Screening of supports for the immobilization of pectinmethylesterase from acerola (Malpighia glabra L)

A partially purified extract of pectinmethylesterase (PME) from acerola fruit was immobilized on various supports: glass, celite, chrysotile, agarose, concanavalin A Sepharose 4B, egg shell, polyacrylamide and gelatin. In addition, reticulation with glutaraldehyde was assessed, as well as the use of gelatin in the presence of celite, glass and silica. The highest immobilization yields were obtained when the pectinmethylesterase was immobilized in concanavalin A Sepharose 4B (81.7%) and in gelatin‐water (78.0%). Copyright © 2004 Society of Chemical Industry     

Intermolecular interactions and formation of the hydration sphere in phosphonic acid model systems as an approach to the description of vinyl phosphonic acid based polymers

Molecular model systems based on propyl phosphonic acid (ppa) were studied by means of density functional theory calculations in order to describe the acid-acid interaction and the formation of the hydration sphere. The formation of ppa dimers is reported and the energetic difference between two dimer structures is presented. The hydration sphere of ppa was represented by model systems ppa(H₂O)_n, for which the system with n=4 formed the first hydration sphere (h¹), while n=7 can be considered a good approximation to the complete inner hydration sphere around the phosphonic acid group. The study of the ppa-H⁺ (H₂O)_n model systems showed an interesting structural behavior comparatively to the ppa(H₂O)_n systems. The protonated acids exhibited equivalent phosphorous-oxygen bonds and a general molecular structure is proposed to represent these protonated species.     

Effects of temperature, ammonium and glucose concentrations on yeast growth in a model wine system

In enology, alcoholic fermentation is a complex process involving several mechanisms. Slow and incomplete alcoholic fermentation is a chronic problem for the wine industry and factors leading to sluggish and stuck fermentations have been extensively studied and reviewed. The most studied cause of sluggish and stuck fermentation is the nitrogen content limitation. Nevertheless, other factors, such as temperature of fermentation and sugar concentration can affect the growth of yeasts. In this study we modelled the yeast growth‐cycle in wine model system as a function of temperature, sugar and ammonium concentrations; the individual effects and the interaction of these factors were analysed by means of a quadratic response surface methodology. Cell concentrations and weight loss were monitored in the whole wine fermentation process. The results of central composite design show that lower is the availability of nitrogen, higher is the cell growth rate; moreover, initial nitrogen concentration also influences survival time of Saccharomyces cerevisiae.     

Thermo-oxidative degradation of some polymer couples containing HNBR

Summary In this paper thermal behavior of some HNBR blends with CPE, PVC, CR and NBR at three temperatures, 150, 170 and 190°C is presented. Changes in characteristic IR bands, gel fraction, and chlorine content were assessed. Some mechanistic differences between the studied systems, regarding the involvement the depletion of chlorine and modification in gel content, were pointed out. Cyclization of nitrile structure was also observed by means of 2240 cm⁻¹ band ascribed to >C=NH. Kinetic considerations are presented. Received: 3 June 2002/Revised version: 14 November 2002/ Accepted 20 November 2002 Correspondence to Traian Zaharescu     

Identification of aroma components of Spanish ‘Verdejo’ wine

Aroma components of ine resulting from fermentation of grape must from the Verdejo cultivar ere isolated by continuous liquid-liquid extraction and further fractionation on a silica gel column. One hundred and thirty-to substances, including alcohols, esters, carbonyl compounds, terpenes, acids and sulphur compounds, ere identified by using GC-MS; some had not been previously detected in ines. Data are given hich could lead to the characterisation of the Verdejo cultivar and the effect of the elaboration of young ines. The sensory contribution of some volatile compounds to the flavour of Verdejo ine is also studied.     

On transitive orientations with restricted covering graphs

We consider the problem of finding a transitive orientation of a comparability graph, such that the edge set of its covering graph contains a given subset of edges. We propose a solution which employs the classical technique of modular tree decomposition. The method leads to a polynomial time algorithm to construct such an orientation or report that it does not exist.     

Simultaneous HPLC quantification of total cholesterol,tocopherols and β-carotene in Barrosã-PDO veal

A simple, rapid and sensitive procedure for the simultaneous determination of total cholesterol, tocopherols and β-carotene in meat is described. The method involves a direct saponification of the meat, a single n-hexane extraction and the analysis of the extracted compounds by normal-phase HPLC, using fluorescence (tocopherols) and UV–Vis photodiode array (cholesterol and β-carotene) detections in tandem. Rates of recovery of spiked meat samples were 93% for cholesterol, 83–86% for (α-, β- and -γ) tocopherols and 89% for β-carotene. Repeatabilities were high (CV < 6%) for all determined compounds, except for δ-tocopherol. This tocopherol, which is not usually present in meat, showed a much lower recovery percentage (73%) and repeatability (12.8%). This methodology was applied for the quantification of total cholesterol, tocopherols and β-carotene in three muscles (longissimus thoracis, longissimus lumborum and semitendinosus) of the Portuguese traditional Barrosã-PDO veal, obtained from autochthonous calves fed extensively during summer (with the least abundant green pastures) and slaughtered in early autumn (October). Barrosã-PDO veal showed median contents of total cholesterol (0.50–0.56 mg/g) and, depending on the analysed muscle, moderate to high contents of α-tocopherol (3.3–3.9 μg/g) and β-carotene (0.07–0.09 μg/g), suggesting an high sensorial and hygienic quality.     

Fatty acid composition of total lipids,neutral lipids and phospholipids in wild and farmed matrinxã (Brycon cephalus) in the Brazilian Amazon area

BACKGROUND: The chemical composition of Amazonian fish is extremely variable, being influenced by the season and the type and amount of food. A special interest in the fish oil composition has been developed owing to the presence of essential fatty acids, since this is directly related to human health. This study aimed to investigate the fatty acid composition (FAC) of the total lipid (TL), neutral lipid (NL) and phospholipid (PL) fractions of the dorsal muscle and orbital cavity of farmed and wild matrinxã in the Amazon area captured in different seasons. RESULTS: Fatty acids (FA) were analysed by high‐resolution gas chromatography/mass spectrometry. Sixty‐five FA were detected in the TL, 66 in the NL and 55 in the PL. The main FA found in farmed and wild fish were oleic, palmitic, stearic and linoleic acids. No distinctions in the quality or quantity of these fractions between dorsal muscle and orbital cavity were found. CONCLUSION: The season had a significant influence on the TL and FAC. Fish captured during the dry season showed lower levels of lipid and a higher percentage of long‐chain polyunsaturated fatty acids. Matrinxã farmed in a semi‐intensive system showed a nutritional quality comparable to that of wild matrinxã captured in the wet season. Copyright © 2007 Society of Chemical Industry     

Influence of electroosmotic treatment on the hydro-mechanical behaviour of clayey silts: preliminary experimental results

Preliminary results of an investigation focused on the influence of electrokinetic treatment on the mechanical and hydraulic behaviour of clayey soils are presented. The experimental programme aims at providing a contribution to the sustainability of contaminant extraction or containment via electroosmosis. Changes in the hydraulic and mechanical properties of two illitic clayey soils, subjected to a DC electric field, were investigated. Samples of the two soils were subjected to electrokinetic filtration, for different periods of time, and under different constant loads. Afterwards, they were tested under one-dimensional compression to detect changes in stiffness and hydraulic conductivity due to the electrical treatment. After the application of a DC field for a few hours, a small reversible increment in the average soil stiffness was observed, with respect to the untreated soil, while the hydraulic conductivity was not affected substantially. Dramatic changes of the mechanical and hydraulic soil properties, correlated to changes of the soil pH, were observed following non-conditioned electrokinetic treatment with duration of the order of days.