Wheat time-temperature curves

Fig. 33.—Time-temperature curves for wheat starch-water systems heated to 85°C by micro-waves (from Ref. 286).

Figure 8.3 Storage modulus (G ) profiles (solid lines) of 15% (w/w) starch suspensions as a function of time during a heating and a cooling cycle (dotted lines) (a) potato starch (b) wheat starch. The maximum heating temperature is indicated in each curve.153...

In order to test the applicability of the model over a wider range of conditions the kinetics derived at 10 C/tnin from Table 1) was used to predict the pyrolysis of wheat straw heated to 300 C at 10°C/min, then kept isothermal for 60 min, before heating to bOO C at 10°C/min, see Fig. 3. The experimental data show that the addition of a 60 min hold time at 300°C results in somewhat different mass loss curve. The initial mass loss follows that of the data heated directly to 600 C, but when 300 C is reached, the mass loss rate becomes much lower, and after 60 min at 300 C, the conversion is only about 0.8. Full conversion is reached when the temperature is raised to 600 C. The char yield for the two experiments was approximately the same. The model, which fit the direct heating to 600°C reasonably well, does not work for the case with a 60 min isothermal segment at 300°C is inserted. The model predicted that the pyrolysis was far too fast, and a full conversion is predicted under the isothermal segment. This shows that first order kinetics only works well on the data on which it was fitted. A single first order model cannot predict the pyrolysis behavior under different conditions. 

Alkali-extracted proteins from simflower oil cake (89% proteins, Nx6.25) and wheat gluten (76.5% proteins, Nx5.7) were reacted with n-octanol in the presence of an acid catalyst. Temperature, reaction time and catalyst concentration were varied according to an experimental design to maximize the esterification yield. The latter was determined by alkaline hydrolysis and subsequent analysis by gas chromatography. The hydrolysis of the peptide chain was traced by the determination of the amount of free amino groups in esterified proteins using 2,4,6-trinitrobenzene-sulfonic acid (TNBS) assays. The solubility curves of modified proteins in water as a function of pH were obtained by Kjeldahl analysis to determine the composition of the soluble and insoluble parts. 

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