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Fieber W.,Firmenich | Hafner V.,Firmenich | Normand V.,Firmenich Inc.
Journal of Colloid and Interface Science

Droplet size distribution of flavor oils in two different solid flavor delivery systems were determined with pulsed field gradient NMR spectroscopy: yeast encapsulation system, a spray dried flavor encapsulation system based on empty yeast cells, and glassy encapsulation system, an extruded solid water soluble carbohydrate delivery system. The oil droplet sizes are limited by the yeast cell walls in the yeast encapsulation system and the size distribution is unimodal according to images from transmission electron microscopy. The droplet size determination with diffusion NMR is based on the Murday and Cotts theory of restricted diffusion of liquids in geometrical confinements. Good fits of the diffusion data could be obtained by applying a unimodal, log-normal size distribution model and average droplet sizes of about 2 μm were found that correspond approximately to the inner diameter of the yeast cells. Scanning electron microscopy images showed a multimodal droplet size distribution in the glassy extruded delivery systems. To fit the NMR data a bimodal log-normal distribution function with five independent fitting parameters was implemented that yielded consistent and robust results. The two size populations were found in the micron and sub-micron range, respectively. The method was sufficiently accurate to depict variation of droplet size distributions in glassy encapsulation systems of different formulation. © 2011 Elsevier Inc. Source

Um E.,Princeton University | Rogers M.E.,Firmenich Inc. | Stone H.A.,Princeton University
Lab on a Chip - Miniaturisation for Chemistry and Biology

We describe a microfluidic system for generating a sequence of liquid droplets of multiple concentrations in a single experimental condition. The series of final droplets has the combination of the compositions varying periodically, with polydispersity of the size less than 8%. By utilizing the design of the microchannel geometry and the passive control of three immiscible fluids (oil, water, and air) including generation, breakup, separation and coalescence of droplets, we can change the system to generate diverse sets of combination of materials. The device can be used for testing different concentration of materials in picoliter volumes and developing a new way to deliver dynamic signals of chemicals with microfluidics. © 2013 The Royal Society of Chemistry. Source

Asadollahi M.A.,Technical University of Denmark | Asadollahi M.A.,University of Isfahan | Maury J.,Technical University of Denmark | Schalk M.,Firmenich | And 3 more authors.
Biotechnology and Bioengineering

The mevalonate pathway in the yeast Saccharomyces cerevisiae was deregulated in order to enhance the intracellular pool of farnesyl diphosphate (FPP), the direct precursor for the biosynthesis of sesquiterpenes. Overexpression of the catalytic domain of HMG1, both from the genome and plasmid, resulted in higher production of cubebol, a plant originating sesquiterpene, and increased squalene accumulation. Down-regulation of ERG9 by replacing its native promoter with the regulatable MET3 promoter, enhanced cubebol titers but simultaneous over-expression of tHMG1 and repression of ERG9 did not further improve cubebol production. Furtheremore, the concentrations of squalene and ergosterol were measured in the engineered strains. Unexpectedly, significant accumulation of squalene and restoring the ergosterol biosynthesis were observed in the ERG9 repressed strains transformed with the plasmids harboring cubebol synthase gene. This could be explained by a toxicity effect of cubebol, possibly resulting in higher transcription levels for the genes under control of MET3 promoter, which could lead to accumulation of squalene and ergosterol. © 2010 Wiley Periodicals, Inc. Source

Rong Y.,Firmenich Inc. | Gregson C.M.,Firmenich Inc. | Parker A.,Firmenich
Journal of Chemical Thermodynamics

A method was developed using thermo-gravimetric analysis (TGA) to determine the vapor pressure of volatile liquids. This is achieved by measuring the rate of evaporation (mass loss) of a pure liquid contained within a cylindrical pan. The influence of factors like sample geometry and vapor diffusion on evaporation rate are discussed. The measurement can be performed across a wide range of temperature yielding reasonable results up to 10 kPa. This approach may be useful as a rapid and automatable method for measuring the volatility of flavor and fragrance raw materials. © 2012 Elsevier Ltd. All rights reserved. Source

Dardelle G.,Firmenich | Subramaniam A.,Firmenich Inc. | Normand V.,Firmenich Inc.
Soft Matter

This study assesses the efficiency of the chemical cross-linking in gelatin, when utilising two different cross-linking reagents. A new method using micro-calorimetry was developed to use the energy involved in renaturation of the protein for probing the efficiency of the cross-linking reaction. The enthalpy of renaturation upon cooling was measured for two different types of cross-linkers, viz. glutaraldehyde and transglutaminase. Gelatin is a polymer with the ability to form a physical thermoreversible network. When cross-linking reactions occur within the gelatin gel, covalent bonds are generated. This in turn creates a second network locked in place by chemical bonds. Therefore two different types of networks coexist. Heat flow measurement at different levels of cross-linking reagent thus permits the measurement of the reduction in enthalpy of gelation as the cross-linking reaction progresses. By introducing the concept of effective concentration, the enthalpy data can be directly related to the degree of cross-linking through an empirical model. This concept emphasizes two different mechanisms taking into consideration the cross-linkers transglutaminase and glutaraldehyde. A mechanism for the polymerisation of glutaraldehyde is proposed. © The Royal Society of Chemistry 2011. Source

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