| Chinese dried noodles(CDN)are one of the traditional staple foods in China and are highly industrialized.The drying process is one of the key processes in the production of noodles and its selection and parameter optimization is closely related to product quality,production efficiency,and energy consumption.Different drying techniques are important factors affecting the drying efficiency and product quality of the noodles.However,there is a lack of clarity regarding the extent to which different drying techniques,particularly dielectric drying(microwave and radiofrequency),affect the quality of CDN products,the structure of protein molecules,starch molecules,and volatile flavor substances,and the relationship between structural changes in protein and starch molecules during drying and product quality.This thesis investigates the changes in product quality and cooking characteristics of CDN during the drying method(hot air,microwave and radiofrequency)and drying process;focusing on the structural changes of protein molecules and starch molecules,it uses SEM,Raman spectroscopy,and DSC analysis techniques to analyze the degree of influence of drying technology on the structure of CDN protein networks,changes in starch molecules,etc.The process or effect of protein and starch structure and physicochemical characteristics on product quality traits is explored.The mechanism of the effect of protein and starch structure and physicochemical properties on product quality and properties was investigated.In addition,the changes in volatile flavor substances during the drying process of the noodles were investigated.The main findings are as follows.(1)There are significant differences in the molecular composition,aggregation state and network structure of proteins in CDN under different drying techniques.MW and RF drying resulted in a certain degree of aggregation denaturation,increased glutenin macromer content and interconversion of secondary structures,with α-helixes transformed into β-folds and β-turns.Laser confocal microscopy images show that the gluten protein network structure of MW and RF dried gluten is more orderly and dense than that of HA dried gluten,and that the starch granules are tightly wrapped in it.(2)The different drying techniques had significant effects on the straight chain starch content,structural properties and characteristic properties of the starch in the noodles.MW and RF drying induce degradation of the starch molecules by causing disruption of the starch molecular structure,which is reflected in a reduction of the straight-chain starch content and loss of the short-stroke ordered structure,which in turn leads to an imperfect starch crystal structure.In addition,the degradation causes a decrease in starch viscosity parameters and an improvement in thermal properties,thus improving the quality of the CDN.(3)Different drying techniques have a significant impact on the quality and cooking characteristics of the noodles.Studies on the drying kinetics of CDNshow that microwave drying is the most efficient under the same power density conditions.At the same time,compared with hot air drying,microwave and RF dried hanged noodles have a small cooking loss rate and good colour and bending resistance characteristics.At the same time,the hardness,elasticity,cohesiveness and recovery of microwave and RF dried hanged noodles are improved after cooking,and this improvement is more obvious in microwave drying.(4)Different drying techniques have significant effects on the content and composition of volatile flavour substances in hanged noodle products.The results showed that the volatile substances in CDNwere mainly aldehydes,alcohols and esters,and that the drying treatment significantly reduced the types of volatile substances in CDNcompared to fresh noodles.When comparing the three drying methods,the microwave dried noodles had the largest variety of flavour substances and the largest concentration. |
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