南果梨褐变因子分布及贮藏过程中的变化趋势

以南果梨为试材,研究果实采后后熟及贮藏期间主要褐变因子在果实中的区域性分布和动态变化.结果表明:果实中酚类物质含量和PPO活性在果心最多,果皮次之,果肉最少.在后熟和贮藏期间,酚类物质含量在贮藏前期呈上升趋势,达到峰值后开始下降;PPO活性呈先升后降趋势,PPO活性最高时正是果实开始出现褐变的时期,同时也是酚类物质大量下降的时期,褐变程度与PPO活性和酚类物质含量呈对应关系.     

低温贮藏期间梨果皮酚类物质及抗氧化性变化

为了研究甘肃省主要梨果低温贮藏期间果皮酚类物质含量及其抗氧化性的变化,在苹果梨、早酥梨和皇冠梨果皮总酚、总黄酮测定的基础上,采用HPLC法分析8种主要酚类物质含量;并通过FRAP、DPPH和ABTS+·法评价不同时期酚类提取物的抗氧化能力,及其与酚类物质含量的相关性。8种主要酚类物质中熊果苷含量最高,其在苹果梨、早酥梨和皇冠梨果皮的平均含量分别达到10. 22、16. 92和11. 17 mg/g FW;除早酥梨果皮中儿茶素和苹果梨、皇冠梨中芦丁含量在低温贮藏期间呈升高趋势外,总酚、总黄酮及其他主要酚类物质均呈下降趋势;果皮酚类提取物的抗氧化能力随贮藏期的延长而下降,且与总酚、总黄酮、阿魏酸含量呈显著正相关(P <0. 05)。梨果皮酚类物质含量及特性因品种、贮藏期而异,该研究为进一步揭示梨果皮酚类物质的变化规律及其开发利用提供理论依据。     

不同种酿酒葡萄酚类物质特性研究

本文对欧亚种,野生种和杂交种共９个酿酒葡萄（种）品种酚类物质特性进行了研究,结果表明不同种酿酒葡萄品种果实酚类物质含量之间存在显著差异;发酵和贮藏过程中各品种酚类物质的变化趋势不同。酚类物质各指标间大都呈极显著相关关系;根据酚类物质特性可以选择适宜的酿酒品种酿造不同类型的葡萄酒。     

超红桃和日川白沙桃果实发育过程中色素及酚类物质含量变化研究

以超红桃和日川白沙桃果实为试材,研究二者果实发育过程中叶绿素、类胡萝卜素、花青苷、类黄酮和酚类物质的变化规律,探讨花青苷与色素和酚类物质的关系。结果表明：在发育过程中,与日川白沙桃相比,超红桃果皮叶绿素和类胡萝卜素含量低且下降快,花青苷含量高且上升多;而超红桃果肉早期色素含量较低,后期含量较高,类黄酮含量呈下降趋势;酚类物质含量呈先降后升趋势;花青苷含量与其他色素和酚类物质含量总体呈现负相关,仅个别指标例外。     

柿酒发醇过程中酚类物质的变化规律研究

以广西恭城"月柿"为试材,应用不同柿酒发酵工艺,探索酚类物质(单宁、黄烷醇类及总黄酮)在柿酒发酵过程中的变化规律及其作用机理.结果表明,在柿酒发酵过程中酚类物质含量总体呈下降趋势,且发酵温度是影响柿酒发酵过程中酚类物质变化的最主要因素.     

陈酿过程对猕猴桃酒多酚及其抗氧化活性的影响

为探究陈酿期间猕猴桃酒中酚类物质与体外抗氧化活性之间的相关性,分析了猕猴桃酒酚类物质种类及其含量、总酚含量以及体外抗氧化能力的变化。结果表明:猕猴桃酒中共检测出11种单体酚,其中儿茶素与表儿茶素的含量较高。随着陈酿时间的延长,猕猴桃酒的抗氧化能力及酚类物质含量均有所降低。原儿茶酸、根皮苷与ABTS+·清除力之间呈显著正相关(P0.01),原儿茶酸、鞣花酸、根皮苷与还原能力之间呈显著正相关(P0.01),阿魏酸与羟基自由基清除能力显著相关(P0.01),而没食子酸、原儿茶酸与DPPH·清除力之间的相关性较低。酚类物质与体外抗氧化活性之间的相关性表明酚类物质对猕猴桃酒体外抗氧化能力起主导作用。     

液态绿茶酒发酵过程中酚类物质的含量变化及发酵影响因素分析

以信阳毛尖绿茶为主要原料生产液态发酵型茶酒,研究发酵过程中酚类物质的含量变化,并通过单因素实验对酚类物质在不同的发酵温度、蔗糖添加量、SO2添加量及pH条件下的保存率进行了比较与分析。结果表明,发酵温度对酚类物质含量的影响较明显,呈负相关;蔗糖添加量较高时酚类物质含量下降;pH<4时酚类物质含量较低;茶酒发酵可以适当降低SO2的使用量。正交优化实验结果表明,酚类物质在一定含量范围内,茶酒的感官质量较好,是影响其感官质量的重要因素之一。茶酒中总酚含量和感官评分值间并不存在正相关性。     

莲藕酚类物质组成分析及合成机制研究

目的 分析莲藕采前不同时期酚类物质的组成,筛选莲藕特征酚类物质代谢相关基因及转录因子。方法 本研究以“鄂莲五号”为试材,基于高效液相色谱及转录组学解析莲藕采前特征酚类物质代谢及转录组调控相关基因。结果 不同生长期莲藕褐变度呈上升趋势,其总酚含量先增加后减少,S3(生长期3)时期总酚含量达到最高峰为16.59 mg GAE/100g。其中酚类物质含量最高的是天麻素,在S4时期含量达到最高峰为191.44 μg/g。苯丙烷和类黄酮代谢途径中参与天麻素、没食子儿茶素、儿茶素合成的基因在莲藕根茎膨大早期和中期高表达。利用实时荧光定量聚合酶链式反应验证转录组分析检测到的酚类化合物生物合成所需的几个差异表达基因。27个转录因子家族在莲藕生长期显著差异表达,其中Nn＿104608167(AP2-EREBP)、Nn＿104608008(MYB)、Nn＿104593222(bHLH)、Nn＿104594756(C2C2-Dof)表达变化与生长期莲藕酚类物质含量变化模式相一致。结论 莲藕生长期酚类物质的不断积累,导致褐变度呈现出不断上升趋势。27个转录因子家族的部分基因表达量与生长期莲藕酚类物质变化趋势相...     

不同处理温度对苦荞抗氧化成分的含量及其抗氧化活性影响的研究

研究苦荞经不同温度处理后,其酚类物质、黄酮类物质、芦丁、槲皮素含量及其抗氧化能力的差异,分析酚类物质、黄酮类物质、芦丁、槲皮素的含量间及抗氧化能力间的相关性,并指出槲皮素产生的温度范围。研究结果发现,当处理温度低于180℃时,酚类物质、黄酮类物质、芦丁含量无明显变化(P0.05);高于180℃时,酚类物质、芦丁含量无明显变化(P0.05),而黄酮类物质含量显著降低(P0.05),槲皮素含量显著增加(P0.05);高于220℃时,酚类物质、黄酮类物质、芦丁含量均显著降低(P0.05),槲皮素含量显著增加(P0.05)。而且,抗氧化能力与酚类物质含量相关性最好,其次依次为芦丁、黄酮类物质含量,而与槲皮素含量呈显著负相关(P0.05)。由此可知,当处理温度高于180℃时,苦荞粉中酚类、黄酮类物质、芦丁分解而减少,槲皮素含量逐渐增加,抗氧化能力大幅度降低。因此,加工过程中应注意保护苦荞的功能活性物质,防止温度过高而导致酚类、黄酮类等抗氧化物质的降解。     

26种酿酒葡萄中抗氧化物质含量测定及品种分类

检测26种红色酿酒葡萄浆果中总酚、总黄酮、花色苷、白藜芦醇和黄酮醇含量。以DPPH自由基法评价其体外抗氧化能力,分析其酚类物质含量和抗氧化活性的相关性。根据酚类物质含量,采用系统聚类法对26种酿酒葡萄进行分类。结果表明:26种酿酒葡萄中酚类物质含量及抗氧化能力有明显的差异;各酚类物质含量与抗氧化活性呈显著或极显著的相关性;对26个酿酒葡萄品种聚类分析,筛选出4个抗氧化物质含量丰富的酿酒品种——巴柯、宝石解百纳、蛇龙珠和黑塞比尔。     

影响园黄梨贮期褐变及品质主要因素试验

研究了采收成熟度、贮藏温度、膨大剂使用和果实大小对园黄梨贮期褐变及品质的影响。结果表明,采收成熟度和贮温较高以及膨大剂使用均促进了园黄梨果心果肉褐变发生与品质变劣,不利于梨果长期贮藏,是影响贮期梨果褐变及品质的主要因素。适宜的采收成熟度为花后果实发育131d,在此条件下将未经膨大剂处理的梨果用微孔保鲜袋包装0℃冷藏,可使园黄梨贮藏120d保持品质不变。     

乳酸菌发酵对梨汁的护色作用

梨汁在加工过程中极易褐变,乳酸菌发酵能有效保护梨汁的色泽。本研究测定梨汁发酵及储藏过程中色泽、多酚氧化酶活性、酚类物质、抗坏血酸含量等指标的变化,并与未发酵梨汁和添加柠檬酸的调酸梨汁对比,探索乳酸菌发酵对果蔬汁的护色机理。30天储藏期内,未发酵梨汁褐变指数从0.073变化至0.310,显著高于发酵梨汁(0.134);乳酸菌发酵作用有效抑制了多酚氧化酶的活性,使得发酵梨汁中的酚类物质的保存率(43%)显著高于未发酵梨汁(16%);发酵梨汁中抗坏血酸稳定性更高,保存率(85%)较未发酵梨汁高(50%),减少了非酶褐变。乳酸菌通过在梨汁中发酵产酸,抑制多酚氧化酶的活性,保存酚类、抗坏血酸等物质,从而保护梨汁色泽。     

Causes of Browning in Pear Juice Concentrate During Storage

Pear juice was treated with cation exchange resin, PVPP, XAD-4, oxygen, and various resin combinations. Samples were concentrated and increases in browning measured during storage at 37°C. Analytical determinations included α-amino nitrogen, total phenolics, metal ions, ascorbic acid, and dehydroascorbic acid. While XAD-4 and PVPP were more effective in lowering phenolic content and reducing initial color, cation exchange treatment removed amino acids and was most effective in preventing browning and providing flavor stability. Addition of glycine to cation-exchange treated samples restored browning rates. Reductone formation during storage resulted in an apparent increase in ascorbic acid. It was concluded that Maillard browning reactions predominated during storage.     

不同贮藏温度下鲜切紫甘薯褐变相关因素研究

为研究鲜切紫甘薯的褐变条件与机理,本文对不同贮藏温度下(4和12℃)的鲜切紫甘薯的褐变程度、褐变相关酶活力以及褐变底物酚类物质进行分析。结果表明,12℃贮藏组的鲜切紫甘薯褐变度始终显著高于4℃贮藏组(P<0.05)。贮藏期间,褐变重的鲜切紫甘薯多酚氧化酶(Polyphenol oxidase,PPO)和过氧化物酶(Peroxidase,POD)活性更高,丙二醛(Malondialdehyde,MDA)含量更多。2~8 d,不同贮藏温度下鲜切紫甘薯绿原酸和阿魏酸含量显著不同(P<0.05),因此推断褐变相关酶活性、膜脂过氧化程度以及酚类物质含量可能是引起鲜切紫甘薯褐变的关键因素。通过相关性分析,多酚氧化酶(PPO)和过氧化物酶(POD)是引起鲜切紫甘薯褐变的关键酶。绿原酸和阿魏酸是鲜切紫甘薯褐变的主要底物。     

苹果梨和鸭梨酶促褐变机理的研究

以苹果梨和鸭梨为研究对象。在一定的贮藏期内,通过定期测定梨中ｐＨ值,可溶性固形物,褐变度,总酚和多酚氧化酶活性及其与不同底物的结合能力,分析梨的酶褐变机是,苹果梨和鸭梨在贮藏期间,ｐＨ值和可溶性固形物的含量总体呈下降趋势;多酚类物质的含量和多酚氧化酶的活性呈上升趋势,与贮藏期间的褐变度的升高是一致的,多酚氧化酶与底物结合能力的强弱依次为：没食子酸〉儿茶酚〉绿原酸〉咖啡酸;抗坏血酸和还原糖含量对水果     

Suppression of internal browning and maintenance of antioxidants in beeswax plus salicylic acid coated pear fruit during different storage conditions

Postharvest application of edible waxes blended with antioxidants is an effective strategy to regulate postharvest quality and antioxidant losses in fruits. Effect of beeswax coatings (BW 1.0% and 2.0%) alone or enriched with salicylic acid (SA) on antioxidant properties of pear fruit was studied during 67 days of cold storage and 20 days of supermarket storage conditions respectively. Results showed that under both the storage conditions fruits coated with BW + SA maintained higher total phenolic content (TPC), antioxidant activity and ascorbic acid content (AsA) as compared to the control. Furthermore, combined coatings significantly reduced polyphenol oxidase (PPO) activities and inhibited internal browning (IB) in pears throughout cold and supermarket storage. Overall, the BW 2.0% + SA 2.0 mM exhibited the most competitive effect in terms of preserving the antioxidant properties and preventing internal browning in pears during storage.     

Inactivation of polyphenol oxidase by ultraviolet irradiation: Protective effect of melanins

Most of the studies about UV irradiation of fruit and vegetable derivatives have been carried out in order to assess its effect on microbial inactivation. Nevertheless, there are few references about UV influence on some enzyme activities that are important in this kind of food, especially polyphenol oxidase, which is responsible for enzymatic browning in fruit and vegetable tissues containing phenolic or polyphenolic compounds. In this work, the effect of UV–Vis irradiation on polyphenol oxidase from Agaricus bisporus was investigated. A reduction of 58.7% in enzyme activity was achieved in the first 90 s, and it was completely inactivated after 35 min of treatment. In addition, the protective effect of melanins synthesized by the action of the same polyphenol oxidase was assessed. These pigments absorbed some of the radiant energy and led to a slower inactivation of polyphenol oxidase.     

低温结合1-MCP处理对突尼斯软籽石榴采后品质的影响

突尼斯软籽石榴在贮藏过程中容易出现果皮褐变、籽粒变质、软化腐烂等问题,严重影响果实的商品价值。以陕西潼关突尼斯软籽石榴为试材,研究低温结合1-甲基环丙烯(1-methyl-cyclopropene,1-MCP)处理对采后突尼斯软籽石榴品质的影响,即在贮藏温度(3±0.5)℃、相对湿度90%~95%条件下,选用0.2、0.5、1.0、1.5 mg/L四种不同质量浓度的1-MCP处理软籽石榴,贮藏期间每20 d测定石榴果实的可滴定酸、可溶性固形物、还原糖含量,呼吸强度、相对电导率、褐变指数及多酚氧化酶、过氧化物酶活性,并计算果实失重率和腐烂率,贮藏120 d时对软籽石榴的感官性状进行综合评价。结果表明,采用1.0 mg/L的1-MCP处理软籽石榴能有效减缓果实腐烂变质,减缓果实呼吸强度,降低褐变指数,较好地保持籽粒可溶性固形物、可滴定酸及还原糖含量,并使多酚氧化酶、过氧化物酶活性处于较低水平,降低果实失重率和腐烂率,保持良好的感官品质。突尼斯软籽石榴适宜的贮藏条件为:贮藏温度(3±0.5)℃、相对湿度90%~95%、1-MCP处理质量浓度1.0 mg/L,并用聚乙烯塑料袋密封包装,保鲜效果理想。     

Two Endogenous Substrates for Polyphenoloxidase in Pericarp Tissues of Postharvest Rambutan Fruit

Abstract: The catalytic oxidation of phenolic substrates by polyphenoloxidase (PPO) causes pericarp browning of postharvest rambutan fruit. In the present study, PPO and its endogenous substrates were extracted from rambutan pericarp tissues (RPT). The substrate extracts were sequentially partitioned with ethyl acetate and n-butanol. The analysis of total phenolic content showed that the most phenolic compounds were distributed in ethyl acetate fraction. By high-performance liquid chromatography (HPLC), (−)-epicatechin (EC) and proanthocyanidin A2 (PA2) were identified from this fraction. After reacting with rambutan PPO, EC turned brown rapidly within 10 min, indicating that it was a significant endogenous substrate. Although PA2 could also be oxidized by the PPO, it turned brown very slowly. In addition, because EC and PA2 were continually catalyzed into browning products by PPO during storage of the fruit at 4 and 25 °C, their contents in RPT gradually declined with the extended storage time. It was further observed that both substrate contents in rambutan fruit storing at 25 °C decreased more rapidly than that storing at 4 °C, suggesting that low temperature inhibited the catalytic oxidation of substrates so as to slow down pericarp browning. Practical Application: Pericarp browning is a serious problem to storage and transport of harvested rambutan fruit. A generally accepted opinion on the browning mechanism is the oxidation of phenolic substrates by PPO. Ascertaining PPO substrates will effectively help us to control enzymatic reaction by chemical methods so as to delay or even prevent pericarp browning of harvested rambutan fruit.     

Inhibition of Browning on Fresh-cut Pear Wedges by Natural Compounds

ABSTRACT: Mechanical operations such as peeling and cutting during minimal processing involve enzymatic browning of fruit tissue. The objective of this work was to evaluate the individual and combined effects of N-acetyl-L-cysteine, reduced glutathione, ascorbic acid, and 4-hexylresorcinol to control pear browning. Browning of fresh-cut pears was prevented by a minimum concentration of 0.75% N-acetyl-L-cysteine up to 28 d at 4°C. Reduced glutathione treatments were also effective along the storage time although browning was observed after 21 d of storage with a dip of 0.75% reduced glutathione. However, ascorbic acid or 4-hexylresorcinol treatments did not seem to completely prevent browning of pear wedges throughout the storage period. An enhanced antibrowning effect was observed when combining both N-acetyl-L-cysteine and reduced glutathione, considering hue angle as color change index. Thus, hue angle reached maximum levels at 1.5% N-acetyl-L-cysteine (NAC) or 1.5% glutathione (GSH) and 1% NAC with 1% GSH for 28 d. Besides, N-acetyl-L-cysteine, reduced glutathione and 4-hexylresorcinol completely inhibited polyphenol oxidase activity as well as browning inhibitors slightly reduced firmness of fresh-cut pears.