Study On The Changes Of Processing,quality And Storage Characteristics Of Purple Sweet Potato Fresh Wet Noodles

Purple sweet potato is nutrient-rich and can be used to prepare wheat fresh wet noodles with a delicate texture and unique color.However,purple sweet potatoes do not contain gluten proteins,and their addition can have adverse effects on processing properties of wheat flour and qualities of fresh wet noodle.In addition,anthocyanins,as the main coloring material in purple sweet potatoes,can be lost during the preparation,consumption,and storage of fresh wet noodles,thus affecting its color and nutritional value.Therefore,this study investigated the effects of different particle sizes and addition amounts of purple sweet potato flour(PSPF)on wheat dough processing properties,microstructure,thermodynamic properties,and water state,as well as the influence mechanism of PSPF on fresh wet noodle qualities and molecular structure.Furthermore,the loss pattern of anthocyanins during the preparation,cooking,and storage of PSPN was studied.The factors affecting the color of PSPN were analyzed,and a shelf-life prediction model was established,aiming to provide theoretical basis for the processing,quality,and stability of PSPN.The main results of the subject are as follows:(1)The effects of different particle sizes and addition amounts of PSPF on wheat dough processing properties was analyzed.The effects of PSPF on wheat dough pasting properties,mixing properties,dynamic rheological properties,microstructure,water state,and water migration were measured.Results showed that the addition of PSPF decreased the processing properties of wheat dough.However,the deterioration tendency decreased as the particle size of PSPF decreased(between 260-59 μm).Dynamic rheology results showed that the addition of PSPF increased the K’ of the dough from 31356.33(pure wheat dough)to 52526.19(20%260 μm purple sweet potato flour dough),giving it a solid-like processing performance.Differential scanning calorimetry and low-field nuclear magnetic resonance results showed that the addition of PSPF decreased the freezeable water content of the dough from 43.20%to 35.44%to 38.19%,while the water content increased from 9.26%to 24.82%to 31.90%.(2)The influences mechanism of PSPF on fresh wet noodle qualities and anthocyanin retention were analyzed,and the effects of particle size of PSPF on qualities of PSPN,noodle structure,and anthocyanin loss during processing were studied.Results showed that the significant reduction(p<0.05)in particle size of PSPF increased the expansion rate,hardness,stickiness,elasticity,chewiness,maximum tensile force,and maximum tensile distance of PSPN,while significantly reducing(p<0.05)the optimal cooking time,cooking loss rate and breakage rate.Fourier transform infrared analysis showed that different particle sizes of PSPF resulted in significant differences(p<0.05)in hydrogen bond numbers,straight chain starch content,protein secondary structure distribution,and starch short-range order in fresh wet noodles,thereby affecting their quality.The total retention rate of anthocyanins during the preparation of purple sweet potato fresh wet noodles was between 85.35%and 98.14%.Diffusion in the cooking process of fresh wet noodles resulted in a large loss of anthocyanins,with a loss rate ranging from 22.10%to 37.16%at the optimal cooking time,and the diffusion behavior was in accordance with the Fick’s second law,with a diffusion coefficient ranging from 8.32 × 10-9 to 14.09 × 10-9 m2/s.Purple sweet potato fresh wet noodles prepared with 15%59 μm PSPF had optimal quality and the highest anthocyanin retention rate.(3)The color change pattern of PSPNs during storage and the influencing factors were analyzed.Results showed that under high temperature(60℃)and high humidity(90%)conditions,the color score of fresh wet noodles decreased from 8.35 points to 3.10 points and 4.00 points,respectively,after 15 days of storage,with a decrease in color acceptability ranging from 90%to 70%.Based on the color score and color acceptability,the threshold value(end-point of shelf life)for the color score of PSPNs was obtained through a confusion matrix algorithm as 5.25 points.A storage quality equation of PSPN was constructed based on the color of the fresh wet noodle,with Y=14.243-0.200X10.021X2+0.074X3+4.235X4,where Y is the color score,X1 is the L*value,X2 is the ABTS free radical scavenging rate,X3 is the DPPH free radical scavenging rate,and X4 is the anthocyanin content.A shelf-life prediction model based on the storage temperature and relative humidity was established,which can predict the shelf life in the storage humidity range of[50.0%,94.7%],and the average error of the validation experiment was 6.65%.