| L-ascorbic acid (vitamin C) is the most unstable vitamin among the food and feed raw materials,but it is vulnerable to light,heat,oxygen,moisture,pH,metal ions and ultraviolet radiation et al,so that the effect decreases quickly.Relevant researches suggest there is about 80-98 percent of L-ascorbic acid was destroyed during the feed pelleting and storage.In recent years,the development of ascorbyl polyphosphate (AsPP) which is one of the L-ascorbic acid derivatives with a strong antioxidant capacity is being payed more and more attention by the domestic and foreign researchers.In this paper,the direct acylation method was applied to obtain AsPP using L-ascorbic acid and Sodium Trimetaphosphate.By studying the effects of material molar ratio,reaction temperature,pH,amount of catalyst,reaction time on the AsPP yield and purity to optimize the best reaction conditions,and used orthogonal experiment to abtain the optimum technological condition of preparating AsPP on the base of single factor experiments,the result shows that n(L-ascorbic acid):n(Sodium Tripolyphosphate):n(catalyst) was 1:1.1:0.2,pH value of reaction system was 8.0,the reaction temperature was 30℃,reaction time was 30min.As the current process of production AsPP powder from the reaction mixture in the feed industry is by evaporation drying or spray drying method,which is complex and a waste of energy,so in this study we used the method of adding some organic solvents to the reaction solution to change the phase equilibrium so that the AsPP can be precipitated from the reaction solution.In this study the effects of organic solvent kind,volume ratio of organic solvents to reaction solution,temperature,pH value,alcohol precipitation time,mass fraction of the organic solvent on the yield and purity of AsPP were investigated by single factor experiment,and used response surface method to further optimize the preparation process of AsPP powder,and the result shows that 95% ethanol was the organic solvents,liquid pH value was 6.74,volume ratio of organic solvents to reaction solution was 2.25:1,the temperature was 30.15℃.Under this optimal process the AsPP theoretical predictive yield value is 89.38%,the theoretical predictive titer value is 41.90%.And by using UV scanning,IR scanning et al to identified the product is AsPP.This paper also studyed some major physical and chemical properties of AsPP,including the solubility in pure water at room temperature,the dissolution equilibrium time,the melting point and the effects of pH,temperature,storage time,the solution ions on the stability of AsPP. By comparing the stability of AsPP with L-ascorbic acid and Ascorbyl monophosphate sodium(SAP) to demonstrate the superiority of AsPP.The result shows that the dissolution equilibrium time at 25℃is 4 hours,the solubility is 18.98mg/mL,the melting point of AsPP powder is 221 ~ 224℃.AsPP is quite stable regardless of in the acidity,the alkalinity or the neutral solution, particularly is stablest in the alkazid solution with pH10,the survival rate still reached as high as 88.6% after depositing for 3 months;and AsPP has a strong anti-high temperature ability, its survival rate was 66.86% after being processed at 140℃for 5minites;AsPP also has a strong antioxidant ability in the heavy metal solution,the survival rates respectively was 53.7% and 47.5% after being deposited in CuSO4 solution and Fe2(SO4)3 solution for 90 days;AsPP still had a 44.3% survival rate after being deposited in water which was added with 30%H2O2 for 90days.
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