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.     

Fixed-width multipliers for the implementation of efficient digital FIR filters

The use of fixed-width multiplier for the implementation of FIR filters is investigated in this paper.The paper presents a review of the existing fixed-width multiplier architectures and analytically calculates the error introduced by the use of fixed-width multipliers in the realization of FIR filters. FIR filters are implemented in TSMC technology using state-of-the-art fixed-width multipliers, varying the architecture and the width of the output.The analysis shows that fixed-width multipliers are a suitable replacement for the full-width multiplier. Furthermore the best trade-off between error, silicon area occupation and power is provided by the LMS fixed-width multiplier. As example a FIR filter with 16b fixed-width multiplier provides a reduction of 16% in area and 18% in power dissipation with a 22% increase of the working frequency, while keeping the mean square error below  LSB².     

Mixtures of 5-hydroxymethylfurfural,levulinic acid,and formic acid have different impact on H2-producing Clostridium strains

Fermentative hydrogen production allows the use of renewable biomasses as feedstocks. However, biomass saccharification results not only in carbohydrates, but also in products that can inhibit fermentation. Although biomass hydrolysates contain mixtures of inhibitors, most studies are performed with a single inhibitor. This study evaluates how 5-hydroxymethylfurfural (HMF, 0.60 g/L), levulinic acid (LA, 2.10 g/L), and/or formic acid (FA, 0.80 g/L) mixtures affect two H₂-producing clostridia, Clostridium beijerinckii Br21 and Clostridium acetobutylicum ATCC 824. Fermentation assays with and without (control) the inhibitors helped to calculate the specific H₂ production, substrate consumption, and bacterial cell growth rates for Clostridium beijerinckii Br21 or Clostridium acetobutylicum ATCC 824. HMF + AL, HMF + AF, AL + AF, and HMF + AL + AF mixtures inhibited H₂ production by C. beijerinckii Br21 by 58.7, 60.0, 46.9, and 83.0%, respectively, and by C. acetobutylicum ATCC 824 by 68.1, 71.4, 58.2, and 89.0%, respectively. Clostridium acetobutylicum ATCC 824 metabolized HMF more efficiently. However, organic acids and their combination with HMF inhibited H₂ production by C. beijerinckii Br21 to a lesser extent, which highlighted that this microorganism is robust for H₂ production from biomass hydrolysates.     

Application of power ultrasound on the convective drying of fruits and vegetables: effects on quality

Drying gives rise to products with a long shelf life by reducing the water activity to a level that is sufficiently low to inhibit the growth of microorganisms, enzymatic reactions and other deteriorative reactions. Despite the benefits of this operation, the quality of heat sensitive products is diminished when high temperatures are used. The use of low drying temperatures reduces the heat damage but, because of a longer drying time, oxidation reactions occur and a reduction of the quality is also observed. Thus, drying is a method that lends itself to being intensified. For this reason, alternative techniques are being studied. Power ultrasound is considered as an emerging and promising technology in the food industry. The potential of this technology relies on its ability to accelerate the mass transfer processes in solid–liquid and solid–gas systems. Intensification of the drying process with power ultrasound can be achieved by modifying the product behavior during drying, using pre‐treatments such as soaking in a liquid medium assisted acoustically or, during the drying process itself, by applying power ultrasound in the gaseous medium. This review summarises the effects of the application of the power ultrasound on the quality of different dried products, such as fruits and vegetables, when the acoustic energy is intended to intensify the drying process, either when the application is performed before pretreatment or during the drying process. © 2017 Society of Chemical Industry