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Raw starch is commonly modified to enhance its functionality for industrial applications. There is increasing demand for 'green' modified starches from both end-consumers and producers. It is well known that environmental conditions are key factors that determine plant growth and yield. An increasing number of studies suggest growth conditions can expand affect starch structure and functionality. In this review, we summarized how water, heat, high nitrogen, salinity, shading, CO 2 stress affect starch biosynthesis and physicochemical properties. We define these treatments as a fifth type of starch modification method - agricultural modification - in addition to chemical, physical, enzymatic and genetic methods. In general, water stress decreases peak viscosity and gelatinization enthalpy of starch, and high temperature stress increases starch gelatinization enthalpy and temperature. High nitrogen increases total starch content and regulates starch viscosity. Salinity stress mainly regulates starch and amylose content, both of which are genotype-dependent. Shading stress and CO 2 stress can both increase starch granule size, but these have different effects on amylose content and amylopectin structure. Compared with other modification methods, agricultural modification has the advantage of operating at a large scale and a low cost and can help meet the ever-rising market of clean-label foods and ingredients. [ABSTRACT FROM AUTHOR]

Abstract The extra-long chain (ELC) of amylopectin influences molecular compositions of starch. In this study, starches were isolated from 22 rice varieties with different ELCs. Molecular compositions of starch were determined, and their relationships with crystalline structure, gelatinization properties, pasting properties, and enzyme hydrolysis were analysed. The results showed that the starches with different ELCs had significantly different structural and functional properties. The ELC was significantly positively related to setback viscosity and negatively related to relative crystallinity, lamellar peak intensity, swelling power, gelatinization enthalpy, and rapidly digestible starch of retrograded starch. The true amylose content was significantly positively related to retrogradation and negatively related to peak viscosity and hydrolysis degree by α-amylase and amyloglucosidase. The short branch-chain of amylopectin was significantly positively related to lamellar peak intensity, swelling power, hydrolysis degree by α-amylase, and rapidly digestible starch of retrograded starch and negatively related to setback viscosity and resistant starch of retrograded starch. The ratio of short to long branch-chain of amylopectin was significantly positively related to swelling power and hydrolysis degree by α-amylase. The principal component analysis and partial least squares discriminant analysis demonstrated that the low-ELC starches were distinguished from the middle- and high-ELC starches, the middle-ELC starches basically clustered together, but the high-ELC starches were highly dispersed. The above results would provide some new information for rice quality breeding and starch applications by changing the ELC in starch. Graphical abstract Image 1 Highlights • Starches from 22 rice varieties had different extra-long chains (ELC) of amylopectin. • GPC profiles of debranched starch and amylopectin measured molecular compositions. • Gelatinization and pasting properties and enzyme hydrolysis of starch were measured. • PLSR showed interrelationship between molecular compositions and starch properties. • PCA and PLS-DA revealed the differences among rice varieties with different ELCs. [ABSTRACT FROM AUTHOR]

The multi-scale structural dynamics of amylopectin-only barley starch (APBS), normal barley starch (NBS), and amylose-only barley starch (AMBS) digested with amylolytic enzymes for 120 min were investigated in this study. For all starches, 0–20 min was identified as a rapid digestion stage, followed by a 20–120 min slow digestion. For APBS and NBS, the content of short chains (DP ≤ 12) and the thickness of crystalline and amorphous nano-lamellae increased, whereas the crystallinity decreased, and pores were generated on the granular surface during the rapid digestion stage. At the following slow digestion stage, the branching degree and relative amount of double helices increased, the crystalline and lamellar structures were lost, and the hydrolyzed starch segments aggregated. For AMBS, the rapid digestion stage was characterized by an increased content of short chains (DP ≤ 8) and B-type crystals and decreased amounts of V-type crystals. Furthermore, the lamellar and granular structures were lost, and digestion residues aggregated during the first stage of AMBS, which were formed in the second digestion stage of APBS and NBS. The second slow digestion stage of AMBS was characterized by an increased branching degree and a decreased relative content of single helices. It is suggested that the aggregated digestion residues at the initial digestion stage are the main reason for the overall low digestibility of AMBS. [Display omitted] • Amylose barley starch (AMBS) lost granular structure at initial digestion stage. • AMBS reorganized immediately and was thereafter hydrolytic resistant. • Single helices and the V-type crystals decreased in AMBS upon hydrolysis. • Amylopectin barley starch (APBS) first generated pores and then reorganized. • APBS had a high content of double helices after digestion. [ABSTRACT FROM AUTHOR]

We investigated the effects of drought stress (DS) on maize varieties with different amylose content (AC). In starches with AC of 33 %, DS increased the contents of amylopectin (AP) chains with a degree of polymerization (DP) > 36 and decreased the AP chains with DP ≤ 36, while the AC was unchanged. DS decreased the crystallinity, the thickness of both amorphous and crystalline lamellae, and average granular size. In contrast, the digestibility increased. For starches with AC of 45 %, DS increased the content of AP chains with DP > 24 and AC, while the contents of AP chains with DP ≤ 24 decreased. DS produced starch with thinner crystalline lamellae, thicker amorphous lamellae, more elongated and larger granules. The digestibility of the starches decreased. In starches with AC of 53 %, moderate DS led to similar structural and functional changes as found for starches with AC of 45 %. Finally, severe DS resulted in the decrease of AC. [Display omitted] [ABSTRACT FROM AUTHOR]