Reactions of n-hexanal with glycine in model systems.

n-Hexanal a common component of off-flavor of various foodstuffs forms in ethanol-water solutions brown coloured pigments with glycine very slowly. The changes in the ultra-violet region of spectrum, especially at the maximum at 280 nm are much quicker. Due to the fact that only the non-protonised amino acid reacts, the reaction rate is the highest in alkaline medium, especially at pH value 8.5-9. The primary product of the condensation of n-hexanal with glycine, the Schiff base, is not stable, as confirmed by the decreasing of the polarographic wave heights. The reaction rate constants of this decomposition were the highest at pH-value 8.5-9 similarly as the changes in the UV-Spectra. The effect of the temperature was negligible.     

Formation of methyl glyoxal in dihydroxyacetone and glycine Maillard reaction: A computational study

By considering the formation of methyl glyoxal as one of the possible intermediates, mechanisms for the intermediate stage of the Maillard reaction of dihydroxyacetone and glycine under different pH conditions have been proposed, following the Hodge-scheme. Density functional theory calculations have been performed at the standard state on the proposed mechanisms to calculated the Gibb’s free energy changes for the formation of different compounds in different steps of the reaction. Thus, the possibility for the formation of different compounds in the proposed mechanisms has been evaluated. Electronic energy changes for the formation of different compounds in the proposed mechanisms have been calculated to observe the internal energy changes of the reaction. The total mass balance has been followed during the calculation of electronic and Gibb’s free energies. The result reveals that methyl glyoxal is one of the most likely intermediates in the reaction, and dihydroxyacetone + deprotonated glycine and dihydroxyacetone + unprotonated glycine reactions are assumed favorable for the production of methyl glyoxal. The gaseous phase reaction is supposed to be more feasible than the aqueous phase reaction for the production of methyl glyoxal. Glyceraldehyde + protonated glycine and glyceraldehyde + glycine zwitterion reactions are postulated as less feasible for the formation of methyl glyoxal.     

Formation of glyoxal in hydroxyacetaldehyde and glycine nonenzymatic browning Maillard reaction: A computational study

Density functional theory (DFT) computations at the standard state on the proposed mechanisms have revealed that glyoxal (Gox) is one of the most possible intermediates in the hydroxyacetaldehyde (Hald) and glycine nonenzymatic browning Maillard reaction under different pH conditions. By following the total mass balance, the gaseous state reaction has been found as more feasible for the formation of Gox than that of the aqueous solution. Hald + deprotonated glycine reaction under basic condition and Hald + unprotonated glycine reaction under neutral condition have been supposed to be more favorable for the production of Gox than Hald + protonated glycine reaction under acidic condition and Hald + glycine zwitterion reaction at the isoelectric point of glycine. Oxidation of Hald to Gox has been found as more plausible in the gaseous state than the aqueous solution. Oxygen has been found as necessary for the production of Gox from Hald. At the standard state, DFT calculations on the proposed mechanisms have evaluated that unprotonated and deprotonated glycine and glycine zwitterion are feasible for liberating NH₃, whereas protonated glycine has been found as unfeasible. DFT computations at the standard state on the proposed mechanisms have also revealed that the gaseous state Hald + NH₃ reaction is more feasible for the formation of Fald than that of the aqueous solution. Water, which is a by-product, has found as necessary for the initiation of both of Hald + glycine and Hald + NH₃ reactions.     

柞蚕丝织物的乙二醛抗皱整理

用乙二醛对柞蚕丝织物进行整理具有明显的抗皱效果(缓弹回复角可以提高28.5%左右)和良好的抗皱耐久性(水洗20次后织物仍然可以保持122.1°的急弹回复角和170.9°的缓弹回复角).通过正交实验和单因素分析得出了乙二醛整理的最佳工艺条件:乙二醛用量2.5%(对整理液质量),165℃焙烘2.5min,甲酸用量为5%(对整理液质量),硫酸铝用量为8%(对整理液质量).采用红外光谱分析纤维结构的变化,证明乙二醛与柞蚕丝纤维发生了充分的交联反应.     

On the reaction of glyoxal with proteins

 The reaction of arginine and arginine derivatives with glyoxal under mild conditions revealed the formation of a previously unknown amino acid, designated as “Glarg”. ¹H-, ¹⁵N- and ¹³C-NMR analysis of the new compound elucidated its structure to be 1-(4-amino-4-carboxybutyl)-2-imino-5-oxo-imidazolidine. Experiments with solutions containing N ^α -acetylarginine and glyoxal showed that “Glarg” is formed quickly under physiological conditions, but is labile at higher temperatures as well as at low pH values. After incubation of β-casein with glyoxal, the formation of protein-bound “Glarg” in enzymatic hydrolysates via amino acid analysis could be demonstrated. Due to the fast reaction of glyoxal with arginine residues, under physiological conditions, proteins may act as scavengers for glyoxal. Received: 8 November 1996 / Revised version: 10 January 1997     

Oligomer formation in evaporating aqueous glyoxal and methyl glyoxal solutions

Glyoxal and methyl glyoxal are common secondary atmospheric pollutants, formed from aromatic and terpene precursors. Both compounds are extremely water-soluble due to dihydrate formation and partition into cloudwater. In this work, FTIR-ATR and mass measurements indicate that both compounds remain primarily in the condensed phase due to oligomer formation when aqueous solution droplets are evaporated, regardless of concentration (> or = 1 mM) or, for glyoxal, droplet evaporation rate. FTIR spectral analyses suggestthat oligomer formation is triggered by conversion from dihydrate to monohydrate forms, which are still nonvolatile but contain reactive carbonyl groups. Methyl glyoxal hemiacetal formation is observed by changes in the C-0/C=0 stretch peak area ratio. The formation of glyoxal oligomers is detected by a dramatic shift of the C-0 stretching peak toward low frequencies. Glyoxal oligomer peaks at 1070 cm(-1), 950 cm(-1), and 980 cm(-1) are assigned to free C-OH stretch, dioxolane-linked C-OC asymmetric stretch, and tentativelyto non-dioxolane-linked C-OC stretches, respectively. Acids have little effect on glyoxal oligomer formation; however, base interrupts oligomer formation by catalyzing glyoxal hydration and disproportionation to glycolic acid. Since glyoxal and methyl glyoxal are commonly found in cloudwater and are expected to remain largely in the aerosol phase when cloud droplets evaporate, this process may be a source of secondary organic aerosol by cloud processing.     

水解淀粉与乙二醛对棉织物的抗皱整理

采用水解淀粉与乙二醛复配整理剂对棉织物进行抗皱整理,通过正交试验,讨论水解淀粉、乙二醛和催化剂用量、焙烘温度和焙烘时间等因素对整理后棉织物折皱回复角提高率和断裂强力保持率的影响。得出最优整理工艺参数:淀粉质量浓度40 g/L、乙二醛质量浓度7 g/L、催化剂质量浓度40 g/L、焙烘温度140℃、焙烘时间5 min。在此最优工艺条件下,整理后棉织物的折皱回复角提高率为30%~45%,断裂强力保持率为88%~95%。     

棉织物用乙二醛加水解淀粉的整理工艺研究

介绍了乙二醛对棉织物进行防皱整理的机理，分析讨论了乙二醛浓度及不同工艺方法和条件对棉织物断裂强力、折皱回复性和透气性的影响。     

盐酸水解淀粉/乙二醛对棉织物抗皱整理的研究

采用盐酸水解淀粉和乙二醛的复配整理剂对棉织物进行抗皱整理,研究了淀粉的盐酸水解工艺及水解淀粉与乙二醛质量比对整理后棉织物性能的影响。试验结果表明当盐酸质量分数为15%,水解温度为90℃,水解时间为60 min时,盐酸水解工艺较优,且经水解淀粉与乙二醛质量比为2∶1的优化工艺整理后,棉织物的干态折皱回复角超过220°,断裂强力保留率高于60%,棉织物的白度降低不明显,但湿态折皱回复角有待提高。     

水解淀粉和乙二醛对棉织物防皱整理的研究

介绍了乙二醛对棉织物进行防皱整理的机理以及抗皱整理液的配制、操作过程，分析了不同因素对棉织物断裂强力和折皱回复性能的影响，得出了最佳工艺条件：整理液中乙二醛为26．4mL/L，水解90min的淀粉（玉米淀粉20g/L盐酸16．8mL／L），MgCl2^＋6H2O为20g／L，在150℃条件下焙烘5min．与未经处理棉织物相比，处理棉织物的折皱回复角提高，但断裂强力却降低了．     

乙二醛整理剂对柞蚕丝织物抗皱整理的研究

介绍了乙二醛整理剂对柞蚕丝织物抗皱整理的方法，讨论了工艺条件对柞蚕丝织物抗皱效果的影响.整理织物抗皱性能有明显的提高，并具有较好的耐洗性，外观光洁，手感柔软，但强力略有下降.通过正交试验确定乙二醛整理的最佳工艺条件为：乙二醛用量2.5%（owf），焙烘温度为165℃，甲酸用量为5%（owf），硫酸铝用量为8%（owf）.     

The existence of the 1,2-dicarbonyl compounds glyoxal,methyl glyoxal and diacetyl in autoxidised edible oils

The 1,2-dicarbonyl compounds glyoxal, methyl glyoxal and diacetyl which are known to be mutagens without metabolic activation in the Salmonella typhimurium TA100 system, were detected in autoxidised edible oils (sesame, safflower and sardine oil). The method is based on the fact that the 1,2-dicarbonyl compounds react with 4-chloro-1,2-phenylenediamine to give 6-chloroquinoxaline derivatives, which can be detected by ⁶³Ni ECD-gas chromatography. Glyoxal, methyl glyoxal and diacetyl were detected at 4.7, 7.0 and 1.6 μg g^?1, respectively, in 20 h autoxidised methyl linolenate. Glyoxal, methyl glyoxal and diacetyl were also detected at 6.5, 7.0 and 3.1 μg g^?1, respectively, in 30 h autoxidised sardine oil.     

Uptake of glyoxal by organic and Inorganic aerosol

The uptake of glyoxal by a variety of organic and inorganic aerosol types was examined in a Teflon chamber. Rapid glyoxal uptake was observed for all liquid-phase aerosols at all relative humidity levels tested (< 5 to 50% RH). Even for aerosol with known water content, Henry's Law cannot predict glyoxal uptake: H* > (3 +/- 1.5) x 10(8) mol kg(-1) atm(-1) for l-tartaric acid, H* > (1 +/- 0.5) x 10(8) for dl-malic acid and H* = (2 +/- 1) x 10(7) for malonic acid aerosol. Other liquid-phase aerosol particles containing amine functional groups (arginine, aspartic acid, and glutamic acid) took up even more glyoxal (H* > 3 x 10(8)). The trend of higher glyoxal uptake onto aerosol containing more nucleophilic organic compounds suggests that glyoxal is reacting with organic compounds in the aerosol phase. Solid-phase aerosol showed RH-dependent glyoxal uptake, likely due to the existence of surface water layers. However, particle growth rates were the highestfor sodium sulfate aerosol. For organic aerosol, growth rates correlated with the acidity of the carboxylic acid groups of the aerosol material, suggesting that glyoxal uptake is enhanced by mildly acidic conditions.     

改进的乙二醛抗水剂GS-235

以三聚氰胺及未改进的乙二醛为基质的抗水剂,因本身会发生聚合反应,会造成纸张质量的负面影响.GS-235抗水剂因自身不会发生聚合反应,仅与-OH及-COOH反应,因而克服了传统乙二醛树脂熟化慢及返黄的缺点,降低了用量,提高了纸张适印性及湿拉毛速度.     

大豆纤维织物的乙二醛树脂整理

将乙二醛树脂用于大豆纤维织物的防皱整理，讨论了整理剂用量、焙烘温度、焙烘时间对抗皱整理效果的影响。对织物在不同整理条件下的折皱回复角、白度、断裂强力和透气性等性能进行测试；确定了优化整理工艺条件：免烫树脂931-33 150g/L、柔软剂30g／L、渗透剂JFC 2g/L，焙烘温度150℃、焙烘时间2min。测试整理后的织物结构和性能表明，整理剂在纤维无定形区大分子链之间发生了交联反应，提高了纤维的热稳定性，纤维的晶区结构基本没有改变。     

乙二醛交联淀粉对纸张增强性能影响的研究

乙二醛作为交联剂用于酶解淀粉改性,研究了反应条件和机理,并将改性淀粉应用于牛皮挂面纸的表面施胶,分析对纸张的增强和增挺作用。用单因素实验法讨论了交联反应温度、反应时间、乙二醛用量、干燥时间对牛皮挂面纸增强与增挺的影响。研究表明：在温度为80℃、反应时间为15min、乙二醛用量为0.5ml/g淀粉,并烘干2min后再自然干燥1h,纸张抗张指数和挺度指数分别提高至56.54N.m/g和313N.m3/g。     

Analysis of glyoxal,methylglyoxal and diacetyl in soy sauce

Food Science and Biotechnology - In this study, an analytical method for the determination of α-dicarbonyl compounds (α-DCs), including glyoxal (GO), methylglyoxal (MGO) and diacetyl...     

紫外分光光度法测定树脂整理剂中游离乙二醛

根据Cannizarro反应机理对乙二醛浓度的标定条件进行了优化,同时利用乙二醛与羟胺反应生成乙二醛二肟在230 nm处具有较强的紫外吸收,测定树脂整理剂中游离乙二醛的含量。乙二醛含量为0.2~4.0μg/mL时,该方法具有良好的线性,相关系数达0.999 99(n=8),相对标准偏差为0.162%,检出限为1.09μg/mL,回收率为95%~105%。