Study On Heat-moisture Treatment Of Sweet Potato Flour And Its Application In Noodles

In this paper,the sweet potato flour was used as raw material and the gelatinization characteristics,thermodynamic characteristics,short-range order characteristics,crystallization characteristics and in vitro digestion characteristics of the sweet potato flour,heat-moisture treatment（HMT）sweet potato flour and fatty acid blending heat moist treatment sweet potato flour were analyzed by rapid viscosity analyzer,differential Scanning Calorimeter,fourier transform infrared spectrometer and X-Ray diffractometer.The rheological properties of sweet potato-wheat mixed flour mixed by sweet potato flour,HMT-sweet potato flour and fatty acid blend heat-moisture treatment sweet potato flour with wheat flour in different proportions were studied by Mixolab mixing tester.On this basis,the production process of slow digestion sweet potato noodles was optimized by single factor and response surface test with vital wheat gluten,sa-son seed gum and salt as modifiers.The particle shape,nutritional properties,physical and chemical properties and in vitro digestibility of three kinds of sweet potato powder（Xinxiang,Jishu 26 and Yanshu 25）were studied.The results showed that there were no significant differences in shape and nutrient types among the three kinds of sweet potatoes.Among them,Xinxiang sweet potato powder has the highest content of protein,fat and cellulose,Yanshu 25 has the highest water content and starch rate,and Jishu 26 has the highest soluble sugar content.Among the three kinds of sweet potato whole powder,Xinxiang sweet potato whole powder has the highest peak viscosity（1169.0/m Pa·s）,the best cold paste stability,the highest phase transition temperature（79.91 ℃）,the best short-range order,the highest relative crystallinity（23.40 %）and the highest slowly digestible starch（20.59 %）.The effects of HMT（different moisture,temperature and time）on the gelatinization characteristics,thermodynamic characteristics,short-range order characteristics,crystallization characteristics and in vitro digestion characteristics of three kinds of sweet potato powder were studied.The results showed that the gelatinization temperature,viscosity and slow-digesting starch content of sweet potato powder increased after HMT with different moisture,temperature and time.The paste had better shear resistance and aging resistance,and had better cold and hot stability and slow digestion.When the water content was 20 %,the heating temperature was 100 ℃ and the treatment time was 4 h,the Xinxiang whole sweet potato powder had the best cold and hot stability and better slow digestion characteristics.The selected sweet potato whole powder was mixed with oleic acid,linoleic acid,palmitic acid and stearic acid in different proportions（2 %,4 %,6 %,8 %,W/W,based on the content of sweet potato powder）and treated with HMT to explore the effects on the physical and chemical properties and in vitro digestibility of sweet potato whole powder.The results showed that the peak viscosity of sweet potato powder decreased,but it had better shear resistance and higher fission resistance temperature.The combination of the whole sweet potato powder and fatty acid produced more stable V-shaped crystal morphology,and the contents of slow-digesting starch and resistant starch in the mixed powder increased,which had better slow digestion characteristics.By comparison,it can be found that 2 % linoleic acid mixed heat moisture treatment sweet potato whole powder has better cold and hot stability and slow digestion characteristics.The raw sweet potato powder,HMT-sweet potato whole powder and linoleic acid mixed heat moisture treatment sweet potato whole powder were mixed with wheat flour.The rheological properties of the three powders were investigated by Mixolab mixing tester.The results showed that with the increase of the proportion of the three kinds of sweet potato powder,the water absorption rate of the mixed dough increased gradually,while the torque,formation time and stability time of the dough decreased gradually,and the stiffness,ductility and flexibility of the dough decreased,the weakening value of the dough increased,and the quality of the dough decreased.Based on the analysis of various test indexes,it was concluded that the appropriate proportion of raw sweet potato powder,HMT-sweet potato powder and 2%linoleic acid mixed with heat moisture treatment sweet potato power were 40%,30% and 40%,respectively.Based on the rheological characteristics analysis of mixed flour,the production process of slow digestion sweet potato noodle was optimized by single factor and response surface test vital wheat gluten,sa-son seed gum and salt as modifiers.The results showed that the appropriate proportion of vital wheat gluten,sa-son seed gum and salt in sweet potato flour-wheat mixed flour noodle,HMT-sweet potato flour-wheat mixed flour noodle and Linoleic acid mixed heat-moisture treatment sweet potato flour-wheat mixed flour noodle were 2.6 %,2 %,1.5 %;3 %,1.5 %,2 % and 3 %,2 %,2 %,respectively.On the basis of the above research,the quality of three optimized sweet potato flour-wheat composite noodles was compared and evaluated from the aspects of cooking characteristics,texture characteristics,sensory characteristics and in vitro digestion characteristics.The results showed that HMT-sweet potato flour-wheat mixed flour noodles had the highest water absorption,elongation,hardness,elasticity,chewability and resilience,and the lowest cooking loss rate,and had the highest scores in color,apparent state,palatability,viscosity,toughness,smoothness and taste,and had good slow digestion characteristics.In this paper,the sweet potato whole powder used as raw material,HMT technology and Linoleic acid mixed heat-moisture treatment technology were introduced into the modification treatment of sweet potato whole powder to explore its influence on the physical and chemical properties and in vitro digestion characteristics of sweet potato whole powder.The preparation process of sweet potato flour-wheat flour noodles was optimized,which provided a reference for producing high quality and slow digestion sweet potato noodles.