Physicochemical Property And Structure Study And Application Of Quinoa Flour And Starch

Three kinds of imports of Chenopodium quinoa(including black, red, white) and one homemade quinoa was used as raw material in this experiment, and four kinds of quinoa starches were prepared by the enzymatic method. The nutritional content, physicochemical properties including solubility and swelling capacity, retrogradation properties, freeze-thaw stability, thermal stability, in vitro digestibility and rheological properties of four kinds of quinoa were systematic analysed. Then the scanning electron microscope(SEM), a laser particle size analyzer, X- diffraction(XRD) and Fourier transform infrared spectrometer instrument(FTIR) were used to research the particle morphology, particle size distribution, crystal structure and the degree of polymerization of four kinds of quinoa. Based on nutritional assessment and properties of quinoa, quinoa-konjac nutritional powder was developed.Nutritional analysis showed that, compared with other common grains such as wheat, rice and millet, quinoa contains lower starch content(57.1%) and higher protein content(14.9%). Quinoa belongs to a high potassium and low sodium foods and can meet the daily needs of minerals of people. Besides, it is a good source of dietary fiber. The total phenol content of four kinds of quinoa ranged from 697 to 841 mg GAE / 100 g. The total phenolic content of yellow quinoa was the highest(841 mg GAE / 100 g), while red quinoa was the lowest(697 mg GAE / 100 g). The flavonoids content was consistent with the depth of four kinds of quinoa color. Besides, the four quinoa had a certain degree of hypoglycemic activity in vitro. White and yellow quinoa in had higher in vitro hypoglycemic activity than red and black quinoa. Amylose content of four kinds of quinoa starch was: black quinoa > white quinoa wheat > red quinoa > yellow quinoa.The solubility and swelling capacity, retrogradation and freeze-thaw stability of yellow quinoa were better than other three kinds of quinoa. Differential scanning calorimetry(DSC) analysis showed black quinoa had the highest pasting temperature. The peak temperature(Tp) of four kinds of quinoa flour ranged from 64.6 to 69.0℃, and the phase change enthalpy(△H) ranged from 6.3 to 6.8 J/g. The peak temperature(Tp) of four kinds of quinoa starches was in the range of 59.0- 61.8℃, phase change enthalpy(△H) was in the range of 8.8- 11.5 J/g.Rheological properties of quinoa starch test showed that four kinds of quinoa starches belong to false shaping non-Newtonian fluid, and shear-thinning degree increased with the concentration of starch. Shear structure recovery ability of quinoa starch was strong. It can return to the original structure quickly after cutting damage in high-speed shear. Among four kinds of quinoa starch, rheopexy value of yellow quinoa was the maximum. The storage modulus(G’) and loss modulus(G’’) increased with the concentration of starch. It indicated that the interaction between starch molecules were enhanced to form a more firmly gel network structure. During the scanning process with temperature elevated from 30 to 100℃, G ’ and G’ have increased first and then decreased, and the higher amylose content, the greater corresponding peak modulus G’max and G’’max. Besides, quinoa has fast digestibility. When digestion process completed, the digestive hydrolysis rate of four kinds of quinoa flour was proportional to starch content, and the digestive hydrolysis rate of four kinds of quinoa starch was inversely proportional to the amylose content. Yellow and red quinoa starch have more rapidly digestible starch, while black and white quinoa have more slowly digestible starch and resistant starch content.SEM and laser particle size analysis showed that the diameter of the four kinds of quinoa starch granules ranged from 0.7 to 2.5 μm, and particle morphology showed a polygonal structure. D95 value of black, red, white quinoa starch were less than 2.5 μm, indicating the starch granules of three kinds of quinoa were more concentrated. Quinoa starch performed A-type crystalline by X- diffraction analysis, with the same type of typical cereal starch. And the crystallinity of four kinds of quinoa starch were 25.8%, 26.5%, 25.3% and 34.3% respectively. Infrared characteristic absorption peak of quinoa starch conforms to the characteristic absorption peaks of starch.With quinoa flour as the main raw material, adding an appropriate amount of konjac powder and whole milk powder, the quinoa-konjac nutritional powder was developed. The optimum parameters of quinoa-konjac nutritional powder were: baking temperature of 120 ℃, baking time of 30 min, particle size of quinoa flour of 91 mesh sieve, click the add formula amount, the quinoa flour addition was 53.8%, konjac flour addition was 6.5%, milk powder addition was 12.9%, sugar addition was 26.8%. According to a preferred production process, the prepared quinoa-konjac nutritional powder contains high nutritional value. It was rich in dietary fiber and protein, but had low fat and sodium content. In addition, physicochemicalindicators and microbial indicators of the nutritional powder were in line with national standards.