Enzymatic Preparation And Application Research Of Starch Phosphate

Starch phosphates is a starch derivative produced by esterification of hydroxyl group and phosphorylated reagents.With its characteristics of high transparency,remarkable freeze-thaw stability,distinguished viscosity,unusual anti-retrogradation et al,starch phosphates have been widely used in food,paper making and other industries.At present,starch phosphates were usually prepared by chemical modification in industrial production.The starch phosphates producing was influenced by many factors and the research of reaction mechanism is not thorough.There is no general rule guiding serialized production,and starch phosphates are produced with lots of by-products.An enzymatic reaction was hardly affected by phosphorylation reagent and reaction conditions,and it has the characteristics of mild conditions,strong specificity and high reaction efficiency.The starch phosphate prepared by enzyme is suitable for the research and it had certain market competitiveness.Therefore,the purpose of this research was to develop a starch phosphate produced by biological methods.With maize starch as the substrate,sodium pyrophosphate as raw material,alkaline phosphatase as catalyst,this research determined and optimized the preparation technology,compared the difference of the structure and chemical properties in starch phosphates prepared by enzymatic and chemical way,discussed the reaction mechanism of alkaline phosphatase reacting with starch,and applied the starch phosphates in minced fish.The contents of this paper mainly were as follows:Firstly,the paper determined the technological condition of alkaline phosphatase reacting with starch.Results shows that:the most suitable substrate to produce starch phosphates is native starch,the best reaction p H is 8.0,the best reaction time is 2 h.In the 100g solution system which starch solid content was 30%,with 0.1 g enzyme,0.2 mol/L concentration of active ion,the phosphorus content of starch phosphate was the highest,which was 1284.7mg/100 g.To guide producing and obtain the expected target product,the prediction formula between phosphorus content and technological conditions was built:Y=523.205X₁+6591.787X₂-110.770,Y,X₁ and X₂are phosphorus content,enzyme amount and active ion concentration respectively.The equation was tested with a high fitting degree.Secondly,using starch phosphate prepared by chemical as control,the influence of phosphorus content on the physicochemical properties and structure of starch phosphate was discussed.Results shows that:while phosphorus content increasing,the pasting temperature of starch phosphate decreased from 84.6°C to 72.2°C,and then increased to 75.0°C.Gelatinization characteristics,thermodynamic properties and thermal stability indicated that the starch phosphate showed the characteristics of esterified starch and then crosslinked starch.While phosphorus content increasing,the thermal decomposition temperature gradually decreased from 332°C to 319°C,relative crystallinity gradually decreased from 22.73 to 16.64,gelatinization enthalpy gradually decreased from 15.53 J/g to 11.84 J/g,indicating that the formation of ester bonds and crosslinked bonds during the reaction process destroyed the internal ordered structure of starch particles.Thirdly,the reaction mechanism of alkaline phosphatase reacting with starch was studied.Results shows that:EDS demonstrated the presence of phosphate groups and To F-SIMS confirmed the covalent bond of phosphate groups and starch.According to the ³¹P NMR test,monostarch monophosphate and distarch monophosphate were both existed in starch phosphate,and they were specifically bound to C-6.XPS determined the chemical bond composition of distarch monophosphate as P-O,P=O and C-O-P,excluding a variety of structures of cross-linked bonds.Therefore,it is inferred that the reaction mechanism of forming monostarch monophosphate and then distarch monophosphate in C-6.The structure of both starch phosphates was discussed.Finally,the application of starch phosphates prepared by enzymatic and chemical methods in minced surimi was evaluated.Results shows that:the starch phosphates prepared by enzymatic method improved the gel strength and water holding capacity of surimi and effectively promoted the formation of dense gel network in surimi gel.The texture properties were enhanced and the application performance of starch in surimi gel was advanced.The application effect of starch phosphate prepared by two methods was similar.