Preservation Of Nutritional Components Of Sweet Potato Granules And Effect Of Texture Recombination On Quality Of Prepared Purple Potato Strips

In this paper,based on sweet potato Shang 19 as raw material,the effects of different processes on the physical and chemical indexes and functional indexes of sweet potato granules were studied,combined with the actual production,by changing the parameters of sweet potato vapor peeling and the pre-steaming temperature,rotational speed,steaming temperature in the production process.The response surface methodology was used to optimize the processing technology of sweet potato granules,and the better nutritional conditions of the granules were obtained,in which the nutritional components of sweet potato granules was preserved.at last,frozen prepared fried purple potato strip was developed,by applying the texture of recombinant technology and the purple potato granules as raw material.The main research contents and results were as follows:1 The vapor peeling process of sweet potato was studied by using the vapor peeling machine and the sweet potato Shang 19.Vapor pressure,vapor pressure drop rate,vapor intake time as the object of study was researched and sweet potato yield and the peeling rate was chosen as the main index.On the basis of single factor test results,response surface analysis was carried out to find out the optimum process parameters: vapor pressure was 0.70 Mpa,vapor pressure drop rate was 0.115Mpa/s,the vapor intake time was 24 s,under this condition,the peeling effect of sweet potato was good and the yield was 89.54%.2 Combined with the actual production,rotational speed: 0.6 r/min,0.9 r/min,1.2r/min,1.5 r/min,1.8 r/min;pre-steaming temperature: 48 C,58 C,68 C,78 C and 88C;steaming temperature: 94 C,97 C,100 C and 103 C,the influence of three different process conditions on the quality of sweet potato granules were studied.The conclusions were as follows:(1)The rotational speed,pre-steaming temperature and steaming temperature had little effect on the physical and chemical indexes of total sugar,protein and starch.With the increase of rotational speed,the content of vitamin C was increased.The content of vitamin C first remained constant,then decreased significantly when thepre-steaming temperature increased.There was no significant difference in the content of vitamin C in different steaming temperatures.The iodine blue value BVI increased with the increase of rotational speed.With the pre-steaming temperature and the steaming temperature increased,the iodine blue value BVI decreased first and then increased.With the increase of steaming speed,the syneresis rate of sweet potato granules decreased first and then increased.The syneresis rate of sweet potato granules increased first and then decreased with the increase of the steaming temperature.With the increase of steaming temperature,The syneresis rate of sweet potato granules increased.There was no significant difference in water holding capacity(WHC)and oil holding capacity(OHC)of sweet potato granules at different steaming temperatures.The difference of water holding capacity and oil holding capacity of sweet potato granules was different between different rotational speed and steaming temperature.Under different conditions,peak viscosity,trough viscosity,breakdown,final viscosity,setback,pasting temperature,peak time of sweet potato granules were different.(2)Sweet potato granules was non Newtonian fluid.With the increase of shear rate,the apparent viscosity of sweet potato granules processed by three kinds of processes increased significantly.With the increase of the pre-steaming temperature,the apparent viscosity of sweet potato granules decreased and the viscosity retention was stable.The shear speed value had no significant difference,when rotational speed is lower than 1.8r/min(60Hz).Starch structure of Sweet potato granules had slow recovery reconstruction,when the rotational speed is 1.8r/min(60Hz)processed by sheared 。(3)Through the response surface experiment and analysis,the relationship between the three factors of rotational speed,pre-steaming temperature and steaming temperature on vitamin C,iodine blue value BVI and syneresis rate were determined.rotational speed was very significant for vitamin C,iodine blue value BVI and syneresis rate(P<0.01).The pre-steaming temperature was very significant for vitamin C(P< 0.01),and the iodine blue value BVI and syneresis rate were significant(P< 0.05).Steaming temperature had no significant effect on vitamin C and iodine blue value BVI(P>0.05),and the syneresis rate was very significant(P< 0.01).(4)The key parameters of sweet potato granules quality were selected,and the nutrient comprehensive value of sweet potato granules were optimized by the weighted method.The rotational speed was 1.35r/min(45Hz),the pre-steamingtemperature was 64 ℃,and the steaming temperature was 100 ℃.Under this condition,the nutrient comprehensive value of sweet potato granules was 0.810,which could preserve the nutritional components of the sweet potato granules.3 Texture recombination technology was applied,and the purple sweet potato granules was as the main raw material,the effect of adding amount of pea starch dosage,water,butter and sugar content on frozen prepared fried purple potato strips were discussed.On the basis of single factor test,response surface analysis was carried out to find out the optimum recipe.The results indicated that the optimum formula for the purple sweet potato strips process were pea starch content of 8.2%,water adding amount of 56.2%,butter content of 1.5%,sugar addition amount of 5%,frying temperature of 1800 C,frying time of 129 s,freezing time of 6h.Under such conditions,purple sweet strips sensory score was the best.