Alcohols starch complexes

Table 10.6 compares the average size (DPn) and size distributions of six laboratory-purified amyloses and one commercial sample of potato amylose, which were determined by classic colorimetric and fluorescent-labeling techniques using 2-ami-nopyridine. The data by the two techniques are consistent and show that wheat and other cereal amyloses are smaller in size than those from root and tuber starches. The molar distribution technique indicated that wheat amylose contained two molecular species, compared with one for rice and com amyloses.209,210 Moreover, the molar size distributions for the cereal amyloses are much narrower than those of the tuber amyloses, and the cereal amyloses contain a preponderance of molecules of DPn < 1000 whereas the tuber amyloses contain 78-95% of molecules with DPn > 1000, and even 3-5% above DPn 10000. None of the amylose samples in Table 10.6 showed molecules with less than DPn 200, possibly because they had been purified as alcohol-inclusion complexes.209... 

In some instances the carrier of the guest plays the role of emulsifier. For example, alcohols and lower fatty acids or their esters are used in the formation of fat-starch complexes.676 In this case, conditions for preparation of complexes resemble conditions for extraction, and unexpected results can accompany both processes. For example, it has been shown that extraction of lipids with 1-propanol from their surface complex with oat starch produced a helical lipid-starch complex that was absent prior to extraction.677... 

Starch complexes with aromas and flavoring agents are usually synthetic in origin. In nature, starch sometimes includes some aroma- and flavor-genic components that generate flavor and aroma on processing (see, for instance, ref. 678). Such agents include mainly aldehydes, ketones, and carboxylic esters however, hydrocarbons, alcohols, carboxylic acids, and haloalkanes have also been used. 

According to Hollo et al.,709 the low stability of starch-alcohol complexes (lower than that of the starch-iodine complex) is caused by the relatively small amount of space inside the amylose helix that is available for the hydrophobic moiety of the alcohol. The data in Table XXX appear to confirm this assumption and indicate iodine sorption amounts by starch complexes with subsequent members of the homologous series of alcohols. With the exception of ferf-butanol, the iodine uptake decreases as the alcohol inside of the helix becomes more bulky. 

Many interactions are of a pure chemical nature and may result from the presence of aldehydes and their reactivity toward amino and thiol groups of proteins. Another frequently occurring type of interaction is the formation of hydrogen bonds between food compounds and polar flavor components such as alcohols. Starch, starch-derived maltodextrins, and (3-cyclodextrin are able to form inclusion complexes with many flavor components. Many other interactions, although of great influence on flavor perception, are of a physical nature and therefore not mentioned in this chapter. 

PuUy hydroly2ed poly(vinyl alcohol) and iodine form a complex that exhibits a characteristic blue color similar to that formed by iodine and starch (171—173). The color of the complex can be enhanced by the addition of boric acid to the solution consisting of iodine and potassium iodide. This affords a good calorimetric method for the deterrnination of poly(vinyl alcohol). Color intensity of the complex is effected by molecular weight, degree of... 

In the early years of the chemical industry, use of biological agents centered on fermentation (qv) techniques for the production of food products, eg, vinegar (qv), cheeses (see Milk and milk products), beer (qv), and of simple organic compounds such as acetone (qv), ethanol (qv), and the butyl alcohols (qv). By the middle of the twentieth century, most simple organic chemicals were produced synthetically. Fermentation was used for food products and for more complex substances such as pharmaceuticals (qv) (see also Antibiotics). Moreover, supports were developed to immobilize enzymes for use in industrial processes such as the hydrolysis of starch (qv) (see Enzyme applications). 

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Starches. In the United States, all potable alcohol, most fermentation industrial alcohol, and most fuel alcohol is currendy made principally from grains com is the principal feedstock for fuel alcohol. Fermentation of starch from grain is somewhat more complex than fermentation of sugars because starch must first be converted to sugar and then to ethanol. This process was known to the ancient Egyptians and Mesopotamians who brewed beer almost 5000 years ago (202). The simplified equations for the conversion of starch to ethanol are... 

Polycrystalline and well-oriented specimens of pure amylose have been trapped both in the A- and B-forms of starch, and their diffraction patterns84-85 are suitable for detailed structure analysis. Further, amylose can be regenerated in the presence of solvents or complexed with such molecules as alcohols, fatty acids, and iodine the molecular structures and crystalline arrangements in these materials are classified under V-amylose. When amylose complexes with alkali or such salts as KBr, the resulting structures86 are surprisingly far from those of V-amyloses. 

The most widely used complexing agents are alcohols (butanol, n-propyl alcohol and n-pentyl alcohol1). Schoch33 now recommends the use of Pen-tasol, a commercial mixture of pentyl alcohols, for the first precipitation, and 1-butanol for recrystallizations. For com (maize) starch, this avoids contamination of the amylopectin with an intermediate fraction which is sufficiently linear to be precipitated with Pentasol and yet has a degree of branching which prevents complex formation with butanol. 

Fermenting grains with yeast produces a grain alcohol. The process also works with other biomass feedstocks. In fermentation, the yeast decomposes carbohydrates which are starches in grains, or sugar from sugar cane juice into ethyl alcohol (ethanol) and carbon dioxide. The process breaks down complex substances into simpler ones. 

Iodine makes blue colored complexes with many substances such as starch [1, 2] nylon-6 [3], poly(vinyl pyrrolidone) [4], poly(vinyl alcohol) PVA [5, 6], From the application point of view, the blue PVA-Iodine complex is the most important among them, for it is widely used for film polarizers [7,8]. The polarizers are prepared by soaking PVA films in a solution of iodine and potassium iodide (KI) with boric acid, and subsequent drawing to cause the high... 

Lipids in starchy foods may occur in the free as well as bound forms. The latter being either in the form of amylose inclusion complexes or linked via ionic or hydrogen bonding to the hydroxyl groups of the starch components. Free lipids are easily extractable at ambient temperatures, while use of nonalcoholic solvents for a prolonged period or disruption of the granular structure by acid hydrolysis (see Basic Protocol 4) may be required for the efficient extraction of bound lipids. While acid hydrolysis allows the release and quantitation of lipids, the procedure leads to destruction of the starch components therefore, the alcohol extraction system involving propanol and water would be most desirable in these cases. This system removes both nonpolar and polar lipids from samples. 

In addition to simple model systems, more complex systems which are closer to actual foodstuffs have been used to investigate the formation of flavor chemicals in the Maillard reaction. Sixty-three volatile chemicals were isolated and identified from starch heated with glycine (4). When beef fat was used as a carbonyl compound precursor in a Maillard model system with glycine, 143 volatile chemicals were identified (6). These included fifteen n-alkanes, twelve n-alkenes, thirteen n-aldehydes, thirteen 2-ketones, twelve n-alcohols, and eleven n-alkylcyclohexanes. Recently, the effect of lipids and carbohydrates on the thermal generation of volatiles from commercial zein was studied (7). 

There is also US research interest in using pectin in polymer applications. Pectin is a complex plant cell wall heteropolysaccharide (based on galactose, rhamnose, arabinose and xylose) that can be blended with synthetic polyvinyl alcohol (PVA) to produce biodegradable polymers with a wider range of properties than those of starch-based polymers alone. The new pectin/PVA biodegradable polymer should be capable of replacing conventional PVA applications in blow-moulded, extruded, film and injection-moulded applications. 

Other WAXD starch patterns, known as V-types, are associated with the amylose fraction. In V-amylose, the chain conformation is a left-handed single helix with six residues per turn (V6) for complexes with aliphatic alcohols and monoacyl lipids with ligands bulkier than a hydrocarbon chain, helices of seven or eight glucose residues per turn are feasible.31 Aliphatic chains within amylose helices are rather locked... 

Amyloses of five commercially important starches (wheat, corn, rice, tapioca and potato) were purified by fractional crystallization of their amylose-alcohol complexes and shown to be free of amylopectin.111,205 All five amyloses showed comparable iodine affinity, blue value and max of their polyiodide complexes (Table 10.5), which is consistent with their being (1 —4)-linked a-glucans with an average DPn of —500 or above.206 The average size of amylose molecules in cereal starches is smaller than... 

It should be noted that the different structures of amylose and amylopectin confer distinctive properties to these polysaccharides (Table II). The linear nature of amylose is responsible for its ability to form complexes with fatty acids, low-molecular-weight alcohols, and iodine these complexes are called clathrates or helical inclusion compounds. This property is the basis for the separation of amylose from amylopectin when starch is solubilized with alkali or with dimethylsulfoxide, amylose can be precipitated by adding 1-butanol and amylopectin remains in solution. 

Inclusion complexes of amylose are rather well defined, and a consistent theory of such complexes is available that explains amylose complexes with iodine, fatty acids, alcohols, and other guest molecules.4,5 This subject is surveyed in this article because of the growing interest and importance of such complexes in pharmacology and in the food industry. It is probable that starch in its biological sources (tubers, granules) exists in the form of native complexes with proteins, lipids, mineral salts, and water. 

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