Starch varieties

While trying to determine the source of a particular structural feature present on some but not all types of starch granules, Fannon et al [61] used conventional SEM and ESEM to determine if the pores in some starch varieties were a result of drying in the kernel, produced by in situ amylases, an artifact of preparation or a natural feature of the granule. While earlier work had been done in this area [62], the ESEM could provide a distinct advantage. By the use of conventional SEM and the ESEM, the list of possible causes of the pores was... 

Fig. 16.—Mass, Q (mg/mL), of water-soluble products as a function of the content of amylose in starch. Variety of starch P, potato AM, amylomaize M, maize R, rice H, haricot bean MN, manioc WM, waxy maize B, bread wheat. Point P relates to potato starch after correction of the result attributable to high water content in that source (from Ref. 102).

Starch variety Acidity a Equilibrium water content11... 

Solid com and cassava starches have been irradiated with 337.8-nm pulsing ultraviolet light (2.6 ns with a peak power of 100 kW) emitted by an atmospheric-pressure nitrogen laser.270a Small changes could be observed in the water solubility of the irradiated starches, their water-binding capacity, and the iodine uptake, provided that promoters (1% w/w) were introduced. The activity of three promoters tested—ZnO, TiOz, and MgO—and the susceptibility of both starch varieties to the irradiation were approximately the same. 

Mutants of maize starch varieties have been extensively studied.12 85-100 Amylose, amylopectin, and intermediate material contents of various single and double mutants have been analyzed the results are shown in Table 6.2. Relationships between structures of the starch polymers and functional properties of these mutant starches have also been reported.12,85-100... 

Fig. 3.—Potentiometric titration with 0.001 N aqueous KI3 solution of 100 mL of 0.04% solution of the following starch varieties x = wheat = rice O = corn = potato A = tapioca. (From Bates et al.65)...

Sorptive capacity is one of the most important properties, and it has been investigated by many authors for several varieties of starch.331-333,335,419 Sair and Fetzer,420 and also Rakowski,331-333 compared the water-retention capacities of wheat, arrowroot, and potato starch, and the results were similar. Among the following starch varieties, the sorptive capacity decreases in the order given potato > arrowroot > wheat. The order potato > corn > wheat was reported by El-Khawas et al.42] Nara el a/.407 reported the order potato > tapioca > waxy rice > sweet potato > rice Smolina422 reported the orders potato > maize > rice > wheat at low humidity and potato > rice > maize > wheat at high humidity. These orders do not agree with the order reported in Table XVII on the effect of desiccation on the water retention of starch. Based on these data, the... 

The hydration of starch evokes thermal effects which are obviously also dependent on the starch variety. This is true because the external temperature does not affect426 the macrostructure and microstructure of starch below 140°C. An estimation of the heat of sorption is useful in determining the concentration of bound water.426-434 The heat of adsorption ranges from 0.255 to 0.100 kJ/mol and depends not only on the variety of starch, but also on the mode of drying of starch prior to measurement (Table XVIII).426... 

Fig. 36.—Changes in electromagnetic wave damping, A, as a function of starch humidity at various pressures. Three potato-starch varieties are denoted by three different point patterns. (Reprinted with permission from M. Boruch, S. Brzezinski, and A. Palka, Acta Aliment. Pol., 11 (1985) 115-124.)...

As with iodine, starch forms an inclusion complex with bromine vapor.205 Depending on the starch variety, different colors are developed by the complex. Maize and wheat produce an ochre color, rice produces a light-buff color, potato and sago develop a pale-yellow color, and cassava forms a cream color.69 Iodine cyanide (and bromine)-amylose complexes are brown-black and dark brown, respectively.206 The adsorption of chlorine and iodine proceeds according to the Freundlich isotherm. A discontinuity on the Freundlich isotherm plot is reported, which possibly results from the swelling of starch granules454... 

Studies by Fischer and Schwaibold521 as well as by Seidemann491 show that there are significant differences between starch varieties in response to their being treated with salts. 

Acetone readily adsorbs on starch and is better sorbed on air-dried starch than on oven-dried starch. Complexation with the solvent boiling under reflux gives better yields than complexation at room temperature. The adsorption depends on the starch variety and decreases in the order po-... 

Several dye coloration scales are used to characterize starch varieties. Perhaps the oldest is the differentiation between starches based on the uptake of Saphranin and Gentiana Violet (see Table XXXVIII).787 Co-vello788 presented another coloration scale which is based on the use of six common acidic and basic dyes (see Table XXXIX). Like the Saphranin and Gentiana Violet dyes, these dyes adsorb directly on starch. Table XL presents a list of synthetic dyes tested in starch dyeing.789-790 Zwikker791 observed the reactions of mechanically damaged starch granules and amylo-... 

Starch Variety Fuchsin Acidic Basic Methyl Violet Methylene Blue Congo Red Eosin... 

Other starch varieties chemically bind metal atoms only to the hydroxyl groups, in the same manner as alcoholates. Alkali metal starchates were obtained for the first time by the use of either metal amides in liquid ammonia641 or metals in liquid amines.642 These methods were subsequently used by others.643 Sodium 2-starchate could be prepared by refluxing an alcohol solution of NaOH and dry starch.644 The reaction of dry starch with controlled amount of NaOH in 1-butanol provided either monosodium 2-starchate or disodium 2,3-starchate.645,646 However, complexes of NaOH with starch were also characterized.37,38 Thallation of starch could be performed with thallous hydroxide.647... 

The reaction in water at pH 7 required either 24 h at room temperature or 12 h at the boiling point.1290 These observations were later confirmed by reaction of aliphatic aldehydes with starch over the temperature interval from room temperature to below the gelatinization temperature.1303 The properties of the products obtained under identical reaction conditions were dependent on the starch variety. Aromatic aldehydes reacted with difficulty under these conditions, as the reactions lasted up to one week at 37 °C.1303 The reaction may be performed without any catalyst, however, it required heating in a sealed tube at 160 °C for 3 h.1304 At lower temperatures, an extended heating time was required and the proportions of water, formaldehyde and starch also affected the outcome of this reaction. As expected for this reversible reaction, an increase in water content shifted the reaction in favor of the reactants. An excess of formaldehyde stopped the reaction at the stage of hemiacetal formation. 

It was reported that phosphorylation during extrusion required less reagents than by the use of classical phosphorylation. The response of various starch varieties to extrusion parameters was similar.1552... 

Studies performed on the etherification of potato amylose and amylopectin with (diethylamino)ethyl chloride showed that amylose in the starch granule was more reactive than amylopectin.2429 However, the relative reactivity of both starch components could be changed by physical pretreatment of the granules, for instance, by milling, heat-moisture treatment, freeze-thawing, and chemisorption. The physicochemical properties of amino starches depend on the starch variety reacted 2430 Among potato, sweet potato, rice, wheat, and tapioca starch studied, the last reacted most readily. 

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