新鲜莲藕的采后生理及其保鲜技术的研究进展

文章指出了莲藕在贮藏过程中发生褐变和衰老的主要原因是组织内部的多酚氧化酶催化氧化酚类物质所产生的黑色素,概述了莲藕多酚氧化酶的催化反应动力学特性、pH值、温度、金属离子等对莲藕多酚氧化酶活性的影响,莲藕采后多酚氧化酶活性与组织褐变、呼吸及衰老之间的关系,以及莲藕褐变和衰老的抑制及其保鲜技术等方面的研究进展。     

壳聚糖处理对鲜切莲藕褐变和抗氧化活性的影响

采用1%壳聚糖溶液处理鲜切莲藕,并于4℃下贮藏,通过对DPPH.和.OH两种自由基的测定评价鲜切莲藕的抗氧化活性。结果表明,随贮藏时间延长,对照组的抗氧化活性和多酚含量明显降低,褐变度不断加重;壳聚糖处理能明显抑制褐变,维持较高的多酚含量和抗氧化活性。多酚是莲藕中重要的抗氧化物质,也是发生褐变的主要底物。     

不同储藏温度下玻璃罐装番茄酱色泽变化的动力学研究

以新疆玻璃罐装番茄酱(24°Brix)为原料,以亮度L*值、红值a*、黄值b*、色差值△E、褐变指数和5-羟甲基糠醛(5-HMF)含量为考察指标,研究不同贮藏温度(10、25、35℃)对新疆玻璃罐装番茄酱色泽变化的影响,并在此基础上建立新疆玻璃罐装番茄酱色泽变化动力学模型,以预测玻璃罐装番茄酱褐变程度。结果表明:玻璃罐装番茄酱的色泽参数L*值、a*值、b*值变化符合一级动力学反应,色差值△E符合零级动力学反应,褐变指数和5-羟甲基糠醛含量变化在25℃和35℃下符合一级动力学反应。褐变指数、5-羟甲基糠醛含量、L*值、红值a*、黄值b*和色差值△E等各指标变化的活化能分别为74.30、65.22、45.46、55.72、102.26和64.21 kJ/mol。     

抗坏血酸和谷胱甘肽复合抗氧化剂对鲜切苹果防褐变效果的研究

为研究抗坏血酸和谷胱甘肽对鲜切苹果防褐变效果,对鲜切苹果进行抗坏血酸和谷胱甘肽复合抗氧化剂浸泡及保鲜处理,通过测定不同试验组鲜切苹果切片的色度(L*)、褐变强度(BD)等多项抗褐变指标探究其防褐变效果。结果表明,采用0.07 mol/L抗坏血酸溶液和400μmol/L谷胱甘肽溶液浸泡的苹果切片,综合各项指标,抗褐变保鲜效果最佳,在此基础上,通过Box-Behnken中心组合设计试验,摸索出最佳的复配抗氧化剂配方为抗坏血酸0.08 mol/L,谷胱甘肽401.62μmol/L,浸泡时间15.70 min,此时L*值为76.54,经试验验证,L*值为76.46±0.58与预测值接近、可靠。     

包装材料对莲藕贮藏保鲜的影响

采用0.10mm和0.08mm厚的低密度聚乙烯(LDPE)以及0.08mm和0.06mm厚的PA/PE复合薄膜真空包装莲藕,探讨包装材料对莲藕贮藏期间褐变的影响.结果表明,PA/PE袋能极显著地抑制莲藕褐变,并能保持较多的营养成分.     

表面处理对莲藕保鲜的影响

莲藕极易发生褐变和腐败变质,从而失去食用价值,涂膜可以有效地延长莲藕的保质期。研究了酸、化学杀菌剂等表面处理对莲藕涂膜保鲜效果的影响。结果表明,浓度为0.06～0.07mol/L柠檬酸处理和0.04～0.07mol/L的磷酸处理均对莲藕保鲜效果明显;质量分数为2%的H2O2处理10min,不能有效抑制莲藕褐变,但可以控制其腐败变质;ClO2不宜用于莲藕的表面处理;涂膜前用质量分数2%的H2O2处理,有利于提高莲藕短期贮藏的感官品质,但会使长期贮藏莲藕变质速度加快。     

鲜切莲藕中褐变因素分析的研究进展

鲜切莲藕的褐变问题很大程度上限制了产品的生产和销售,分析其褐变因素对解决贮运保鲜问题具有重要意义。本文针对文献资料介绍的导致鲜切莲藕褐变的各因素(酚类物质、多酚氧化酶及环境条件)进行总结和分析,阐明各因素在保鲜贮藏中的变化规律,以期为莲藕加工提供理论借鉴和技术指导。     

荔枝果肉热泵干燥及其储藏特性研究

为了探讨荔枝果肉热泵干燥特性及储藏过程中一些品质指标的变化规律,将去皮去核后的果肉进行热泵干燥,测定其干燥特性及储藏过程中色泽、褐变度、总酸、糖组分、质构及微生物指标的变化。结果表明：荔枝果肉在60 ℃下热泵干燥2 h,干燥速度升至最大值后进入降速干燥阶段,干燥过程中,亮度L*值变化不大,a*值和b*值显著增大;干燥18~20 h,样品的水分含量达25%左右、颜色呈金黄色;不同水分含量的荔枝果肉干在储藏过程中,L*值、a*值和b*值下降,果肉发生褐变,总酸含量呈上升趋势,果糖、葡萄糖和蔗糖呈减少趋势;水分含量35%的样品储藏180 d褐变明显;荔枝果干的硬度和咀嚼性在储藏后期明显增大,黏着性变化不显著。采用热泵干燥荔枝果肉,25%水分含量的样品品质和储藏性较佳。     

莲藕贮藏保鲜

莲藕是我国重要的出口创汇蔬菜之一,但在贮运过程中易发生褐变,影响销售及出口,因此对莲藕进行贮藏保鲜,具有重要的经济意义。下面介绍几种莲藕的贮藏保鲜方法。1．沙藏法选择地势高、背风、避雨处,用细沙铺衬地面,其湿度以手捏成团放手即散为宜(下同),并在四周开好排水沟,码1层莲藕铺1层     

一氧化氮对冷藏鲜切桃贮藏品质的影响

为探究适宜的鲜切桃冷藏条件下抑制褐变的方法,将鲜切"蒙阴"桃分别在清水(对照)、5、10、15μmol/L一氧化氮(NO)溶液中浸泡5 min,并于5℃下贮藏10 d,研究NO对鲜切桃贮藏期间品质的影响。结果表明,与对照相比,NO处理有效延缓了鲜切桃片褐变度的升高以及硬度、L^*值、可溶性固形物含量的下降,从而使鲜切桃在贮藏期间保持了较好的外观品质;同时NO处理减低了多酚氧化酶(PPO)和过氧化物酶(POD)活性高峰值,从而降低了褐变程度,提高了鲜切桃超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性,抑制了丙二醛(MDA)、活性氧(ROS)和总酚含量的上升,提高了鲜切桃片的贮藏品质,其中以10μmol/L NO保鲜效果最好。由此表明,10μmol/L NO处理是一种较好的抑制鲜切桃褐变的加工方法。     

Location of a high-lysine gene and the DDT-resistance gene on barley chromosome 7

Summary The high-lysine gene in Risø mutant 1508 conditions an increased lysine content in the endosperm via a changed protein composition, a decreased seed size, and several other characters of the seed. The designation lys3a, lys3b, and lys3c, is proposed for the allelic high-lysine genes in three Risø mutants, nos 1508, 18, and 19. Linkage studies with translocations locate the lys3 locus in the centromere region of chromosome 7. A linkage study involving the loci lys3 and ddt (resistance to DDT) together with the marker loci fs (fragile stem), s (short rachilla hairs), and r (smooth awn) show that the order of the five loci on chromosome 7 from the long to the short chromosome arm is r, s, fs, lys3, ddt. The distance from locus r to locus ddt is about 100 centimorgans.     

Biological Activity and Quantification of Suspected Allelochemicals from Alfalfa Plant Parts

Autotoxicity restricts reseeding of alfalfa (Medicago sativa L.) after alfalfa until autotoxic chemical(s) breaks down or is dispersed into external environments. A series of aqueous extracts from leaves, stems, roots and seeds of alfalfa ‘Vernal’ were bioassayed against alfalfa seedlings of the same cultivar to determine their autotoxicity. The highest inhibition was found in the extracts from the leaves. Extracts at 40 g dry tissue l^?1 from alfalfa leaves were 15.4, 17.5 and 28.7 times more toxic to alfalfa root growth than were those from roots, stems and seeds, respectively. A high‐performance liquid chromatography (HPLC) analysis with nine standard compounds showed that the concentrations and compositions of allelopathic compounds depended on the plant parts. In leaf extracts that showed the most inhibitory effect on root growth, the highest amounts of allelochemicals were detected. Among nine phenolic compounds assayed for their phytotoxicity on root growth of alfalfa, coumarin, trans‐cinnamic acid and o‐coumaric acid at 10^?3 m were most inhibitory. The type and amount of causative allelochemicals found in alfalfa plant parts were highly correlated with the results of the bioassay, indicating that the autotoxic effects of alfalfa plant parts significantly differed.     

Simultaneous Determination of Four Phenolic Acids in Radix Salviae Miltiorrhizae Formula Granules by QAMS

[Objectives]This study aimed to establish a QAMS(quantitative analysis of multi-components by single-marker)method for simultaneous determination of four phenol...     

Changes in Seed Yield and Quality with Maturity in Onion (Allium cepa L., cv. 'Early Cream Gold')

Development of onion (Allium cepa L., cv. ‘Early Cream Gold’) seed under cool climate conditions in Tasmania, Australia occurred over a longer duration than previously reported, but similar patterns of change in yield components were recorded. In contrast to previous studies, umbel moisture content declined from 85 to 67 % over 57 days while seed moisture content decreased from 85 to 31 %. Seed yield continued to increase over the duration of crop development, with increasing seed weight compensating for seed loss resulting from capsule dehiscence in the later stages of maturation. Germination percentage was high and did not vary significantly from 53 to 77 days after full bloom (DAF), but mean germination time declined and uniformity of germination increased significantly over the same time period. The percentage abnormal seedlings declined with later harvest date, resulting in highest seed quality at 77 DAF. The results of this study suggest that the decision to harvest cool climate onion seed crops before capsule dehiscence will result in a loss of potential seed yield and quality.     

Pollen and pollination experiments. III. The viability of apple and pear pollen as affected by irradiation and storage

Summary Apple and pear pollen was irradiated with doses of 0, 50, 100, 250 and 500 krad (gamma rays) and stored at 4°C and 0–10% r.h. From the in-vitro germination percentages an average LD 50 dose of about 220 krad was estimated. For both irradiated and untreated pollen a close and corresponding lineair relationship existed between germination percentage and pollen tube growth.Irradiated pollen was much more sensitive to dry storage conditions than untreated pollen, resulting in less germination and more bursting. Apparently, irradiation caused the pollen cell membrane to lose its flexibility faster than normal. Rehydration of dry-stored, irradiated pollen in water-saturated air restored germination percentages up to their initial levels. The importance of this procedure in germination trials is stressed.     

Water Extraction Process of Chinese Herbal Compound Man Gan Ning

[Objectives]To optimize the water extraction process of Chinese Herbal Compound Man Gan Ning and establish a method for its extraction and content determination...     

Present status and future strategy in breeding faba beans (Vicia Faba L.) for resistance to biotic and abiotic stresses

Progress is being made, mainly by ICARDA but also elsewhere, in breeding for resistance to Botrytis, AScochyta, Uromyces, and Orobanche; and some lines have resistance to more than one pathogen. The strategy is to extend multiple resistance but also to seek new and durable forms of resistance. Internationally coordinated programs are needed to maintain the momentum of this work.Tolerance of abiotic stresses leads to types suited to dry or cold environments rather than broad adaptability, but in this cross-pollinated species, the more hybrid vigor expressed by a cultivar, the more it is likely to tolerate various stresses.     

Optimization of Extraction Technology and Determination of Content of Total Phenols of Leaves in Acanthopanax giraldii Harms

[Objectives] To determine the optimum extraction technology for total phenols of leaves in Acanthopanax giraldii Harms.[Methods]The single factor test and ortho...     

Cytoplasmic male sterility,resistance to gall mite and mildew,and season of leafing out in black currants

Summary Cytoplasmic male sterility (cms) is described in the F₁ hybrids Ribes × carrierei (R. glutinosum albidum × R. nigrum) and R. sanguineum × R. nigrum. In backcrosses to R. nigrum, progenies with R. glutinosum cytoplasm were either all male sterile, or segregated for full male fertility (F) and complete (S) and partial (I) male sterility. Ratios of F:I+S suggested that two linked genes controlled cms, F plants being dominant for one (Rf ₁) and recessive for the other (Rf ₂).Segregation for cms in relation to three linded genes, Ce (resistance to the gall mite, Cecidophyopsis ribes), Sph ₃(resistance to American gooseberry mildew, Sphaerotheca mors-uvae) and Lf ₁(one of two dominant additive genes controlling early season leafing out) indicated that Rf ₁and Rf ₂were in this linkage group. The gene order and approximate crossover values appeared to be: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqef0uAJj3BZ9Mz0bYu% H52CGmvzYLMzaerbd9wDYLwzYbItLDharqqr1ngBPrgifHhDYfgasa% acOqpw0xe9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% aabaqaciGacaGaamqadaabaeaafaaakeaacaWGdbGaamyzamaamaaa% baGaaiiiaiaacccacaGGWaGaaiOlaiaacgdacaGG0aGaaiiiaiaacc% caaaGaaiiiaiaacccacaGGGaGaamOuaiaadAgaliaaigdakmaamaaa% baGaaiiiaiaacccacaGGGaGaaiiiaiaaccdacaGGUaGaaiOmaiaacs% dacaGGGaGaaiiiaiaacccacaGGGaGaaiiiaaaacaWGsbGaamOzaSGa% aGOmaOWaaWaaaeaacaGGGaGaaiiiaiaacccacaGGGaGaaiiiaiaacc% cacaGGGaGaaiiiaiaacccaaaGaamitaiaadAgaliaaigdakmaamaaa% baGaaiiiaiaacccacaGGGaGaaiiiaiaacccacaGGGaGaaiiiaiaacc% cacaGGGaGaaiiiaiaacccacaGGGaaaaiaadofacaWGWbGaamiAaSGa% aG4maaaa!6E4D!\[Ce\underline { 0.14 } Rf1\underline { 0.24 } Rf2\underline { } Lf1\underline { } Sph3\]. Crossover values of 0.36 for Ce-Lf ₁, and 0.15 for Lf ₁-Sph ₃were estimated from the relative mean differences in season of leafing out between seedlings dominant and recessive for Ce and Sph ₃.It is suggested that competitive disadvantage of lf ₁-carrying gametes and/or zygotes at low temperatures may be implicated in the almost invariable deficit of plants dominant for the closely linked mildew resistance allele Sph ₃. Poor performance of lf ₁- (and possibly lf ₂-) carrying gametes and young zygotes during periods of low temperature at flowering might also account for the liability of some late season cultivars and selections to premature fruit drop (running off).     

Screening techniques and sources of resistance to parasitic angiosperms

Parasitic angiosperms cause great losses in many important crops under different climatic conditions and soil types. The most widespread and important parasitic angiosperms belong to the genera Orobanche, Striga, and Cuscuta. The most important economical hosts belong to the Poaceae, Asteraceae, Solanaceae, Cucurbitaceae, and Fabaceae. Although some resistant cultivars have been identified in several crops, great gaps exist in our knowledge of the parasites and the genetic basis of the resistance, as well as the availability of in vitro screening techniques. Screening techniques are based on reactions of the host root or foliage. In vitro or greenhouse screening methods based on the reaction of root and/or foliar tissues are usually superior to field screenings and can be used with many species. To utilize them in plant breeding, it is necessary to demonstrate a strong correlation between in vitro and field data. The correlation should be calculated for every environment in which selection is practiced. Using biochemical analysis as a screening technique has had limited success. The reason seems to be the complex host-parasite interactions which lead to germination, rhizotropism, infection, and growth of the parasite. Germination results from chemicals produced by the host. Resistance is only available in a small group of crops. Resistance has been found in cultivated, primitive and wild forms, depending on the specific host-parasite system. An additional problem is the existence of pathotypes in the parasites. Inheritance of host resistance is usually polygenic and its transfer is slow and tedious. Molecular techniques have yet to be used to locate resistance to parasitic angiosperms. While intensifying the search for genes that control resistance to specific parasitic angiosperms, the best strategy to screen for resistance is to improve the already existing in vitro or greenhouse screening techniques.