Oleogelation is one of the most potential technologies to prepare plastic fats with zero trans-fatty acid and low saturated-fatty acid content. This process fabricates oleogels with thermo-reversibility and solid-like behaviors under different processing conditions (e.g., heating and stirring, or templated dehydration) after addition of an oleogelator to vegetable oils. Natural waxes have been demonstrated to be the most efficient crystalline oleogelators by virtue of their low price, easy accessibility and use at low concentrations for the preparation of oleogels with good texture. Herein, the fabrication technologies for oleogels based on natural waxes of different composition are systematically reviewed, with a focus on the factors affecting the crystallinity of wax-based oleogels, and the advantages and applications of wax-based oleogels are briefly described. Furthermore, the challenges and future trends in the development of natural wax-based oleogels in the industrial production of special oils and fats for foods are discussed.

In order to develop a rapid and efficient method for the industrial production of rice protein-glucose conjugates, rice protein was extruded and then subjected to the Maillard reaction with glucose. Herein, rice protein was extruded at different temperatures (80, 90, 100, 110, 120 and 130 ℃) and then conjugated with glucose for 30 minutes at pH 10.5. We analyzed the effect of different extrusion temperatures on the functional properties (solubility, emulsification activity index (EAI) and emulsion stability index (ESI)) and structural properties of extruded rice protein and glucose (ERPG) conjugates and characterized ERPG conjugates using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Compared to native rice protein and glucose (NRPG) conjugate, the degree of glycosylation (DG) of ERPG conjugate prepared with rice protein extruded at 90 ℃ was the highest, and the solubility of ERPG conjugates prepared with rice protein extruded at 90–120 ℃ decreased. The EAI, ESI and surface hydrophobicity of ERPG conjugates prepared with rice protein extruded at 80–90 ℃ increased, while those of ERPG conjugates prepared with rice protein extruded at 100–130 ℃ slowly decreased. The FTIR results showed that ERPG conjugate had higher contents of α-helix, β-turn and random coil and a lower content of β-sheet than NRPG. The SDS-PAGE indicated that the protein was aggregated into larger particles by extrusion. Under SEM, ERPG conjugates exhibited more disordered structure with irregular fragments.

In order to improve the quality of pea protein-based meat analog, this study investigated the effect of interaction between sodium carboxymethyl cellulose (CMC) and protein on the quality of extruded pea protein products. CMC and pea protein were employed as raw materials to prepare protein-based meat analog by high-moisture extrusion (HME). Next, the effects of CMC contents (0%, 2%, 4%, 6% and 8%) on the textural properties, color, microstructure and protein-protein interaction forces of meat analog were explored. The correlation of secondary structure content and protein-protein interaction forces with quality attributes (textural properties and color) was established. The results showed that the main interaction force was disulfide bonds. Compared with meat analog without CMC, the addition of 4% CMC promoted the formation of disulfide bonds and increased the hardness of meat analog by 95%. Meanwhile, pea protein-based meat analog exhibited a smooth and homogeneous surface. It was also found that the random coil content increased, and was correlated with higher lightness, indicating that CMC could improve the quality of pea protein-based meat analog.

The retrogradation of rice starch is the major factor that restricts its application. Recent studies have suggested that extrusion combined with glutelin has an obvious inhibitory effect on the retrogradation of rice starch. This study was executed in order to clarify the influence of extrusion parameters including screw speed, extrusion temperature, raw material moisture content and mass ratio of rice starch to glutelin on the retrogradation properties of rice starch-glutelin mixed system. Furthermore, how extrusion treatment could delay the regeneration of the mixed system was analyzed using a rapid viscosity analyzer (RVA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, low-field nuclear magnetic resonance (LF-NMR), scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM) and a rheometer. The results showed that the most pronounced retarding effect on the retrogradation of the mixed system was observed when the screw speed was 300 r/min, the extrusion temperature was 90 ℃, the moisture content of the raw material was 34%, and the starch/protein ratio (material ratio) was 91:9. Extrusion treatment significantly decreased the peak viscosity, disintegration value and retrogradation value of the composite system from (3005.00 ± 25.00), (1193.00 ± 6.00), and (164.33 ± 3.51) cP to (429.00 ± 5.00), (213.00 ± 3.00) and (27.05 ± 0.14) cP, respectively (P < 0.05), and reduced the relative crystallinity from (20.18 ± 0.13)% to (2.17 ± 0.43)%. Moreover, the endothermic peak of the mixture disappeared, and the ratio between the peak intensities at 1047 and 1022 cm^-1 in the infrared spectra was decreased significantly to 0.43 ± 0.08 (P < 0.05). After extrusion treatment, the microstructure became more uniform and compact, the water retention property was enhanced, the shear stress was decreased, the hysteresis loop area was increased, and the storage modulus (G’) and the loss modulus (G”) were decreased, indicating good resistance to retrogradation. The results of this study provide a theoretical reference for the application of extrusion treatment in delaying the retrogradation of rice starch–glutelin mixed system.

In order to investigate the synergistic effect of extrusion and polyphenol treatment on the physicochemical and structural characteristics of corn starch (CS), four polyphenols (ferulic acid, gallic acid, quercetin and curcumin) were selected in this study. The solubility, swelling power, pasting properties, thermal characteristics, antioxidant capacity, in vitro digestibility and crystal structure of the extruded CS with polyphenols were evaluated. The results showed that extrusion combined with polyphenol treatment resulted in an increase in the solubility, swelling power and pasting temperature of CS, and a decrease in the gelatinization enthalpy, peak viscosity and setback value, as well as a significant improvement in the scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation and anti-digestive properties. The binding of polyphenols to CS was dominated by hydrogen bonding during the extrusion process, leading to a decrease in the short-range orderliness of CS and eventually the formation of a special V-shaped crystal structure. After the combined treatment, the structure of CS became denser as observed by scanning electron microscope (SEM). This study provides theoretical guidance for the application of polyphenols in extruded starch-based functional foods.

Frozen pasta products have been ever increasingly favored in recent years, because of their convenience. Wheat starch is one of the most important components of buns, noodles, and cookies in the staple and leisure foods. The performance and quality of starch-based foods can depend seriously on the processing of wheat starches. Furthermore, starch-based foods easily lose water to be hard in the storage of retrogradation, indicating reduced elasticity. Therefore, it is very necessary to enhance the structure and properties of wheat starch. Starch can also be often modified by physical, chemical, biological and composite methods. Among them, physical modification has been widely used to modulate the properties of starch using hydrophilic colloids, due to their environmental friendliness, excellent performance and lower energy. Fortunately, the curdlan can be expected to compound with the starch for better functional properties, due to the excellent resistance to freeze-thaw stability and dehydration, water-holding, extreme stability, and emulsifying properties. In addition to being a prebiotic, curdlan can also improve the gastrointestinal health. The extrusion can be used as a biochemical reactor to promote the combination of wheat starch and curdlan, particularly for the high yield, easy operation, high degree of integration, and high temperature. The reason is that the high pressure, high shear and hydration can be generated to significantly change the structure and physicochemical properties of starch during operation. The complexes of curdlan and wheat starch can then be prepared to change the physicochemical properties of starch. The retrogradation and syneresis of wheat starch during freezing have been two of the most important limiting steps in the development of pasta products. This study aims to explore an effective way to inhibit the retrogradation and syneresis of wheat starch gels during freeze-thaw cycles. The composites with different concentrations of curdlan-wheat starch were investigated in the extrusion system. The effects of curdlan addition on the structural properties and freeze-thaw stability of wheat starch were analyzed using differential scanning calorimetry, X-ray diffractometry, and Fourier infrared spectrometry. In addition, the binding mechanism of curdlan-wheat starch composites in the extrusion field was revealed by combining the chemical reagents, Texture Analyzer and Scanning Electron Microscope. The results showed that the retrogradation of curdlan-wheat starch composites decreased and then increased with the increasing concentration of curdlan, while the syneresis rate showed a trend of decreasing and then increasing. The freeze-thaw stability of wheat starch was significantly improved to markedly inhibit the retrogradation with the addition of 0.6% curdlan in the extrusion system. The pasting temperature of wheat starch increased with the addition of 0.6% curdlan, compared with extruded starch. There was a decrease in the relative crystallinity, short-range ordering, and iodine binding of wheat starch, where the recrystallization of amylose was suppressed. Texture Analyzer and Scanning Electron Microscope revealed that the curdlan-wheat starch composites were dominated by the hydrogen bonding and weak electrostatic interaction forces in the extruded system. Furthermore, the curdlan-wheat starch composites presented a more intact and dense structure, indicating better freeze-thaw stability. The retrogradation was also effectively inhibited. The finding can provide a strong reference to produce wheat starch-based foods with resistance retrogradation and low syneresis using an extrusion process.

The properties of starch are determined by its own multiscale structure. Appropriate modification has also been adopted to regulate its properties in the multiscale structure of starch. Extrusion processing can be expected to apply in the food manufacturing industry, due to its continuous production, easy operation, green environmental protection, and safety. The mixing, stirring, crushing, shearing, and thermal effects generated by extrusion can be used to destroy the original structure of starch, and then induce the starch molecules for the new structure and properties. Among them, polyphenol has been added into the starch system as small molecules with physiological activity function in recent years. The hydrophilicity of starch molecular, hydrogen bond and van der Waals force interacted to promote the evolution of starch multi-scale structure for better properties. The polyphenol-starch-based foods have also been applied to increase the nutritional properties of foods. New functional foods can be produced to prevent and treat diseases, such as hyperglycemia. The polyphenols can dominate the structure of rice products and the product properties. This study aims to investigate the functional and structural properties of quercetin (Q) on the formation of complexes of rice (R) under the extrusion field. Q was also added (0-10%) into the rice. Scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), rapid viscosity analyzer (RVA), differential scanning calorimeter (DSC), and Ultraviolet visible spectrophotometer were carried out to characterize the structural properties. Furthermore, a systematic investigation was implemented to explore the effects of Q on water solubility index (WSI), water absorption index (WAI), and particle size of the complexes. The experimental results showed that the relaxation time of T₂₃ was advanced significantly when the Q concentration was 4%. The starch crystal structure was damaged by extrusion, compared with the R, thus leading to the WAI and WSI of ER increased significantly (P<0.05). The DSC results showed that the heat absorption peak outstandingly disappeared in the range of 57.88-76.39 ℃. The crystallinity of starch was destroyed to depolymerise the double-helix orderly arrangement structure. The FTIR results showed that the characteristic absorption bands of benzene ring bond stretching appeared in 1 519.59 and 1 320.15 cm⁻¹. The XRD results showed that a new crystal structure appeared near 27.4° with the addition of Q, and the relative crystallinity increased from 8.31% to 16.81%. Meanwhile, the smaller particle size of E-QR was obtained, compared with the ER. The morphological results showed that the Q was attached to the surface of the complex, indicating more three-dimensional and compact particles. The iodine binding capacity showed that the Q inhibited the recrystallization of starch, and then delayed the regeneration of amylose, compared with the ER. The setback of E-4% QR decreased by 23.16%. In summary, the hydroxyl group of Q was tightly bound to starch via hydrogen bonding. The recrystallization of starch was inhibited to promote molecular rearrangement, thus leading to the modified structural and functional properties of starch. This finding can provide a theoretical basis for the development of new rice products.