Research On Influence Of High Temperature And Relative Humidity Drying Process On Quality Of CDNs

An attempt has been made to investigate the influence of high temperature and relative humidity drying process on the quality of Chinese dried noodles(CDNs)and starch properties in order to improve the drying process and product quality,and provide a theoretical basis for further clarifying the mechanism of starch contributing to the product quality.The wheat variety Yongliang No.4 was used to make CDNs in the laboratory.The experiment was designed with two factors at three levels for the drying conditions with varying drying temperatures(40?,60?and 80?)and relative humidity(65%,75%and 85%).The drying time was 300 min.The main conclusions in the paper are as follows:(1)The influence of high temperature and high relative humidity drying process on quality characteristics of uncooked noodle was evaluated.The relative humidity had the greatest impact on the quality characteristics of dried noodle products,followed by temperature and factor interaction.Compared with the conventional drying method(40?,75%),high-temperature and high humidity drying process(85?,85%)contributed a slight decrease in the L*value of CDNs,a slight increase in the a*value,and a significant increase in the b*value,the bending strength,breaking distance and breaking work of CDNs.Relative humidity was the main factor that changed the density of the noodles.The high temperature and high relative humidity environment increased the density of the product.(2)The effect of high temperature and high relative humidity drying process on the quality characteristics of cooked noodle was investigated.The drying temperature was the most important factors affecting the quality of cooked noodle products,followed by factor interaction and relative humidity.Compared with the conventional drying process,the optimal cooking time of CDNs dried by high temperature was significantly prolonged and the cooking loss rate increased.The cooking absorption rate was the highest when CDNs dried at high temperature and low humidity(80?,65%).Compared with the conventional drying process,the hardness,adhesiveness,gumminess and chewiness of cooked CDNs dried by the high temperature and high relative humidity increased,while the elasticity,cohesiveness and resilience were significantly reduced.(3)The effect of different drying parameters on the physicochemical properties of starch in CDNs was researched.Compared with low-temperature drying,the amylose content in CDNs under high temperature drying conditions increased and the swelling power decreased significantly.The high temperature drying technology significantly increased the pasting temperature,onset temperature(T_o),peak temperature(T_p),and conclude temperature(T_c)of the starch in CDNs.At 65%or 75%relative humidity conditions,high temperature drying process significantly increased the peak viscosity,trough viscosity,final viscosity and setback.Under 80?drying conditions,each viscosity and enthalpy value of the starch in CDNs dropped significantly,while To,Tp,and Tc increased significantly with increasing relative humidity.And the relative crystallinity of starch was lower.It was observed that the polarized cross of some starch granules became weakened or even disappeared under high temperature drying conditions.(4)The relationship between starch characteristics and quality of CDNs was studied.The correlation analysis showed that there was an extremely significant negative correlation between starch swelling power and dry noodle color b*value,cooking loss and post-cooking hardness.Amylose content had a significant or extremely significant positive correlation with shrinkage ratio,cooking loss and post-cooking hardness.Starch pasting properties had a strong correlation with cooking loss,hardness,adhesiveness,and cohesiveness of cooked noodles.Starch thermodynamic properties were mainly very significantly or significantly related to cooking loss,hardness,cohesiveness,and gumminess of the cooked CDNs.(5)The physicochemical properties of starch during the drying process were also investigated.After undergoing the drying process,amylose content in CDNs increased slightly,the swelling power decreased significantly,peak viscosity,tough viscosity,breakdown value,final viscosity,setback value,peak time,pasting temperature and the enthalpy value decreased while T_o and T_p increased.