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The effects of carboxymethyl chitosan (CMCS) on the pasting, rheological, and physical properties of yam starch (YS) were investigated. Different concentrations of CMCS were added to the YS, followed by heating paste treatment at 95 °C. Then the blends were subjected to the determination of physicochemical, rheological properties and in vitro digestibility. Our results showed that CMCS reduced the paste viscosity of YS and the addition of CMCS did not effectively inhibit the movement of water molecules. Rheological measurements results showed that YS-CMCS blends exhibited shear thinning behavior. Furthermore, because of the presence of amylose inhibited the swelling of the starch and leaching of amylose, the addition of CMCS had no significant difference between solubility and swelling power of YS., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Starches from two yam species, viz. Dioscorea alata and Dioscorea esculenta were subjected to heat moisture treatment (HMT) with 20 and 30% moisture at 110 °C for 3 h and annealing (ANN) at 1:2 and 1:4 starch to water ratio and 50 °C for 24 h, and their effect on functional, thermal, pasting, morphological, and rheological properties, and in vitro digestibility was investigated. HMT and ANN modifications decreased the swelling and solubility of the starches compared to the native starches. D. alata showed a higher amylose leaching than D. esculenta due to its higher amylose content. An increase in the transition enthalpy (∆H) after ANN and a decrease in ∆H after HMT were observed. ANN modification increased the setback viscosity, while HMT modification decreased the setback viscosity compared to the corresponding native starches of both the species. Both HMT and ANN decreased the peak viscosity, hot paste viscosity and breakdown viscosity of the starch granules. The steady shear and dynamic rheological properties of the starch paste at 25 °C were evaluated by the power-law model and indicated non-Newtonian flow properties with shear-thinning behaviour. ANN modified starch exhibited a greater impact than HMT on the rheological properties, indicating stronger molecular interactions in the pastes. An increase in slowly digestible and resistant starch with a decrease in rapidly digestible starch was noticed after HMT and ANN modifications. [ABSTRACT FROM AUTHOR]

Extrusion is a method of processing that changes the physicochemical and rheological properties of starch and protein under specific temperature and pressure conditions. In this study, twin-screw extrusion technology was employed to prepare yam starch–soy protein isolate complexes. The structure and properties of the complexes and their effects on the quality of dough were studied. The results showed changes in the X-ray diffraction, rheology, and in vitro digestibility of the complexes. The extruded starch–protein complex formed an A+V-type crystal structure with the addition of soy protein isolate. A small amount of soy protein isolate could improve the complex's viscoelasticity. As the content of soy protein isolate increased, the content of slow-digesting starch and resistant starch in the complexes increased, and the digestibility decreased. The microstructure of the dough indicated that the network structure of the puffed yam starch–protein complex dough was more uniform than that of the same amount of puffed yam starch. The moisture distribution of the dough showed that with the addition of extruded flour, the closely bound water content of the dough increased, and the weakly bound water content decreased. The hardness, gumminess, chewiness, and resilience of the dough decreased. In conclusion, extruded starch–protein complexes can improve dough quality and provide technical support for the broad application of yam. [ABSTRACT FROM AUTHOR]

This paper investigated the effects of twin-screw extrusion treatment on the formation, structure and properties of yam starch-gallic acid complexes. Yam starch and gallic acid were extruded. The microstructure, gelatinization characteristics, and rheological properties of the samples were determined. The microstructure of extruded yam starch-gallic acid complexes presented a rough granular morphology, low swelling, and high solubility. The X-ray diffraction analysis showed that the extruded yam starch-gallic acid complexes exhibited A + V-type crystalline structure. Fourier transform infrared spectroscopy results showed that the extrusion treatment could destroy the internal orderly structure of yam starch, and the addition of gallic acid could further reduce its molecular orderliness. Differential scanning calorimetry analysis showed a decrease in the enthalpy of gelatinization of the sample. Dynamic rheological analysis showed that the storage modulus and loss modulus of the extruded yam starch-gallic acid complexes were significantly reduced, exhibiting a weak gel system. The results of viscosity showed that extrusion synergistic gallic acid reduced the peak viscosity and setback value of starch. In addition, extrusion treatment had an inhibitory effect on the digestibility of yam starch, and enhanced the interaction of gallic acid with yam starch or hydrolytic enzymes. Therefore, extrusion synergistic gallic acid has improved the structure and properties of yam starch-related products, which can provide new directions and new ideas for the development of yam starch. • The addition of gallic acid facilitated the formation of V-type complexes from EYS. • The addition of GA reduced the viscosity of the EYS-GA system. • With the addition increase of GA, the RS of the EYS-GA increased. [ABSTRACT FROM AUTHOR]

Yam tubers (Dioscorea alata) are a non-traditional starch source that could be used as food ingredient. The stability of yam starch pastes (6/100 g suspension) submitted to different pH conditions during gelatinization and the effect of hydrocolloids addition (guar and xanthan gums) on starch syneresis under refrigeration were analyzed. Changes in pH (3, 5, 6) or the addition of gums (0.1–0.5/100 g suspension) did not affect the starch gelatinization temperature nor the gelatinization enthalpy as determined by differential scanning calorimetry. Rheological behavior was characterized by amylograph profiles and oscillatory rheometry. Amylograms showed that yam starch pastes maintained a high viscosity under heat treatment and mechanical stirring in neutral to slightly acidic conditions. Brabender viscosity increased when gums were added; the effect of guar gum on viscosity was more marked than that of xanthan gum. During refrigerated storage exudate production was observed of pastes without gums. Xanthan gum, at a concentration of 0.5/100 g suspension, showed higher effectiveness than guar gum to reduce exudate production during refrigerated storage. The addition of hydrocolloids could allow yam starch to be used in foods requiring low temperatures. [Copyright &y& Elsevier]