Effects Of Wheat Farina Addition On Noodle Quality And Starch Digestibility

Dried noodles,as one of the traditional staple foods in China,are mainly made of common wheat flour.With the development of intelligent and technological industrialization,in order to achieve good steaming quality of dried noodles,the industry often uses refined white wheat flour with high processing precision and single nutritional composition as raw material,which leads to the increase of refined grain starch content in dried noodles and increases the risk of obesity and type II diabetes with long-term consumption.In order to meet consumer demand for nutritious and healthy noodles,low glycemic index(GI)noodles have become a hot topic of current research.Recent studies have shown that the plant cell wall is an effective physical barrier to enzyme-substrate contact,but little research has been reported on the endosperm cell wall of wheat flour.In order to systematically study the changes of wheat endosperm cell wall from raw materials to products,this project selects wheat farina with large particle size as the research object to clarify the integrity of wheat farina endosperm cell wall and its influence on the in vitro digestion of starch;further investigate the influence of mixing wheat farina and wheat flour on the dough and dried noodles quality,and reveal the influence of adding wheat farina on the digestive characteristics of dried noodles;on this basis,further investigate On this basis,the influence of the key processes of noodle processing on the endosperm cell wall integrity of wheat farina will be further investigated.The completion of this project can provide a new research direction and theoretical support for the development and application of wheat farina.First,the study of wheat farina with different particle sizes showed that:component-wise,the starch content,protein content,gluten solubility index and sedimentation value of the wheat farina showed a significant decrease with increasing particle size;while the dietary fiber content of the larger particle size wheat farina(4.11%)was significantly higher than that of wheat flour(2.55%).Microstructurally,the wheat farina mainly existed as endosperm agglomerates,and the endosperm cell wall wrapped the starch and protein,so that the starch and protein particles could hardly be observed;microscopic observation showed that the integrity of the endosperm cell wall of wheat farina gradually decreased with decreasing particle size;the intact endosperm cell wall of wheat farina could be observed before and after steaming treatment,indicating that proper steaming treatment would not seriously damage the endosperm cell wall integrity.The pasting characteristics of starch showed that the swelling potential and solubility of starch gradually increased as the particle size of wheat farina decreased,and the endosperm cell wall had a significant hindering effect on the dissolution and swelling of starch;the larger the particle size of wheat farina was,the trough viscosity,final viscosity,rebound value,pasting temperature and peak time increased significantly,while the peak viscosity and disintegration value decreased significantly,indicating that the coarse wheat farina was thermally stable in the pasting process,but it was easy to cause starch aging.However,it is easy to cause aging of starch.In vitro digestion of starch showed that the endosperm cell wall of the wheat farina could limit the contact between enzyme and substrate,which effectively reduced the digestion rate and degree of digestion of starch.Next,the wheat farina was mixed with wheat flour in the ratio of 6:4 to make dough and dried noodles.The rheological study of the dough showed that the addition of wheat farina tended to form a rigid dough with high tensile resistance and low elongation;the addition of larger particle size wheat farina weakened the gluten strength,which was not conducive to the formation of gluten network and reduced the thermal resistance of the dough in the battering process.The analysis of noodle quality characteristics showed that the addition of larger particle size wheat farina reduced the cooking quality of noodles as well as the hardness,elasticity,adhesion,chewiness,breaking force and breaking distance of cooked noodles;while the addition of smaller particle size wheat farina not only improved the bending resistance and flexibility of dried noodles,but also helped to improve the texture and sensory quality of cooked noodles.Microscopic observation showed that the larger particle size was not conducive to the formation of gluten network,resulting in holes of different sizes in the noodle structure,while the smaller particle size was able to combine well with the gluten network structure and form a dense noodle structure.Meanwhile,the complete endosperm cell wall was observed before and after cooking for the noodles with larger particle size.The in vitro digestibility analysis of starch showed that the noodles made with the addition of larger particle size wheat farina reduced the digestibility of starch,but not significantly,indicating that even though the endosperm cell wall was partially intact during the noodle making process,its hindering effect on the digestibility of starch was significantly reduced compared to that before the noodles were made,probably due to the increase in cell wall permeability.Finally,the study on the integrity and permeability of wheat farina endosperm cell walls in the process point samples by noodle processing(flour mixing,dough mixing,waking,compound calendering,continuous calendering,and steaming)showed that the noodle processing process had less effect on protein and starch components,but more effect on pentosan content in the endosperm cell walls.As the sampling points moved back,the total pentosan and insoluble pentosan content decreased and the water-soluble pentosan content increased significantly,with a maximum increase of 0.87%,indicating that the noodle processing process had a greater effect on the permeability of the endosperm cells;among them,the cooking treatment caused the greatest decrease in the total pentosan content in the dough.Microstructural studies showed that the process point samples with the addition of wheat farina mainly formed small spherical doughs during the dough mixing process,while wheat flour formed irregular dough flocs.The analysis of the pasting characteristics of starch showed that the noodle processing process increased the swelling potential and solubility of the process point samples,and the peak viscosity,trough viscosity,disintegration value and final viscosity mainly showed an increasing trend followed by a decreasing trend,while the regeneration value showed a significant decrease,which confirmed that the endosperm cell wall destruction caused by the noodle processing process decreased its hindering effect on the water absorption and swelling of starch,while the leaching of pentosan and straight chain starch which decreased the paste viscosity value.Analysis of the thermal properties of the starch showed a gradual but not significant increase in the thermal stability of the added wheat farina samples and a gradual decrease in the relative crystallinity of the process point samples,indicating that the noodle processing process has an effect on the crystal structure of the starch but does not destroy the crystal structure of the starch granules.The in vitro digestion study further confirmed that before cooking,the noodle processing process increased the digestibility and digestibility of the process point samples,especially from the calendering process,probably due to the increase in cell wall permeability;after cooking,the digestibility of different samples increased greatly,indicating that cooking has a greater effect on the permeability of the cell wall.