【作者】 徐超炯；

【导师】 汪俏梅；

【作者基本信息】 浙江大学 ， 蔬菜学， 2010， 博士

【摘要】 目前功能性食品科学的研究正方兴未艾,青花菜(Brassica oleracea var. italica)以其丰富的食用营养价值和独特的抗癌保健功效,成为深受国内外消费者青睐的大众型蔬菜,近年来,青花菜在我国的种植面积不断增加,已成为我国的重要主栽蔬菜和出口创汇蔬菜。萝卜硫苷是青花菜中最主要的芥子油苷组分,也是迄今为止鉴定到的在抗癌代谢中具有解毒作用的阶段2酶(如醌还原酶等)的最有效的天然诱导剂。本研究以功能性蔬菜青花菜花球和芽菜为试验材料,在青花菜产品采前、采中和采后的连续过程中,研究了品种、施肥、外源植物激素、采收成熟度和采后冷藏、气调等因子对青花菜品质的影响,特别是在动态的过程中系统研究了不同处理对青花菜中的抗癌类芥子油苷萝卜硫苷和醌还原酶诱导活性等的影响及其可能的机理,也探讨了外源激素处理对青花菜芽菜中的芥子油苷,总多酚和花青素等的含量和抗氧化能力的影响。所取得的主要结果如下：1.研究了氮肥施用(0,100,200,300 and 400kg N ha-1)对青花菜萝卜硫苷、醌还原酶诱导活性和品质的影响。在“优秀”和“绿岭”两个品种青花菜中,花球的直径和重量都随着氮肥施用量的增加而升高；花球和花茎5℃下的贮藏寿命、抗坏血酸含量、萝卜硫苷含量和醌还原酶诱导活性都随着氮肥施用量的增加而降低,其中施氮量300-400 kg N ha-1时抗坏血酸含量最低,400kg N ha-1时贮藏寿命最短且萝卜硫苷含量最低,醌还原酶诱导活性与萝卜硫苷含量的变化一致。综合考虑各方面的因素,氮的施用量为中等(200-300 kg N ha-1)比较适宜。“优秀”品种青花菜有更好的营养和保健价值,其抗癌的萝卜硫苷的含量比“绿岭”品种高40%左右。青花菜小花球的萝卜硫苷含量与抗癌活性均高于主茎部分。2.研究了冷藏对青花菜萝卜硫苷、醌还原酶诱导活性和品质的影响。青花菜在O℃、5℃、10℃和20℃下的贮藏寿命分别为34.7天、17.5天、9天和2天：不同贮藏温度还对产品的品质有较大影响,较高的温度除了引起花球的黄花和外观品质下降外,还会使花球的营养品质以及萝卜硫苷和醌还原酶诱导活性下降,而较低的温度可以延迟青花菜的贮藏寿命并维持较好的产品品质。在0℃、5℃和10℃下,花球中萝卜硫苷含量和醌还原酶诱导活性在前6天增强,之后则出现迅速下降。0℃和5℃快速冷藏可以维持青花菜花球较高的萝卜硫苷与醌还原酶诱导活性12天以上,而20℃条件下延迟冷藏时间不超过6小时,才能维持青花菜产品的外观品质、萝卜硫苷含量和QR诱导活性。因此,从延长青花菜产品贮藏寿命和维持产品品质的角度,冷链运输和冷藏(0-5℃)是一种较好的贮藏方式。3.研究了气调(CA)对青花菜萝卜硫苷、醌还原酶诱导活性和品质的影响。在5℃条件下,四种气调贮藏方式(Air+10%CO2,Air+20%CO2,1%O2,and 1%O2+10%CO2)都能使青花菜花球的贮藏寿命达到20天以上。各种处理对贮藏期间产品中萝卜硫苷和醌还原酶诱导活性的影响是不一致的,较高的CO2使其在贮藏前期增加,而较低的O：则使其明显降低。所以,从青花菜产品的外观品质,萝卜硫苷含量和抗癌活性变化等方面综合考虑,10%CO2条件的气调贮藏是一种较好的贮藏方式。4.研究了外源茉莉酸甲酯(MeJA)对青花菜芥子油苷和品质的影响。以0,0.01,0.1,1 mM MeJA处理7天苗龄的青花菜芽菜,研究结果表明,MeJA处理并不显著影响总多酚和花青素含量以及抗氧化活性,但与对照相比,0.01和0.1 mM MeJA处理24 h后青花菜芽菜总的芥子油苷含量显著增加,而0.01和0.1mM MeJA处理48 h后青花菜芽菜总的芥子油苷含量显著降低。这表明短时间内(24 h)低浓度MeJA处理能提高总的吲哚类芥子油苷含量和总的芥子油苷的含量；而随着处理时间的延长(处理后48 h),吲哚类芥子油苷和总的芥子油苷含量又显著降低。5.研究了外源24-表油菜素内酯(EBR)对青花菜芥子油苷和品质的影响。以0,0.01,0.1,1μM EBR处理7天苗龄的青花菜芽菜,研究结果表明,与对照相比,EBR在处理24 h后并不显著影响总多酚和花青素含量以及抗氧化活性,但是48 h后则显著降低。0.01μM-0.1μM EBR处理24 h至48 h后青花菜芽菜重要萝卜硫苷含量和总芥子油苷含量显著增加。不同EBR处理前期对青花菜芽菜中吲哚类芥子油苷差异不显著,在48 h时0.1μM EBR处理则使主要的两种吲哚类芥子油苷含量显著增加。这表明在24 h至48 h内适中浓度的EBR处理能提高萝卜硫苷和总芥子油苷含量,而且维持比较好的营养品质。更多还原

【Abstract】 Broccoli (Brassica oleracea var. italica) is consumed popularly by human being as functional food due to its high nutritional and anticarcinogenic value, and it has been one of the most important vegetables in China for domestic market and export in recent years. Broccoli contains a high level of glucoraphanin, which is the most potent, naturally occurring, monofunctional phase 2 enzyme (such as quinone reductase) inducer identified thus far. In this study, the effect of different preharvest and postharvest factors, including broccoli cultivars, nitrogen fertilization, cooling and controlled atmosphere treatments on glucosinolate and quality of brocolli were investigated with an emphasis on anticancer glucoraphanin and quinone reductase (QR) activity. We also studied the effect of plant hormones (Jasmonate and Brassinosteroid) on content of glucosinolate, total phenolics and anthocyanin in broccoli sproutsThe results are as follows:1. The effect of five levels of nitrogen fertilization (0,100,200,300 and 400 kg N ha-1) on head size, shelf life, concentrations of ascorbic acid, glucoraphanin and QR activity of broccoli was investigated in two broccoli cultivars,’Youxiu’and’Lvling’. The results showed that both the average weight and diameter of main head were significantly increased with the increase of nitrogen fertilization in both cultivars. However, the ascorbic acid and glucoraphanin concentrations in broccoli floret and stem were decreased with the increase in nitrogen application and significant low levels of ascorbic acid were detected by nitrogen fertilization at range of 300-400 kg N ha-1. The nitrogen fertilization at 400 kg N ha-1 also significantly reduced the shelf life of broccoli as well as glucoraphanin concentration in broccoli floret and stem. The QR activity in broccoli floret and stem supplied with different nitrogen paralleled their glucoraphanin concentrations. In conclusion, moderate nitrogen fertilization rate (200-300 kg N ha-1) could significantly increase the head size and maintain the storage life, glucoraphanin concentration and QR activity.2. The effect of storage temperatures on shelf life, glucoraphanin concentrations and QR activity of broccoli was investigated. The results showed that the shelf life of stored broccoli is 34.7d,17.5d,9.0d,2.0d under 0℃,5℃,10℃,20℃conditions respectively, which indicated that storage at lower temperature is better for the quality maintenance of broccoli. The results also showed that both the glucoraphanin content and QR activity of broccoli florets increased during the initial 6 days of storage, and then decreased markedly at different temperatures of 0℃,5℃, and 10℃. Immediate cooling of broccoli florets at 0℃and 5℃could preserve the glucoraphanin content and QR activity for 12 days. Cooling delay treatment was recommended no more than 6 hours at 20℃, and therefore "cool as soon as possible" is the general recommendation for postharvest handling of broccoli.3.The effect of controlled atmosphere on shelf life, glucoraphanin concentrations and QR activity of broccoli was investigated. Controlled atmosphere (CA) treatments with elevated CO2 (21% O2+10% CO2, and 21% O2+20% CO2) and air treatment (21% O2) were found to increase the glucoraphanin content and the QR activity at first 5 days of storage at 5℃, while CA treatments with reduced O2 concentration (1% O2,1% O2+10% CO2) led to a steady decrease of glucoraphanin content and the QR activity during the 20 days of storage at 5℃. The highest content of glucoraphanin content and QR activity of broccoli florets was observed when stored under 21% O2+10% CO2 at 5℃. This condition was able to maintain the visual quality, glucoraphanin content and QR activity of the broccoli florets for 20 days.4. The effect of four levels of MeJA (0,0.01,0.1 and 1 mM MeJA) on quality, composition and content of glucosinolates in 7d broccoli sprouts was investigated. The results showed that MeJA treatment did not significantly affect antioxidant activity, concentrations of total phenolics and anthocyanin in broccoli sprouts. Significant increase in content of indole glucosinolates and total glucosinolates was observed 24 hours after 0.01 and 0.1 mM MeJA treatments. However, content of indole glucosinolates and total glucosinolates decreased 48 hours after treatments compared with the control. 5. The effect of of four levels of EBR (0,0.01,0.1 and 1μM EBR) on quality, composition and content of glucosinolates in 7d broccoli sprouts was investigated. The results showed that EBR treatments did not significantly affect antioxidant activity, concentrations of total phenolics and anthocyanin in broccoli sprouts within 24 hours after treatment. Significant increase in contents of glucoraphanin and total glucosinolates was observed under EBR treatments at moderate concentrations (0.01 and 0.1μM) from 24 to 48 hours after treatment, which helps to maintain good nutritional quality.更多还原