Effect Of Sweet Potato Flour On The Rheology Properties Of Gluten-free Dough And The Quality Characteristics Of Fresh Noodles

Noodles are a staple and popular food in Asian cultures,made from wheat flour,but celiac people can’t eat wheat noodles due to gastrointestinal issues（auto immune response causes cramps,damage of small intestinal,nutrient absorption deficiency,anemia,etc.,）.Gluten-free meals are the only choice for gluten-intolerant people for healthy life.Previous research used non-gluten materials such as rice,corn,starches,buckwheat,and pulses to make noodles.Nevertheless,it does not have the same texture or nutritional value as wheat noodles and is still under development to mimic wheat noodle behaviors（extensibility,elasticity,and consistency）.Sweet potatoes are gluten-free and contain various nutrients that may help with nutritional deficiencies and maintain food security.In this research,gluten-free fresh noodles（GFFN）were made using functional ingredients（gluten-free,50%）and sweet potato flour（SPF,0-50%）in replace with corn flour,comparable to corn（C）or wheat（WF）noodles.The effects of SPF on thermomechanical（MIXOLAB）properties of dough,the amino acid and fiber contents of uncooked GFFN were optimized using single factor experiment,then after the cooked noodles were assessed following texture analysis,color,cooking quality,microstructure（SEM）and secondary protein structure（FTIR）,in vitro starch digestibility,total phenolic content,and antioxidant activity.Furthermore,the qualified sample was chosen for enhancing the texture and reducing the cooking loss using potato starch（32%）modified by heat moisture treatment(without additives,Na Cl,and Na₅P₃O₁₀)or microwave radiation（90 S.and 270 S.）and the effect of modification methods on potato starch granules and GFFN were assessed by differential scanning calorimeter,SEM,texture,sensory analysis,etc.The main findings were shown as follows:（1）Adding SPF up to 40%（SC4）enhanced the dough’s rheology characteristics significantly in terms of C2 and slopeαin SC4（0.44 and-0.035,respectively）compared to WF（0.40 and-0.081,respectively）which representing the dough’s resistance during mixing.Meanwhile,uncooked noodles（SC4）exhibited an increase in ash（1.97g/100g db）,crude fiber（3g/100g db）,threonine（0.52 g/100 g db）,methionine（0.28 g/100 g db）,and lysine（0.57 g/100 g db）.SEM illustrated that starch granules were encased in a thin protein layer,promoting binding and resulting in a compact noodles microstructure.（2）As well,the GFFN（SC4）showed a rise in FRAP（2.76 mg AAE/g）,cooked weight（113.53%）,cooked volume（151.5%）,and cooking loss（10.420.79%）values.Also,as compared to C noodles,yellowness（b*,39.31）,springiness（80.12%）,and chewiness（15.08 g）values increased.SEM figures showed that cooked SPF-noodles established a structured network that mimicked the gluten network roleplay of wheat-noodles.Interestingly,SPF-noodles had higher totalβ-sheet（amide I,C=O,and N-H vibration）andβ-sheet bands(1614-1633&1683-1704 cm^-1)than wheat-noodles.In-vitro starch digestibility was lowest at 20 minutes of the intestinal phase for 40%SPF-noodles due to the compact structure against the hydrolysis enzyme.Furthermore,adding SPF%into noodles did not change the sensory qualities of the noodles from WF except for the color,which was more orange than WF noodles.（3）The influence of modified potato starch using various techniques（heat moisture treatments（HMT）or microwave（MW）radiation）on the microstructure and cooking quality of 40%SPF-noodles（SC4）was investigated.HMT treatment（gelatinization degree,77.81%）increased starch granule-size without causing significant granular structural degradation;furthermore,the cooked noodles had homogeneous alveolar dimensions with a honeycomb structure,a significant weight increase,and acceptable cooking loss（114.04%and 10.30%,respectively）.Moreover,MW for 90 and 270 seconds resulted in the highest weight increase percentages without statistical significance compared to C noodles;they are also higher in hardness（221.72 g and 253.13 g,respectively）and resilience（13.68%and 11.76%,respectively）than SC4（195.9 g and 8.94%,respectively）.All HMT treatments and SC4 had no significance in springiness and chewiness values.Moreover,the HMT of starch with salt complexes（12%sodium chloride or 12%sodium triphosphate）increases cooking loss values（12.75 and 14.13%,respectively）due to the uneven alveolar structure of swollen starch in cooked noodles.The MW treatments（90 and 270 seconds）resulted in a moderate cooking loss（9.37%and 9.23%,respectively）with tiny alveoli,as shown by SEM.In conclusion,SPF and MW-modified potato starch have a novel roleplay in enhancing gluten-free noodles’microstructure,texture,antioxidant activity,and essential amino acids.