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Moderate Heating (moderate + heating)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Pasteurization of Fruit Juices by Means of a Pulsed High Pressure Process

JOURNAL OF FOOD SCIENCE, Issue 3 2010
Giorgio Donsì
ABSTRACT:, The use of pulsed high hydrostatic pressure was investigated as a possible approach to stabilize foodstuffs. The objective of this article was to investigate the effect of the main processing variables (pressure [150 to 300 MPa], temperature levels [25 to 50 °C], and pulse number [1 to 10]) on the sanitation of nonpasteurized clear Annurca apple juice as well as freshly-squeezed clear orange juice. The aim of the article was the optimization of the process parameters in step-wise pressure treatment (pressure holding time of each pulse: 60 s, compression rate: 10.5 MPa/s, decompression time: 2 to 5s). The shelf life of the samples, processed at optimized conditions, was evaluated in terms of microbiological stability and quality retention. According to our experimental results, the efficiency of pulsed high pressure processes depends on the combination of pulse holding time and number of pulses. The pulsed high pressure cycles have no additive or synergetic effect on microbial count. The efficacy of the single pulses decreases with the increase of the pulse number and pressure level. Therefore the first pulse cycle is more effective than the following ones. By coupling moderate heating to high pressure, the lethality of the process increases but thermal degradation of the products can be detected. The optimization of the process condition thus results in a compromise between the reduction of the pressure value, due to the synergetic temperature action, and the achievement of quality of the final production. The juices processed under optimal processing conditions show a minimum shelf life of 21 d at a storage temperature of 4 °C. [source]

Reconstructing P,T paths during continental collision using multi-stage garnet (Gran Paradiso nappe, Western Alps)

JOURNAL OF METAMORPHIC GEOLOGY, Issue 6 2006
B. LE BAYON
Abstract Garnet,chloritoid-bearing micaschists from the Gran Paradiso massif (Western Alps) contain evidence of a polymetamorphic evolution. Detailed textural observations reveal that two stages of garnet growth are present in the micaschists, interpreted as: (i) relics of an early metamorphism of pre-Alpine age and (ii) newly grown Alpine garnet, respectively. Both generations of garnet preserve growth zoning. From thermocalc -based numerical modelling of mineral assemblages in pressure,temperature (P,T) pseudosections, we infer that garnet 1 grew at increasing temperature and slightly increasing pressure, whereas garnet 2 grew at decreasing pressure and slightly increasing temperature. Estimated P,T conditions are ,620 °C, 6 kbar for the peak of the pre-Alpine event, and of 490 °C, 18,20 kbar for the pressure peak of the Alpine event. Modelling of the modal proportion and chemical composition of garnet (i) shows that the subsequent decompression (to 14,15 kbar at 550 °C) must have been accompanied by moderate heating and (ii) does not support a stage of final temperature increase following decompressional cooling. This argues against a late thermal pulse associated with mantle delamination. Preservation of growth zoning in both generations of garnet and the limited amount of diffusive re-equilibration at the boundary between the two garnets suggests that the rocks were subjected to fast burial and exhumation rates, consistent with data obtained from other internal Alpine units. [source]

Functionalization of Copper Surfaces by Plasma Treatments to Improve Adhesion of Epoxy Resins

PLASMA PROCESSES AND POLYMERS, Issue S1 2009
Juliano Nestor Borges
Abstract Adhesion of epoxy resins on copper foils for printed circuit board (PCB) applications is improved by nearly a factor of 5, using surface cleaning and deposition of a 15-nm-thick film in a low-pressure remote plasma-enhanced chemical vapor deposition process. The cleaning pretreatment, using an N2,O2 oxidizing gas mixture with moderate heating (343 K), gives the best results. This pretreatment removes the carbonaceous contaminants present on the topmost surface of the sample and slightly oxidizes the copper into CuO. This oxide is then reduced during the deposition treatment, presumably by reaction with the aminopropyltrimethoxysilane (APTMS) precursor. The surface roughness is unchanged after treatment, thereby showing that the improvement of the copper/epoxy adhesion is only due to the chemistry of the plasma coating. Applying these results to dielectric barrier discharges allows us to achieve the same level of adhesion, which, therefore, does not depend on the process. [source]

Formamide Chemistry and the Origin of Informational Polymers

CHEMISTRY & BIODIVERSITY, Issue 4 2007
Raffaele Saladino
Abstract Formamide (HCONH2) provides a chemical frame potentially affording all the monomeric components necessary for the formation of nucleic polymers. In the presence of the appropriate catalysts, and by moderate heating, formamide yields a complete set of nucleic bases, acyclonucleosides, and favors both phosphorylations and transphosphorylations. Physico-chemical conditions exist in which formamide favors the stability of the phosphoester bonds in nucleic polymers more than that of the same bonds in monomers. This property establishes ,thermodynamic niches' in which the polymeric forms are favored. The hypothesis that these specific attributes of formamide allowed the onset of prebiotic chemical equilibria capable of Darwinian evolution is discussed. [source]