Study On The Effect And Mechanism Of Mechanical Force Form And Resting Process On Dough Characteristics And Noodle Quality

The application of different methods to improve the quality of wheat flour,the processing properties of the dough,and the quality of the final product has always been a hot topic in wheat flour and pasta research.As one of the more industrialized noodle products,the quality of noodles have always failed to be equated with the hand-made noodles strongly pursued by consumers.The difference in processing methods may be the main reason for the difference in taste between traditional hand-made noodles and industrialized noodles,and there is a lack of in-depth and systematic research on traditional processing schemes.Therefore,the project aims to provide a new method for the industrial production of good noodle products through the analysis of the influence in the simple force during the mixing process,the direction and intensity of force during the sheeting process,the temperature and time during the resting process,and the repeated sheeting-resting process on the rheological properties of the dough,and the elucidation of the related molecular mechanism,as well as to provide a new method for the industrial production of good noodle products in the traditional noodle processing and to realize the targeted regulation of the process scheme in the application of the series method through the mechanism study.(1)Several simple dough preparation methods were proposed to imitate traditional manual dough preparation behavior.The water state,rheological properties,and protein properties of doughs were analyzed.The results indicated that the BPD and URD had better tensile resistance and deformation recovery than that of UPD and BRD.Additionally,the BPD and URD had better gluten network connectivity,and fewer holes.Further chemical interaction analysis showed that rolling promoted the formation of more hydrogen and hydrophobic bonds in doughs,and that the strong slip caused by intermediate state water may improve the gluten protein extraction rate of UPD and BPD.Meanwhile,there was more disulfide bonds formed in the BPD and URD.While,the simple pressing or rolling did not contribute significantly to the formation of GMP.Physical entanglement due to non-covalent interactions(mainly hydrogen bonding and hydrophobic interactions)played an important role in the formation of doughs.In addition,hand-made noodles gave the noodles a brighter color and higher water absorption,and exhibited less firmness and elasticity.Pressing and rolling in one direction gave noodles a texture closer to that of the CHD.Pressing and rolling in one direction helps to obtain noodles with textural characteristics closer to those of traditional hand-made noodles(CHD).(2)The effects of sheeting direction and strength on the rheological properties of dough and the molecular mechanisms were investigated.The results indicated that bi-directional sheeting enhanced the promotion of gluten network formation by weak calendering and inhibit its destruction by strong sheeting,giving the dough greater strength and resistance to deformation.Meanwhile,continuous sheeting promoted the conversion of free sulfhydryl groups to disulfide bonds,and obtained lower GMP content(17.43 mg/g).Meanwhile,the ionic bonding content and hydrophobic interactions increased,hydrogen bonding gradually weakened as the strength of mechanical interaction increased.Bidirectional sheeting not only expanded the degree of SH/SS conversion,but also alleviated the disruptive effect of strong mechanical forces on disulfide bonds.The AFM images showed the formation of dense gluten protein chains observed at 15 or 10 passes of unidirectional and bidirectional sheeting,respectively,while the gluten chains existed in a finely fragmented form under strong force.In addition,bi-directional sheeting promoted the formation of bright appearance noodles with a firmer structure and more cooking losses than that of uni-directional sheeted noodles.(3)Rheological properties and chemical interactions of doughs pretreated at different temperatures were evaluated.The results showed that the rigidity of pretreated doughs was enhanced,and the processing performance of doughs was weakened.Preheating resulted in the polymerization of gluten through the conversion of sulfhydryl groups to disulfide bonds,leading to the production of GMP(55.77mg/g).Image analysis verified that preheating promoted the formation of the coarse and scattered gluten network,and preheating at 80 °C led to a structure with lower lacunarity.Meanwhile,the effect of high pretreated temperature(65-80°C)caused a drastic change in gelatinization behavior and crystallinity,resulting in a compact gel structure.The pretreated noodles exhibited higher hardness and chewiness,as well as lower water absorption and higher cooking loss.Hydrolysis kinetics analysis showed that high-temperature pretreatment(80°C)resulted in a significant increase in RDS and SDS.In addition,the difference in digestibility between samples due to pretreated temperatures was narrowed after cooking.High-temperature pretreatment help to improve the digestion rate of cooked-noodles.(4)The physicochemical properties of the dough were evaluated at two temperatures with different resting times.The results showed that the tensile resistance of the dough decreased and the elongation increased with the resting time increasing.The low-temperature treating caused the dough difficult to deform,and the prolonged resting at 35°C caused the dough to be less elastic.In addition,the formation of macromolecular polymers was promoted at 35°C,and the effect of resting time on the non-covalent interactions in doughs was relatively weak at low temperatures.The doughs had a higher level of ionic bonding,hydrogen bonding,and lower hydrophobic interaction after resting at 4°C for 5 h and 35°C for 1.5 h.The observation of the microstructure revealed that the temperature of 35°C induced the production of polymers with larger diameter,and the gluten chains aggregated at 5 h(4°C)and 1.5 h(35°C).Evaluation of noodle quality disclosed that prolonged resting time caused the noodles to be dull and yellow,while the low-temperature environment substantially reduced the possibility of darkening of fresh noodles.The maximum water absorption and the minimum cooking loss were obtained at 3 h(35°C)and 5 h(4°C)for the noodles,respectively.Prolonged resting at 35°C resulted in the reducing hardness and chewiness of noodles,at which the tensile strength and elongation of the noodles were significantly lower,but it was still higher than those at low temperature.(5)The changes in the rheological properties and molecular mechanisms of the dough after repeated sheeting-resting treatment at two temperatures were investigated.The results indicated that the compounding process led to the weaker viscoelasticity of doughs but stronger resistance to deformation.The dough pretreated by compound treatment at low temperature reached a stable state quickly after compression.The doughs treated with low-temperature compounding reached the steady state quickly.Meanwhile,the microstructure showed that repeated sheeting-resting was beneficial to promote the orderly arrangement network structure.Multiple compounding treatment at low-temperature affected the proportion of small polymeric and monomeric proteins,while repeated treatment at 35°C promoted the formation of large polymeric proteins.The doughs had the most ionic and hydrogen bonding contributions at 2(4°C)and 3(35°C)compounds,respectively,while the level of hydrophobic interactions was weaker.In addition,the adverse effect of resting on the color of noodles was greater than that of the improvement in the glossiness of noodles brought about by the sheeting,which led to the dull color of noodles.The maximum water absorption and minimum cooking loss were obtained at 4°C at 2 times of repeated treatment,while there was a greater cooking loss at 2-3 times of repeated treatment at 35°C.The compounding treatment at 35°C resulted in an increase in hardness,chewiness and elasticity and a significant decrease in tensile strength of cooked noodles.Noodles with good textural properties were obtained by compounding three times at 35°C and two times at 4°C.(6)The rheological properties and noodle quality of doughs produced under the combined conditions of mixing,sheeting and resting were investigated.The results showed that the bi-directional pressing,bi-directional strong sheeting,and sheeting-resting processes exhibited weakening,strengthening,and intensifying phenomena on dough processing properties(tensile and compression treatments),respectively,and showed offsetting or superimposing effect in combined treatments.In addition,the bi-directional sheeting promoted the regular arrangement of gluten network,which was combined with the pressed-mixing and sheeting-resting process to present a " honeycombing ","filamentous ",and " rice cob-shaped " gluten chain structure.Moreover,the treatment at 35°C promoted the formation of denser network structures and more continuous polymer chain segments in doughs.Similarly,the two-two or three combined treatments of mixing,sheeting,and resting had synergistic or antagonistic effect on the intensity of covalent and non-covalent interactions in dough samples to a certain extent.In addition,there may be a degree of resistance effect between the bi-directional pressing and the repeated sheeting-resting treatment,resulting in a weakened network structure of noodles.In the case of composite processing,the enhancing effect on the water absorption and the increasing effect on cooking losses of the noodles caused by multiple strong sheeting were enhanced and superimposed,respectively.Repeated resting at low-temperature had a significant mitigating effect on the disruption of gluten network by multiple strong sheeting.The combination of the mixing and compounding processes had a much stronger effect on the qualitative properties of the noodles than any single processing operation.