154,554 research outputs found

    Surface pre-coating of talc particles by carboxyl methyl cellulose adsorption : study of adsorption and consequences on surface properties and settling rate

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    This paper investigates the adsorption of different sized carboxyl methyl cellulose (CMC) onto talc particles (adsorption isotherm, adsorption reversibility), its consequences on the particles properties (electrophoretic mobility and surface wetting) and its effect on their dispersion (settling coefficient). Throughout the paper, the properties of talc particles dispersed in CMC solution are compared to CMC pre-coated talc particles: talc particles dried in a solution of CMC before their redispersion. The adsorption of CMC onto talc was quantified at around 0.4 mg of CMC per m2 of talc and was seen to be irreversible on washing the talc particles with distilled water. When characterising talc surface properties, it was found that CMC adsorption leads to an increase of the negative surface charge and to an increase of the wettability. The settling velocity of CMC pre-coated talc particles in water can be around 50 % lower than that of the initial talc particles. The pre-coating of talc particles by CMC is then assumed to increase their stabilization : particle aggregation is hindered by adsorbed CMC layer inducing electrosteric repulsion between the talc particles. The technique of talc pre-coating with CMC makes the talc dispersion easier and could open interesting perspectives in engineering processes using talc dispersions

    Biopreservation of Fresh Strawberries by Carboxymethyl Cellulose Edible Coatings Enriched with a Bacteriocin of Bacillus methylotrophicus BM47

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    Bacteriocins are a large group of antimicrobial compoundsthat aresynthesized byrepresentatives ofthegenus Bacillusand lactic acid bacteria (LAB). Bacteriocinsare used extensively in thefood industry as biopreservatives. Incorporatedin the composition of edible coatings, bacteriocins canreduce microbial growthand decay incidencein perishable fruits, thusimproving productshelf-life and commercial appearance. The present study aims to investigatethe effect of edible coatings of0.5% carboxymethyl cellulose (CMC) enriched with a purified bacteriocin fromBacillus methylotrophicusBM47 on the shelf-life extension of fresh strawberries. During storage at 4\ub0Cand 75 % relative humidity(RH) for 16 days, measurements of massloss, decay percentage, total soluble solids(TSS), titratable acidity(TA),pH, organic acids, total phenolic and anthocyaninscontents and antioxidant activity were taken.The results demonstrated that the application of 0.5% CMC and 0.5% CMC+bacteriocin (CMC+B) edible coatings led to a significant decrease of massloss in treated strawberriescompared to the uncoated fruit. After the 8-th day of storage, significant reductions in decay percentage along with the absence of fungal growth in CMC+B-coated fruit wereobserved in comparison to the CMC-coated and control strawberries. During the second half of the storage period, CMC and CMC+B treatmentsreduced TSS levels inthe coated fruitcompared to the control, but did not affectincreasedTA and loweredpH valuesthat arenormally associated with post-harvest changes. The CMC and CMC+B coatings wereineffectiveagainst thedecrease inascorbic acid, total phenolics and anthocyanins contentduringcold storage. The application of CMC and CMC+B coatingsexhibited a significant inhibitory effect on decreasing antioxidant activity throughout the storage period and maintained the antioxidant levels inboth treatmentsclose to the initial value of 76.8 mmol TE/100 g of fm

    Constant mean curvature slicings of Kantowski-Sachs spacetimes

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    We investigate existence, uniqueness, and the asymptotic properties of constant mean curvature (CMC) slicings in vacuum Kantowski-Sachs spacetimes with positive cosmological constant. Since these spacetimes violate the strong energy condition, most of the general theorems on CMC slicings do not apply. Although there are in fact Kantowski-Sachs spacetimes with a unique CMC foliation or CMC time function, we prove that there also exist Kantowski-Sachs spacetimes with an arbitrary number of (families of) CMC slicings. The properties of these slicings are analyzed in some detail
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