共查询到18条相似文献，搜索用时 187 毫秒
1.
以水蒸气作为保护气,将橡胶木分别于125、145、165、185℃处理2h,采用高氯酸法测定热处理橡胶木中的淀粉含量。研究表明,橡胶木素材中的淀粉含量高达11.681%,经过高温(125、145、165、185℃)处理后,其淀粉含量逐步降低。当热处理条件为125、145、165、185℃/2 h时,测出相应的淀粉含量分别为8.792%、8.500%、7.529%、4.386%。结果表明,橡胶木中的淀粉含量随着热处理温度的升高而下降。FTIR谱图分析表明淀粉发生降解。 相似文献
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为研究介质压力在木材高温热改性过程中的作用,采用压力蒸汽作为传热介质,于155℃/0.4 MPa,170℃/0.4 MPa,170℃/0.8 MPa处理条件对橡胶木进行热改性,测试热改性材的质量损失率、明度、抗弯强度、抗弯弹性模量等指标,探讨不同处理压力和温度改性橡胶木的物理力学性能变化。结果表明,在压强0.4 MPa条件下,155℃和170℃处理的试材,其各项性能可以达到或接近常压条件下更高温度热改性材的性能。介质压强由0.4 MPa增加至0.8 MPa,炭化橡胶木的质量损失率、颜色变化、抗弯强度损失均增大,说明压强越大,热改性程度越剧烈。介质压强对试材的热改性程度有显著影响,提高蒸汽压力可以在较低温度下加快橡胶木的炭化过程,实现木材的高效热改性处理。 相似文献
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以水蒸汽作为保护气,将橡胶木分别置于155℃处理2、6 h,185℃处理2、6 h,215℃处理2 h,测定了热改性后的橡胶木颜色,并通过紫外-可见光谱(UV-Vis)和傅里叶变换红外光谱(FTIR)对木材热改性前后的化学结构进行了表征。结果表明,高温热改性处理使橡胶木的颜色从浅黄白色变为橙色然后转向深棕褐色,随着处理程度加深,明度值L*持续降低。热改性程度较浅时色饱和度C*略有增加,木材颜色趋于鲜艳,而随着处理程度加深色饱和度C*大幅降低,颜色趋于黯淡。木材颜色变化的总色差ΔE*可反映热改性的程度,改性处理越剧烈,总色差ΔE*越大,处理温度比处理时间对木材颜色变化的影响更为显著。UV-Vis光谱显示,热改性材在350～550nm波段的吸收显著增强,说明有大量发色基团和助色基团生成。结合FTIR光谱,可以推测热改性过程木质素的相对含量升高,紫丁香基团上的甲氧基脱落,木素上苯环氧键的含量稳步降低,从侧面印证可能发生了生成醌的反应。同时,FTIR光谱中有迹象显示可能在155℃处理2 h时半纤维素的乙酰基就开始大量脱落。 相似文献
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以过热蒸汽为介质常压高温热改性人工林橡胶树木材,处理温度为170、185、200和215℃,处理时间均为3 h。分析了处理温度对热改性橡胶木物理力学性能的影响,结果表明:提高热处理温度,橡胶木的平衡含水率显著降低,降幅为34.33%～62.97%;干缩率显著降低,降幅为3.1%～51.75%(弦向)和2.72%～48.57%(径向);湿胀率显著降低,降幅为37.80%～69.85%(弦向)和28.04%～68.57%(径向);吸水率轻微下降,但不显著;热改性后,橡胶木的尺寸稳定性明显提高。气干密度、全干密度仅在215℃处理时明显下降,其余处理温度变化不显著;弦面硬度先略微增加,后急剧降低,整体呈下降态势;弦、径向局部横纹抗压强度先升高后下降,整体呈增加态势;抗弯强度显著降低,降幅为9.26%～37.52%;抗弯弹性模量有增加,但不显著。 相似文献
5.
通过硅溶胶浸注预处理获得橡胶木浸注材,再将橡胶木和浸注材分别于185℃和200℃下热改性处理,研究了硅溶胶预处理对炭化橡胶木防白蚁及阻燃性能的影响。结果表明:蚁蛀等级分别从4提升至3.8和4提升至3.75;埋地1 a后完好指数分别从1.3提升至5.9和2.5提升至5.4;氧指数分别提高16.40%和20.16%;EMC无显著变化;气干密度分别提高18.58%和22.03%;弦向气干湿胀率分别降低了10.27%和9.17%,径向气干湿胀率分别降低了15.00%和17.57%;弦向ASE分别提高了21.75%和11.56%,径向ASE分别提高了20.00%和19.71%。 相似文献
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目的 探究夜温变化对水稻淀粉形成的影响及其生理机制【方法】以优质软米浙禾香2号为材料,在灌浆初期设置31℃/20℃ (LT)、31℃/24℃ (NT)、31℃/28℃ (HT)3个夜间温度模式,测定其直链淀粉和支链淀粉含量及合成关键酶活性及相关基因的表达。结果 1)与NT相比,LT和HT处理显著降低粒重和淀粉积累,降低糊化温度和胶稠度,并影响支链淀粉链长,降低支链淀粉含量,提高直链淀粉含量,HT的影响要大于LT;2) LT和HT处理对白天叶片净光合速率的影响不显著,但显著降低籽粒中非结构性碳水化合物积累,抑制蔗糖转运基因OsSUT1、OsSUT2和OsSUT4在夜间和白天表达;3) LT 和HT处理降低夜间和白天蔗糖水解相关酶活性,增加淀粉水解酶活性,导致可溶性糖含量升高,籽粒中糖利用受阻;4)与NT相比,LT和HT处理下腺苷二磷酸葡萄糖含量呈现白天降低而夜晚升高的趋势,腺苷二磷酸葡萄糖积累及利用受到抑制,颗粒结合淀粉合酶活性随处理时间延长而显著降低,且白天酶活性也受夜间温度的影响;5)与NT相比,LT和HT处理降低了夜间支链淀粉合成相关酶活性,抑制了夜间相关基因的表达,导致支链淀粉合成受阻,但对白天酶活及相关基因表达的影响不大。结论 夜间高温对淀粉积累的影响要大于夜温降低,夜间高温/低温抑制全天蔗糖转运及代谢,进而抑制淀粉积累;支链淀粉合成受阻是导致直链淀粉相对含量升高的主要原因,直链淀粉合成相关酶活性(白天)受夜温变化影响,而支链淀粉合成相关酶活性(白天)受夜温变化的影响不显著。 相似文献
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采用磷酸二氢铵（DAP）和硼砂（SB）复配制备磷-氮-硼（P-N-B）复合阻燃剂,对橡胶木进行真空加压浸渍处理。通过极限氧指数（LOI）和锥形量热仪（CONE）测试不同配方阻燃剂处理橡胶木的燃烧性能。结果表明：P-N-B复合阻燃剂对橡胶木表现出较好的阻燃抑烟效果。载药率为10.67 wt%时,阻燃橡胶木的LOI值为52.3%,达到难燃或不燃材料标准;阻燃橡胶木的热释放速率降低约60%,热释放总量降低约50%,有效燃烧热明显降低,质量损失速率降低,总发烟量最高减少约97%,CO和CO2生成总量降低95%以上。氮磷硼协效阻燃橡胶木达到建筑材料阻燃B1级,3种元素协同抑烟效果显著。 相似文献
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目的考察冷藏对鲜人参中淀粉转化蔗糖含量变化的影响。方法将采收的鲜人参放置于2℃的冷库中,放置0、5、10、15、20天后分别取样,,采用高效液相色谱法结合蒸发光检测器(HPLC-ELSD)测定鲜人参中的蔗糖含量,并同时测定鲜人参中的淀粉含量。结果鲜人参中蔗糖含量随冷藏天数逐渐增高,6年生鲜人参中蔗糖含量从0天的4.2%增长到20天的27.1%。5年生鲜人参中蔗糖含量从0天的3.6%增长到20天的24.2%,鲜人参中淀粉含量随冷藏天数逐渐降低,6年生鲜人参中淀粉含量从0天的32.0%降低到20天的9.7%。5年生鲜人参中淀粉含量从0天的28.6%降低到20天的8.2%。结论冷藏对鲜人参中淀粉转化蔗糖的含量有显著影响。 相似文献
11.
高温胁迫对华石斛幼苗的形态和生理参数的影响 总被引：1，自引：0，他引：1
华石斛为海南特有兰科植物,原产海南海拔1 000 m以上的云雾林或山地雨林。为研究高温对华石斛生长的影响,本试验测定了昼/夜(10 h/14 h)温度梯度(25/20、30/25、35/30、40/35℃)的人工气候箱中生长1、2、4、8 d以及解除胁迫15 d(恢复生长)后华石斛幼苗的形态和生理生化指标。结果表明:高温30℃和35℃处理1 d时,形态和各项生理生化指标变化不显著,幼苗没有受到热害。30℃和35℃处理2~4 d和40℃处理1~2 d时,细胞膜稳定性遭到破坏,导致膜脂过氧化,相对电导率、MDA含量升高,SPAD值下降,此时植物通过增加可溶性糖、可溶性蛋白含量,提高SOD、POD活性进行自我调节。30、35℃处理8 d和40℃处理4 d时,各项生理指标急剧下降,膜系统和抗氧化酶系统遭到破坏,植物受到严重热害。40℃处理8 d时,95%的幼苗褐化死亡。不同处理天数下温度均与相对电导率和MDA含量呈极强正相关,与SPAD呈负相关。研究认为,相对电导率、SPAD、MDA可作为鉴定华石斛幼苗耐热性的参考指标。 相似文献
12.
ZHANG Yuping WANG Junke WANG Yaliang CHEN Yanhua ZHU Dengfeng CHEN Huizhe XIANG Jing ZHANG Yikai LIU Xiaojun ZHU Yan CAO Weixing 《中国水稻科学》1986,34(6):525-538
【Objective】To clarify the effect of night temperature changes on rice starch accumulation, and to explore circadian changes of physiological characteristics of rice amylose/amylopectin formation at various night temperatures.【Method】High-quality japonica rice ‘Zhehexiang 2’ was subjected to three night temperature gradients of 31℃/20℃ (LT), 31℃/24℃ (NT), and 31℃/28℃ (HT) at the beginning of grain ripening stage, and the amylose and amylopectin contents, the key enzyme activities involved in amylose and amylopectin formation and the expression of related genes were measured at noon and midnight. 【Result】 The results showed that 1) compared with NT, LT and HT treatments significantly reduced grain weight and starch accumulation, LT and HT both reduced amylopectin content and increased amylose content, meanwhile the effect of HT was greater than LT. LT and HT treatments decreased grain pasting temperature and gel consistency, and had a significant influence on branched chain length. 2) The net photosynthetic rate of leaves under LT and HT presented no significant difference compared to NT, but LT and HT significantly reduced the accumulation of non-structural carbohydrates, meanwhile down-regulated the expression level of sucrose transporter genes OsSUT1, OsSUT2, and OsSUT4 both at noon and midnight. 3) LT and HT treatment reduced sucrose hydrolysis-related enzyme activities, meanwhile promoted starch hydrolase activities, resulting in increased soluble sugar contents, sugar utilization in grain was blocked. 4) Compared with NT, the adenosine diphosphate glucose content showed a downward tendency during the day and a rising trend at night under the treatment of LT and HT, which presented that the accumulation and utilization of adenosine diphosphate glucose were inhibited. And the granules bound starch synthetase activity were significantly reduced under LT and HT compared to NT with the prolongation of the treatment, and the enzyme activity at daytime was significantly influenced by temperature changing at night. 5) Compared with NT, LT and HT reduced the activities of night-time amylopectin synthesis-related enzymes and inhibited the expression of night-time related genes, which retarded formation of amylopectin, but the enzyme activities related to amylopectin synthesis was not significantly influenced by night temperature changing. 【Conclusion】High night temperature had a less effect on starch accumulation than low night temperature. High or low night temperature inhibited sucrose transport and metabolism, resulting in declined starch accumulation. The retarding of amylopectin formation was the main reason for the increase of relative content of amylose at high or low night temperature. Night temperature changes directly affected the metabolic process of starch formation at night, but the daytime activities of amylose-related enzymes were affected by night temperature changes, while the daytime activities of amylopectin-related enzymes were not significantly affected by night temperature changes. 相似文献
13.
Xiao Wang Jian Cai Fulai Liu Mei Jin Hongxi Yu Dong Jiang Bernd Wollenweber Tingbo Dai Weixing Cao 《Journal of Cereal Science》2012
The potential role of pre-anthesis high temperature acclimation in alleviating the negative effects of post-anthesis heat stress on stem stored carbohydrate remobilization and grain starch accumulation in wheat was investigated. The treatments included no heat-stress (CC), heat stress at pre-anthesis only (HC), heat at post-anthesis only (CH), and heat stress at both stages (HH). Post-anthesis heat stress decreased grain starch content, reduced the content of fructans and depressed activities of related synthesis enzymes of sucrose:sucrose fructosyltransferase and fructan:fructan fructosyltransferase. Interestingly, HH plants had significantly higher grain yield than the CH plants. In addition, post-anthesis high temperature lowered grain starch content and increased percentages of volume, number and surface area of B-type starch granules in CH and HH than in CC treatment. However, HH plants had much higher starch content, and caused less modified B-type starch granule size indicators than the CH plants. Our results indicated that, compared with the non-acclimated plants, the pre-anthesis high temperature acclimation effectively enhanced carbohydrate remobilization from stems to grains, led to less changed starch content and starch granule size distribution in grains of wheat under post-anthesis heat stress. 相似文献
14.
为了改善小麦淀粉的性能,采用湿法工艺制备小麦辛烯基琥珀酸淀粉酯,并从表面结构、糊的黏度、透明度和凝沉性四个方面分析了小麦淀粉辛烯基琥珀酸酐改性前后理化性质的差异。小麦辛烯基琥珀酸淀粉酯的湿法制备工艺为：反应时间3 h,pH值8.0,反应温度35℃,淀粉乳液浓度35%,酸酐加入量为淀粉干基重的3.0％~7.0%。该工艺所制备的小麦辛烯基琥珀酸淀粉酯的取代度为0.012 4~0.019 4。扫描电镜分析表明,经过辛烯基琥珀酸酐改性之后,小麦淀粉颗粒表面产生凹陷现象;小麦淀粉糊的黏度和透明度明显提高,并且随着取代度的增加呈增大趋势;小麦淀粉糊的凝沉性降低。 相似文献
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为鉴定黄淮麦区小麦品种干热风抗性以及不同抗性品种热激蛋白(TaHSPs)基因的表达差异,以98个小麦品种为试验材料,于花后10~20d进行人工模拟干热风处理,通过测定小麦不同生长时期的叶绿素含量、收获后的千粒重与籽粒品质,评价不同品种干热风抗性;对筛选出的干热风抗性不同的品种在出苗15d进行热胁迫处理,通过荧光定量PCR测定热胁迫0~4.5h内TaHSPs基因表达量的变化。结果表明,干热风处理后,供试小麦品种旗叶的叶绿素含量均降低,高抗干热风品种降幅较小,热敏感型品种降幅较大;供试小麦品种的千粒重均降低。山农23号等3个品种达到高、中抗干热风等级,且抗性比较稳定,师栾02-1为热敏感型品种。干热风处理后籽粒蛋白质含量升高,总淀粉含量降低,抗干热风小麦品种总淀粉相对含量降幅较小。不同小麦品种幼苗在热胁迫0~4.5h期间,TaHSPs基因表达量均为抛物线趋势,抗干热风品种在热胁迫1h时TaHSP16.9基因表达上调幅度大于热敏感型品种。对于TaHSP17.8基因,抗干热风品种在热胁迫期间,上调表达反应时间均早于热敏感型品种;在热胁迫0.5h时,山农23号、周麦18与泰山9818三个抗干热风品种基因表达均上调至590倍以上,而师栾02-1与济南17号的上调幅度在300倍以下。对于TaHSP23.6基因,山农23号的上调表达峰值远高于其他品种。对于TaHSP26.6基因,热敏感型品种在热胁迫后期的上调倍数高于抗干热风品种,师栾02-1与济南17号两个热敏感型品种在热胁迫4.5h时上调幅度均在4 000倍以上,而抗干热风品种山农23号、周麦18与泰山9818上调幅度均在3 000倍以下。 相似文献
16.
宁麦9号花后内源激素和蔗糖含量变化及其与籽粒淀粉合成的关系 总被引：1，自引：0，他引：1
为研究小麦花后旗叶和籽粒中内源激素、蔗糖含量及籽粒中淀粉积累的动态变化,以弱筋小麦宁麦9号为供试材料在两种施肥处理条件下分析了花后内源激素和蔗糖含量变化与籽粒淀粉合成的关系.结果表明,氮肥后移的处理旗叶中ZRs、iPAs含量的增加及ABA含量的减少,有利于光合产物的合成;蔗糖含量较高,为籽粒合成淀粉提供了充足的碳源物质.籽粒中淀粉及其组分积累量灌浆期呈不断上升的趋势,积累速率呈单峰曲线,直、支链淀粉和总淀粉积累速率峰值期均在花后21～28 d,氮肥后移表现为增加趋势.相关分析表明,籽粒中内源激素ABA与蔗糖含量呈极显著负相关,GA1/3/ABA与蔗糖含量呈极显著正相关,IAA、GA1/3与淀粉积累速率呈极显著正相关.通径分析表明,籽粒中内源激素IAA对淀粉积累速率有极显著促进作用,直接通径系数达0.9627**,GA1/3主要是通过提高IAA含量间接促进籽粒中淀粉的积累,说明适当提高IAA含量有利于促进籽粒淀粉的积累. 相似文献
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《Industrial Crops and Products》2005,21(3):343-351
Starch was isolated from breadfruit (Artocarpus artilis). It was further modified by oxidation, acetylation, heat–moisture-treatment and annealing. The functional properties of native and modified starches were then studied. Proximate analysis revealed that following modifications, the annealed (BANS), oxidised (BOS) and acetylated (BACS) starches retained higher moisture content compared to native starch (BNS), while heat–moisture treated starch (BHMTS) had lower moisture content. Crude fibre was reduced by following modifications, except that BNS and BANS had the same value (0.42%). Protein and fat contents were also reduced after modifications. Acetylation, oxidation and heat–moisture-treatment improved the swelling power of the native starch. The result indicates that all forms of modification reduced the solubility of native breadfruit starch. For all the starches, replacing the wheat flour by the starch resulted in increased alkaline water retention of the blends. Gelation studies revealed that native breadfruit starch is a better gelating food material than the modified derivatives. All forms of modification reduced pasting temperature, peak viscosity, hot paste viscosity and cold paste viscosity of the native starch, except that heat–moisture-treatment increased the pasting temperature. Setback value reduced after modifications, indicating that modifications would minimize starch retrogradation. 相似文献
18.
Rheological and Thermal Properties
of Potato Starch 总被引：2，自引：0，他引：2
<正>Particle size, rheological and thermal properties of potato starch from Yunnan province of China was investigated. The particle size ranges from 0.429-102.3 μm determined by laser light-scatter. The major flow type of 6 w/v% potato starch was shear-thinning fluid even the shear rate up to 800·s-1, and the gel formed by 6 w/v% potato starch fell to weak gel for its little difference between G′ and G′′, high dependence on frequency and low value of G′(Pa). The hardness and cohesiveness of potato starch gel were 31.3 g and 131.9 g·s, respectively. The thermal properties of potato starch were also determined by DSC at the starch∶ water = 3∶ 1. The To, Tp, and △H of potato starch were 62.23℃, 67.31℃, and 2.22 J·g-1. 相似文献