Dynamic and Thermo-Mechanical Properties of Some Specialty Fluoroelastomers for Low Tg Seal Materials

The viscoelastic behaviour of three different low Tg fluoroelastomer materials belonging to the class of Fluorosilicones (FVMQ), Perfluoropolyether-hydrosilanes (Sifel™) and Perfluoropolyether-polyurethanes (FEU) was investigated. Materials considered were high hardness rubbers and were characterized by dynamic-mechanical analysis (DMA), thermo-mechanical analysis (TMA), and swelling tests in Fuel C and other solvent mixtures. DMA spectra in dynamic scan allowed the determination of Tg and other minor intensity relaxation phenomena. Thermo-mechanical analysis was used to measure the thermal expansion coefficient α _L and the low temperature retraction curve R _e(T) in creep and recovery experiments with different test conditions. Highly diversified behaviours were observed, apparently related to polymer Tg and damping in the rubbery plateau. Swelling measurements showed a better performance for the two perfluoropolyether samples than for fluorosilicones.     

Degradative enzymatic activities in fresh-cut blood-orange slices during chilled-storage

Blood-orange fruits are suitable to fresh-cut fruit production because of their chemical compositions. Nevertheless, the main limitation of using freshly cut oranges is their susceptibility to juiciness loss and ascorbic acid degradation because of enzymatic alterations. The aim of this work is: to identify some of the enzymes causing the qualitative decay in blood-orange slices during 15 days of chilled storage (at 4 ± 0.5 °C and 85% RH); to investigate the susceptibility to the previous alterations of five blood-orange clones ( Moro nucellare, Sanguinello nucellare , Tarocco arcimusa, Tarocco gallo and Tarocco meli ) to select the most suitable one for fresh-cut production. The enzymes studied were: pectinmethylesterase (PME) as index of juiciness loss, ascorbate oxidase (AAO) as index of ascorbic acid's degradation and polyphenol oxidase (PPO) as browning index. As far as we know, the changes of AAO activity during chilled storage of blood-orange fresh-cut slices has not previously reported and studied. Different clones showed different enzymatic activities and quality changes during chilled-storage. In particular a low juiciness loss in orange slices was correlated with a lower PME activity, as described in T. meli clone, while a high degradation of ascorbic acid was correlated with an higher AAO activity, as described in T. gallo clone; PPO activity seemed to have no significant action in quality degradation. Tarocco meli was the most suitable clone to the fresh-cut blood-orange production because it has the lowest enzymatic activity (PME, PPO and AAO) and the highest sensorial quality.     

Minimal complete sets of words

A characterization of minimal complete sets of words of a free monoid which are codes, is given.     

Balance between nutrients and anti-nutrients in nine Italian potato cultivars

Nine commercial potato cultivars have been analyzed in order to detect differences in nutritional quality, considering the balance between nutrients and anti-nutrient compounds present in each. The most important nutrients studied in this paper were: water, starch, free sugars, such as glucose, fructose and sucrose, malic acid, citric acid, ascorbic acid and chlorogenic acid. The anti-nutrients measured included α-solanine, α-chaconine and asparagine. This last compound was added to the anti-nutrient compounds because it is involved in the formation of acrylamide during thermal food processes. From this study, by considering the nutritional quality of each cultivar, we can divide the potato cultivars into three groups, each being suitable for a different technological processes.     

Simultaneous mass spectrometric measurement of prostaglandins E1 (PGE1) and PGE2 with a deuterated internal standard

The use of (3,3,4,4-²H₄)PGE₂ as internal standard for the quantitative measurement of PGE₁ by gas chromatography-mass spectrometry is reported. A method for the simultaneous analysis of PGE₁ and PGE₂ is also described. The prostaglandins were analyzed by selected ion monitoring as the methyl ester-trimethylsilyl ether (ME-TMS) derivatives of PGB₁ and PGB₂, respectively. In all cases, a linear response over the range 1 to 70 ng (2.8 to 198 pmoles) was demonstrated. The use of this procedure is exemplified by its application to the PG analysis of sheep seminal vesicles. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.     

Co-metabolism of citrate and maltose byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain: effect on growth,end-products and sourdough fermentation

Growth, substrates and end-product formation of the maltose and citrate co-metabolization byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain were initially studied in synthetic medium. Compared to maltose (19 g/l) fermentation, the co-metabolization of maltose (10 g/l) plus citrate (9 g/l) caused faster cell growth, increased the concentrations of lactic acid and especially of acetic acid (from 0.7 g/l to 2.9 g/l), produced succinic acid (0.5 g/l) and reduced ethanol synthesis. Highest activities of acetate kinase, the same of lactate dehydrogenase and a reduced alcohol dehydrogenase activity were detected in cytoplasmic extracts of cells growing on maltose plus citrate. The breakdown of citrate depended upon the continuous presence of maltose in the growth medium. Upon depletion of citrate, the cells continued through the normal maltose fermentation, having a diauxic metabolic curve as shown by impedance measurements. Concentrations of citrate from 3 g/l to 15 g/l led to increases of acetic acid from 1.25 g/l to 5.55 g/l. Since maltose was naturally present during sourdough fermentation, the addition of 9 g citrate per kg wheat dough enabled the co-metabolization of maltose and citrate byL. brevis subsp.lindneri CB1. Compared with traditional sourdough fermentation, faster cell growth, a higher acetic acid concentration and a reduced quotient of fermentation were obtained by co-metabolism.     

On some properties of very pure codes

Some results on synchronization and maximality of very pure codes are given.