Physicochemical properties of A- and B-type granules isolated from waxy and normal hull-less barley starch

Enhanced B-type starch granules proportion modulates starch-gluten interactions during the thermal processing of reconstituted doughs

This work investigated structure-properties changes of reconstituted wheat A/B starch doughs under different ratios during dynamic thermal processing. Results indicated that a change in spatial conformation and aggregation structure of the starch-gluten system was induced with heating (30 °C-86 °C). Moderately increased B starch ratio can effectively fill the gluten network and improve starch-protein interactions, which promotes the free sulfhydryl group oxidation and results in the formation of more glutenin macropolymer; this contributes to a higher degree of cross-linking and stability to the gluten network matrix. This improvement is enhanced as the heating temperature is increased. Notably, the B starch ratio requires to be controlled within a suitable range (≤ 75%) to avoid aggregation and accumulation on the gluten matrix triggered by its excess. This work may provide insights and optimization for clarifying the on-demand regulation strategy of A/B starch in dough processing.

A review of endogenous non-starch components in cereal matrix: spatial distribution and mechanisms for inhibiting starch digestion

As compared with exogenous components, non-starch components (NSCS), such as proteins, lipids, non-starch polysaccharides (NSPs), and polyphenols, inherently present in cereals, are more effective at inhibiting starch digestibility. Existing research has mostly focused on complex systems but overlooked the analysis of the in-situ role of the NSCS. This study reviews the crucial mechanisms by which endogenous NSCS inhibit starch digestion, emphasizing the spatial distribution-function relationship. Starch granules are filled with pores/channels-associated proteins and lipids, embedding in the protein matrix, and maintained by endosperm cell walls. The potential starch digestion inhibition of endogenous NSCS is achieved by altering starch gelatinization, molecular structure, digestive enzyme activity, and accessibility. Starch gelatinization is constrained by endogenous NSCS, particularly cell wall NSPs and matrix proteins. The stability of the starch crystal structure is enhanced by the proteins and lipids distributed in the starch granule pores and channels. Endogenous polyphenols greatly inhibit digestive enzymes and participate in the cross-linking of NSPs in the cell wall space, which together constitute a physical barrier that hinders amylase diffusion. Additionally, the spatial entanglement of NSCS and starch under heat and non-heat processing conditions reduces starch accessibility. This review provides novel evidence for the health benefits of whole cereals.

The combined actions of the granule surface barrier and multiscale structural evolution of starch on in vitro digestion of oat flour

The digestive properties of oat-based food have garnered considerable interest. This study aimed to explore the internal and external factors contributing to different digestion properties of oat flour under actual processing conditions. Analysis of the ordered structure of oat starch revealed that an increase in gelatinization moisture to 60 % led to a decrease in crystallinity, R1047/1022 value, and helical structures content to 0, 0.48 %, and 1.45 %, respectively. Even when the crystal structure was completely destroyed, the short-range structure retained a certain degree of order. Surface structure observations of starch granules and penetration experiments with amylase-sized polysaccharide fluorescence probes indicated that non-starch components and small pores effectively hindered the diffusion of the probes but low-moisture (20 %) gelatinization substantially damaged this barrier. Furthermore, investigations into starch digestibility and starch molecular structure revealed that the ordered structure remaining inside the starch after high gelatinization delayed the digestion rate (0.028 min-1) and did not increase the content of resistant starch (7.10 %). It was concluded that the surface structure and non-starch components of starch granules limited the extent of starch digestion, whereas the spatial barrier of the residual ordered structure affected the starch digestion rate.

Effects of heat-moisture treatment on structural characteristics and in vitro digestibility of A- and B-type wheat starch

In this study, A- and B-type wheat starch granules (AWS and BWS) were separated and modified by heat-moisture treatment (HMT) with different moisture content (10 %-40 %). The effects of HMT on the structure characteristics and digestibility of raw/cooked AWS and BWS were investigated by SEM, FT-IR, XRD, DSC, TGA and NMR. SEM and FT-IR results showed that BWS was more sensitive to HMT than AWS. Interestingly, crystalline conformation of AWS and BWS changed from A type to A + V type after HMT, and the relative crystallinity (V-type) of starch increased to 2.7 % and 3.4 %, respectively. XRD and NMR results verified the formation of V-type crystalline structure. The resistant starch (RS) content of cooked starch was increased, especially for BWS (from 11.46 % to 28.29 %). Compared to the cooked starch, the RS content of raw AWS and BWS was affected by relative crystallinity and the size of starch granules. Furthermore, structure characteristics and digestion kinetics results indicated that the digestion rate of cooked AWS increased due to the deconstruction of starch chains, opposite to BWS (because of the more V-type crystals). The results enrich our understanding of the mechanism of digestion subjected to HMT by different grain sizes of the same wheat starch.

Regulation of multi-scale structures and retrogradation property of A- and B-type wheat starch granules with maltogenic α-amylase

Maltogenic α-amylase (MA) is widely used to modify starch for improving properties. In this work, A- and B-type starches were separated from wheat completely and submitted to MA hydrolysis. Firstly, research in morphological features (SEM) suggested that MA treatment did not destroy the granule integrity. Next, crystalline features from XRD and SAXS assay showed that MA treatment did not change the crystal form, but deceased crystalline sheet (dc) and amorphous sheet (da) thickness in both modified starches. And amorphous sheet was more severely destroyed at higher MA dosage than crystalline sheet. Then changes in molecule structure (HPAEC) showed that MA mainly acted on sides chains with degree of polymerization 12-24 in amylopectin for both starches, resulting in a reduce in peak, trough, and final viscosity obtained from RVA assay. At last, RVA and DSC assay showed that the short-term and long-term retrogradation were retarded in both modified starches. This range of techniques covered changes in multi-scale structures and retrogradation property resulted from MA treatment on both starches, which provided references for studying the changes in structures and properties of MA modified starch granules and provided an important method for retarding retrogradation of starchy foods without gelatinization processing.

Removing starch granule-associated surface lipids affects structure of heat-moisture treated hull-less barley starch

The effects of starch granule-associated surface lipids removal on hull-less barley starch structure formed by heat-moisture treatment were investigated. Removing surface lipids made the peak at 2θ of 13^° disappear and resulted in higher lamellar peak intensity after harsh treatment and a lower reduction in mass fractal dimension (from 2.49 to 2.43) and radius of gyration (from 24.3 to 24.0) when temperature increased from 100 to 120 °C at 20 % moisture. Treatment at 25 % moisture and 120 °C decreased relative crystallinity (from 15.73 % to 7.43 %) and Gaussian peak area (from 646.7 to 137.7) of native starch, and decreased relative crystallinity (from 14.24 % to 12.56 %) and Gaussian peak area (from 604.1 to 539.6) for starch without surface lipids. Different trends of change in lamellar thickness, linear crystallinity, peak temperatures, and enthalpy of gelatinization were observed among modified starches with increasing temperature and/or moisture content. These results demonstrate that removing surface lipids changes structure of heat-moisture treated starch.