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Model Mixture (model + mixture)
Selected AbstractsEVALUATION OF THE CHARACTER IMPACT ODORANTS IN SKIM MILK POWDER BY SENSORY STUDIES ON MODEL MIXTURESJOURNAL OF SENSORY STUDIES, Issue 1 2004Y. KARAGÜL-YÜCEER ABSTRACT The objective of this study was to verify key aroma-active compounds responsible for reconstituted fresh skim milk powder (SMP) aroma using threshold analysis, odor activity values, and model systems. Twelve odor-active compounds of SMP and one odor-active compound from fluid milk were selected based on flavor dilution factors from gas chromatography-olfactometry. Thresholds for the 13 odor-active compounds were identified using five-set ascending forced choice threshold analysis in odor-free water and fluid skim milk. Model systems were prepared using rehydrated milk retentate (RMR). The aroma of each model was evaluated by descriptive sensory analysis and by difference-from-control testing using a trained panel. The aroma of reconstituted fresh SMP and liquid skim milk were used as controls. Models containing a mixture of twelve of the thirteen chemicals had the most similar odor characteristics to rehydrated SMP aroma (9.0/10) indicating that these compounds constitute the character impact odorants of rehydrated fresh SMP. [source] Determination of 1-methylhistidine and 3-methylhistidine by capillary and chip electrophoresis with contactless conductivity detectionELECTROPHORESIS, Issue 13 2007Petr T, ma Dr. Abstract CE with capacitively coupled contactless detection (C4D) was used to determine 3-methylhistidine (3-MH) and 1-methylhistidine (1-MH). The C4D response to 3-MH was studied in a BGE consisting of 500,mM acetic acid and ammonia at varying concentration and the results were compared with the theory. Complete separation of a model mixture of 3-MH, 1-MH, and histidine (His) was attained in two optimized BGEs, one containing 500,mM HAc, 20,mM NH4OH, and 0.1 % m/v hydroxyethylcellulose (HEC), pH,3.4 (I) and the other consisting of 100,mM morpholinoethanesulfonic acid (MES), 25,mM LiOH, and 0.1 % m/v HEC, pH,5.5 (II). These optimized BGEs were tested in CE/C4D analyses of urine. Promising results were obtained for separation and determination of 3-MH, 1-MH, and His on a silicon microchip, using aluminum strips as the C4D electrodes; the three analytes were baseline-separated within less than 30,s with a separation channel effective length of 38,mm. The LOD were satisfactory and amounted to 26.4,,M for 3-MH and 18.3,,M for 1-MH. [source] Effects of ,-Glucan Addition to a Probiotic Containing YogurtJOURNAL OF FOOD SCIENCE, Issue 7 2007T. Vasiljevic ABSTRACT:, This study investigated the effects of addition of ,-glucan from 2 different cereal sources (oat and barley) on growth and metabolic activity of Bifidobacterium animalis ssp. lactis (Bb-12Ô) as determined by plating on a selective medium in yogurt during prolonged cold storage. These yogurt batches were compared to unsupplemented and inulin supplemented controls. All batches were also assessed for syneresis. Oat ,-glucan addition resulted in improved probiotic viability and stability comparable to that of inulin. It also enhanced lactic and propionic acid production. The barley ,-glucan addition suppressed proteolytic activity more than that from oat. These improvements were hindered by greater syneresis caused likely by thermodynamic incompatibility. Small amplitude oscillatory measurements of acidified model mixture of ,-glucan/skim milk solids showed formation of casein gel within the ,-glucan network. Binary mixtures of ,-glucan and skim milk solids had apparent pseudoplastic and non-Newtonian behavior governed mainly by ,-glucan contribution. Above critical concentrations, the mixtures underwent phase separation with the lower phase rich in protein. The phase diagram also showed that the addition of ,-glucan may be possible at or below 0.24 w/w%. [source] Detection system for electro-separation analytical methodsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2005Radek Abstract The paper provides information about the on-line monitoring of components analysed by capillary electrophoresis. For this purposes we developed a whole-capillary transverse scanning detection system, which helps to improve and control the separation processes. A picture from a colour line scanner was used as a source of basic information for autonomous control of the separation process by regulation of the high voltage source. The application and algorithms for machine vision were designed in the progressive graphic development system LabVIEW. Real-time control of the separation process was implemented in a compact control process logic controller. The performance of the detection system was evaluated and the function of the overall system was tested by performing isotachophoretic analysis of a model mixture. [source] A validated spectrophotometric method for quantification of prenylated flavanones in pacific propolis from TaiwanPHYTOCHEMICAL ANALYSIS, Issue 2 2010Milena Popova Abstract Introduction , Because of its chemical diversity, the only way to standardise propolis is to specify multiple standards for different propolis types according to the corresponding chemical profile. So far, this has been done only for European propolis. Objective , To develop a rapid low-cost spectrophotometric procedure for quantification of bioactive prenylated flavanones in Taiwanese propolis. Methodology , The proposed method quantifies the total flavanones on the basis of their absorption as coloured phenylhydrazones formed by interaction with 2,4-dinitrophenylhydrazine. The procedure was validated through model mixture of compounds representing the composition of Taiwanese propolis according to previous studies. The major flavanones of the propolis samples (propolins C, D, F and G) were quantified by HPLC. Antiradical activity against DPPH was also measured. The DNP (dinitrophenylhydrazine) spectrophotometric method is applied for the first time for quantification of prenylated flavanones. Results , Spectophotometric procedure applicable to new type propolis (Macaranga type) was developed with recovery between 105 and 110% at the concentration range of 0.573,1.791,mg/mL. Six propolis samples were analysed by spectrophotometry using the procedure developed and validated, and by HPLC as the results demonstrated satisfactory agreement. Neither the spectrophotometric data nor the values measured by HPLC showed significant correlation with the antiradical activity against DPPH. Conclusion , The proposed spectrophotometric procedure is useful for routine analyses of Macaranga -type propolis, because of its simplicity, repeatability and acceptable accuracy. Its application to a number of commercial samples could be used as a basis for standardisation and quality control of Pacific propolis. Copyright © 2009 John Wiley & Sons, Ltd. [source] Influence of NO on the Reduction of NO2 with CO over Pt/SiO2 in the Presence of O2CHINESE JOURNAL OF CHEMISTRY, Issue 4 2007Ming-Shi Li Abstract Reduction of NO2 with CO in the presence of NO and excess oxygen, a model mixture for flue gas, over a 0.1% Pt/SiO2 catalyst was studied. The related reaction mechanisms, such as oxidation of CO and NO, were discussed. It was found that there was a narrow temperature window (180,190 °C) for the reduction of NO2 by CO. When the temperature was lower than the lower limit of the window, the reduction hardly occurred, while when the temperature was higher than the upper limit of the window, the direct oxidation of CO by O2 occurred and thereby NO2 could not be effectively reduced by CO. The presence of NO shifted the window to higher temperatures owing to the inhibition effect of NO on the activation of O2 on Pt, which made it possible to reduce NO2 by CO in flue gas. [source] | ||||||||||