【作者】 陈健初；

【导师】 席玙芳；

【作者基本信息】 浙江大学 ， 食品科学， 2005， 博士

【摘要】 杨梅(Myrica.rubra Sieb.et Zucc)为我国的特产水果,杨梅果汁在加工和贮藏过程中易变色和沉淀,货架寿命较短。因此提高杨梅果汁色泽稳定性、澄清和防止沉淀是杨梅果汁生产的关键问题。本论文研究了抗坏血酸、糖和槲皮素对杨梅花色苷溶液和杨梅果汁色泽稳定性的影响;单宁明胶法和超滤对杨梅果汁的澄清作用和理化指标的影响;三种不同杨梅果汁的沉淀规律和沉淀的组成;不同品种加工的杨梅果汁的抗氧化特性,结果表明: 抗坏血酸能显著降低杨梅花色苷溶液和杨梅果汁的色泽稳定性,抗坏血酸浓度越高,花色苷的降解越快。当杨梅花色苷溶液中加入50mg/L和100mg/L的抗坏血酸时,经70℃,5h热处理后,其花色苷含量分别为对照的70.7%和43.1%,Hunter A值分别为对照的76.2%和48.8%;杨梅果汁中加入50mg/L和100mg/L的抗坏血酸时,经70℃,5h热处理后,其花色苷含量分别为对照的78.8%和53.0%,Hunter A值分别为对照的63.1%和42.4%;在20℃下贮藏6个月后,其花色苷含量分别为对照的61.6%和37.3%,Hunter A值分别为对照的73.8%和49.2%。 葡萄糖、果糖和蔗糖对杨梅花色苷稳定性有不同的影响。当糖溶液的浓度为10%时,经80℃10小时加热后,含葡萄糖、果糖和蔗糖的杨梅花色苷溶液的花色苷含量分别为对照的94.7%、51.0%和64.1%;Hunter A值分别为对照的96.3%、56.9%和60.4%;糖浓度对杨梅花色苷溶液稳定性的影响虽然不是很显著,但对于同一种糖来说,随着糖浓度的提高,杨梅花色苷的降解有延缓的趋势。 槲皮素能显著提高杨梅果汁的色泽稳定性。含25mg/L槲皮素的杨梅果汁经过6个月贮藏后,其花色苷含量和Hunter A值分别为22.32mg/L和32.32,而对照杨梅果汁的花色苷含量和Hunter A值分别为14.12mg/L和20.12。 当单宁和明胶的用量均为0.1g/L～0.5g/L时,杨梅果汁的澄清度达80%以上,而混浊度在3～20ppm之间。澄清后,杨梅果汁的蛋白质含量明显下降,Hunter A值约上升10%～15%,花色苷含量、可溶性固形物含量均无显著影响。 三种不同超滤膜过滤后杨梅果汁的澄清度提高25.8～30.8%;杨梅果汁的花色苷含量降低4.5%～8.5%;聚合色素百分率从23.98%减少到2～3%;蛋白质含量大大降低;可溶性固形物含量下降2.7～4.9%;但总酚、总酸及pH值均无显著影响;Hunter A值发生不同的变化,聚砜膜UWIS和聚丙烯腈膜过滤后杨梅果汁的Hunter A值有一定程度的降低,但聚砜膜UEIS过滤后却使杨梅果汁的Hunter A值反而有所提高。 混浊果汁沉淀最快且沉淀的量也最多,其次为经明胶—单宁澄清并经硅藻土过滤的澄清果汁,经超滤的澄清果汁沉淀形成的速度最慢,且沉淀的数量也最少。更多还原

【Abstract】 Yangmei(Myrica rubra Sieb.et Zucc) is a specific fruit species in China. Because yangmei is rich in anthocyanin, decoloration and precipitation of yangmei juice occurs rapidly during process and storage, which limits its shelf life. Therefore, increasing the stability of anthocyanin, clarifying and preventing precipitation become key problems in the production of yangmei juice. Effects of ascorbic acid, sugar and quercetin on stability of yangmei juice and the dissolved anthocyanin from yangmei, effects of the concentration of tannin and gelatin and ultra-filtration on the clarity and the other physico-chemical index of yangmei juice, the regularity of precipitation of yangmei juice and the main constituent of precipitants from three kinds of yangmei juice and the antioxidant activity of yangmei juice produced with four varieties of yangmei were studied in this dissertation. The results were as follows:Ascorbic acid decreased the stability of color of the anthocyanin solution and yangmei juice. The higher the concentration of ascorbic acid was, the more rapid the degradation of anthocyanin would be. When the anthocyanin solution contained 50mg and 100mg ascorbic acid /L, the concentration of anthocyanin were 70.7% and 43.1% and the corresponding value of Hunter A were 76.2% and 48.8% that for the control after heating for 5h at 70℃, respectively. When yangmei juice contained 50mg and 100mg ascorbic acid /L, the concentration of anthocyanin were 78.8% and 53.0% and the corresponding value of Hunter a were 63.1% and 42.4% that for the control after heating for 5h at 70℃, and the concentration of anthocyanin were 61.6% and 37.3% and the corresponding value of Hunter a were 73.8% and 49.2% that for the control after storage for 6 months at 20℃, respectively.Glucose, fructose and sucrose have different effect on the stability of anthocyanin from yangmei. When the concentration of glucose, fructose and sucrose were 10%, the concentration of anthocyanin in the dissolved anthocyanin from yangmei were 94.7%,51.0% and 64.1% and the corresponding value of Hunter a were 96.3%, 56.9% and 60.4% that for the control after heating for 10h at 80℃, respectively. Although the concentration of glucose, fructose and sucrose had no significant effect on the stability of anthocyanin from yangmei, but the degradation of anthocyanin from yangmei decreaced with increase of the concentration of sugar.Quercetin could increase the stability of the color of yangmei juice significantly. When yangmei juice contained 25mg quercetin /L, its concentration of anthocyanin was 22.32mg/L and the corresponding value of Hunter a was 32.32, but the concentration of anthocyanin in the control yangmei juice was 14.12mg/L and the corresponding value of Hunter a was 20.12 after storage for 6 months at 20℃.更多还原