Analysis of starch amylolysis using plots for first-order kinetics

This article surveys methods for the enzymatic conversion of starch, involving hydrolases and nonhydrolyzing enzymes, as well as the role of microorganisms producing such enzymes. The sources of the most common enzymes are listed. These starch conversions are also presented in relation to their applications in the food, pharmaceutical, pulp, textile, and other branches of industry. Some sections are devoted to the fermentation of starch to ethanol and other products, and to the production of cyclodextrins, along with the properties of these products. Light is also shed on the enzymes involved in the digestion of starch in human and animal organisms. Enzymatic processes acting on starch are useful in structural studies of the substrates and in understanding the characteristics of digesting enzymes. One section presents the application of enzymes to these problems. The information that is included covers the period from the early 19th century up to 2009.

Enzymatic conversions of starch.

Milling or grinding of cereal grains to produce flour is frequently accompanied by damage to starch granules, disruption of starch crystalline structure, and degradation of starch molecules. Amylopectin (AP) molecules are more susceptible to degradation than amylose (AM) molecules as AM molecules, present in amorphous conformation in native starch granules, are more flexible than the rigid double helical crystallites made of AP branches. The changes of starch structures caused by milling alter starch properties, including gelatinization, pasting, swelling, solubility, and digestibility, and thus affect flour quality. The changes in starch structures and properties, however, are different between the grinding of cereal grains and that of isolated starch granules as the latter ignores the influences from non-starch components in grains. Hence, the grinding of isolated starch granules, commonly used to understand the effects of milling, does not represent the grinding of cereal grains. This review allows a better understanding in the changes of starch structures and properties by milling, which is important in the production of flour with desirable properties.

Effects of grain milling on starch structures and flour/starch properties

Influence of sorghum flour addition on flat bread in vitro starch digestibility, antioxidant capacity and consumer acceptability

Starch samples isolated from wheat flour that represented four possible waxy states (0, 1, 2, and 3-gene waxy) were subjected to crushing loads under both dry and wet conditions. Calibrated loads of 0.5–20 kg were applied to the starch samples and the percentage of damaged granules was visually determined. Under dry crushing conditions, starches containing amylose (0, 1, and 2-gene waxy) had between 1% (5-kg load) to 3% (15- and 20-kg load) damaged granules, whereas waxy starch (3- gene waxy; <1% amylose) began rupturing at 0.5-kg load (3.5% damaged granules) and had 13% damaged granules when ≥10-kg load was applied. Under wet crushing conditions, normal and partial waxy starch (0, 1, and 2-gene waxy) showed little difference in percentage of damaged granules when compared to the results of dry crushing. Waxy starch (3-gene waxy), however, showed substantially increased numbers of damaged granules: 12% damaged granules at 0.5-kg load, rising to 55% damaged granules at 15-kg load. The results indi...

H. Al Qalla

Papers

An improved enzymic method for the measurement of starch damage in wheat flour