甲酸-盐酸混合溶液水解麦草制备木糖的工艺研究

本文对甲酸-盐酸混合溶液水解麦草制备木糖的工艺进行研究.实验发现含10 % HCl的饱和甲酸溶液在65 ℃水解麦草0.5 h后,麦草木糖的水解得率达到23.62 %.水解液经D311阴离子交换树脂脱酸脱色、活性炭脱色、真空结晶等一系列工艺后,结晶木糖产率为干燥麦草质量的15.87 %,工艺可行.     

麦草甲酸不溶木质素的结构研究

采用FT-IR、GPC、^1HNMR、Py-GC-MS等手段，分析了麦草在甲酸水解体系中不同温度、不同时间条件下反应后其固体残渣中木质素的结构。FT-IR分析发现，纯化木质素有羧基存在，表明麦草木质素分子结构在甲酸作用下发生了明显的氧化。Py-GC-MS和^1HNMR分析显示，甲酸不溶木质素以愈刨木基为主，紫丁香基含量略高于对羟苯基。Py-GC-MS及GPC分析发现，甲酸反应体系中随着温度、时间的增加，木质素分子质量会降低，各种木质素型的酚类物质占总木质素的高温分类产物的比例都呈下降趋势，表明该反应体系既能促进木质素α-芳基醚键、β-芳基醚键断裂，使得木质素很快溶解在溶液中，同时也能促进木质素的缩合，但总的趋势是使木质素的分子质量下降。     

麦草酸水解提取木糖的探究

探究了不同条件下麦草硫酸水解木糖溶出的变化。结果表明,在水解温度120℃,水解时间60 min,硫酸的质量分数4%时,木糖提取量达到最大值0.20 g/g麦草,木糖的溶出过程随着水解反应强度的增强可分为三个阶段。X射线衍射、傅里叶红外光谱和环境扫描电镜分析表明,硫酸质量分数和水解温度是影响水解过程中麦草纤维素结晶区破坏的主要因素,在木糖提取量最大时,半纤维素几乎完全降解溶出。     

N-甲基咪唑硫酸氢盐蒸煮麦草浆中木糖和葡萄糖含量的变化

利用N-甲基咪唑硫酸氢盐在离子液体中蒸煮麦草进行制浆,在20 g绝干麦草,离子液体与麦草质量比为6:1的条件下,研究制浆过程中木糖和葡萄糖的变化规律和趋势。结果表明:较短时间和较低温度下戊糖和葡萄糖呈增长趋势,有利于戊糖和葡萄糖溶出;较长时间和较高温度下木糖和葡萄糖呈递减趋势,有利于木糖和葡萄糖进一步水解。     

麦草热水预水解过程产物分析及木糖生成模型

为了探究麦草热水预水解过程中产物的生成变化规律,分别采用离子色谱和高效液相色谱检测预水解液中糖类(阿拉伯糖、半乳糖、葡萄糖和木糖)和发酵抑制物(甲酸、乙酸、5-羟甲基糠醛和糠醛)的含量,分析了单因素实验中糖类和发酵抑制物的生成变化规律;同时采用响应面法对影响麦草热水预水解液中木糖生成的固液比、水解温度和水解时间进行了优化研究,建立了木糖生成量的二次多项式数学模型。结果表明,在固液比1∶11.67、水解时间57.76 min和水解温度173.96℃的条件下,木糖的生成量达到最高,为83.91 mg/g麦草。     

麦草自水解工艺的优化及其产物特性

为了选择性水解麦草中的半纤维素,对麦草自水解处理进行了探讨。利用强度因子评估了温度（150～240℃）和非等温反应时间对麦草自水解后所得固相和液相组分的影响。当强度因子为3.96时,水解液中半纤维素衍生糖的得率最高,约为原生聚木糖（阿拉伯糖）的64%（其中80%为低聚木糖）。在此条件下,58%的聚木糖、83%的聚阿拉伯糖和98%的乙酰基被溶解。葡聚糖主要保留于固相中（最多溶解16%）,这使得固相中葡聚糖的含量高达61%。木素去除量并不高,最多为15%。实验所得可溶性产物（包括糖类、乙酸）和降解成分（如糠醛、5-羟甲基糠醛）的生成量表明其液相适合用于发酵,或得到可应用于食品、药品和化妆品行业所需的低聚木糖。     

亚硫酸铵预处理提高麦草备料废渣的酶水解效率

为高效经济利用制浆厂的备料废渣,研究了亚硫酸铵预处理对麦草备料废渣主要化学成分及酶水解糖化效率的影响。结果表明,原料的木素脱除率随预处理温度升高和亚硫酸铵用量增加而提高,半纤维素的降解受温度影响较大,纤维素在预处理中几乎没有降解。在本研究范围内,随着预处理强度的增大,碳水化合物的酶水解糖转化率先上升后下降,相比于提高温度,增加亚硫酸铵用量对提高酶水解效率的影响更为显著。麦草备料废渣在165℃下用16%亚硫酸铵预处理,经PFI磨磨浆得到的底物,其酶水解(以聚葡萄糖为基准的酶用量为40 FPU/g)聚葡萄糖和聚木糖转化率分别为88.9%和44.9%,总糖转化率为67.0%。     

麦草黑液中糖组分及其含量的气相色谱-质谱联用测定

造纸废液中糖类含量很高,麦草浆黑液中戊糖含量高达25.56%.这部分糖类若能提取回收,则造纸的污染有望减轻,且资源也得到了合理利用.用气相色谱-质谱联用(GC-MS)测定了麦草黑液中的单糖组分及其含量,得出麦草黑液中含有阿拉伯糖、木糖、甘露糖、葡萄糖和半乳糖,7mL麦草黑液中单糖总含量达0.003056g,其中阿拉伯糖最多,为0.0021g,甘露糖次之,为0.000646g.依据质谱得出,麦草黑液中还含有香草醛乳糖苷、植醇、赤藓糖醇和蔗糖.     

预水解及液比对麦草制浆性能影响的研究

以水为介质对麦草进行蒸煮前的预处理,以最大限度的溶出麦草中的半纤维素,同时伴有少量的木素的溶出。在此基础上,提高在下一步蒸煮中麦草对碱溶液的吸收,提高制浆得率且减少制浆黑液的处理难度。研究表明:预水解的工艺条件为:水解温度150℃、水解时间1小时、液比1∶20。经此工艺条件处理后的麦草得率为83.05%,预水解残液高锰酸钾消耗值为1.005,pH值为4.8,还原糖含量为10.01%;经过AP-AQ法蒸煮得率44.55%,卡伯值21.38;相同蒸煮工艺条件下未水解的麦草浆得率为47.12%,卡伯值20.01。大液比有利于纸浆得率提高、蒸煮均一。     

木聚糖酶Shearzyme 500 L对蔗渣木聚糖的特性研究

以木聚糖酶Shearzyme 500L水解蔗渣木聚糖制备低聚木糖,用DNS法测定酶解液中的总糖和还原糖,HPLC法测定酶解产物组成,其适宜的水解条件为底物质量浓度3g/100mL、pH5.0、60℃、木聚糖中酶用量50U/g、水解时间24h。在此条件下底物水解率约为63.1%,水解产物的81.5% 为低聚木糖,其中木二糖占54.8%,木三糖占26.7%。Shearzyme 500L 不能将一分子木二糖水解为两个木糖单糖,但能水解木三糖并相应生成木二糖与木糖。副产物木糖能显著抑制Shearzyme 500L 活性,降低木聚糖的水解率。     

Determination of ethanol,volatile fatty acids,lactic and succinic acids in fermentation liquids by gas chromatography

A rapid and simple quantitative method was developed to determine, by gas chromatography, the concentrations in fermentation liquids of ethanol, the C₂-C₆ volatile fatty acids, and lactic and succinic acids. Aqueous samples were acidified with 250μlml^?1 metaphosphoric acid (5:1 ratio), centrifuged, and injected directly on to a column containing a porous aromatic polymer (Chromosorb 101) maintained at 200°C in a gas chromatograph fitted with a flame ionisation detector. It was unnecessary to purify samples further before injection, although distillation and ion-exchange methods were examined. Derivatisation of lactic and succinic acids before injection was not necessary, but the lowest level of detection of these two relatively non-volatile acids was about four times greater than that for the volatile fatty acids. The method described was suitable for the analysis of rumen fluid, methane digester fluid, silage extracts and other anaerobic fermentation fluids. The relative retention times are given for 23 organic acids and six other fermentation end-products.     

Effects of abomasal infusions of fatty acids and 1-carbon donors on apparent fatty acid digestibility and incorporation into milk fat in cows

Our primary objective was to determine the effects of the abomasal infusion of 16-carbon (16C) and 22-carbon (22C) fatty acids (FA) on apparent FA digestibility, plasma FA concentrations, and their incorporation into milk fat in cows. Our secondary objective was to study the effects of 1-carbon donors choline and l-serine on these variables. Five rumen-cannulated Holstein cows (214 ± 4.9 d in milk; 3.2 ± 1.1 parity) were enrolled in a 5 × 5 Latin square experiment with experimental periods lasting 6 d. Abomasal infusates consisted of (1) palmitic acid (PA; 98% 16:0 of total fat), (2) PA + choline chloride (PA+CC; 50 g/d of choline chloride), (3) PA + l-serine (PA+S; 170 g/d of l-serine), (4) behenic acid (BA; 92% 22:0 of total fat), and (5) docosahexaenoic acid algal oil (DHA; 47.5% DHA of total fat). Emulsions were formulated to provide 301 g/d of total FA and were balanced to provide a minimum of 40 and 19 g/d of 16:0 and glycerol, respectively, to match the content found in the infused algal oil. Apparent digestibility of FA was highest in DHA, intermediate in PA, and lowest in BA. Digestibility of 16C FA was lowest in BA and highest in PA. The digestibility of 22C FA was highest in DHA relative to BA (99 vs. 58%), whereas 1-carbon donors had no effect on 22C FA digestibility. Plasma 16C FA concentrations were greatest with PA treatment, and 22C FA concentrations were ~3-fold greater in DHA-treated cows relative to all other treatments. Milk fat 16:0 content was highest in PA relative to BA and DHA (e.g., 37 vs. 27% in PA and DHA), whereas the milk yield of 16:0 was higher in PA relative to DHA (i.e., 454 vs. 235 g/d). Similarly, milk 22:0 content and yield were ~10-fold higher in BA relative to all other treatments, whereas DHA treatment resulted in higher content and yield of 22:6 in milk fat relative to all other treatments (41- and 38-fold higher, respectively). Consequently, the content of FA >16C (i.e., preformed) was higher in milk fat from cows infused with BA and DHA relative to PA. De novo FA content in milk did not differ between PA, PA+CC, and PA+S (~16% of milk fat) but was higher in BA and DHA treatments (19 and 21%, respectively). We conclude that FA carbon chain length and degree of saturation affected FA digestibility and availability for absorption as well as their incorporation into milk fat. The abomasal infusion of choline chloride and l-serine did not modify these variables relative to infusing palmitic acid alone.     

Short communication: Eicosatrienoic acid and docosatrienoic acid do not promote vaccenic acid accumulation in mixed ruminal cultures

Previous research found that docosahexaenoic acid (C22:6n-3) was a component of fish oil that promotes trans-C18:1 accumulation in ruminal cultures when incubated with linoleic acid. The objective of this study was to determine if eicosatrienoic acid (C20:3n-3) and docosatrienoic acid (C22:3n-3), n-3 fatty acids in fish oil, promote accumulation of trans-C18:1, vaccenic acid (VA) in particular, using cultures of mixed ruminal microorganisms. Treatments consisted of control, control plus 5 mg of C20:3n-3 (ETA), control plus 5 mg of C22:3n-3 (DTA), control plus 15 mg of linoleic acid (LA), control plus 5 mg of C20:3n-3 and 15 mg of linoleic acid (ETALA), and control plus 5 mg of C22:3n-3 and 15 mg of linoleic acid (DTALA). Treatments were incubated in triplicate in 125-mL flasks, and 5 mL of culture contents was taken at 0 and 24 h for fatty acid analysis by gas-liquid chromatography. After 24 h of incubation, the concentrations of trans-C18:1 (0.87, 0.88, and 0.99 mg/culture), and VA (0.52, 0.56, and 0.62 mg/culture) were similar for the control, ETA, and DTA cultures, respectively. The concentrations of trans-C18:1 (5.51, 5.41, and 5.36 mg/culture), and VA (4.78, 4.62, and 4.59 mg/culture) were also similar between LA, ETALA, and DTALA cultures, respectively. These data suggest that C20:3n-3 and C22:3n-3 are not the active components in fish oil that promote VA accumulation when incubated with linoleic acid.     

奶粉脂肪酸与乳制品风味关系研究

用气质（GC—MS）联用色谱分析了11个商业奶粉样品的脂肪酸组成以及含量,每个样品均检测到了28种脂肪酸,在表现奶粉风味的4个呈味脂肪酸,也即辛酸、己酸、壬酸和葵酸中只检测到了辛酸和葵酸。辛酸和葵酸含量在进口奶粉中普遍高于国产奶粉。国产奶粉中辛酸和葵酸的含量以2号最好,3号其次。亚油酸含量在国产奶粉中普遍高于进口奶粉。     

气相色谱法同时快速测定食品中丙酸、山梨酸、苯甲酸及脱氢乙酸

通过液液萃取净化样品研究,建立了食品中丙酸、山梨酸、苯甲酸、脱氢乙酸及其盐含量气相色谱同时快速测定方法,适用于固体非酯(脂)类食品的检测。结果表明:丙酸的回收率在85.1%~91.3%之间,其余3种防腐剂的回收率均在95.2%~99.4%之间;实验室内变异系数(CV,n=6)最大值≤4.7%,4种防腐剂检出限均在0.002 g/kg以下。4种目标物在有杂质干扰时,可用不同的极性毛细管柱做进一步的确认。本方法具有适用范围广、检测效率高、重现性好、准确度高、检出限低的特点,推广应用对我国食品安全的监督检验具有重要的意义。     

花生四烯酸、二十二碳六烯酸和二十碳五烯酸 在炎症中的作用概述

心脑血管疾病、肿瘤、糖尿病、神经系统疾病、自身免疫等疾病严重危害着人类的生命和健康,并消耗着大量医疗资源。事实上,很多疾病发生和发展的背后都伴随着炎症反应,炎症是众多疾病的病理基础,甚至是导致这些疾病的诱因。炎症本身是机体的防御性反应,但过度的炎症反应和长期慢性炎症会损害机体的稳态。炎症的调节和控制由炎症介质介导,花生四烯酸(arachidonic acid,AA)、二十二碳六烯酸(docosahexaenoic acid,DHA)和二十碳五烯酸(eicosapentaenoic acid,EPA)等长链多不饱和脂肪酸(10ng-chain polyunsaturated fatty acids,LC-PUFAs)的衍生物是一类重要的调控炎症的介质。炎性细胞间的交流和细胞内信号传递与LC-PUFAs有关。AA经环氧酶和脂氧合酶合成的类二十烷酸主要起促炎作用,但有的也有抗炎作用。DHA和EPA在体内起抗炎作用,由它们合成的消退素(resolvins,Rvs)和保护素(protectin,PD)是重要的抗炎活性物质。DHA和EPA还可以干扰炎性细胞内信号传导途径来抑制炎症反应。本文从炎症与疾病的关系、LC-PUFAs的衍生物及其促炎和抗炎机制等方面综述了AA、DHA和EPA在炎症中的作用。     

酸味酿造产品中三酸比例评析

酸味酿造产品中乳酸、醋酸、丁酸共存,但比例不同形成的酸味特征也不同。控制不同的环境条件,创造出不同的微生物区系,形成不同的三酸比例,才能形成不同的产品风格。该文对常见的酸味酿造产品中微生物区系的变化及三酸含量进行了分析。     

Growth of Aeromonas hydrophila K144 as Affected by Organic Acids

The influence of different acids on the aerobic growth kinetics of Aeromonas hydrophila was studied in BHI broth with 0.5 and 2.0% NaCl incubated at 5 and 19°C. Growth curve data were analyzed by the Gompertz equation and a nonlinear regression program; generation and lag times were calculated from the Gompertz parameters. Type of acid, pH, NaCl level and temperature influenced lag and generation times. The organic acids (acetic, lactic, citric and tartaric) inhibited growth at higher pH values than inorganic acids (HCl and H₂SO₄). The high NaCl level interacted with type of acid and pH to restrict growth of the organism at the lower temperature of incubation. Acetic and lactic acids were effective in controlling the growth of A. hydrophila and could readily be combined with low holding temperature to render foods free of the organism.     

杂多酸催化合成辛酸蔗糖酯

以蔗糖、辛酸为原料,杂多酸为催化剂合成辛酸蔗糖酯。用L16(45)正交设计优化实验,高效液相色谱法分析反应液组成。考察了催化剂种类和用量、反应温度、原料配比、反应时间等因素对辛酸蔗糖酯产率的影响,发现以二甲基亚砜为溶剂、蔗糖与辛酸摩尔比1∶9、磷钨酸用量为蔗糖质量的2.0%、110℃反应时间6h,蔗糖转化率达60%,产物产要是二酯。动力学研究发现,蔗糖反应级数为一级,反应表观速率常数为0.0059min-1(90℃)、0.0117min-1(110℃),反应表观活化能Ea=39.57kJ/mol。     

气相色谱法同时测定保健食品中的5种 不饱和脂肪酸

目的建立气相色谱法同时测定保健食品中亚油酸、α-亚麻酸、二十碳五烯酸(eicosapentaenoic acid,EPA)、二十二碳六烯酸(docosahexaenoic acid,DHA)和二十二碳五烯酸(docosapentaenoic acid,DPA)的含量。方法样品先采用氢氧化钾甲醇溶液进行皂化处理,再用三氟化硼甲醇溶液甲酯化,经HP-FFAP色谱柱(30m×0.53 mm,1.0μm)分离测定。结果 EPA甲酯、DHA甲酯、DPA甲酯、亚油酸甲酯、α-亚麻酸甲酯分别在0.03927~1.178、0.04200~1.260、0.03449~1.035、0.08368~1.255、0.08482~4.241 mg/mL的浓度范围内线性关系良好,相关系数r均大于0.999;检出限分别为0.0039、0.0042、0.0034、0.0042、0.0042 mg/mL;加标回收率在91.1%~109.3%之间,相对标准偏差均小于5%。结论该方法操作简单快捷,适用于保健食品中亚油酸、α-亚麻酸、EPA、DPA和DHA的测定。