This study investigated the effects of different extrusion temperatures and feed moisture contents on starch structure, functional components, and physicochemical properties of extrusion modified black highland barley flour. An X-ray diffractometer, a Fourier transform infrared spectrometer, a colorimeter, a rapid viscosity analyzer, and a dynamic rheometer were used to characterize the ordered structure of starch and physicochemical properties of the extrudate. Changes in functional components were examined, and the correlations between starch structure, functional components, and physicochemical properties were explored. The results showed that increasing the extrusion temperature significantly increased the degree of gelatinization and the short-range order of starch in extrudates, while decreasing the long-range order of starch. Extruded flour produced at high temperatures had lower polyphenol and β-glucan contents. Moreover, it had lower pasting characteristic values such as trough viscosity, final viscosity, and setback value, and higher water absorption index, swelling power, peak viscosity, and breakdown value. At lower extrusion temperatures, the degree of order of starch molecules decreased more slowly, more polyphenols were retained, and the contents of soluble dietary fiber and β-glucan increased significantly. Increased feed moisture content significantly reduced specific mechanical energy (SME), decreased storage and loss moduli, and resulted in weaker elastic solid-like behavior. The correlation analysis indicated that the extrusion temperature was highly significantly positively correlated with gelatinization degree, insoluble dietary fiber content, peak viscosity, and breakdown value, but highly significantly negatively correlated with polyphenol and β-glucan contents as well as relative crystallinity; feed moisture content was extremely significantly negatively correlated with SME. The above findings provide a theoretical basis for the industrial production of extruded black highland barley flour and the development of functional foods based on it.

The volatile composition of whole wheat flour and quick-frozen pre-fried whole wheat Youtiao before and after different reheating methods was analyzed comparatively using electronic nose and headspace solid phase microextraction combined with gas chromatography and mass spectrometry (HS-SPME-GC-MS). Meanwhile, the effect of different reheating methods on polyphenolic contents and antioxidant properties of quick-frozen pre-fried Youtiao was explored. It was found that different characteristic flavor substances were produced after different reheating methods. During the pre-frying and reheating processes, some flavor substances in whole wheat flour disappeared. The relative peak area of aldehydes in quick-frozen pre-fried Youtiao was 50%, which indicates that aldehydes may be the major flavor component of Youtiao. Among the three reheating methods evaluated, refrying produced the largest number of aldehydes and heterocyclic compounds. The contents of acids and hydrocarbons increased in the microwaved sample, and the highest content of aldehydes mostly non-flavor-active saturated aldehydes was observed in the steamed sample. Moreover, all three reheating processes reduced the content of polyphenols in Youtiao, and the loss of polyphenols in pre-fried and reheated Youtiao was ranked in decreasing order of steaming > microwave > pre-frying > refrying, while the opposite was observed for the antioxidant properties.

The effects of addition of different amounts (10%, 20%, 25% and 30%) of high amylose corn starch (m/m, based on buckwheat flour) on the structure, cooking quality and digestive characteristics of extruded buckwheat noodles were explored. The results showed that the diameter and gelatinization degree of extruded noodles decreased with increasing addition of high amylose corn starch. The X-ray diffraction results showed that noodles with added high amylose corn starch exhibited the typical B-type peaks of amylose not completely gelatinized in addition to V-type crystallization peaks. Thermodynamic properties also indicated partial gelatinization of amylose. After addition of high amylose corn starch, the color of noodles became lighter and brighter, the optimal cooking time was shortened, and the cooking loss percentage increased from 9.90% to 12.43%. When the addition of high amylose corn starch was 25%, the noodles began to break. The hardness of noodles increased from 2105.709 to 3680.401 g, and the elasticity decreased from 0.961 to 0.866. The results of scanning electron microscopy (SEM) showed that with increasing amount of added high amylose corn starch, cracks appeared in the dense structure of noodles gradually, and more starch grains were not completely gelatinized in the crosssection of noodles. In vitro starch digestion experiments showed that with increasing addition of high amylose corn starch, the rate of starch hydrolysis and predicted glycemic index (pGI) decreased, and resistant starch (RS) content increased. The pGI of extruded buckwheat noodles decreased from 74.28 to 66.31 and RS content increased from 34.43% to 47.86% after addition of 30% high amylose corn starch.

In this study, high-internal phase Pickering emulsions (HIPPEs) were prepared by high speed shearing using quinoa protein isolate (QPI) as interfacial particles, corn oil as dispersed phase, and beef bone broth or beef powder solution as continuous phase, and their rheological properties, thermodynamic properties, color and volatile components were analyzed. The results showed that all 5 emulsions exhibited obvious shear thinning behavior of a pseudoplastic fluid, and their apparent viscosities decreased with the increase in shear rate. However, at the same shear rate, the emulsion with fish gelatin added to the aqueous phase showed the highest viscosity, which was more conducive to simulating the sticky taste of beef tallow. Addition of fish gelatin or starch into the aqueous phase significantly increased the storage modulus (G’), loss modulus (G”) and viscoelastic properties of Pickering emulsions, and the emulsion with fish gelatin had better viscoelastic properties and rheological properties closer to those of beef tallow than the emulsion with starch. Adding fish gelatin to the aqueous phase containing beef bone broth significantly increased the brightness and whiteness of Pickering emulsion(P < 0.05), whereas the opposite effect was observed when the aqueous phase was beef powder solution. Moreover, adding starch or fish gelatin into the aqueous phase could significantly increase the melting point of quinoa protein-stabilized Pickering emulsion. The results of gas chromatography-mass spectrometry (GC-MS) showed that using beef bone broth as the aqueous phase increased the contents of flavor components such as hexanal, 4-isopropyl toluene, and pentadecylene, imparting the emulsion with part of the flavor of beef tallow. The composition of flavor components in the emulsion with beef powder solution was similar to that in the emulsion with beef bone broth, but the content of flavor compounds was lower in the emulsion with beef powder solution than with beef bone broth. In summary, quinoa protein-stabilized Pickering emulsion with an aqueous phase containing bovine bone broth and fish gelatin showed similar rheological properties, appearance and volatile flavor composition to beef tallow, and it possessed higher melting point, showing its potential and sustained research value in simulating saturated fat.