Study On The Quality Characteristics Of Purple Sweet Potato Flour And The Processing Technology Of Purple Sweet Potato Biscuits

Beautiful color, plentiful nutrition and significant health effect, Purple sweet potato flourbecome one of the hot research at home and abroad. The quality characteristics of purplesweet potato flour have important influence on its application and quality of the products.This paper mainly studied the quality characteristics of purple sweet potato raw flour andcooked flour, focus on the physicochemical properties, processing characteristics and stabilityof anthocyanin of purple sweet potato flour. On the basis, application of purple sweet potatoflour on biscuits was also studied. The main results following:1, Through the study on physicochemical characteristics of purple sweet potato raw andcooked flour, the results show that: purple sweet potato cooked flour has good retention ofcolor and health factors, while purple sweet potato raw flour has high starch content, lowreducing sugar content, cell integrity is better.2, Through the study on processing characteristics of of purple sweet potato raw andcooked flour, the results show that: the processing characteristics of purple sweet potato rawflour is far superior to that of cooked flour. Raw flour is more powerful on water holdingcapacity than that of cooked flour. Purple sweet potato raw flour can form a stable paste atquality concentrations of50g/L，while80g/L for cooked flour. Under the condition of acid oradding salt, sugar, an increasing trend of paste stability for raw flour, while decreasing tocooked flour. Purple sweet potato raw flour is better than cooked flour on gelatinizationcapacity. The gelatinization capacity is improved when adding30g/L salt or100g/L sugar.Purple sweet potato raw is better than cooked flour on freeze-thaw stability. Under thecondition of acid or adding salt, an increasing trend of freeze-thaw stability for raw flour,while is opposite to cooked flour. It can be seen from the Brabender viscosity that the rawfour is easy to gelatinization（63.7℃）. It has poor thermal stability, strong retrogradation, butnot easy to ageing. Cooked flour has been basically gelatinization complete.3, Further study on the stability of purple sweet potato flour anthocyanin was carried out.The results show that: anthocyanin of purple sweet potato raw flour and cooked flour hadsimilar stability on processing factors. The effects of different processing factors onanthocyanins stability of purple sweet potato flour as following: pH value had a significant effect on the stability of anthocyanin. with the increase of pH value, the color of solutionchanges from red to blue and become unstable, maximum absorption peak redshifts; At thebuffer solution of pH3, the anthocyanin concentration is higher, the stability is better; At thebuffer solution of pH3, anthocyanin is stable to low temperature, but when the processingtemperature is higher than80℃, damage to anthocyanins is significant. With the rise of theheating temperature and prolong of heating time, color preservation rate decreased; At thebuffer solution of pH3, anthocyanin is stable to indoor natural light, great damage to bulbshining. At the buffer solution of pH3, Fe³⁺, Cu²⁺, Zn²⁺would decrease the stability ofanthocyanin, Al³⁺could increase the stability of anthocyanin, Mg²⁺had no significant effecton anthocyanin; At the buffer solution of pH3, the stability of anthocyanins on carbohydrates:lactose> maltose> glucose> sucrose, sugar content is greater, the more significant damageeffect.4, Purple sweet potato raw flour has good processing stability; Partial replacement offlour to make biscuits can improve nutritional value and add health benefits. The maininfluences of the biscuit production technology when adding purple sweet potato flour werestudied, and the processing technology of purple sweet potato biscuits was discussed also.There has certain effect on the production process of the biscuit with the addition ofpurple sweet potato flour. Osteoporosis agent should be selected in neutral or acidic duringthe production of purple sweet potato biscuit. And the osteoporosis agent should be evenlymixed with all the wet material at first. Baking temperature of purple sweet potato biscuitswas170℃for surface fire and150℃for primer.Through single factor and L9（34） orthogonal experiment, the optimal basic ingredient ofpurple sweet potato biscuits was determined as: per100g wheat flour adding30g purple sweetpotato flour,30g butter,25g egg,30g white granulated sugar.