobic conditions, with temperature and pH controlled. 

On cooking maize starch the viscosity increases when the starch begins to gelatinise. As the temperature rises towards 95°C the viscosity falls. When the paste is cooled the viscosity rapidly increases. The variation of viscosity with temperature is characteristic for each different origin of starch. Potato starch, for example, has a lower gelatinisation temperature than maize starch but has a higher maximum viscosity. When cooled the viscosity of potato starch rises less. Once again amylopectin starches do not show this behaviour as they do not gel. 

FIG. 25 The distribution of water proton transverse relaxation times for a water-saturated, packed bed of potato starch granules at two temperatures [reproduced with permission from Tang et al. (2000)]. 

Evans, I. D. and Haisman, D. R. (1982). The effect of solutes on the gelatinization temperature range of potato starch. Starch/Stdrke 34, 224 231. 

Shiotsubo, T. (1984). Gelatinization temperature of potato starch at the equilibrium state. Agric. Biol. Chem. 48, 1-7. 

The production of CDs via enzymatic reaction with starch has been recently reviewed (i 7). CGTase is an extracellular protein and is usually isolated as a crude mixture from the medium. This crude protein is used directly for industrial fermentations. The basic process involves standard enz3miatic fermentation, with careful attention to reaction temperature. All three CDs and some Unear oligosaccharides are normally produced. Yields are highly dependent on the source of starch substrate. Potato starch is normally used or an extract of potato starch is often added to other starches 18-19), The potato starch component(s) responsible for stimulating CD formation have not been determined. Low starch concentrations (5%-10%) are normally used industrially. Published yields are in the 50% - 80% conversion range. 

Tablets prepared with dicalcium phosphate dihydrate increased in crushing strength due to increasing temperatures (A,sir(s) ). The relative humidity had a negative effect on the SIR of crushing strength of the tablets prepared with dicalcium phosphate dihydrate, except for the tablets prepared with potato starch. Also a significant interaction between the temperature and relative humidity effect was seen (A3,sir(S) 0), indicating that the effect of the relative humidity on the SIR of crushing strength of dicalcium phosphate dihydrate tablets depended on the level of temperature and vice versa.

Figure 8.4 Storage to Initial Ratio of crushing strength (SIR(S)) off-lactose/potato starch tablets, as a function of storage temperature (°C) and storage relative humidity (%RH)...

DSC can also be used to determine starch retrogradation. After heating potato starch (30% (w/w)) to 180°C, samples are cooled to 5°C. Once the temperature reaches 5°C, the sample is immediately removed from the DSC and stored at low temperature. After a certain number of days, the sample pan is placed into the sample holder of the DSC, and heated from 5 to 180°C at 10°C /min. The instrument is calibrated using indium and an empty pan as a reference. The enthalpy (AH) of phase transitions is measured from the endotherm of DSC thermograms based on the mass of dry solid. Transition temperatures such as onset, peak, and completion temperature are also measured. 

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. 

Barichello, V., Yada, R. Y, Coffin, R. H., Stanley, D. W. (1990). Low temperature sweetening in susceptible and resistant potatoes Starch structure and composition. J. FoodScL, 54, 1054-1059. 

Potato starch contains fewer lipids than the cereal starches. Free latty acids in rice and maize starches result in amylose-lipid complex formation, thereby contributing to their higher transition temperatures and lower retrogradation. 

OPT is a new method of physical modification, in which potato starch is suspended in solution saturated with a salt such as sodium sulfate and heated (autoclaved) at temperatures above 100° C for different times. This treatment has been reported to have the same effects on the starch properties as HMT but the starch modified using OPT exhibits better homogeneity (Pukkahuta et al., 2007). 

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