Starch aldehyde content

Alcoholysis, of trityl ethers, III, 81 Aldehyde content, of starch, I, 276 Aldehyde group, in starch molecule, I, 253... 

A simplified alkali lability method has been employed in the author s laboratory, whereby the rate of alkali degradation is estimated from the amount of acidic substances produced by alkali degradation. This is expressed as alkali number, and represents the ml. of 0.1 N acid formed from 1 g. of the starch substance under specified conditions of alkali digestion. It is entirely an arbitrary value, and cannot be construed as an absolute measurement of aldehyde content or of molecular weight. It serves only to indicate whether the aldehyde content of the starch has remained constant, or whether it has increased or decreased. Farley and Hixon have found that the alkali number detects hydrolytic changes in the starch before they are measurable by copper or ferri-cyanide reduction. 

Alkali lability supplied the first positive evidence of chemical differences between the starch fractions as separated by butyl alcohol. The alkali number of defatted com starch is 10-11 values for the crude A and B fractions are 25 and 5.5, respectively. The observed alkali lability of the original starch coincides with the value calculated from the percentage composition and alkali numbers of the indi idual fractions (viz., 23% X 25 -H 77% X 5.5 = 10). These values are in agreement with the presumed structure of the A and B fractions as linear and branched glucose polymers respectively. Alkali decomposition of the A-fraction should be more extensive than with the B-fraction, since the latter possesses a lower aldehyde content. Also, a branched structure may impede the decomposition in hot alkali. 

We have developed an efficient and practical method for clean oxidation of starch (21-23) resulting in the oxidation of primary alcohol function in Ce position and the cleavage of vicinal diols in C2 and C3 position (Figure 30.2). We used small amounts of cheap iron tetrasulfophthalocyanine catalyst, pure water as reaction medium and H2O2 as clean oxidant to achieve a one-pot conversion of starch resulting in the introduction of aldehyde and carboxyl functions in polymer chains. The iron content... 

Pineapple oil, peel-oil content and aldehyde composition, see also Citrus oils Pin milling, starch isolation, 673, 677 Pipetting technique, 754-755 PL. see Pectic lyase... 

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. 

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. 

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