Amylose solution

The chromatogram zones colored by iodine can be fixed later by treatment with a 0.5-1 Vo aqueous starch (amylose) solution. This yields the well known, deep blue iodine-starch inclusion complex which is stable over a prolonged period. This reaction... 

Although the dipolar and resonating nature of the interaction of amylose and iodine is well established, Schlamowitz173 regards the iodine in a starch complex as being in a predominantly non-polar form, and Meyer and Bern-feld174 refute the helix theory and consider that adsorption of iodine occurs on colloidal micelles in amylose solutions. Most of the experimental facts which Meyer presents can, however, be satisfactorily explained on the helical model. 

Of the methods available for potentiometrically estimating the amount of iodine bound by amylose, the differential method of Gilbert and Marriott36 is by far the most satisfactory for accurate work as it eliminates corrections for reagent blanks. In this method, the amylose solution and control solution form two half-cells connected by a salt-bridge, and the... 

Figure 11. Possible mechanism of crystalline gel formation from aqueous amylose solutions ( left solution middle gel right crystalline gel) (42)...

An amylose solution is colorless. The iodine solution is reddish-brown. Yet when you combine these two solutions, you observe an intense blue color. What changes in molecular structures give this coloration ... 

In the literature there has been a certain disagreement as to whether amylose is saccharified completely by /3-amylase. The experiments are complicated by the fact that amylose solutions have a tendency to deposit amylose (retrograde) in which state it is not attacked by the enzyme. But if a sufficient amount of enzyme is used the amylose is, without... 

Ring, S.G., I Anson, K.J. and Morris, V.J. 1985. Static and dynamic light scattering studies of amylose solutions, Macromolecules, 18 182-188. 

Dilute Systems. We will first consider what will happen in an amylose solution. Actually, amylose is very poorly soluble in water at room temperature (although it is well soluble in some salt solutions, notable KC1 cf. Table 6.1). It readily forms helices in water, of which at least part are double helices. These helices tend to align, forming parallel stacks that may be considered microcrystallites. X-ray diffraction shows the chain packing to be similar to that of B type crystallites in native starch. As much as 70% of the amylose may become crystalline. It depends on amylose concentration what the consequences will be. An amylose solution at 65°C has a chain overlap concentration c (see Section 6.4.2) of about 1.5%. If a more dilute solution is cooled, precipitation of amylose will occur. 

In more concentrated amylose solutions, a gel will be formed. The gel stiffens during keeping, although the correlation between the increase in AH and the increase in stiffness is far from perfect Figure 6.26. Much the same happens in a gelatinized starch solution. Here, amylose and amylopectin have phase separated, and the swollen granules contain virtually no amylose. This implies that the amount of water available for amylose is... 

FIGURE 6.26 Retrogradation of a 7% amylose solution. The solution was cooled from 90 to 26°C and then kept for the time indicated. Stiffness (as shear modulus) and melting enthalpy (AH) were monitored arbitrary scales. (After results by M. J. Miles et al. Carbohydr. Res. 135 (1985) 271. 

Preparation of Amylose Solutions. Amylose (100 mg) was dissolved into 3 ml of 1 N KOH solution. Then, the solution was... 

It should be noted that the complex solution containing 5.8x 10 N NaCl as a product of neutralization of alkaline amylose solution gave a symmetric pair of CD bands with a normal pattern... 

Consequently, the conformations of the complex in aqueous solution must be seriously affected by the in-situ conformation of uncomplexed amylose depending strongly on the method and cation-effect in the neutralization of alkaline amylose solution. 

Ultrafiltration studies have demonstrated that addition of excess of iodine to amylose solution completely prevents the passage of amylose molecules through the filter. This is attributed to the iodine induced coil— helix transition, forming rather tight helices in the amylose-iodlne-complex (4),... 

Because of the inherent instability of the aqueous amylose solutions viscosity changes on binding of complexing agents, e.g. butanol or iodine, have often been used for deducing the initial chain conformation (, 9, J, j ). Observations with amylose-iodine solutions also contribute valuable information. 

Fractional Precipitation of Amylose-lodine Solutions. Fairly concentrated amylose solutions containing a mixture of two to five components (DP 90-56CXJ) were precipitated by successive addition of KI2 solution. The purified fractions were converted into tricarbanilate derivatives and were then separated over a high performance GPC column. The ratio of the components was obtained from careful evaluation of the peak areas using the concentration dependence of the single components and various mixtures of known composition. Figure 9 shows the elution curves of fractions a-d obtained from a two component system (DP 90 and DP 1800, 1 1). 

Figure 11. Stepwise retrogradation of amyloses DP 100 and 2270 (1 1). HPLC-GPC of tricarbanilates in THF. (Amylose solution 200 mg DP 100 and 200 mg DP 2270 in 4 mL DMSO and diluted with water to 100 mL.)...

Aqueous amylose solution (1%) was prepared by dissolving amylose powder in hot water (80°C). A 1% salt free aqueous water-soluble chitosan (WSC) was obtained by the dialysis of a WSC solution that included NaCl produced by the neutralization of a dilute hydrochloric acid solution of WSC with NaOH. Each film having a thickness of 40-50 om was prepared by casting the amylose, WSC, or their mixed solutions at 60°C. A film of fully deacetylated chitosan was obtained by casting a 0.1 M aqueous AcOH solution of fully deacetylated chitosan (1%) on a Kapton (polyimide) film. The resulting acidic chitosan film was neutralized with 1M aqueous NaOH followed by washing with water and then dried. 

Amylose starch (Chapter 10.1) can be fabricated in film or tube form for food use, by extruding sodium amylose solutions into a coagulating bath of phosphoric acid [102]. 

In the case of dextran (0.1-1%) and amyiopectin (0.05%) the potentiometric measurements do not indicate any interaction with NaDS, the activity of NaDS solutions is the same with and without these polymers. An amylose solution of 0.025% was turbid and it did not clear up even in the presence of 20 mmoLkg" NaDS. However, the potentiometric measurements showed binding of NaDS according to a Langmuir isotherm with a saturation value of 0.27 mmol/g amylose. The binding of NaDS on amylose is regarded as an adsorption on solid amylose particles and not as an interaction between them in solution. It is concluded that the investigated polysaccharides do not interact with NaDS in aqueous solution. 

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