Dextrin references

The term, dextrins, refer to starches which were depolymerized and then restractured to form short, highly branched or cyclic polymers. These polymer products are dextrorotatory, thus the name dextrins. The primary mechanisms for dextrin production include a depolymerization step, by acid or enzymes... 

In low-acid wines, the growth of pediococci may result in formation of extracellular dextrins. Referred to as ropiness, the defect is detected as increased viscosity and oiliness. Ropiness usually begins in the bottom of cooperage and eventually envelopes the container. Although generally associated with the activity of Pediococcus sp. in high-pH, low-acid sweet wines, Leuconostoc sp. have also been implicated (Mayer, 1974). 

After 30 hours, the maximum and critical fermentation is underway and the pH must remain above 4.0 for optimal fermentation. However, accompanying bacterial contamination from various sources such as yeast contamination, improper cleaning procedures, slow yeast growth, or excessive temperatures can result in a pH below 4.0. The remaining amylase enzymes, referred to as secondary conversion agents, are inactivated and can no longer convert the dextrins to maltose. Under these circumstances, the fermentor pH continues to drop because of acid production of the bacteria, and the pH can drop to as low as 3.0. The obvious result is a low ethanol yield and quaUty deterioration. 

Note. The cyclic oligosaccharides arising from enzymic transglycosylation of starch have been referred to as Schardinger dextrins. These names (and those of the cyclohexaamylose type) are not recommended, but the abbreviation CD is tolerated. 

Cycloamyloses are also referred to as eyelodextrins, eycloglucans, or Schardinger dextrins, preceded, in each case, by a Greek letter to denote the number of glucose units (< - for 6, 0- for 7, y- for 8, etc.). 

The first report in the literature of the isolation of a substance recognizable as a cyclodextrin was that of Villiers which appeared in 1891. From digests of Bacillus amylobacter on potato starch, Villiers obtained a small amount (3 g per 1000 g of starch) of a crystalline material, which he named cellulosine because of its resemblance in some respects to cellulose. The foundations of cyclodextrin chemistry were laid down, however, in the period 1903-1911 by Schardinger, and, in fact, some of the older literature frequently refers to the cyclodextrins as Schardinger dextrins. 

It is noteworthy that most of the chemical shift values for all three polymers may be closely approximated ( ) by calculations based on data for monomeric reference compounds. These findings illustrate, therefore, the general validity of studies on low molecular weight model compounds for einalysis of spectra of carbohydrate polymers. Many examples of equally satisfactory comparisons of this kind are to be found in studies on other polysaccharides (11,23). These polymers include glucans (l6), mannans (2k, 2 ), limit dextrins (26), lichenin (2j), agarose (28) and various polysaccharides of fungal and microbial orgins (e.g., 7,8,29-31). Observed departures from expectation have been attributed to specific conformational influences ( 8). 

This enzyme [EC 3.2.1.10] (also referred to as oUgo-1,6-glucosidase, sucrase-isomaltase, and limit dextrinase) catalyzes the hydrolysis of l,6-o -D-glucosidic linkages in isomaltose and dextrin products generated from starch and glycogen via a-amylase. See also Sucrase... 

The last-named authority has remarked with reference to British gum prepared by sulphuric acid, that it possesses the disadvantageous property of being deliquescent. This method is, therefore, never employed, as besides this, the products are often colored. He also states that when nitric arid is employed in the preparation of dextrin, it must be perfectly pwe. Commercial nitrio acid, as obtained by the action of oil of vitriol upon nitrats of Soda, always contains a small amount of chlorine and although this element is contained in diminished proportion in the dextrin, it is nevertheless sufficient to considerably lessen the brilliancy of the colors prepared with the dextrin. Several printers upon paper and vegetal tissues have observed this, but have been unable to account for it otherwise than by attributing it to the iaferior quality of the gum. 

Dextrin.—When it is necessary to determine this, the method indicated for flours (p. 63) is applied to the defatted and dried substance (the residue from the extraction of the fatty matters, dried at ioo0, may be used, but the results are referred to the substance itself). 

Freudenberg used the terms J-dextrin and <-dextrin to refer to higher rotating fractions obtained in separation of Schardinger dextrin mixtures. These fractions most likely contained lower Schardinger dextrins plus starchy residues with little if any of the 9- or 10-membered rings. 

When making very dehcate materials it may be necessary to use a yam which is so fine that it would break down under the stresses imposed on it during manufacture. The strength, however, is sufficient once the fabric is made because of the mutual support of adjacent threads. In such cases it is customary to impart temporary strength to the yam by a process known as sizing. This consists of impregnating the thread with some easily removed substance such as starch or dextrine and, in the case of the more modern man-made fibres, with a synthetic product such as polyvinyl alcohol or polyacrylic acid. The size is usually removed before the article is dyed or bleached. Yarns are frequently referred to as warp or weft yarns. In a... 

The basic process has been documented in readily available sources [7,8], thus it will suffice to mention only the critical parameters for reference in comparing the more recent modifications to the processes and products. Dextrinated lead azide is made by adding over a period of 30 min a dilute (3%) solution of sodium azide to an equal volume of a 7% lead acetate solution, maintained at 60°C. The sodium azide solution, which contains an amount of potato dextrin roughly equal to 6% of the expected yield of lead azide, is made slightly alkaline with sodium hydroxide. The lead azide is thus formed mainly in the presence of excess dissolved lead salt and with a reasonably constant concentration of dextrin. The indir idual granules of dextrinated azide are formed by accretion in concentric layers of microcrystals bound with lead dextrinate (Figure 11). giving a product which is about 92% pure. 

Dextrinization is conducted mainly to promote aqueous flow and aqueous solubility. Solubility-time relationships, reported by many authors,are usually not comparable, as they do not always refer the results to a particular source. Thus, according to Grzesko-wiak, in the case of experiments conducted at 160°, the solubility of dextrins increases as a function of time, as shown in Fig. 8, depending on (a) the type of starch, (b) the size of the starch granules, and (c) the content of amylose and amylopectin. 

The first reference to cyclodextrins was published in 1891 by the French scientist A. Villiers. He described the isolation of 3 g of crystalline substance from bacterial digest of 1000 g of starch [7]. He named the substance cellulosine , assuming that this substance is some sort of cellulose. Soon after, the Austrian microbiologist F. Schardinger isolated two crystalline compounds from bacterial digest of potato starch. He named these compounds crystalline dextrins and later changed the names to a-dextrin and P-dextrin [8], In 1935, Freudenberg and Jacobi discovered y-cyclodextrin [9]. 

Coinclusion of the aromatic guest and a small molecule, usually an aliphatic alcohol, in the cavity of a dextrin (i.e., the formation of a three-component complex) often enhances the emission. In this type of complex, the fluorophore is sandwiched between the CD wall and the alcohol, which acts as a spacer. More water molecules are expelled from the cavity and the fluorophore experiences an environment less polar than that experienced in the absence of a spacer. The phenomenon was first reported in reference 61 the enhanced fluorescence of a-naphthylacetic acid observed after addition of y-CD was further increased by addition of cyclohexanol. 

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