Starch water content

The mixture of the swollen and fragmented granules depends on the botanical source of the starch, water content, temperature, and shearing during heating. The extent of leaching of... 

Figure 9.9. Different applications of starch. Water content on the basis of the level ofde-structuring...

Plant material water contents range from high (>90%, e.g. vegetables) to low (< 10%, e.g. straw, herbs, tea, hops, etc.). Thus the ratio between the analytes (residues) and the organic matter potentially interfering with the analysis is very different for, e.g., cucumber and camomile tea. Other ingredients in plant materials such as acids, oil, sugars, starch or substances typically for the taste and effect of plant materials may have properties similar to those of the analytes and thus interfere in or influence the cleanup procedures. 

FIGURE 5.9 DSC profiles of potato starch at different water contents (volume fraction of water indicated next to each profile). Heating rate=10 °C/min. Donovan (1979), Phase transitions of starch-water system. Biopolymers, 18, 263-275. Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced with permission. 

Starch annealing involves heating starches with sufficient hydration below their Tq to facilitate molecular mobility (Tester et ah, 2001). Annealing is defined as "a physical treatment that involves incubation of starch granules in excess (>60% w/w) or at intermediate (40-55% w/w) water content during a certain period of time at a temperature above the glass... 

Eliasson, A.-C. (1980). Effect of water content on the gelatinization of wheat starch. Starch/ Starke. 32, 270-272. 

However, some of these methods are experimentally limited by certain parameters, such as starch/water ratio and the temperature range over which gelatinization can be studied. For example, DSC is particularly well suited to investigate the phase transition of starch-water systems because it permits the study of starch transitions over a wide range of moisture content, the determination of transition temperatures over 100°C, and the enthalpy changes during transitions. 

Microencapsulation using extrusion is mainly described for glassy carbohydrate matrices [14-16, 28-29]. The glassy carbohydrates, such as starch and maltodextrins, are melted at elevated temperature and low water contents and are intensively mixed with the active in the extrusion barrel. Extrusion has been used for volatile and unstable flavours. The shelf life of flavour oils could be extended from several months to 5 years, compared with 1 year for spray-dried materials. The main drawbacks of the technology are the high investments costs and the formation of rather large particles (500-1,000 pm). 

Figure 7.7 Clausius-Clapeyron relationship between water activity and temperature for native potato starch. Numbers on curves indicate water content, in g per g dry starch (from Fennema,...

This is the fundamental deformation band. It overlaps the protein amide I band. This band can be used to monitor changes in water content in a variety of materials including meats, protein isolates, and starch. 

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).

Fig. 20.—Quantity, Q (absorbance), of radioinduced hydrogen peroxide as a function of the water content (%) for starches of various origins, (from Ref. 102). See Fig. 16 for notations.

FIG. 21.—Quantities (Q) [mg/mL] of water-soluble dextrins as a function of water content (W) in potato starch (o, irradiation under oxygen , irradiation under nitrogen) (from Ref. 101). 

Maize starch may be separated after irradiation into several fractions, based on solubility in alcohol and aqueous alcohol. The size of the fractions and their composition depends on the radiation dose, as shown in Table X which also shows the distribution of organic products of destruction (aldehydes and carboxylic acids) in particular fractions.118 The relations presented in this Table are S-shaped. Under irradiation with increasing doses, the destruction of starch obviously increases. The nature of the increase of acidity in com starch has also been studied by Athanassiades and Berger.119 Thollier and Guilbot120 have conducted similar studies on potato starch, and Raffi et al99 have extended their studies to more varieties of starch. The results expressed as free and total acidities, as well as the quantity of formic acid at equilibrium water content, are given in Table XI. These data vary rather nonlinearly with increase of the irradiation dose and water content. 

Starch Equilibrium water content Yield of Hj02°... 

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