Study On The Effect And Mechanism Of Multi-frequency Ultrasound Modified Of Gluten On Its Noodle Quality

Multi-frequency ultrasound technology is a new type of physical processing technology.Existing experiments have found that ultrasound technology has demonstrated its wide application prospects in enzymatic hydrolysis reactions,modification of biological macromolecules and biochemical reactions.At present,the research on ultrasonic preparation is mainly high-power single-frequency ultrasonic intermittent preparation,but because of the high energy consumption,high noise,and poor generality of single-frequency ultrasound,it has affected the promotion of its industrial-scale applications.The cavitation effect of a multi-frequency combination is a combination of multiple single-frequency ultrasound,so its effect is better than single-frequency ultrasound,and its energy efficiency is much higher than that of single-frequency ultrasound.Wheat gluten protein is a kind of natural plant protein material with rich amino acid variety and low price.It has great application value in the food field.However,because gluten protein contains more hydrophobic amino acids,its solubility,emulsification,and foaming properties are poor,which limits its application in some food industry fields.Gluten protein is an important component in wheat flour,and its quality affects the quality of later flour products.Therefore,it is of great significance to develop and utilize gluten protein as a functional food ingredient.At present,some studies focus on the effect of wheat starch properties on dough,and wheat gluten protein is one of the important ingredients in flour.Whether the changes in its properties affect the quality of dough and its final product has not been discussed.With the development of the food industry,consumer demand for new dough products,especially dough products with low gluten protein content and rich in other physiological efficacy factors,is increasing.Reducing the content of gluten protein in the dough can reduce production costs,while improving the functional quality of the dough by introducing other physiological efficacy factors,and enriching the diversity of dough products.The multigrain does not contain gluten protein itself,and the formed dough is loose,not easy to form lumps,and has a poor taste.Therefore,in order to overcome these shortcomings and improve the cooking and sensory quality of noodles,most multi-grain noodles often add various noodleimprovers such as gluten protein.However,the addition of these additives will increase the production cost of multi-grain noodles.At present,there is no research report that physically changes the properties of gluten protein,which further affects the quality characteristics of dough and later noodle products.Therefore,this paper first studied the thermomechanical and rheological properties of multi-frequency ultrasonically treated modified gluten-wheat starch model dough.Furthermore,the single-frequency,simultaneous dual-frequency combination,and synchronous three-frequency combination ultrasound with the best quality characteristics of ultrasonically modified modified gluten-wheat starch model dough were found to have the modification condition parameters.On this basis,the best single-frequency,synchronous dual-frequency combination and synchronous three-frequency combination ultrasonic treatment of gluten protein noodles with cooking quality,texture characteristics and tensile properties are further studied.It is hoped that the quality characteristics of ordinary white noodles(with a gluten content of 14%)can be achieved by reducing the amount of ultrasonically modified gluten protein in noodles.Finally,taking gluten protein as the research object,the inherent mechanism of multi-frequency ultrasonic treatment of gluten protein was explored,which provided theoretical support for the aforementioned research.The main findings are as follows:1.Study on the effects of ultrasonically modified gluten protein at different frequencies on its dough properties and noodle quality.Use single frequency(20,28,40,68,80 kHz),synchronous dual frequency combination(20/40,28/40,68/40,80/40 kHz)and synchronous tri-frequency combination(20/28/40 kHz,28/40/68 kHz,28/40/80 kHz)modified gluten protein.First,the thermomechanical and rheological properties of wheat starch-modified gluten protein model dough were measured,and the water absorption rate,formation time,stabilization time,protein weakening degree,and dough viscoelasticity were used as evaluation indicators to find out single-frequency ultrasonic frequency,synchronous dual-frequency ultrasonic frequency combination,and synchronous tri-frequency ultrasonic frequency combination with the best dough properties.Then the best multi-frequency combined ultrasonic-modified gluten protein and wheat starch were mixed to make noodles in different proportions.The noodle cooking quality,texture characteristics,and tensile properties were used as indicators to evaluate the noodle quality characteristics.The results show that ultrasonic treatment of gluten protein at different frequencies can increase the water absorption,formation time,stabilization time,and viscoelasticity of its model dough,but reduce the degree of weakening,viscosity disintegration,and regeneration of its dough.There was no significant difference in the cooking and texture characteristics between commercial noodles and noodles with 12%,11%,and 10% gluten pretreated by single-frequency(40 kHz),dual-frequency(28/40 kHz),and triple-frequency sonication(28/40/80 kHz),respectively.It shows that the quality of noodles produced by using a lower amount of ultrasonically modified gluten protein can reach the quality of ordinary noodles(gluten protein content is 14%),and the effect sequence is synchronous three-frequency ultrasound combination(28/40/80 kHz)> Synchronous dual-frequency ultrasound combination(28/40 kHz)> single-frequency ultrasound(40 kHz).2.The effect of multi-frequency combined ultrasound treatment on the physicochemical and functional properties of gluten protein.Use single frequency(20,28,40,68,80 kHz),synchronous dual frequency combination(20/40,28/40,68/40,80/40 kHz)and synchronous tri-frequency combination(20/28/40 kHz,28/40/68 kHz,28/40/80 kHz)modified gluten protein,studied the solubility,water retention,oil retention,emulsification and emulsification stability,foamability and foam stability of the modified gluten protein The effects of multi-frequency combined ultrasonic treatment on the physicochemical and functional properties of gluten protein were analyzed.The results show that after multi-frequency combined ultrasound treatment,the solubility,water-holding and oil-holding properties,hydrophobicity,foamability,and emulsification of gluten protein have significantly improved(p<0.05).Chemical and mechanical effects cause the gluten protein molecular structure to stretch,leading to the exposure of some hydrophobic and hydrophilic groups,thereby causing changes in these functional properties.After sonication,the particle size of gluten protein decreased from 197.93±5.28 nm to 110.15±2.61 nm.The small particle size protein may help the protein migrate to the air-water interface and increase the interaction with water,thereby increasing the properties of solubility and foaming.In addition,the three frequency combinations of40 kHz,28/40 kHz,and 28/40/80 kHz proved to be sensitive frequencies of gluten protein,and the effect on gluten protein were most obvious.Because the multi-frequency combined ultrasound eliminates the dead space of cavitation and generates frequency superposition or cancellation,the ultrasonic effect produced by frequency superposition will be enhanced.After ultrasonic treatment,the molecular structure of gluten protein is loose,and some hydrophobic groups and hydrophilic groups are exposed,which is conducive to interaction with starch.This is also the cause of the changes in dough properties and rheological properties.Correlation analysis was performed on the functional index of gluten protein with multi-frequency ultrasound,the noodle quality index,and the mixing characteristic index of model dough.It was found that the functionality of sonicated gluten protein mainly affected the water absorption,hardness,cooking loss,Gelling,chewing,elasticity of noodles,and settling time,forming time,and protein weakening of the model dough.3.The effect of multi-frequency ultrasound on the structural characteristics of gluten protein.Use single frequency(20,28,40,68,80 kHz),synchronous dual frequency combination(20/40,28/40,68/40,80/40 kHz)and synchronous tri-frequency combination(20/28/40 kHz,28/40/68 kHz,28/40/80 kHz)modified gluten protein.The changes of ultraviolet absorption intensity,fluorescence intensity,Raman spectrum analysis,free sulfhydryl group and disulfide bond content,molecular weight and SEM of modified gluten protein were studied.,in order to clarify the structural characteristics of modified gluten-wheat starch model dough and model noodle quality.The results showed that the combination of ultrasonic treatment with different frequencies changed the secondary and tertiary structure of gluten protein.The ultraviolet absorption intensity and fluorescence intensity of ultrasonically modified gluten protein increased significantly.This may be due to the cavitation effect of ultrasound,which caused the protein to unfold and expose some chromophores(such as tryptophan and tyrosine).From the Raman spectrum analysis,the relative content of the ?-helical structure was reduced from 33.54±0.76%(untreated)to 21.85±0.88%(28/40/80 kHz),indicating that the structure of gluten protein stretched,which was also confirmed by scanning electron microscopy.Tryptophan residues and tyrosine residues tend to be exposed,which is also due to the unfolding effect of gluten protein,which exposes the internal groups to the molecular surface,which also explains the reason for the increased hydrophobicity.Due to the cavitation effect and shear force of ultrasound,the protein was unfolded and the internal free sulfhydryl groups were exposed to increase its content,while the content of disulfide bonds remained unchanged,which was also consistent with the SDS-PAGE results.With the increase of the number of ultrasound frequency combinations,the cavitation effect gradually increases,and the effect of synchronous three-frequency ultrasound is the most significant,which can cause changes in protein structure,and the effect sequence is synchronous three-frequency ultrasound combination(28/40/80 kHz)> Synchronous dual-frequency ultrasound combination(28/40 kHz)>Single-frequency ultrasound(40 kHz).In addition,correlation analysis was performed between the structural index of gluten protein and the noodle quality index and the mixing characteristic index of model dough by multi-frequency ultrasonic treatment.The characteristics are highly correlated.These results indicate that the combined treatment of multi-frequency ultrasound changes the functional and structural properties of gluten protein,which affects the properties of its model dough.Therefore,it also reveals that the quality characteristics of dough and noodles can be predicted by the functional and structural characteristics of gluten protein.In summary,the multi-frequency combined ultrasound changes the functional and structural properties of gluten protein,thereby affecting the mixing characteristics of the model dough and the quality characteristics of noodles.