| Purple Dioscorea alata L.,an annual or perennial vine trailing plants,belongs to dioscorea batatas.It is mainly distributed in Africa,South America and subtropical zones,and also planted in Jiangxi,Guangxi and other areas in China.Purple Dioscorea alata L.contains a variety of nutrients such as protein,starch and vitamin.It is also rich in saponin,glue polysaccharide and pigment,which are good for human's health.The pigment of purple Dioscorea alata L.,a kind of natural water-soluble flavonoids compounds,belongs to anthocyan pigments.The present study was subjected to extract anthocyanin from purple Dioscorea alata L.with ultrasonic assistance;the starch,obtained from purple Dioscorea alata L.slag after extracting pigment,was prepared into resistant starch with pressure-heat treatment;and a kind of beverage was developed,which contains purple Dioscorea alata L.resistant starch and anthocyanin.The study will not only make full use of the resource of purple Dioscorea alata L.,but also provide a certain direction for expanding the development of food pigment.(1)The yield of anthocyanin,which was derived from fresh purple Dioscorea alata L.by using water as the solvent,was determined with pH-differential method.The effects of four factors,such as solid-liquid ratio,extraction time,ultrasonic power and extraction temperature,on the anthocyanin yield were studied through the single factor test.And the optimum technology conditions for extracting anthocyanin were optimized by using the orthogonal experiment.It's shown in the results that the primary and secondary sequence of the factors affecting the anthocyanin yield were:solid-liquid ratio>extraction temperature>ultrasonic power>extraction time.And the optimal conditions were obtained as following:solid-liquid ratio 1:6(g/mL),extraction time 30 min at 30 ? with ultrasonic power 300 W,and the anthocyanin yield could reach up to 4.57 mg/100g under these conditions.(2)The purple Dioscorea alata L.resistant starch was prepared from the starch of purple Dioscorea alata L.with the method of pressure-heat treatment.By adopting the productivity of resistant starch as evaluation index,the preparation technology was optimized with orthogonal test on the base of single factor experiment.The study result showed that the order of the factors influencing the productivity of resistant starch was:starch milk concentration>temperature>pH value>time.And the optimum preparation technology condition was following as:starch milk concentration 30.0%,temperature 120 ?,pH 7.0,time 60 min.Under these conditions,the productivity of resistant starch was 12.92%.The in vitro digestibility characteristic of purple Dioscorea alata L.starch and resistant starch was also pilotly studied.(3)The best formula of purple Dioscorea alata L.beverage was determined with sensory evaluation and orthogonal test.The results indicated that the optimal formula were:anthocyanin extracting solution 40.0%,sugar 6.0%,citric acid 0.18%and resistant starch 5.0%.Considering that resistant starch is the main factor affecting the stability of beverage,stabilizer and its adding amount were investigated,and the best formula of compound stabilizers was determined as following:the ratio of CMC-Na to Xanthan gum 2:1,adding amount 0.15%.The homogeneous and sterilizing conditions for the beverage were gotten by using deposition rate and sensory score as the indicators.The best homogeneous parameters was:pressure 40 MPa,temperature 45 ?,treatment for twice,and the sterilizing condition was:heating 15 min at 121 ?.The purple Dioscorea alata L.beverage,produced according to these conditions,was characterized by the unique fragrance and color of purple Dioscorea alata L.and good stability. |
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