ROLE OF WATER IN THE KINETIC MODELING OF METHANOL TRANSFORMATION INTO HYDROCARBONS ON HZSM-5 ZEOLITE

The attenuating effect of reaction-medium water (feed and/or reaction product) on the kinetics of the steps of methanol transformation into hydrocarbons on a HZSM-5 zeolite catalyst was studied by means of a kinetic model. In this model, the effect of water was quantified in all the steps of the kinetic scheme by means of a kinetic parameter, which is constant with temperature under the conditions of the MTG process. At low temperature, under conditions in which only methanol dehydration occurs, the kinetics of this reaction is attenuated by the presence of water, and the coefficient that quantifies the attenuation decreases as temperature is increased. In addition to considering the effect of water content in the reaction medium, another innovation of the kinetic model proposed, compared to those proposed in the literature consisting of lumps, is the fact that the higher reactivity of dimethyl ether over methanol is taken into account. A step of cracking of gasoline lump hydrocarbons to produce light olefins (ethene and propene) was also taken into account. The kinetic model proposed was verified by using the results obtained in an integral isothermal fixed bed reactor, in the 573–723 K range, for an ample range of space time values. The results revealed that the effect of water is due to its adsorption on the active sites by competition with the intermediate compounds of the kinetic scheme.     

Behavior of a Formed Fish Product Under the Stress-Relaxation Text

Factors affecting the efficiency of the stress-relaxation test for differentiating between textural properties of fish loaves prepared with NaCI and CaCI² were studied. Speed, level of deformation, sample thickness and surface area variously affected the compression forces and the relaxation times. The highest ratios between the NaCl and CaCI² samples with respect to compression forces and relaxation times were obtained with a speed of 20 cm/min, up to 50% deformation, and sample thickness above 1.5 cm. Surface area did not affect the ratios. The test was sensitive enough to detect changes caused by small salt increments. Testing conditions that minimize compression force and relaxation time ratios of different textures should be avoided.     

ASSESSMENT OF GLUCOSINOLATES IN BROCCOLI BY THREE DIFFERENT METHODOLOGIES

ABSTRACT Three different methodologies were used to assess the glucosinolate content in four broccoli cultivars. The assessment was performed by the thymol, enzyme immobilization and gas liquid chromatography (GLC) techniques. The cultivars used were Green Valiant, Green Duke, Marathon and Samurai. The three techniques demonstrated that Samurai and Green Valiant were the cultivars with the highest content of glucosinolates. It was also evident that, compared to stem and leaves, the floret of the four cultivars exhibited in general the highest amount of this component. Of the tested methodologies, the GLC technique showed the lowest data variability, although this technique was unable to estimate all the glucosinolates present in the broccoli samples because of its poor performance for the quantitation of indole and sulfinyl glucosinolates. In conclusion, the thymol technique appeared the most adequate procedure for the assessment of glucosinolates in broccoli samples.     

Chemical composition and microbial evaluation of Argentinean Corrientes cheese

The chemical and microbial composition of an artisanal cheese made from raw cow's milk produced and consumed in the province of Corrientes (north-eastern Argentina) was evaluated using standard methods. Corrientes cheese has high moisture content (50–60%), normal protein and fat contents (21–27 and 22–26% respectively), and is low in salt (0.5–2.0% w/w). Microbial counts also varied significantly between samples (colony-forming units per gram ranges covering logs of 5–11), probably due to environmental contamination in the raw material. These results will help produce higher quality Corrientes cheeses with well-defined characteristics.     

La Plata: an advanced nineteenth century new town with ancient roots

La Plata, the new capital of the Buenos Aires province was founded as a descendant of the rich and homogeneous family of new towns based on the Spanish American model. The Spaniards established hundreds of settlements in America according to the early rules that were soon officially acknowledged and imposed by the Crown. King Philip II established in 1573 his ‘Ordinances concerning discoveries, settlements and pacification’. This system worked for more than four centuries because the Spanish American countries accepted the colonial rules long after their independence. La Plata offered one of the last opportunities for the development of these ideas. The urban theories which were originated during the nineteenth century left clear traces in La Plata's layout. La Plata became one of the first cases in which the nineteenth century ‘progressist model’ – the hygienic city, as defined by Françoise Choay – was adopted and actually built. The fortunate combination of the two models turned La Plata, its qualities and elements into a complex and unique example in urban history.