Studies on Dextrinization. Part I. Pyrodextrinization of Corn Starch in the Absence of Any Added Catalyst

Abstract

Corn starch has been dextrinized at a bath temperature of 121 '-213 OC. In certain cases, the moisture content o f the starch was reduced to 2010 before it was subjected to dextrinization. Under the various conditions of dextrinization, the changes that take place in the properties of starch such as solubility, reducing power, alkali lability, intrinsic viscosity and B-amylolysis have been recorded. These results show that at lower temperatures o f 121 O and 110 O C hardly any reaction is perceptible, the dextrinization reaction taking place at 200 OC or thereabouts. Decreasing the moisture content of starch increases the rate of dextrinization reaction. Various theories o f pyrodextrinization of starch are discussed.

Studies on Pyrodextrinization of Corn Starch

“…The star& (H,O 6 o/o, 70 g) was roasted in a glass flask a t various times and temperatures (see Table 1). [4,9,101. Dextrin ( 5 g) was immersed in ethanol (4 ml), and then diluted with water to 100 ml.…”

“…At higher temperature, the shortened units are repolymerized and the degree of branching increases considerably. More recently, Greenwood [ 11, Srivastava [9], Kainuma [lo], and several workers [2,11,121 studied dextrinization and reported many interesting results.…”

“…Srivastawa [9] suggested that satisfactory dextrinization of starch takes place only around 200 "C (corresponding to a material temperature of approximately 185 "C). This result approximates the present findings, but Srivastava's data also indicated that solubility curves of dextrins show a n initial steep rise and after the maximum solubility is reached, the curves show a downward trend.…”

“…Sugars [ 1, 2,9,131 The changes in reducing value and reducing sugar content are shown graphically in Figures 3 and 4. The curves of reducing value and reducing sugar content are similar figures in the whole range of temperatures.…”

Physical and Molecular Properties of Re‐extruded Starches as Affected by Extruder Screw Configuration

“…These studies reported that extrusion cooking resulted in the transformation of native starches into lower molecular weight fragments, and that fragmentation was a function of extrusion conditions and possibly, starch source. Greenwood (1967) and Srivastava et al (1970) suggested that starch, when subjected to high temperatures (125 to 213ЊC), underwent covalent reassociation. This was not confirmed by Wen et al (1990) or Wasserman and Tampa (1991).…”