Volatile Components in Salt-Fermented Fish and Shrimp Pastes

Volatile compounds in salt-fermented anchovy, big-eyed herring, hair tail viscera, and shrimp pastes were compared by simultaneous steam distillation-solvent extraction/gas chromatography/mass spectrometry (SDE/GC/MS). A total of 155 volatile compounds were detected. Of these, 111 were positively identified consisting mainly of aldehydes, ketones, alcohols, esters, aromatics, nitrogen-, and sulfur-containing compounds. Lipid-derived components, such as aldehydes, alcohols, and esters, comprised the majority of volatile compounds from fish pastes, while heterocyclic nitrogen-containing compounds, such as pyrazines, were predominant in shrimp paste.     

Stability of Non-Pasteurized, Refrigerated Muscadine Grape Juice

The stability of nonpasteurized muscadine grape juice processed with and without 100 mg/L potassium metabisulfite was monitored during storage at 3°C. The muscadine flavor intensity, sweetness, off-flavor levels, and color of white juices remained stable, and ethanol levels remained low for 7 wk. However, the flavor intensity and sweetness of nonsulfited white juice decreased, and off-flavor and ethanol levels increased after 7 wk. Sulfite lowered microbial levels in white juice throughout 9 wk. Red juices did not develop significant levels of off-flavors or ethanol during 9 wk, although the flavor intensity declined, especially in nonsulfited red juice. Sulfite lightened the color of red juice, but the color was stable in both sulfited and nonsulfited red juices.     

Time-intensity Measurement of Flavor Release from a Model Gel System: Effect of Gelling Agent Type and Concentration

Flavor release from cornstarch, gelatin or iota carrageenan gels flavored with benzaldehyde, d-limonene or ethyl butyrate was measured at three gel strengths (soft, medium, firm) by 20 trained judges using the time-intensity (TI) method. At comparable gel strengths, starch and gelatin displayed greater flavor release properties than carrageenan, i.e., mean values for perceived maximum intensity (Imax) and total duration (Tdur) of flavor were higher for starch and gelatin than for carrageenan across flavors. Firm gelatin and carrageenan gels released flavor with a lower Imax than soft or medium gels, but Imax and Tdur did not vary across starch gel strengths. Results indicate both texture (firmness) and gelling agent affect flavor release from a gel.     

低热水泥胶凝体系力学及热学综合性能评价

为了对低热硅酸盐水泥胶凝体系力学和热学综合性能进行评价,从而为低热水泥在大体积混凝土中的应用提供参考,以胶凝材料不同龄期抗压强度、抗折强度和水化热为指标,通过限定上限/下限线性计算规则建立评价目标函数,计算不同矿物掺合料下的低热水泥胶凝体系综合性能满意度,并绘制满意度等值线图。研究结果表明:低热水泥胶凝体系综合性能满意度等值线分布可以近似看作系列同心椭圆线;粉煤灰掺量在区间、矿渣粉掺量在区间范围内其综合性能满意度较高,具备较好的早强低热性能。该性能评价函数以及满意度等值线图的联合运用,为复合胶凝材料体系力学及热学综合性能评价提供了新的思路。     

水泥土搅拌桩复合地基承载力灰色系统分析

本文根据灰色系统理论中的GM(0,N)模型,对复合地基承载力与桩间土物理性质指标及桩长之间的关系进行建模分析,结果表明,该模型所需样本量少,且快捷准确,为今后的工程实践提供了一种有效预测水泥土搅拌桩承载力的方法。     

半柔性复合路面设计与施工方法的探讨

半柔性复合路面是指在开级配的大孔隙基体沥青混合料中,灌入以水泥为主要成分的特殊浆体而复合形成的一种路面结构,它兼具有沥青路面与水泥混凝土路面的优点,具有优良的高温稳定性能和抗疲劳性能,具有较好的低温抗裂性能和水稳定性。介绍了半柔性路面的设计方法和施工工艺,为推广半柔性路面作了有益的探索。     

复式断面河槽流速横向分布及其对滩唇形成的影响

通过对水流微小控制体进行受力分析,建立了复式断面流速横向分布模型,该模型考虑了侧向副流惯性力的影响。采用实验资料对该模型进行检验,模型计算值与实测值符合较好。运用该模型计算了不同条件下复式断面流速和挟沙力的横向分布,并定量分析了横向分布特性对滩唇形成的影响。分析表明,水流漫滩时,复式断面的横向挟沙力变幅较大,尤其是在主槽和河漫滩交界处,挟沙力减小迅速,而含沙量减小相对较小,泥沙发生淤积,容易形成滩唇。单从水流挟沙力角度考虑,水流漫滩后水深越小、滩槽的糙率差越大,越容易形成滩唇。     

水源水质标准中嗅味标准的研究

在我国现有的《生活饮用水水源水质标准》(CJ3020-93)标准中并未对嗅味做定性和定量的规定。嗅味层次分析方法能够对水样中的嗅味种类以及嗅味强度做出定性和定量化的判断,通过嗅味层次分析方法以及SPME-GC/MS化学分析的结果,给出了饮用水嗅味的推荐值。按不同水源地类型对二甲基异莰醇(2-MIB)的标准进行了研究,综合考虑感官分析和化学分析结果,水厂可处理程度以及消费者可接受情况,给出2-MIB标准的推荐值,一级、二级水源地的标准推荐值为10 ng/L,三级水源地的标准推荐值为50 ng/L。二甲基异莰醇(2-MIB)嗅味标准推荐值的给出在一定程度上对水源地的划分又提供了一个参考依据,开辟了水质感官分析的新思路,为我国城市水源中2-MIB含量的划分提供了参考。     

分散性催化剂作用下噻吩类化合物的临氢转化规律

以有机钼为前驱体制备了分散性纳米RDC-Mo催化剂,采用微型反应釜进行了噻吩类模型化合物噻吩、苯并噻吩和二苯并噻吩(DBT)热转化及RDC-Mo催化临氢热转化反应,对比了热转化及催化临氢过程噻吩类模型化合物热转化反应效果。采用X射线衍射(XRD)及高分辨率的透射电镜(HRTEM)对所制备的分散型催化剂进行了分析表征。采用模拟计算方法深入研究了分散型催化剂催化临氢热转化显著提高噻吩类化合物转化率以及不同结构噻吩类反应差异的内因。结果表明：制备的分散型催化剂RDC-Mo具有高度分散纳米尺寸特征,其晶粒尺寸为3.63 nm。相比于热转化,高分散纳米催化剂RDC-Mo作用的催化临氢过程显著强化了噻吩类化合物的转化,使其转化率大幅度提高。高分散度纳米催化剂显著强化了噻吩类化合物与催化剂活性中心、H₂的可接近性;H₂经纳米催化剂活化形成的氢自由基强化噻吩类化合物中与S相连的芳环碳定向加氢,促使C—S键断裂能垒大幅下降,在较低温发生断裂;该反应路径正是造成分散型催化剂临氢体系显著提高噻吩类化合物裂化转化率的内在原因。受定向加氢的概率、在活性中心MoS₂吸附难易以及定向加氢后C—S键键长变化3方面的影响,不同结构噻吩类化合物转化率由大到小顺序为苯并噻吩、噻吩、二苯并噻吩。