Starch volatile products

Ethylene coordinates the expression of genes responsible for enhanced respiratory metabolism, chlorophyll degradation, carotenoid synthesis, conversion of starch to sugars, increased activity of cell wall-degrading enzymes, aroma volatile production, and so on. All these events stimulate a series of biochemical, physiological, and structural changes making fruits mature and attractive to the consumer. 

Semiquantitative studies on the yield of volatile products from the pyrolysis of various carbohydrates in the range of 200 to 800° have been con-ducted. The most information about the pyrolysis of starch was published by Bryce and Greenwood. They identified the... 

Amounts of Volatile Products from Starch and Related Materials after Pyrolysis for 18 h at 300 ... 

Volatile product Starch Amylopectin Amylose D-Glucose... 

A study of the cumulative yields of volatile products at various temperatures showed that, after pyrolysis for 18 hours at 156 and 188°, although water was the main product from the starches, carbon dioxide and carbon monoxide were also formed. Limited, pyrolytic degradation must, therefore, have occurred at these temperatures. There was a large increase in all three products at 218.6°, indicating that major decomposition occurs near this temperature. In contrast, cellulose did not form comparable quantities of carbon dioxide and carbon monoxide until temperatures of 260-270° were reached. 

The nature, mode of production, and quantitative aspects of the production of levoglucosan require further investigation. Although the nature of the minor volatile products is reasonably well established, the mechanism by which they arise is not yet understood. To date, kinetic investigations of the breakdown of starch into its major, gaseous products (namely, water, carbon monoxide, and carbon dioxide) are limited. More investigations are required, perhaps on model compounds, in order to establish their mode of formation. It is apparent that the course of thermal decomposition may be profoundly affected by the presence of small proportions of simple inorganic salts, but the reason for this behavior has not yet been established. 

The bomb method for sulfur determination (ASTM D129) uses sample combustion in oxygen and conversion of the sulfur to barium sulfate, which is determined by mass. This method is suitable for samples containing 0.1 to 5.0% w/w sulfur and can be used for most low-volatility petroleum products. Elements that produce residues insoluble in hydrochloric acid interfere with this method this includes aluminum, calcium, iron, lead, and silicon, plus minerals such as asbestos, mica, and silica, and an alternative method (ASTM D1552) is preferred. This method describes three procedures the sample is first pyrolyzed in either an induction furnace or a resistance furnace the sulfur is then converted to sulfur dioxide, and the sulfur dioxide is either titrated with potassium iodate-starch reagent or is analyzed by infrared spectroscopy. This method is generally suitable for samples containing from 0.06 to 8.0% w/w sulfur that distill at temperatures above 177°C (351°F). 

Wheat grain, legumes Colon cancer Contains digestion-resistant starch and other non-digestible carbohydrates which increase fermentation in colon and hence production of volatile fatty acids... 

This deficiency has been overcome by the development of "lipophilic" starches (18,19) starch hydrolyzates incorporating a covalently bound lipophilic species, 1-octenyl succinate. In this manner, a lipophilic polymer is produced which allows for excellent aqueous flavor emulsion stability, good water solubility (40% w/w), excellent retentions of the volatile flavoring material following drying and minimal "extractable" oil in the finished product (9), functional properties only exhibited by gum arabic prior to their development. 

The hydrolyzed starches are inexpensive, bland in flavor, very soluble (up to 75 ), and exhibit low viscosity in solution. The major shortcomings of these products are a virtual lack of emulsifying capacity and marginal retention of volatiles. 

Headspace-GC-MS analysis is useful for the determination of volatile compounds in samples that are difficult to analyze by conventional chromatographic means, e.g., when the matrix is too complex or contains substances that seriously interfere with the analysis or even damage the column. Peak area for equilibrium headspace gas chromatography depends on, e.g., sample volume and the partition coefficient of the compound of interest between the gas phase and matrix. The need to include the partition coefficient and thus the sample matrix into the calibration procedure causes serious problems with certain sample types, for which no calibration sample can be prepared. These problems can, however, be handled with multiple headspace extraction (MHE) [118]. Headspace-GC-MS has been used for studying the volatile organic compounds in polymers [119]. The degradation products of starch/polyethylene blends [120] and PHB [121] have also been identified. 

Many pyrazines were isolated and identified in cooked foods, especially in cooked meats (27). Pyrazines comprised over 40% of the volatile compounds found in cooked pork liver (28). Two pyrazines, 2-methyl-3(or 6)-pentylpyrazine and 2,5-dimethyl-3-pentylpyrazine were among 52 volatiles identified as lipid-protein-carbohydrate interaction products in a zein regular or waxy corn starch-corn oil model system (7). 

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