Effect Of Potato Starch Granularity On Model Dough Properties

Potato(Solanum tuberosum),annual plant in the Solanaceae family,which is widely planted in the world.And potato is an important food crop with strong adaptability,tolerance to barren drought,high yields and high nutritional value.Potato starch is the main component of potato and has special properties,such as low gelatinization temperature,good swelling performance,high transparency,high water retention capacity,excellent gelling properties,etc.Potato starch is widely used by the food processing industry as a general thickener,texturizer or gelling agent,etc.In recent years,the effect of potato starch on the quality of flour products has been widely studied.Compared with other starches,potato starch has a wide particle size distribution and variable particle shapes.Thus,the quality of flour products could be affected by the composition and physicochemical properties of potato starch.From the perspective of different particle size,revealing the effect of potato starch on the quality of flour products can provide scientific basis for rational utilization of potato starch in flour products processing.Therefore,fractionated potato starch and gluten were used as raw materials to prepare model dough.And the influence of different particle sizes of potato starch on the rheological properties of model dough was explored in the research.The effect of freeze-thaw cycle treatment on the rheological properties of model dough was also studied.The main resultss are as follows:(1)Potato starch was extracted from fresh potatoes by water extraction method.And potato starches of different particle sizes were obtained through physical classification.As the particle size of potato starch increased,the amylose content increased,and the lipid and phosphorus content decreased.The particle size distribution and average particle size of fractionated potato starch were significantly different.And the dispersion coefficient of fractionated potato starch was significantly reduced.As the particle size of potato starch increased,the shape of starch granules was gradually changed from irregular,rectangular or elliptical to spherical or elliptical.Small size starch granules showed higher swelling power;starch granules with large size showed higher solubility.The ratio of 1045 cm^-1/1022cm^-1 of large-size starch granules was significantly higher than the other components.And large-size starch granules had higher degree of short-range order.The thermodynamic parameters of different granular starches showed no significant differences,such as the initial gelatinization temperature,peak temperature,and conversion temperature.(2)The original potato starch and fractionated potato starch were mixed with gluten to prepare model dough(starch:glunten=85:15),respectively.The study found that compared with the model dough prepared by original starch,the model dough prepared by fractionated starch showed higher structural strength.The model dough prepared by large-size starch had higher G?and G?values.And it showed higher elasticity,viscosity and higher structural strength.The model dough prepared by small-size starch had higher the contents of disulfide bonds,?-turns and?-sheet secondary structure.At the same time,the LVR(Linear Viscoelastic Range,0.213%)value of small-size starch model dough was higher and the tan?of small-size starch model dough was lower.Therefore,the model dough prepared by small-size starch showed higher stability and compactness.And fractionated starch granules were distributed more evenly in the model dough according to the microstructure observation.(3)The model doughs prepared from original and fractionated potato starches were subjected to freeze-thaw cycle treatment,respectively.As the particle size of potato starch particles increased,the variation of model dough tan?increased.And model dough prepared by large-size starch was more sensitive to freeze-thaw cycle treatment.The model dough prepared by small-size starch also showed stronger tolerance and better stability.With the increase in the number of freeze-thaw cycles,the moisture migrated in the model dough,the bound water(A₂₁)content decreased,whereas the free water(A₂₂)content increased.The water was more tightly bound with small-size starch in the model dough.With the increase in the number of freeze-thaw cycles,the gelatinization onset temperature(To),peak temperature(Tp)and end temperature(Tc)all increased with varying degrees.The relative crystallinity of the model doughs was significantly reduced.They content of?-helix,?-turn and?-sheet of the model doughs changed significantly.At the same time,the result of scanning electron microscopy showed that the model dough of large-size starch were damaged firstly with the increase of the number of freeze-thaw cycles.And the small-size starch model dough showed compactness structure.