Effect of nutmeg (Myristica fragrans) essential oil on the oxidative and microbial stability of cooked sausage during refrigerated storage

This paper examines the oxidative and microbial stability of cooked sausages, produced with the addition of 10 ppm (NO1) and 20 ppm (NO2) nutmeg (Myristica fragrans) essential oil. Instrumental parameters of color (CIE L*, CIE a* and CIE b*), Thiobarbituric acid-reactive substance (TBARS) values, microbial profile and sensory properties of aroma have been determined on the 1st, 30th, 45th, and 60th day of storage. Addition of the nutmeg essential oil had no effect on the color of cooked sausages. At the end of the storage, NO2 sausages had the best oxidative and microbial stability. TBARS values of NO1 and NO2 sausages were 1.21 mg MDA/kg and 0.95 mg MDA/kg, respectively, and were significantly lower (P < 0.05) compared to control (1.53 mg MDA/kg). Total number of aerobic mesophilic bacteria was lowest in NO2 sausages (78.3 cfu/g) and highest in control (185 cfu/g). After 45 and 60 days of storage, sensory properties of aroma of NO1 (4.21; 3.92) and NO2 sausages (4.39, 4.28) were better compared to those in control (4.07, 3.25). Hence, the addition of nutmeg essential oil in amount of 20 ppm can be successfully applied in order to extend the shelf life of cooked sausages.     

Heterogeneity of Adsorption Sites and Adsorption Kinetics of n-Hexane on Metal-Organic Framework MIL-101(Cr)

abstract The heterogeneity of adsorption sites and adsorption kinetics of n-hexane on a chromium terephthalate-based metal-organic framework MIL-101(Cr) were studied by gravimetric method and temperatu...     

Degradation of polystyrene in supercritical n-Hexane

Degradation of polystyrene was carried out in supercritical n-hexane under reaction temperature ranging from 330 °C to 390 °C, pressure ranging from 30 bar to 70 bar and reaction duration of 90 min. The conversion of polystyrene increased with rising temperature and pressure. The degradation performance was influenced by the temperature rather than applied pressure. Polystyrene rapidly degraded in 30 min after reaching a prescribed temperature ranging from 350 °C to 390 °C. At a prescribed temperature of 390 °C, the degree of degradation was higher than 90%. The degradation reaction was examined experimentally at a relatively low temperature of 330 °C. The degradation of polystyrene by using supercritical n-hexane has been found to be more effective compared to general pyrolysis (thermal degradation). Among the selectivity of liquid products, that of a single aromatic ring group like styrene at 390 °C increased up to 65% in 90 min. It was found from the analysis by a gel permeation Chromatograph (GPC), that high molecular-weight compounds decreased but oligomers increased with rising temperature.     

Synthesis of Polyynes with Electric Arc Part 5: Detection of PAHs as Minor Products

The main products of the submerged electric arc between graphite electrodes in n-hexane and in methanol are the polyynes series. The liquid chromatographic analysis (HPLC) of the arcing products in n-hexane reveals also the presence of a mixture of polycyclic aromatic hydrocarbons (PAHs) as minor products. Naphthalene, acenaphthylene, phenanthrene, perylene, fluoranthene, benzo[b]fluoranthene, pyrene, and the related compound cyclopenta[c,d]pyrene have been identified. Even crysene and acenaphthene were reasonably identified from the PAHs mixture. The PAHs mixture appears to derive essentially from the plasmalysis of the solvent where the electric arc is conducted, while the polyynes are formed from the elemental carbon supplied from the graphite electrodes. Another minor product is represented in all cases by the formation of carbon black or carbon coke, which appears more abundant in n-hexane rather than in methanol. The different results are explained thermodynamically in terms of different carbonization tendency of the solvents used.     

Nickel impregnated Pt/H-β and Pt/H-mordenite catalysts for hydroisomerization of n-hexane

Nickel impregnated Pt/H-β and Pt/H-MOR catalysts with different Ni content were prepared and subjected to hydroisomerization of n-hexane in the presence of flowing H₂ gas. The states of Pt and Ni were identified by ESCA. The particle size measured by TEM shows that average particle size increases with increasing Ni loading. The acidity of the catalysts was measured by TPD of ammonia. The catalytic activity of Ni containing and Ni free Pt/H-β and Pt/H-MOR catalysts was compared and found that addition of Ni up to a threshold value (0.3 wt% for β and 0.1 wt% for MOR) increases the n-hexane conversion and dimethyl butanes selectivity due to better metal-acid synergism and decreases the amount of cracked products. When the Ni amount exceeds the threshold values the conversion decreases and cracked products increase. Further the Ni impregnation of Pt containing acidic supports increases the sustainability of the catalysts and was found to favor the protonated cyclopropane (PCP) intermediate mechanism in n-hexane isomerization. β zeolite was found to be a better potential support than mordenite and the isomerized product mixture shows better octane number.     

Sulfated zirconia grafted on a mesoporous silica aerogel: Influence of the preparation parameters on textural, structural and catalytic properties

Silica supported sulfated zirconia catalysts were synthesized via a new method by grafting sulfated zirconia on the surface of a silica aerogel previously prepared. The main parameters studied in this work were the S/Zr, Zr/Si molar ratios and the support nature. The synthesized solids were characterized using XRD, N₂ physisorption at 77 K, TG-DTA/SM, sulfur chemical analysis and adsorption–desorption of pyridine followed by infrared spectroscopy. These solids were tested in the n-hexane isomerization reaction. Two types of mesopores were observed on the silica aerogel. This mesoporosity was affected depending on the preparation parameters.

The increase of the Zr/Si molar ratio induces the decrease of the size of zirconia particles deposed on the support. In this case, appreciable amounts of sulfur are retained with the presence of a relatively strong Brönsted and Lewis acid sites on the catalyst surface. A high density of Brönsted sites seems to be interesting in the n-hexane isomerization reaction.     

Sulfur- and water-tolerance of Pt/KL aromatization catalysts promoted with Ce and Yb

Different Pt/KL catalysts containing rare earth (RE; Ce and Yb) promoters were prepared by two techniques, incipient wetness impregnation (IWI) and vapor phase impregnation (VPI). The catalysts were tested for the activity and the selectivity of n-hexane aromatization to benzene under clean, sulfur-containing, and water-containing feeds at 500 °C. It was observed that the catalysts prepared by the VPI technique exhibited much higher activity and selectivity than those prepared by IWI. It was also found that although under clean conditions, the addition of Ce or Yb caused a decrease in activity, in the presence of sulfur the addition of Ce and to a lesser extent Yb, significantly inhibited catalyst deactivation.

The influence of water in the feed was investigated by contacting the catalysts for 1 h to a feed containing 3 mol.% water. After this treatment, all the catalysts exhibited a significant activity loss. This loss was more pronounced for the catalyst prepared by the VPI method. The catalyst prepared by IWI already had suffered a significant deactivation before the water treatment, so the activity drop was not so pronounced. The sample prepared by VPI not only showed a drop in activity immediately after the water treatment but it became more susceptible to deactivation afterwards. By contrast, the Ce-promoted catalyst showed a more stable activity after the water treatment.

All catalysts were characterized before and after reaction by a number of techniques. In agreement with previous studies, FT-IR of adsorbed CO and chemisorption results indicated that the VPI method resulted in higher Pt dispersion than that obtained by the IWI method. After reaction in the presence of sulfur, the Ce-promoted Pt/KL catalyst showed a higher resistance to metal agglomeration and a lower rate of coke formation than the unpromoted Pt/KL. On all the catalysts, the amount of carbon deposits was greater in the presence of sulfur and after exposure to water vapor than under the reaction with clean feeds. This difference is explained in terms of metal particle growth and location in the zeolite.     

丁酮肟-丁酮、正己烷、环己烷二元体系密度和黏度的测定及关联

丁酮肟由于其低毒、低污染和高脱氧效果而被用作防结皮剂、锅炉的除氧剂和脱酮肟基硅烷交联剂的生产原料,然而丁酮肟及其二元混合体系的密度与黏度却鲜有报道。本文利用密度瓶,测定了丁酮肟-丁酮、丁酮肟-环己烷和丁酮肟-正己烷三个二元体系在(293.15～303.15)K、常压条件下的密度,用乌氏黏度计测定了三个二元混合体系在(293.15～303.15)K、常压条件下的黏度。对不同温度下混合密度与组成的关系,通过多项式方程进行了拟合;对不同温度下混合黏度与组成的关系,分别通过Grunberg-Nissan和Eyring-UNIQUAC方程进行了拟合,并给出了回归系数和平均相对偏差。本文数据和关联可为丁酮肟相关工业过程的设计、模拟和优化提供便利。     

气体中油含量的分析

在吸收管中加正己烷和脱脂棉可以很好的吸附气体中的油分,其吸附率达９０％以上,用紫外分光光度计在２６０ｎｍ处可测出溶解在正己烷中的油分。     

Isomerization of hexane on PtAu nanoparticles supported on zeolites

When lead-based anti-knock additives were withdrawn, petrol was enriched with benzene and benzene derivatives in order to maintain an excellent octane number. However, because of their toxicity, it is planned to eliminate these also and to replace them by methylated alkanes, whence the importance of n-alkane isomerization.

Some PtAu-zeolite catalysts tested for n-hexane isomerization reveal that the addition of gold to platinum generally changes the activity and/or the selectivity for methylpentane to the detriment of cracking. The influence of the zeolite structure is also important. At 275 °C, the activity and selectivity of PtAu-HZSM5 are about 75%, showing that this catalyst can be useful for such a reaction.