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In this study, the effect of konjac glucomannan (KGM, 0–5%) on the structure, physicochemical properties, and in vitro digestibility of extruded yam starch (EYS) was investigated. The EYS became rougher on the surface and the particle size increased as observed using scanning electron microscopy and particle size analysis. X-ray diffraction and Raman results revealed that the relative crystallinity (18.30% to 22.30%) of EYS increased, and the full width at half maxima at 480 cm−1 decreased with increasing KGM content, indicating the increment of long-range and short-range ordered structure. Differential scanning calorimetry and rheological results demonstrated that KGM enhanced thermal stability and the gel strength of EYS due to enhanced interaction between KGM and YS molecules. Additionally, a decrease in the swelling power and viscosity of EYS was observed with increased KGM content. The inclusion of KGM in the EYS increased the resistant starch content from 11.89% to 43.51%. This study provides a dual-modified method using extrusion and KGM for modified YS with high thermal stability, gel strength, and resistance to digestion.

This study was conducted to modify yam starch to create slowly digestible starch (SDS) by the acid method to create the highest SDS starch on the basis of evaluating the effect of citric acid concentration (15 – 45%), temperature (37.5 – 52.5oC) and hydrolysis time (1.5 – 10.5 h) was performed based on the multivariable model by CCD method, and the starch content SDSmax was the dependent response. The results showed that the quadratic model obtained is significant (p < 0.05), the reliability of the model R2 = 0.979 showed that the built regression model is suitable for the data set whether 97.9%. As a result, the highest SDS starch content is 18.052% at an acid concentration of 40,009%, a temperature of 39.962oC and a hydrolysis time of 8.933 h. Solubility increases due to temperature, swelling increases in the range temperature of 50 – 70oC and decreases from 70 – 90oC; the viscosity of starch tends to decrease after denaturation.

The potential uses of starches and flours depend on their physicochemical and functional properties. The chemical composition, functional and pasting properties of starch and flours obtained from some newly developed yam varieties from the Crops Research Institute (CRI), Ghana were evaluated, and compared with the existing local varieties. The results showed that the physicochemical and functional properties varied among the varieties studied. The CRI varieties were grouped in a principal component analysis as moisture (afase pa), amylose content (ahodenfo, soanyinto, afase biri), high starch content, bulk density and water absorption capacity (kukrupa, Mankrong pona, CRI pona). Starch pasting characteristics showed that Mankrong pona, CRI pona and afase pa exhibited stable pastes whereas afase biri, Mankrong pona and, afase soanyinto could be utilized for high-temperature processing. Overall, the new CRI varieties showed considerable functionalities that could be explored for potential food and industrial applications as compared to the existing local varieties.

In order to study the effect of oat β-glucan on yam starch, the yam starch/oat β-glucan blends were prepared by rapid visco analyzer. The gelatinizing properties, thermal properties, rheological properties and digestive properties of the blends were investigated. The gelatinization analysis showed that oat β-glucan could reduce the viscosity and regeneration value of yam starch, and inhibit the short-term regeneration of yam starch. The results of thermal properties showed that the gelatinization enthalpy ΔH of blends was significantly decreased with the addition of oat β-glucan (P

In this study, yam starch was extracted from yam tubers using water and used for preparation of glycerol plasticized and titanium dioxide (TiO2) nanofiller reinforced films. The effects of TiO2 nanofiller concentration on the properties of the film were studied. Concentration of TiO2 nanofiller affects the mechanical and morphological properties of the film. The tensile strength and percent elongation were modeled and optimized by a three-variable, three-level Box-Behnken Design (BBD) using Response Surface Methodology (RSM). An optimal tensile strength (4.68 MPa) and elongation percentage (32.96%) were observed with the model at starch (3.60 g), glycerol (1.40 mL) and TiO2 nanofiller concentration (0.35 g) for the reinforced starch film. The experimental tensile strength and elongation percentage at break were 4.45 MPa and 37.77%, respectively. This shows the model can reasonably predict the optimum tensile strength and elongation of the current biofilms. Moreover, the biodegradability and antimicrobial properties of biofilms prepared at optimum tensile strength and elongation percentage were conducted. About 29% of the initial weight of the film was decomposed in the soil in the first 15 days. Moreover, an E. Coli inhibition zone of 3.25 mm was observed for the TiO2 reinforced films.

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.

The current consumer demand for fresh food and the interest in caring for the environment have driven the development of biodegradable film packaging to replace synthetic films to preserve the integrity of food. The objective of this work was to evaluate the effects of starch modifications (oxidized, cross-linked, and dual: oxidized/cross-linked), starch concentration (1 and 2%), and glycerol concentration (5 and 15%) on water vapor permeability (WVP), mechanical properties (tensile strength and elongation), optical, and structural properties of films based on “hawthorn” yam starch. The WVP of the films was 4.4 × 10−10 to 1.5 × 10−9 g/m∗s∗Pa, where the films with oxidized yam starch showed a 58.04% reduction concerning the native starch. The tensile strength of oxidized yam starch films showed a decrease of 17.51% with an increase in glycerol concentration. For the 1% starch concentration, elongation increased by 17.03% when the glycerol concentration was increased from 5 to 15%. Modification of starch, starch concentration, and glycerol have a significant effect on the barrier, mechanical, physical, and structural properties of films made with yam starch, where films made with oxidized yam starches at a concentration of 1% starch and 5% glycerol showed the best responses of the properties evaluated.

Heat-moisture treatment, a physical modification method of starch, causes changes in the internal structure of starch and thereby produces resistant starch (RS). In this study, the heat-moisture treatment conditions (moisture content, heating temperature, and incubation time) was optimized to maximise the RS contents of the treated sweet potato and yam starches, using the Box-Behnken design and response surface analysis. The predicted maximised RS content of the treated sweet potato starch (43.9%) was obtained under optimal conditions of 34.76% moisture content, heating temperature of 100.11oC, and incubation time of 6.01h; the predicted maximised RS content of the treated yam starch (36.8%) was obtained under optimal conditions of 30.06% moisture content, heating temperature of 109.68oC, and incubation time of 6.59h using a quadratic model within the range of various process variables. The experimental RS contents of the treated sweet potato and yam starches obtained under optimal treatment conditions were 42.4% and 35.4%, respectively; this confirms that the models were valid and adequate because the predicted data and experiment data did not differ significantly. The results also indicate that the RS contents of the treated sweet potato starch were significantly higher than that of the treated yam starch. As a result, both starch structure and treatment conditions were determined to significantly affect the formation of RS in the heatmoisture treated starches.

The starches obtained from two different yam residues, which were treated with alkali(starch-A) or enzyme (starch-E), were studied and compared with yam starch isolated using ordinary method (starch-O) for morphological, crystalline pattern, thermal, and pasting properties. The results revealed that the amylose content of three starches ranged from 19.47 to 22.17%. The granule surfaces of starch-A and starch-E were as smooth as that of starch-O. The crystalline pattern of the three starches was a C-type. The transition temperatures (To, Tp and Tc) varied from 70.11 to 73.64, 79.23 to 81.74, and 84.30 to 86.65 ºC, respectively. The starch-E showed the highest Δ Hgel, followed by the starch-A, while it was lowest for the starch-O. According to the viscosity measurement, starch-O had the lowest pasting temperature, highest peak viscosity and breakdown viscosity, which were contrary to those of starch-E.