| Comparative analysis of the contents of anthocyanins, starch, protein and constituents of anthocyanins in different varieties of purple sweet potato, PSP,(Ipomoea batatas(L.) Lam) was carried out and effects of processing and preservation methods on the content of anthocyanins were investigated, and then the extraction process parameters with acidified ethanol, supersonic assisted acidified ethanol and yeast fermentation were optimized. The stability to pH value, heat, light and metal ion and antioxidative activity of the pigment extracted from the PSP pulp fermented by Saccharomyces cerevisiae were observed. The composition and structure of purple sweet potato anthocyanins were analyzed and identified. The main results and findings were summarized as follows:Spectrometry analysis of HPLC-DAD for PSP anthocyanins and their acid hydrolyzed compounds showed that most of anthocyanins in different PSP variaties are acylated anthocyanins, and derived from Cy and Pn. The difference of the contents and constituents of anthocyanins in different PSP varieties were significant. The number of constituents of anthocyanins in the varieties of Chuanshanzi, Jishu 18, Anhuizi, ZiA0 and was 21, 17, 16, 15 and 14, respectively. The ratio of acylated anthocyanins content to total anthocyanins content in those varieties mentioned above were 92.05 %, 80.65 %, 93.13 %, 74.96 % and 93.47 %, respectively. There were seven acylated anthocyanins in each variety of ZiA1, Anhuizi and Chuanshanzi, four in ZiA0 and three in Jishu 18, respectively. Among the five varieties of PSP, the contents of anthocyanins, starch and protein in ZiA1 were highest, reaching to 76.63, 326.70 and 14.86 mg/100g FW, respectively.The content of anthocyanins in PSP decreased with time by putting PSP in 4℃refrigerator, directly-20℃freezing storage and-20℃freezing storage after heating PSP with microwave and boiling water vapor. The former two storage methods for 7-day could get 92.3% and 92.1% retention of anthocyanins in PSP respectively, but the latter two could obtain 84.5% and 83.3%, respectively, loss of a non-acylated anthocyanin and large decrease of the contents of two acylated anthocyanins in Xushu 1 variety had been observed within 7-day storage at-20℃. The direct solar shining could lead to serious destroy. With hot wind drying method, the adequate temperature was 50℃.With hydrochloric acidified ethanol as reagent, the optimum process parameters of temperature 80℃, ratio of solid to liquid 1: 28.7 and time 74.7 min were obtained for anthocyanins extraction from PSP powder by RSM. The maximum predicted anthocyanins yield was 157.29 mg/100 g(db), but actual anthocyanins yield 155.24 mg/100 g(db). With the extraction method of supersonic wave assisted hydrochloric acid-ethanol, a maximum extraction yield of 170.57 mg/100g(db) was obtained under supersonic power of 225 W, ratio of solid to liguid 1:30 and temperature 60℃for 40 min. Compared to the former extraction method, the extraction yield of anthocyanins from PSP increased by 9.88%, and extraction duration reduced nearly half(34.7 min), but the color value reduced 21 u.The extraction yield of anthocyanins from fresh PSP treated with pectinase increased significantly(p<0.01). Under the conditions of temperature 35℃, pH value 4.0 and addition pectinase dose of 80 U/mL for 120 minutes, the extraction yield of anthocyanins from fresh PSP pulp reached 105μg/mL, two times more than that of non addition of pectinase. After treated with pectinase, the PSP pulp was then treated with a-amylosase and saccharified enzyme consequently in order to convert the starch into reducing sugar, at the same time, the content of anthocyanins in PSP pulp kept high level. The adequate action conditions of a-amylosase were dose of a-amylosase 200 U /mL, temperature 60℃and time 1 hour. The highest content of reducing sugar and minimum loss of anthocyanins in PSP pulp were reached at the temperature of 60℃, initial pH value 4.5, dose of saccharified enzyme 200 U/mL for 2 hours. Optimization for anthocyanins extraction in saccharified PSP pulp fermented by yeast was investigated using response surface methodology. The maximum anthocyanins extraction yield of 66.6μg/mL was obtained at the temperature of 27℃, initial pH value 3.0, quantity of yeast inoculation 10 % for 72 hours. Compared to the extraction method of acid-ethanol, extraction yield reduced by 14.39%, but the color value of the anthocyanins pigment extracted with yeast fermentation increased 49 u, meanwhile, 200 mL 6% alcohol liquid was produced from 100 g fresh PSP.Static absorption dynamics and thermodynamics of four kinds of macroporous resins, viz., AB-8, S-8, NKA-Ⅱ, and NKA-9 used in purple sweet potato pigments(PSPPs) purification were investigated. It was indicated that AB-8 was a preferable macroporous resins with the adsorption equilibrium rate constant of 0.0246/min and the adsorption equation fits the Freundlich empirical equation well. The maximum adsorption of AB-8 to the PSP pigments was adsorbed at the concentration of pigment 0.992(A535</sub>, temperature 40℃for 30 min. and adequate eluted agent was 80% ethanol solutionThe pH value had obvious effect on the color and stability of PSPPs solution. At pH 3 below, the color of PSPPs solution is red and stable, with the increase of pH value, the color of PSPPs solution change from red, purple to blue-violet and become unstable. The color of PSPPs solution at pH 2 and 3 still kept red after 40-day storage at room temperature and darkness, the others at pH 4 above were colourless. Thermal degradation kinetics of PSPPs in aqueous solution followed first-order kinetics. The computed values of activation energies were 39.64 kJ/mol; the half-life value of PSPPs was 14.3 hour at 98℃. At the buffer solution of pH 3, the high retention of PSPPs was observed shining with light for 15 days at room temperature. But at the buffer solution of pH 5, light adduced degradation kinetics of PSPPs in aqueous solution followed zero-order kinetics. The degradation dgree of PSPPs shining with fluorescence was higher than that under bulb light and darkness. At the buffer solution of pH 3, both Cu2+ and Fe3+ could not only increase the color intensity of PSPPs, but accelerate anthocyanins to degrade and browning color occur. At the buffer solution of pH 5, both Mg2+ and Ca2+ could prevent the color from degradation.Addition of copigments could significantly improve PSPPs aqueous solution stability. The obvious difference of retention of PSPPs added with different copigments was observed. The retentions of the PSPPs added with tannic acid, rutoside, and coumarin were 72.77%,61.40%,57.38% and 48.65%, respectively, all higher than control treatment of 39.85% after 80-day storage at room temperature and darkness. The polymerized pigments in PSPPs aqueous solution increased with time. The contents of polymerized pigments in PSPPs aqueous solution added with ferulic acid and rutoside were higher than that with coumarin, tannic acid and control treatment. The half lives of PSPPs in pH 3 buffer solution added with tannic acid, coumarin, ferulic acid and rutoside at 98℃water bath were increased by 13.26%,2.95%,7.28% and 1.00%, respectively, compared with control treatment. The half life of PSPPs in pH 4 buffer solution added with copigments increased more than that in pH 3 buffer solution.The reducing power, DPPH radical-scavenging activity and superoxide radicalscavenging activity of PSPPs2 extracted from yeast fermented PSP liquid were higher than those of PSPPs1 extracted from PSP powder with acid-ethanol. Both PSPPs1 and PSPPs2 were higher than those of BHT. Those capacities depended on their concentration. Both PSPPs1 and PSPPs2 had the capacities of chelating metal ion and antioxidant activity in linoleic acid system, but were weaker than those of EDTA and BHT.The spectral analysis of HPLC-DAD-MS for PSPPs2 and PSPPs1 showed that the anthocyanins constituents of PSPPs2 and PSPPs1 were similar, which mainly derived from Cy and Pn. The probable sugar were glucose, sophorose and rotinose and probable acylated groups were caffeic acid, ferulic acid, p-hydroxybenzoic acid and p-Coumaric acid.
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