Shear scission through extrusion diminishes inter-molecular interactions of starch molecules during storage

Assessing the impact of plasma-activated water-assisted heat-moisture treatment on the extrusion-recrystallization process of hausa potato starch

The study explored the plasma-activated water (PAW)-assisted heat-moisture treatment (HMT) on the structural, physico-chemical properties, and in vitro digestibility of extrusion-recrystallized starch. Native starch of hausa potatoes underwent modification through a dual process involving PAW-assisted HMT (PHMT) followed by extrusion-recrystallization (PERH) using a twin-screw extruder. The PHMT sample showed surface roughness and etching with a significantly greater (p ≤ 0.05) RC (20.12 %) and ΔH (5.86 J/g) compared to DHMT. In contrast, PERH-induced structural damage, resulting in an irregular block structure, and altered the crystalline pattern from A to B + V-type characterized by peaks at 17.04°, 19.74°, 22°, and 23.94°. DSC analysis showed two endothermic peaks in all the extrusion-recrystallized samples, having the initial peak attributed to the melting of structured amylopectin chains and the second one linked to the melting of complexes formed during retrogradation. Dual-modified samples displayed notably increased transition temperatures (To1 74.54 and 74.17 °C, To2 122.65 and 121.49 °C), along with increased RS content (43.76 %-45.30 %). This study envisages a novel approach for RS preparation and broadens the utilization of PAW in starch modification synergistically with environmentally friendly techniques.

Understanding effects of glutelin on physicochemical and structural properties of extruded starch and the underlying mechanism

This work studied effects of different amounts of rice glutelin (RG) on physicochemical and structural properties of extruded rice starch (ERS) and explored the underlying mechanism of interaction between rice starch and RG upon extrusion processing. The results showed that the addition of RG altered the pasting properties, improved the viscoelastic, and increased the water mobility of ERS. The weight loss of ERS decreased from 71.40 % to 62.61 %, while the degradation temperature increased from 290.48 °C to 296.25 °C as the RG content increased from 0 % to 12 %. The complex index of extruded starch-glutelin complexes significantly elevated from 10.40 % to 35.81 % when RG content increased from 6 % to 12 %. Fourier-transform infrared spectra confirmed that RG interacted with starch via Maillard reactions, and the binding strength between RG and starch was enhanced at a higher RG content. Furthermore, results of rheological property and chemical interactions demonstrated that hydrogen bonding, hydrophobic, and electrostatic interaction were formed between RG and starch during extrusion. In summary, the obtained results of this study can further enrich the theory of starch-protein interactions and show the possibility of RG applied in the extruded starchy foods.

Investigating the potential of slow-retrograding starches to reduce staling in soft savory bread and sweet cake model systems

The potential anti-staling property of starches with slow-retrograding amylopectin was studied in soft wheat bread and cake model systems. Normal rice, waxy rice, and wheat starches were processed by drum drying or extrusion, and native starch was used as a comparator. Extrusion processing causing amylopectin fragmentation can reduce intermolecular retrogradation of rice starch. Starches were incorporated into model breads and cakes as partial replacements for flour on a dry weight basis (3 and 6% for cakes, 5 and 15% for breads). Starches pregelatinized by extrusion had moderate molecular fragmentation, as indicated by RVA and HPSEC-MALLS-RI. Starches previously shown to have lower intermolecular retrograding amylopectin (normal rice, waxy rice) resulted in minor to moderate reductions in hardness and other textural properties as indicated by texture profile analysis (TPA) in breads and cakes upon storage for up to 12 wk. A higher degree of starch fragmentation is suggested to produce lower staling. Incorporation of normal and waxy rice starches resulted in softer breads and cakes than wheat starch, which could be attributed to the shorter external and internal amylopectin chains of rice starch. Higher inclusion (15%) of slow-retrograding waxy rice in the bread model system showed the most potential for anti-staling property.

On the role of the internal chain length distribution of amylopectins during retrogradation: Double helix lateral aggregation and slow digestibility

A structure-digestion model is proposed to explain the formation of α-amylase-slowly digestible structures during amylopectin retrogradation. Maize and potato (normal and waxy) and banana starch (normal and purified amylopectin through alcohol precipitation), were analyzed for amylose ratio and size (HPSEC) and amylopectin unit- and internal-chain length distribution (HPAEC). Banana amylopectin (BA), like waxy potato (WP), exhibited a larger number of B3-chains, fewer BS- and B_fp-chains and lower S:L and BS:BL ratios than maize, categorizing BA structurally as type-4. WP exhibited a significantly greater tendency to form double helices (DSC and ¹³C-NMR) than BA, which was attributed to its higher internal chain length (ICL) and fewer DP6-12-chains. However, retrograded BA was remarkably more resistant to digestion than WP. Lower number of phosphorylated B-chains, more S- and B_fp-chains and shorter ICL, were suggested to result in α-amylase-slowly digestible structures through further lateral packing of double helices (suggested by thermo-rheology) in type-4 amylopectins.