果蔬中单宁测定技术研究

为研究、建立快速、简便测定蔬菜、水果中单宁含量的方法,选用当前测定单宁应用最为广泛的可见分光光度法为基础进行可行性研究。采用配对t检验,用同一样品对不同单宁提取溶剂、温度和时间及测定的显色时间分别进行比较测定,从而选出最佳单宁提取和测定条件,并对建立的方法进行线性、精密度、准确度等的验证试验。确定了最佳的提取和检测条件为500W超声波提取,超声时间20min,提取溶剂水,温度60℃,显色时间1h。单宁测定线性范围为0~30mg/L,方法检出限0.2mg/g,加标回收率为95.8%~101.9%,相对标准偏差(RSD)1.07%~4.29%。该法具有操作简便、快速、精密度高、重现性好、加标回收率较高、分析成本低等特点。适合于果蔬中单宁酸的快速检测。     

Morphology,tannin concentration and forage value of 15 Swiss accessions of sainfoin (Onobrychis viciifolia Scop.) as influenced by harvest time and cultivation site

Fifteen accessions of sainfoin (Onobrychis viciifolia Scop.) were characterized for morphological and phenological traits at Reckenholz in the Swiss lowlands (Experiment 1). The effects of accession, harvest time and site on dry‐matter yield, condensed tannin (CT) concentration and forage value (Experiment 2) were determined at three sites in Switzerland varying in altitude from 440 to 559 m. Three to four harvests were taken in the first year after establishment (second year of stand) with harvests 1 and 2 chemically analysed. From the characterization in Experiment 1, a clear grouping of single flowering (Communis) and multiple flowering (Bifera) accessions emerged. Additionally, within the Communis accessions, distinct groupings were identified (historical landraces and newly collected ecotypes) based on morphological characteristics. Experiment 2 showed that Communis and Bifera accessions had a similar chemical composition in the first harvest. In the second harvest, Communis accessions were higher in crude protein and CT and lower in neutral and acid detergent fibre concentrations than Bifera accessions. Total dry‐matter yields were higher for Bifera accessions. Among the Communis accessions, ecotypes had consistently higher CT concentrations than landraces. In vitro organic matter digestibility did not significantly differ among accessions. There were clear effects of harvest time and site for most variables, with clear harvest time × sainfoin group interaction but no site × sainfoin group interactions. The results clearly demonstrate that historical landraces and newly collected ecotypes expand the range of available genetic variation for sainfoin breeding.     

Influence of harvesting site on chemical composition and potential protein value of Acacia erioloba,A. nilotica and Ziziphus mucronata leaves for ruminants

This study was designed to evaluate the chemical composition, buffer N solubility, in vitro ruminal N degradation and in vitro ruminal biological activity of condensed tannins in Acacia erioloba, Acacia nilotica and Ziziphus mucronata leaves harvested from two sites (Masuthle communal grazing land and Molelwane private farm). Leaves were harvested, dried at 60 °C and milled. The highest crude protein (CP) content was found in leaves of Z. mucronata (177.7 g/kg DM). Leaves harvested from Masuthle had higher (p < 0.05) soluble phenolics (SPh) (44.6 g TAE/kg DM) compared to those harvested from Molelwane (29.8 g TAE/kg DM). In both Molelwane and Masuthle, leaves of A. nilotica had higher levels of condensed tannins (CT) (0.76 AU_550/200 mg and 0.52 AU_550/200 mg respectively) followed by A. erioloba and Z. mucronata, which did not differ (p > 0.05). Nitrogen degradability at 24 h was the same (p > 0.05) for all tree species but not at 12 and 36 h. No linear association (p > 0.05) was found between buffer‐soluble N and in vitro ruminal N degradability in leaves with high SPh content. The largest polyethylene glycol (PEG) effect was in leaves of A. nilotica (448%) harvested from Masuthle after 36 h of incubation. Ziziphus mucronata leaves harvested from Molelwane had the least PEG effect at 48 h. There was no linear association (p > 0.05) between PEG effect and SPh for all incubation periods, but a positive relationship was observed between PEG effect and condensed tannins content. There was no linear association between solubility index (SI) and in vitro ruminal N degradability for tannin‐rich leaves. It was concluded that higher browsing pressure in Masuthle communal rangeland resulted in leaves with higher levels of condensed tannins, which had higher in vitro ruminal biological activity, compared to those harvested from Molelwane.     

氮素对羽叶决明缩合单宁及相关酶活性的影响

缩合单宁对牧草品质的影响极大,适量的缩合单宁含量对于提高牧草的利用率和营养品质非常重要。研究以豆科牧草羽叶决明Cassia nictitoms为材料,分析了氮素梯度处理后茎和叶中缩合单宁的含量及其生物合成酶二氢黄酮醇还原酶(DFR)活性的变化特征。结果表明,羽叶决明叶片的缩合单宁含量高于茎,随氮素的增加,叶片中缩合单宁含量从14.78%下降到1.14%;茎中从4.62%开始降低,达到0.98%后趋于稳定;DFR活性表现出与缩合单宁相似的变化规律,二者在叶和茎中都呈显著(P0.01)的二次曲线关系。植株粗蛋白含量测定发现,随氮素的增加粗蛋白含量无显著增加(P0.05)。因此,适当增加氮素的使用量可以达到减少缩合单宁含量,从而提高羽叶决明的利用率和营养品质。     

Use of Fura 2 Fluorescent Dyes as Indicator for Studying Calcium Distribution in Several Plant Tissues

Calcium (Ca) is an essential plant nutrient and is important in determining quality of fruits in storage. The analytical method presently known to determine Ca concentration in vegetables measures total Ca, and there is a need to develop methods that can determine the distribution of Ca within vegetable tissues. The objective of this study was to determine the ability of fluorescent probes to visualize Ca location and distribution in vegetable tissues. We examined three protocols using fluorescent dyes developed to detect Ca. The first tested Fura 2 acetoximetil (AM) probe in fresh cuts from grapes at different combinations of temperatures and incubation times. The second protocol was developed with the aim of lowering the natural autofluorescense. In the third protocol, the Fura 2 probe was used in tissues previously fixed in formalin, acetic acid, and alcohol solution (FAA). Tissues were observed under an epifluorescence microscope and, to compare and complement the observations, under a scanning electron microscope (SEM). No sign of fluorescence was observed in fixed and fresh tissue using the Fura 2 AM. In fresh cuts, there was autofluorescent interference, provoked mainly by chlorophyll, but also from the vascular system and tannins. The Fura 2 probe was introduced to vegetable tissues by utilizing a pH of 4.5, and a more intense signal was observed in tissues with greater Ca concentration. This signal was also associated with Ca crystals, which might have had some degree of hydrolysis at low pH. Under a SEM microscope, Ca oxalate crystals were clearly observed in those tissues. Our results show that Fura 2 probe can be used to detect Ca and its distribution in vegetable tissues.     

影响黑果枸杞缩合单宁测定的因素分析

为了探讨黑果枸杞中缩合单宁的测定,采用方差分析方法研究了干燥方法、粉碎度以及提取溶剂对黑果枸杞枝叶中缩合单宁提取量的影响。结果表明各因素中主效与互作同时存在,尤其是干燥方法与提取液之间、提取液与粉碎度之间的搭配会影响最终的缩合单宁提取量。冷冻干燥、粉碎后过80￣100目筛以及用甲醇酸水溶液提取能够获得最大的提取量。     

沙坡头地区凝结水及其在生态环境中的意义

本文论述了草原化荒漠区在之灌溉条件下,仅依靠自然降水,植物生长与水分平衡的关系,指出吸湿凝结水是地表植被,尤其是对土著植物,隐花植物,微生物有一定侵润和水分的补给作用。对线根性一年生植物也有滋养意义。对强化固沙植物,固沙植物的生化活性、生物循环和能量转化有相当积极的生态意义。     

Effects of heat on the removal of polyphenols and in vitro protein digestibility of cowpea (Vigna unguiculata (L.) Walp.)

Simple wet heat treatments like simple boiling (atmospheric pressure, 100 °C) and pressurized boiling (higher than 100 °C) reduced the polyphenol content of mature dark red seeds of cowpea (Vigna unguiculata (L.) Walp.) cultivar UPL Cp 3 by 61 to 80% and improved in vitro protein digestibility (IVPD) by 6 to 26%. Pressurized steaming (higher than 100 °C) removed 48 to 83% of the polyphenols but increased IVPD by only 1.1 to 4.2%. Dry heat as exemplified by roasting and microwave treatment inactivated 58 to 71% of the tannins but increased IVPD by only 1%. All the heat treatments were effective in removing/inactivating polyphenols though different responses were observed with the resulting in vitro protein digestibilities.     

Effects of soaking in aqueous acidic and alkali solutions on removal of polyphenols and in vitro digestibility of cowpea

Mature dark red seeds of cowpea (Vigna unguiculata (L.) Walp.) UPL Cp 3, were subjected to several soaking treatments to remove their polyphenols. Soaking in water at room temperature for 8 and 24 h resulted in 17% and 21% loss of assayable polyphenols, respectively. Dilute solutions of alkali (Na₂CO₃, NaHCO₃, NH₄OH and KOH) and acid (CH₃ COOH, HCl and H₂ SO₄) were more effective in removing polyphenols up to 88% than higher concentrations of alkali and acid solutions.Vinegar (0.005–0.65 M CH₃ COOH) decreased polyphenols from 55 to 62% with a 6 to 14% improvement in in vitro protein digestibility (IVPD). Commercial lime (65% CaO) removed polyphenols from seeds soaked for 8 to 24 h by 70% with 2 to 10% increase in in vitro protein digestibility. Ash removed 40 to 60% of the polyphenols after 8 and 24 h of soaking with an increase in IVPD of 7 to 13%. Total polyphenols were significantly correlated (+0.92**) with protein precipitable polyphenols (condensed tannins).     

单宁基木材胶黏剂的研究进展

在常见凝缩类单宁结构特征基础上,讨论了单宁与醛的反应机理,总结了单宁基木材胶黏剂存在的问题及其解决办法,并综述了单宁基木材胶黏剂的应用研究进展.