New catalyst for the synthesis of poly(butylene terephthalate) with high thermo‐oxidative stability

In this paper we report the employment of Ti(acac)₂(O‐iPr)₂ (titanium bisacetylacetonate diisopropylate) as a novel catalyst for the synthesis of poly(butylene terephthalate) (PBT). Large scale synthesis of several polymers with the new catalytic system and with the standard catalyst Ti(O‐nBu)₄ (titanium tetra‐n‐butylate) have been performed in a 20 L pilot plant. In the optimized reaction conditions, Ti(acac)₂(O‐iPr)₂ has shown significantly higher activity than standard catalyst, Ti(O‐nBu)_4. Furthermore, a stabilized PBT has been synthesized in the presence of Ti(O‐nBu)₄ as catalyst with the addition of the stabilizer U626. Then, the stability of the synthesized polymers toward thermo‐oxidation has been tested in a forced circulating air oven. The polymers obtained in the presence of Ti(acac)₂(O‐iPr)₂ system showed higher stability towards thermo‐oxidation than stabilized and not stabilized PBT, synthesized in the presence of Ti(O‐nBu)₄. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of storage on the phenolic content,volatile composition and colour of white wines from the varieties Zalema and Colombard

Different quality attributes and chemical components of wines change during storage as a function of a series of factors. Thus, in young white wines, changes in phenolics, that lead to modifications of their colour as a result of oxidation processes, are well-known. These reactions can also alter their volatile profile giving rise to the appearance of new aromas, which in some cases are undesirable. In this study we have carried out a thorough evaluation of the changes in the colour, volatiles and phenolics of Zalema and Colombard wines during 1 year of storage under different conditions of temperature and position. The phenolics and colour were more affected than was the volatiles profile and wines kept in the cold could be clearly distinguished from the others, whilst the position of the bottles onlt slightly affected the wines during storage. Results showed that the blending of Zalema wines with Colombard wines may be an appropriate means of enhancing the acidity of the former without dramatically affecting its character.     

Effects of air-drying temperature on the cell walls of kiwifruit processed at different stages of ripening

The effects of air-drying temperature on the cell wall components of three sets of fresh kiwifruits at different degrees of ripening, unripe, half-ripe and ripe samples, have been evaluated. The modifications affecting the physico-chemical properties of cell wall polysaccharides were largely dependent, not only on the air-drying temperature used (from 30 °C to 90 °C), but also on the initial stage of ripening of the processed kiwifruits. Thus, whereas in comparison with the fresh fruits, dehydrated unripe and half-ripe kiwifruits maintained their overall cell wall composition better, processed ripe kiwifruits seemed to be more sensitive to cell wall degradation/solubilisation. In fact, important losses of cell wall material (CWM), mainly pectins and, also, hemicelluloses, were detected in the riper kiwifruits when these samples were dehydrated at high temperature (up to 30% CWM losses when drying was carried out at 90 °C). Heating also promoted considerable modifications of the degree of methyl-esterification (DME) of pectins. In general, an increase in the DME corresponded to an increase in the degree of ripening of the processed samples, suggesting that methylated pectins exhibited a higher resistance to the degradation/solubilisation caused by heating. All these changes in composition were clearly reflected in the solubility and functional properties (FP) of processed CWMs. Hydration properties, swelling and water retention, and, in particular, the capacity to absorb lipids, were modified after processing. In general, CWMs from processed half-ripe kiwifruits exhibited the highest FP values. Overall, the study clearly reflects the importance of taking into consideration the stage of ripening of fruits in order to determine the final quality of CWMs, and therefore, the properties of the dietary fibre (DF) which could be obtained from processed kiwifruit samples.     

Partial dehydration of cherry tomato at different temperature, and nutritional quality of the products

This study concerns the partial dehydration of cherry tomatoes (Lycopersicon esculentum, var. Shiren) to obtain a product with 25% initial water content. Two kinds of dried tomatoes were obtained using a forced air oven at 40, 60 and 80 °C for different lengths of treatment. The first type was dehydrated after immersion of the fresh tomatoes in an aqueous solution of citric acid, sodium and calcium chloride (10:10:24 g/l); the second was obtained with no pre-treatment. The products were characterised by measuring their CIE L*a*b* colour parameters and levels of l-ascorbic acid, lycopene and β-carotene to evaluate thermal damage during processing under the different conditions. Moreover, water activity and the formation of 5-hydroxymethylfurfural were also determined as an index of sugar heat degradation. Treatment with a dipping solution protected both the nutritional and chemical qualities of the partially dried cherry tomatoes. Temperature was directly related to browning, ascorbic acid loss and HMF formation, while no clear influence could be found for carotenoid degradation.     

A mitochondrial mechanism is involved in apoptosis of Robertsonian mouse male germ cells

The aim of this study was to determine whether the intrinsic mechanism of apoptosis is involved in the death of germ cells in Robertsonian (Rb) heterozygous adult male mice. Testes from 5-month-old Rb heterozygous CD1 x Milano II mice were obtained and compared with those from homozygous CD1 (2n=40) and Milano II (2n=24) mice. For histological evaluation of apoptosis, TUNEL labelling and immunohistochemistry were used to localise Bax and cytochrome c. Expression of calbindin D(28k) (CB), an anti-apoptotic molecule, was also analysed by immunohistochemistry and immunoblotting. Testicular ultrastructure was visualised by electron microscopy. Morphology and cell associations were abnormal in the Rb heterozygous seminiferous epithelium. An intense apoptotic process was observed in tubules at stage XII, mainly in metaphase spermatocytes. Metaphase spermatocytes also showed Bax and cytochrome c redistributions. Mitochondria relocated close to the paranuclear region of spermatocytes. CB was mainly expressed in metaphase spermatocytes, but also in pachytene spermatocytes, spermatids and Sertoli cells at stage XII. The co-localisation of CB and TUNEL labelling was very limited. Sixty per cent of metaphase spermatocytes were apoptotic and calbindin negative, while 40% were calbindin positive without signs of apoptosis. Ten per cent of the Bax- and cytochrome c-positive cells were also calbindin positive. These data suggest that apoptosis of the germ cells in heterozygous mice occurs, at least in part, through a mitochondrial-dependent mechanism. Calbindin overexpression might prevent or reduce the apoptosis of germ cells caused by Rb heterozygosity, which could partially explain the subfertility of these mice.     

The Anisotropy of Young's Modulus in Bones

In this paper, yet another method for evaluating the elastic modulus for human bones is introduced and investigated. This method adopts the Jankowski and Tsakalakos strain energy function in which, the Born-Mayer energy term is the predominant term for calculations the elastic constants. By taking accounts the directional aspects of the spatial structure of bones, we obtain different values for the Young's modulus depending on the direction of the applied force with respect to the material's structure. The inverse problem analyzed in this paper is solved by inversion of the experimental data. An efficient stopping criterion is adopted to cease the iterative process in order to retrieve stable numerical solutions. The numerical implementation of the aforementioned method is realized by employing a genetic algorithm.     

Heat and mass transfer modeling during continuous flow processing of fluid food by direct steam injection

Fluid food products, in the agri-food industry, are commonly subject to thermal treatments to ensure their safety and quality characteristics. Therefore, these treatments must be accurately selected and monitored to avoid over-processing, as consumer safety and product acceptability must be preserved.     

Highly Enantioselective Copper‐Phosphoramidite‐Catalyzed Conjugate Addition of Dialkylzinc Reagents to Acyclic α,β‐Unsaturated Imides

A new and practical way to introduce an alkyl fragment in the β‐position of aliphatic carboxylic acid derivatives with high enantioselectivities by the use of a commercially available chiral ligand is reported. N‐Acylpyrrolidinones, as simple derivatives of an α,β‐unsaturated carboxylic acid, were found to be the substrates of choice featuring good reactivity and high enantioselectivities (up to >99% ee).