Physicochemical and structural properties of pregelatinized starch prepared by improved extrusion cooking technology

Dual modification of various starches: Synthesis, properties and applications

The problems associated with native starches (NSs) and single modified starches were stated in order to justify dual modification of various starches. Broadly, there are two types of dual modification, i.e., homogeneous dual modification and heterogeneous dual modification. The combination of two physical modifications, e.g., (extrusion/annealing); two chemical modifications, e.g., (succinylation/cross-linking) and two enzymes modification (α-amylase/pullulanase) falls under the former classification and the latter classification is the combination of two of each of the differently stated modifications, e.g., acetylation/annealing, extrusion/succinylation, and microwave-assisted phosphorylation, etc. The classification, synthesis, properties and applications of dually modified starches were discussed. There is an attempt to elucidate the problems of each of the single modification in order to justify dual modifications. In dual modifications, the order of reactions, the reaction conditions, the medium of reaction, and the botanical sources of the various starches are very important parameters.

Autoclaving and extrusion improve the functional properties and chemical composition of black bean carbohydrate extracts

Common beans (Phaseolus vulgaris L.) are rich in starch with a high content of amylose, which is associated with the production of retrograded and pregelatinized starch through thermal treatments. The purpose of this study was to evaluate the composition, morphology, thermal, functional, and physicochemical properties of carbohydrate extracts (CE) obtained from autoclaved (100 and 121 °C) and extruded (90, 105, and 120 °C) black beans. After evaluation of the functional properties, the CE from autoclaved beans at 100 °C for 30 min and 121 °C for 15 min 2×, and extruded beans at 120 °C and 10 rpm, were selected to continue the remaining analysis. Autoclaving treatments at 100 °C for 30 min and 121 °C for 15 min 2× showed a reduction of resistant starch by 14.4% and 26.6%, respectively, compared to dehulled raw bean CE. Meanwhile, extrusion showed a reduction in resistant starch of 54.2%. Autoclaving and extrusion treatments also decreased the dietary fiber content. Extrusion reduced almost entirely the content of α-galactooligosaccharides, in comparison to dehulled raw bean CE. The results showed differences in color and granule morphology. The onset, peak, and conclusion temperatures, transition temperature range, and enthalpy of autoclaved and extruded bean CE were lower than dehulled raw bean CE. The CE from autoclaved and extruded beans contain retrograded and pregelatinized starch, which could be incorporated in food products as a thickening agent for puddings, sauces, creams, or dairy products. PRACTICAL APPLICATION: Thermally treated black bean carbohydrate extracts are rich in starch, fiber, and protein. Because these extracts are already cooked, they can be added to products that do not require a thermal process such as puddings, sauces, creams, or dairy products, acting as a thickening agent.

Supramolecular structure of Artocarpus heterophyllus Lam seed starch prepared by improved extrusion cooking technology and its relationship with in vitro digestibility

Jackfruit seed starch (JFSS) was modified by an improved extrusion cooking technology (IECT), and the supramolecular structure, molecular weight, debranched chain length distributions, relative crystallinity (Rc), and amylose content, were studied. During IECT, the α-1.4-glycosidic bond in amylopectin was broken, which led to decreased radius of gyration (Rg), number-average molar mass (Mn), weight-average molar mass (Mw), long chains and Rc. The medium and short chains and PI (Mw/Mn) increased, while the amylose content hardly changed. The crystalline structure of JFSS was converted from A-type to V-type. Increasing the temperature and screw speed during the treatment significantly increased the medium and short chains and Rg, while it decreased the long chains, amylose, Mn, Mw, PI, and Rc. However, the opposite effect was observed when increasing the moisture content. The in vitro digestibility of JFSS was significantly improved after IECT, due to destruction of starch supramolecular structure according to principal component analysis.

Evaluation of the processing quality of noodle dough containing a high Tartary buckwheat flour content through texture analysis

A texture analysis method for evaluating the processing quality of noodle dough with a high Tartary buckwheat flour (BF) content was established. And then the improvement of wheat flour (WF), wheat gluten (WG), and pre-gelatinized Tartary buckwheat flour (PBF) for the processing quality of buckwheat noodle dough was compared quantitatively, and the mechanism was explored through the observation of gluten network in dough sheets. Texture results showed that the coefficients of variation of tensile strength and adhesiveness of dough sheets among 16 groups were 17.76% and 40.72%, respectively, and the intragroup variation coefficients were only 4.17% and 7.07%, respectively. The tensile strength of dough sheets was significantly positively correlated with gluten index of WF and WG. In addition, with the increase of WG and PBF addition, the tensile strength and adhesiveness of dough sheets showed a linearly increase trend. Furthermore, the gluten network in the dough sheets containing WF or WG with high gluten index distributed more evenly and compactly than that with low gluten index. The dough sheet with 9% PBF showed more uniform gluten network, compared with that without added PBF. Overall, texture analysis of dough sheet can be used to evaluate the processing quality of noodle dough containing 70% BF, and the WF and WG with high gluten index had better improvement than PBF.

Impact of Feed Moisture on Microstructure, Crystallinity, Pasting, Physico-Functional Properties and In Vitro Digestibility of Twin-Screw Extruded Corn and Potato Starches

The effect of extrusion feed moisture (FM) on the microstructure, pasting, physico-functional properties and in vitro starch digestibility (IVSD) of corn and potato starches was investigated using scanning electron microscopy (SEM), X-ray diffractometry and a rapid visco-analyser. Starches were extruded at 14, 18 and 22% FM with an extrusion temperature of 100 °C and a screw speed of 100 rpm. Extruded starches showed lower L* (lightness) values and higher a* and b* values than native starches. An increase in FM increased the L* values and decreased the a* and b* values of extruded starches. Extrusion resulted in complete destruction and reduced crystallinity of the starch structure. Extruded starches showed a lower water absorption index (WAI), peak viscosity (PV), final viscosity (FV), breakdown viscosity (BDV) and setback viscosity (SBV) with a higher water solubility index (WSI) and IVSD than native starches. FM showed a negative correlation with the WSI and IVSD and a positive correlation with the WAI, PV, FV, BDV and SBV of extruded starches.

A new pre-gelatinized starch preparing by gelatinization and spray drying of rice starch with hydrocolloids

Rice starch with hydrocolloids (pectin, xanthan gum, sodium alginate or ι-carrageenan) was gelatinized and subsequently spray dried to prepare pre-gelatinized rice starch (PRS) with hydrocolloids (PRS-H). The PRS-H displayed concave granular shape with amorphous structure, indicating rice starch in PRS-H was completely gelatinized. Cold paste viscosity of PRS-H was enhanced in comparison with that of PRS. Especially, xanthan and ι-carrageenan increased cold paste viscosity of PRS-H more than pectin and alginate did. Cold paste viscosity of physically mixed PRS and hydrocolloids (PRS+H), and flow behavior of hydrocolloids themselves as well as gelatinized starch-hydrocolloids without spray drying (GRS-H) indicated interactions existed between starch and hydrocolloids during the preparation. Swelling power, water solubility index, and dynamic viscoelastic properties of PRS-H were also adjusted by different hydrocolloids. These results showed that premixing hydrocolloids with starch before gelatinization in method of spray drying would be a suitable methodology for manufacture PRS with altered properties.

Optimized germinated soybean/cornstarch extrudate and its in vitro fermentation with human inoculum

The aim of this work was to optimise a soybean/cornstarch extrudate by adjusting a central composite design and to maximise a product with a high protein and resistant starch (RS) content by evaluating the indigestible fractions through in vitro colonic fermentation and production of short-chain fatty acids (SCFAs) with potential health benefits. According to the response surface analysis and RS maximisation results, an optimisation of the independent variables was obtained as follows: 32.5% feed moisture, 144 °C extrusion temperature and a proportion of 44% germinated soybean flour and 56% cornstarch. A product with a 2.11% expansion index, 6.25 N hardness, a glycaemic index of 49 and 12% resistant starch was obtained. The optimised extrudate showed a 36% indigestible fraction and high fermentability with respect to that of the lactulose control. Furthermore, the decrease in pH was inversely proportional to the production of SCFAs and the volume of gas generated. Acetic, propionic, and butyric acids were produced at a molar ratio of 62:27:11, while the highest SCFA concentrations were found 48 h after incubation. The RS of the optimised extruder was a viable substrate for in vitro colonic fermentation, suggesting that it is a good food source to produce SCFAs, which could exert an effect on the regulation of lipid and glucose metabolism.

Adsorption of Pregelatinized Starch for Selective Flocculation and Flotation of Fine Siderite

Pregelatinized starch (PS) was used for the selective flocculation and flotation of fine siderite in a carbonate-containing iron ore. With PS, the flotation of fine siderite was improved. The repulsive forces between fine siderite particles and the attractive forces between siderite and hematite or quartz were decreased after treatment with PS, indicating that the aggregation of siderite was enhanced and the aggregations of mixed minerals were weakened. An analysis of the changes in X-ray photoelectron spectra showed that coordination bonds were formed when PS was adsorbed on siderite and hematite. However, PS could not adsorb on quartz. Moreover, the molecular simulation showed that the main mechanism for PS adsorption on siderite was confirmed as a "tail model" with end -OH coordinated with Fe²⁺. The bridge connection of PS enhanced the flocculation of fine siderite. The flotation of fine siderite was also enhanced. For hematite treated with PS, the combination of coordination bond and hydrogen bond resulted in the "loop model" and "train model" as the main adsorption mechanisms of PS. The molecules covered the hematite surface and prevented the adsorption of the collector. The flotation of hematite was depressed. As a result, the selective flocculation and flotation of fine siderite were realized.

Extruded whole buckwheat noodles: effects of processing variables on the degree of starch gelatinization, changes of nutritional components, cooking characteristics and in vitro starch digestibility

The effects of processing variables on the degree of gelatinization (DG), changes of nutritional components, cooking characteristics and in vitro starch digestibility of extruded whole buckwheat noodles were investigated.

Modification of the digestibility of extruded rice starch by enzyme treatment (β-amylolysis): An in vitro study

The rate and extent of starch hydrolysis in the digestive tract impacts blood glucose levels, which may influence an individual's susceptibility to diabetes and obesity. Strategies for decreasing starch digestibility are therefore useful for developing healthier foods. β-amylase is an exo-hydrolase that specifically cleaves α-1,4 glycosidic linkages of gelatinized starches. In this study, starch granules were disrupted by extrusion under different feed moisture conditions, and then subjected to β-amylolysis. The degree of starch gelatinization increased with increasing feed moisture content during extrusion, leading to faster β-amylolysis. The hydrolysis of in vitro starch digestion study was reduced for extruded samples treated with β-amylase, which was attributed to an increase in resistant starch (RS) after β-amylase treatment. Indeed, X-ray diffraction (XRD) indicated that the crystalline structure in the extruded starch was either partially or fully lost after β-amylase treatment. Similarly, Fourier transform infrared (FTIR) analysis indicated there was a higher level of amorphous regions in the starch after β-amylase treatment. Overall, our results suggest that enzymatic treatment of extruded starch with β-amylolysis reduces the ratio of crystalline-to-amorphous regions, which increases the level of resistant starch, thereby slowing down digestion. These results have important implications for the development of healthier starch-based foods.