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

Abstract

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.

Relationships of damaged starch granules and particle size distribution with pasting and thermal profiles of milled MR263 rice flour

“…While according to Song, Lee, Lee, and Yoon (2014), particle size is an important factor in biochemical reactions, as it significantly affects the physicochemical properties of flour by increasing the surface area per volume unit. The differences in damaged starch content and particle size distribution between flours would affect the pasting (Ashida, 2014) and thermal profiles, which have great influence on the quality of processed food products (Li, Dhital, & Hasjim, 2014) such as noodles (Hormdok & Noomhorm, 2007).…”

Physicochemical characterization of white, yellow and purple maize flours and rheological characterization of their doughs

“…It was also found that DS content of maize flours increased with increasing average particle size (employing the same sieve during milling). The milling operation affects directly the starch structure (Li et al 2014). It can be observed that the flours obtained with a sieve of 200 μm showed higher DS content than 500 μm flours due to higher mechanical and thermal damage caused during milling.…”

Impact of variety type and particle size distribution on starch enzymatic hydrolysis and functional properties of tef flours

“…As TS was not dependent on milling SDRI was also higher in flours from mill 2. Li et al (2014) indicate that damaged starch granules in flour (level 6 structure) have greater enzyme digestibility than intact native starch granules and starch digestibility of flours from milled cereal grains increases with the decreasing flour size. Tef flours from mill 2 have the lower mean particle size and higher starch damage ( Table 2).…”