Starch glycerol mixture

Figure 5.2 Starch/glycerol mixtures a) before and b) after shearing-heating process in shear cell device.

C for potato starch/glycerol mixtures mixed at 80rpm, depending on water content in the treated sample (unpublished data). Higher levels of water resulted in lower melting temperatures and lower maximum torque values in the tests (Figure 5.3). 

Almost all parameters calculated for samples of starch/glycerol mixtures without water addition showed lower values than with 5% added water [26]. Much lower values in SME and in shear stress multiplied by time were noted. According to previous data [20] it may be concluded that increasing moisture content should lower values of maximal shear stress and should thus reduce the macromolecular degradation. This can be confirmed by intrinsic viscosity measurement There are some differences in the extrusion behavior of potato and of cornstarch, as reported by Della Valle et al. [27]. Molten potato starch under the same conditions... 

The microstructures of shear-heated samples differ with glycerol and water levels (Figure 5.9). Figure 5.10 shows the structures of starch/glycerol mixtures with 10% added water. The smaller starch granules, in comparison with Figure 5.9,... 

In the preparation of the sodium hypochlorite solution it is quite necessary that the mixture be kept cold and be alkaline to red litmus paper at the end of the reaction, if good yields of hydrazine are to be obtained. Since iron is an anti-catalyzer, it is necessary to use distilled water throughout the process. As a viscolizer, a substance such as starch, glycerol, glue or gelatine may be used the last, however, gives by far the most satisfactory results. 

Myllymaki O., Eerikainen T., Suortti T., Forssele P., Linko P., Poutanen K., Depolymerization of barley starch during extrusion in water glycerol mixtures. Food ScL TechnoL, Lebensm. Wiss. TechnoL, 30, 1997, 351-358. 

ForseU EM., Mikkila J.M., Moates G.K., Parker R. Phase and glass transition behaviour of concentrated barley starch-glycerol-water mixtures, a model for thermoplastic starch, Carbohydr. Polym. 34(1997)275. 

Plasticizers combinations are reported in literature as well as the use of additives and lubricants, which can be included before entering the extruder. For example, Yan et al. (2012) made mixtures of starch, glycerol (25, 30, 35, 40, 45, 50 wt% of starch), pullulan (5 wt% of starch), stearic acid (1 wt% of starch), and glyceryl monostearate (0.5 wt% of starch) in a mixer at room temperature for 30 min. Blended mixmres were stored in polyethylene bags at room temperature overnight to equilibrate all components and finally after this procedure the extruder was fed with these mixtures. 

In this method starch, glycerol, filler, and distilled water were mixed together to obtain composite solution with homogeneous dispersion. The mixmre was then heated under reflux and stirred to ensure complete gelatinization of starch. The mixture was casted in a PVC dish and dried to obtain the films. 

Debiagi et al. (2010) investigated the production of foam composites by extrusion, from the mixture cassava starch, glycerol (plasticizer), and two different types of natural fibers (oat hulls and sugarcane bagasse). The composites were prepared in a single screw extruder, with three different levels of each fiber (0, 5, and 10 g/100 g starch), two levels of humidity (18 and 26%), and a fixed level of glycerol (20 g/100 g solids). The addition of fibers reduced the water solubility index of the foams. 

Figure 4.23 tan 5 as a function of the temperature for granulate produced from potato starch/25% glycerol mixtures (notation as in Figure 4.22). 

Table 5.1 Results of main parameters calculated for potato starch/glycerol/water mixtures processed in the shear cell [25].

Figure 5.4 Influence of water addition on torque value during thermomechanical treatment of potato starch/glycerol (80 20) mixtures in the Brabender Mixograph (Wojtowicz, in print).

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