Effects Of Adding Sweet Potato Starch On The Quality Of Noodles

To expand the application of sweet potato resources in the noodles processing, noodles adding sweet potato starch were studied and improved in this issue. The potato Xushu 22, wheat flour and gluten powder provided by the market were selected as raw material. Firstly, the sweet potato starch was extracted from Xushu 22, and the basic physicochemical properties of sweet potato starch, wheat flour and gluten powder were measured, which would establish some foundations for the subsequent research. Secondly, mixing sweet potato starch with wheat flour in different proportions and making them into noodles, the quality characteristics of the noodles were studied. And then, when making the noodles containing 20%, 25% or 30% of the sweet potato starch, different proportions of gluten powder were added to study effects of the gluten powder on the noodles properties. Finally, the process conditions for making noodles adding 4.2% gluten power and 30% sweet potato starch were optimized. The results showed that:(1) The physicochemical parameters of the wheat flour were as follows: both in dry basis, the total starch content was 76.30%, the protein content was 14.12%, the wet gluten content was 33.08g/100 g, the dough stability time was 5.7min, and this kind of flour was bread flour. The physicochemical properties of the sweet potato starch were as follows: both in dry basis, the total starch content was 99.15%, the amylose content was 25.22%, the protein content was 0.26%, the crude fat content was 0.12%, the crude fiber content was 0.01%; the swelling potential and solubility of the sweet potato starch at 90 ℃were 26.35g/g and 14.66%, respectively; the RVA test results showed that: the gelatinization temperature of the sweet potato starch was 53.45℃, and the peak viscosity of the paste was 4928/cP. The protein content of the gluten powder was 83.95%, and the water absorption was 164.36%.(2) With increasing of the addition of sweet potato starch, the gelatinization temperature of the blends mixing together flour and sweet potato starch decreased, the viscosity parameters and the viscosity damping values increased; the dough development time shorten, water absorption decreased, dough stability time shorten gradually after slightly prolonged, and the weakening of the dough increased after slightly reduced. Quality properties of the noodles were significantly correlated with the amounts of sweet potato starch added. With the suitable addition of sweet potato starch, qualities of the noodles were improved: structures of the noodles were more stable, and the tensile properties and viscoelastic properties were improved. In this study, the optimal addition proportion of sweet potato starch was 5%-10%, if more, qualities of the noodles deteriorated sharply.(3) With increasing of the addition of gluten, the gelatinization temperature of the blends mixing together gluten, sweet potato starch and wheat flour increased, the viscosity parameters and the viscosity damping values decreased; The dough stability time prolonged, and the weakening of dough decreased. Qualities of the noodles made with the blends were improved with appropriate addition of gluten: structure of the noodles were more stable, rate of dry matter lost of cooking noodles were significantly reduced. The optimal addition proportion of gluten added was 2.7%-3.7% for the blends containing 20 percent of the sweet potato starch, it was 3.5%-4.5% for the blends containing 25 percent of the sweet potato starch, and was 4.2%-5.2% for the blends containing 30 percent of the sweet potato starch.(4) After the optimization experiments, the optimal processing parameters for making noodles adding 4.2% gluten power and 30% sweet potato starch were determined: weighing samples, adding 30.8% of water, mixing, resting for 60 min, mixing secondarily for 15 min, resting secondarily for 90 min, sheeting into 4mm sheets, resting for 60 min, sheeting secondarily, and cutting. With this method, noodles with good apparent, integrated and homogeneous micro-structure, and similar texture and cooking properties with the noodles made with wheat flour were made.(5) The way of raising the amount of sweet potato starch to 30% in noodles making were explored. Not only 4.2% gluten power needed to be added, but the processing parameters for making noodles also needed to be adjusted to: weighing samples, adding 30.8% of water, mixing, resting for 60 min, mixing secondarily for 15 min, resting secondarily for 90 min, sheeting into 4mm sheets, resting for 60 min, sheeting secondarily, and cutting.