scholarly journals Green methods for methyl esters determination in foodstuffs

2013 ◽  
Author(s):  
Lucyna Marta Lekawska-Andrinopoulou
Keyword(s):  
Methyl Ester ◽  
Flow Rate ◽  
Methyl Esters ◽  
Alcohol Oxidase ◽  
Pectin Methylesterase ◽  
Enzymatic Reactions ◽  
Automated Method ◽  
Chemiluminescent Detection ◽  
Through Flow ◽  
Diet Drinks

In this thesis development of novel, green methods for methyl esters in foodstuffs is described. Methods are based on enzymatic reactions and fluidics. Study focuses on two methyl esters: pectin methyl ester and aspartame, a methyl ester of aspartic acid/phenylalanine dipeptide. Pectin and aspartame are enzymatically hydrolysed by pectin methylesterase or _- chymotrypsin, respectively. Methanol is released and quantified. Several methanol determination methods have been tested, with the method with 4-AAP and phenol showing the best prospects for automation. Method was optimized and its robustness was investigated. Ascorbic acid interference removal with 4-hydroxy TEMPO was tested. Development of two automated methods for methyl esters determination is described: spectrophotometric pectin methyl esters determination and chemiluminescent aspartame determination.The method for pectin methyl esters is the first work on pectin analysis through flow injection. Detection limit down to 1.47 mM was achieved at the analysis rate of 7 samples h-1. The method provides identical results with manual off-line method. The development of the aspartame analyzer was preceded by the development of a spectrophotometric method, which showed good results in samples containing higher aspartame concentrations than expected in beverages. In order to improve method for possible application in beverages chemiluminescent detection was selected for the automated method. The chemistry from kinetic study was modified to accommodate luminol chemiluminescent detection and optimization of the system was performed. Several manifolds were constructed and the effect of following parameters was tested: flow rate, mixing coils length, location and number, preincubation time, alcohol oxidase concentration, use of separate solutions of AOX and HRP. 0.8 ml/min/line flow rate in combination with one 100 cm mixing coil, 60 s preincubation and use of separated solutions of AOX an HRP resulted in sufficient sensitivity that allowed for construction of a calibration curve within the range of aspartame concentration found in diet drinks. Additionally, following side projects related to the main topic of the study are described: development of PME activity assay and galacturonic acid determination.

scholarly journals Rapid Enzymatic Method for Pectin Methyl Esters Determination

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Lucyna Łękawska-Andrinopoulou ◽  
Efstathios G. Vasiliou ◽  
Dimitrios G. Georgakopoulos ◽  
Constantinos P. Yialouris ◽  
Constantinos A. Georgiou
Keyword(s):  
Reverse Flow ◽  
Methyl Esters ◽  
Flow Analysis ◽  
Alcohol Oxidase ◽  
Pectin Methylesterase ◽  
Ocean Optics ◽  
Manual Method ◽  
Automated Method ◽  
Natural Polysaccharide ◽  
Working Solution

Pectin is a natural polysaccharide used in food and pharma industries. Pectin degree of methylation is an important parameter having significant influence on pectin applications. A rapid, fully automated, kinetic flow method for determination of pectin methyl esters has been developed. The method is based on a lab-made analyzer using the reverse flow-injection/stopped flow principle. Methanol is released from pectin by pectin methylesterase in the first mixing coil. Enzyme working solution is injected further downstream and it is mixed with pectin/pectin methylesterase stream in the second mixing coil. Methanol is oxidized by alcohol oxidase releasing formaldehyde and hydrogen peroxide. This reaction is coupled to horse radish peroxidase catalyzed reaction, which gives the colored product 4-N-(p-benzoquinoneimine)-antipyrine. Reaction rate is proportional to methanol concentration and it is followed using Ocean Optics USB 2000+ spectrophotometer. The analyzer is fully regulated by a lab written LabVIEW program. The detection limit was 1.47 mM with an analysis rate of 7 samples h−1. A pairedt-test with results from manual method showed that the automated method results are equivalent to the manual method at the 95% confidence interval. The developed method is rapid and sustainable and it is the first application of flow analysis in pectin analysis.

scholarly journals Pectin methylesterase activity determined by different methods and thermal inactivation of exogenous pme in mango juice

2011 ◽  
Vol 35 (5) ◽  
pp. 987-994 ◽  
Author(s):  
Samantha Lemke Gonzalez ◽  
Regina Cristina Aparecida Lima ◽  
Eliana Beleski Borba Carneiro ◽  
Mareci Mendes de Almeida ◽  
Neiva Deliberali Rosso
Keyword(s):  
Methyl Ester ◽  
Thermal Inactivation ◽  
Alcohol Oxidase ◽  
Pectin Methylesterase ◽  
Bromophenol Blue ◽  
Vis Spectroscopy ◽  
Optimum Ph ◽  
Carboxylic Groups ◽  
Mango Juice

Pectin methylesterase (PME) hydrolyzes methyl ester groups in pectin chains to form carboxylic groups, releasing methanol and H3O+. The aim of this study was to determine PME activity in samples of pectinases by UV-VIS spectroscopy, to measure the acid and methanol produced in the reaction of pectin with pectinase and to verify the thermal inactivation of exogenous PME in mango juice. The activity of PME in samples of pectinase was determined by potentiometry, UV-VIS spectroscopy, and by the action of alcohol oxidase. The reaction showed greater activity at pH 4.0 to 4.5 and at a temperature of 45° C. PME activity determined by UV-VIS spectroscopy with bromophenol blue indicator showed a good correlation with the activity determined by potentiometry and with alcohol oxidase. The results showed that bromophenol blue indicators can be used to determine PME activity in samples of pectinases where the optimum pH is located in the acidic range. The thermal inactivation of exogenous PME in mango juice occurred at 75° C for 20 min of exposure.

scholarly journals A Methylotrophic Pathway Participates in Pectin Utilization by Candida boidinii

2000 ◽  
Vol 66 (10) ◽  
pp. 4253-4257 ◽  
Author(s):  
Tomoyuki Nakagawa ◽  
Tatsuro Miyaji ◽  
Hiroya Yurimoto ◽  
Yasuyoshi Sakai ◽  
Nobuo Kato ◽  
...  
Keyword(s):  
Methyl Ester ◽  
Alcohol Oxidase ◽  
Pectate Lyase ◽  
Methylotrophic Yeast ◽  
Pectin Methylesterase ◽  
Candida Boidinii ◽  
Methanol Metabolism ◽  
Genes Encoding ◽  
Dihydroxyacetone Synthase ◽  
In Cells

ABSTRACT The methylotrophic yeast Candida boidinii S2 was found to be able to grow on pectin or polygalacturonate as a carbon source. When cells were grown on 1% (wt/vol) pectin, C. boidinii exhibited induced levels of the pectin-depolymerizing enzymes pectin methylesterase (208 mU/mg of protein), pectin lyase (673 mU/mg), pectate lyase (673 mU/mg), and polygalacturonase (3.45 U/mg) and two methanol-metabolizing peroxisomal enzymes, alcohol oxidase (0.26 U/mg) and dihydroxyacetone synthase (94 mU/mg). The numbers of peroxisomes also increased ca. two- to threefold in cells grown on these pectic compounds (3.34 and 2.76 peroxisomes/cell for cells grown on pectin and polygalacturonate, respectively) compared to the numbers in cells grown on glucose (1.29 peroxisomes/cell). The cell density obtained with pectin increased as the degree of methyl esterification of pectic compounds increased, and it decreased in strains from which genes encoding alcohol oxidase and dihydroxyacetone synthase were deleted and in a peroxisome assembly mutant. Our study showed that methanol metabolism and peroxisome assembly play important roles in the degradation of pectin, especially in the utilization of its methyl ester moieties.

scholarly journals Partially esterified oligogalacturonides are the preferred substrates for pectin methylesterase of Aspergillus niger

2003 ◽  
Vol 372 (1) ◽  
pp. 211-218 ◽  
Author(s):  
Gert-Jan W. M. van ALEBEEK ◽  
Katrien van SCHERPENZEEL ◽  
Gerrit BELDMAN ◽  
Henk A. SCHOLS ◽  
Alphons G. J. VORAGEN
Keyword(s):  
Methyl Ester ◽  
Aspergillus Niger ◽  
Methyl Esters ◽  
Pectin Methylesterase ◽  
Degree Of Polymerization ◽  
Specific Pattern ◽  
Specific Product ◽  
Ionization Time ◽  
Active Site Cleft

Investigations on the mode of action of Aspergillus niger pectin methylesterase (PME) towards differently C6- and C1-substituted oligogalacturonides (oligoGalpA) are described. De-esterification of methyl-esterified (un)saturated oligoGalpA proceeds via a specific pattern, depending on the degree of polymerization. Initially, a first methyl ester of the oligomer is hydrolysed, resulting in one free carboxyl group. Subsequently, this first product is preferred as a substrate and is de-esterified for a second time. This product is then accumulated and hereafter de-esterified further to the final product, i.e. oligoGalpA containing one methyl ester located at the non-reducing end residue for both saturated and unsaturated oligoGalpA, as found by post-source decay matrix-assisted laser-desorption/ionization–time-of-flight MS. The saturated hexamer is an exception to this: three methyl esters are removed very rapidly, instead of two methyl esters. When unsaturated oligoGalpA were used, the formation of the end product differed slightly, suggesting that the unsaturated bond at the non-reducing end influences the de-esterification process. In vivo, PME prefers methyl esters, but the enzyme appeared to be tolerant for other C6- and C1-substituents. Changing the type of ester (ethyl esterification) or addition of a methyl glycoside (C1) only reduced the activity or had no effect respectively. The specific product pattern was identical for all methyl- and ethyl-esterified oligoGalpA and methyl-glycosidated oligoGalpA, which strongly indicates that one or perhaps two non-esterified oligoGalpA are preferred in the active-site cleft.

Activity of Plasmin and Streptokinase-Activator on Substituted Arginine and Lysine Esters

1966 ◽  
Vol 16 (01/02) ◽  
pp. 018-031 ◽  
Author(s):  
S Sherry ◽  
Norma Alkjaersig ◽  
A. P Fletcher
Keyword(s):  
Molecular Structure ◽  
Methyl Ester ◽  
Comparative Studies ◽  
Esterase Activity ◽  
Methyl Esters ◽  
Hydrolytic Activity ◽  
The Other ◽  
Other Hand

SummaryComparative studies have been made of the esterase activity of plasmin and the streptokinase-activator of plasminogen on a variety of substituted arginine and lysine esters. Human plasmin preparations derived by different methods of activation (spontaneous in glycerol, trypsin, streptokinase (SK) and urokinase) are similar in their esterase activity; this suggests that the molecular structure required for such esterase activity is similar for all of these human plasmins. Bovine plasmin, on the other hand, differs from human plasmin in its activity on several of the substrates studied (e.g., the methyl esters of benzoyl arginine and tosyl, acetyl and carbobenzoxy lysine), a finding which supports the view that molecular differences exist between the two animal plasmins. The streptokinase-activator hydrolyzes both arginine and lysine esters but the ratios of hydrolytic activity are distinct from those of plasmin and of other activators of plasminogen. The use of benzoyl arginine methyl ester as a substrate for the measurement of the esterase activity of the streptokinase-activator is described.

scholarly journals Evaluation of 3-Methylbutanoic Acid Methyl Ester as a Factor Influencing Flavor Cleanness in Arabica Specialty Coffee

2021 ◽  
Vol 11 (12) ◽  
pp. 5413
Author(s):  
Keiko Iwasa ◽  
Harumichi Seta ◽  
Yoshihide Matsuo ◽  
Koichi Nakahara
Keyword(s):  
Methyl Ester ◽  
Methyl Esters ◽  
Acid Methyl Ester ◽  
Chemical Compounds ◽  
Gas Chromatography Mass Spectrometry ◽  
Arabica Coffee ◽  
Acid Methyl ◽  
Coffee Brew ◽  
Coffee Beans ◽  
Specialty Coffee

This paper reports on the chemical compounds in arabica coffee beans with a high Specialty Coffee Association (SCA) cupping score, especially those in specialty coffee beans. We investigated the relationship between the chemical compounds and cupping scores by considering 16 types of Coffea arabica (arabica coffee) beans from Guatemala (SCA cupping score of 76.5–89.0 points). Non-targeted gas chromatography-mass spectrometry-based chemometric profiling indicated that specialty beans with a high cupping score contained considerable amounts of methyl-esterified compounds (MECs), including 3-methylbutanoic acid methyl ester (3-MBM), and other fatty acid methyl esters. The effect of MECs on flavor quality was verified by spiking the coffee brew with 3-MBM, which was the top-ranked component, as obtained through a regression model associated with cupping scores. Notably, 3-MBM was responsible for the fresh-fruity aroma and cleanness of the coffee brew. Although cleanness is a significant factor for specialty beans, the identification of compounds that contribute to cleanness has not been reported in previous research. The chemometric profiling approach coupled with spiking test validation will improve the identification and characterization of 3-MBM commonly found in arabica specialty beans. Therefore, 3-MBM, either alone or together with MECs, can be used as a marker in coffee production.

Slip Factors of Centrifugal Slurry Pumps

1987 ◽  
Vol 109 (3) ◽  
pp. 313-318 ◽  
Author(s):  
K. K. Sheth ◽  
G. L. Morrison ◽  
W. W. Peng
Keyword(s):  
Flow Rate ◽  
Glass Bead ◽  
Power Flow ◽  
Mixture Density ◽  
Slip Factor ◽  
Friction Factors ◽  
Through Flow ◽  
Data Correlations ◽  
Power Measurements ◽  
Made In

Experiments have been carried out in order to determine the effects on slip factor due to the various parameters affecting the performance characteristics of a centrifugal slurry pump. The experiments were conducted with water, sand slurry, and a glass bead slurry at three different pump speeds. Measurements of power, flow rate, head developed by the pump and the density of the slurry were made in order to obtain the characteristic curves of the pump. Using Euler’s equation, equations were derived for calculating the slip and friction factors of the flow. The deduced slip factors for centrifugal slurry pump can be correlated well with suggested non dimensional groups. It shows a consistent trend of decreasing slip factor with increasing slurry mixture density and impeller rotation, or with a decreasing through flow rate. The sizes of the sand and glass bead particles are significantly different (0.71 mm versus 0.09 mm), however, the data correlations do not suggest its effect on the slip factors significantly as the other parameters. The slip factors deduced from head-flow rate curves are more reliable than those deduced from power-flow rate curves, since the shut-off power measurements are likely subjected to errors associated with the particles settling, or the transient effect if the measurements are taken momentarily.

scholarly journals An Integrated Methodology towards Mitigation of Global Warming and Biomass Production for Biodiesel using Chlorella sorokiniana BTA 9031

2019 ◽  
Vol 8 (4) ◽  
pp. 3054-3058
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Methyl Esters ◽  
Research Work ◽  
Co2 Concentration ◽  
Chlorella Sorokiniana ◽  
Biodiesel Production ◽  
Co2 Absorption ◽  
Microalgal Biomass ◽  
Microalgal Cultivation

The rise of atmospheric carbon dioxide (CO2 )concentration as well as depletion of fossil fuel reserves calls for the development of clean and ecofriendly alternative fuel source. Recently, lipid rich microalgal biomass is being extensively studied for generation of biodiesel however, the expensesincurred on production of microalgal biomassis a significant hurdle. Almost 80 % of the production costis generated from the cultivation medium which majorly comprise of carbon, nitrogen and phosphate. If the microalgal cultivation could be linked to a CO2 capturing unit than the cost of production could be reduced to a large extent. CO2 absorption by means of aqueous amine solvents is known to be a mature technology and could be integrated with microalgal cultivation unit for efficient utilization of the captured CO2 . In this present research work, blended solution of piperazine (PZ) and2-amino2-methyl-1-propanol (AMP) (5/25 wt. %) was used to capture CO2 and then the captured CO2 was utilized as an inorganic carbon stream for growing Chlorella sorokiniana BTA 9031 for biodiesel production. The CO2rate absorption was governed by series of process variablesviz.solvent flow rate ranges (1.5 to 3) ×10⁻4 m 3 min-1 , absorption temperature (298 to 313) K,concentration of CO2 (10 to 15) kPa and gas flow rate(5 to 8) ×10⁻3 m 3 min-1 . The detected final biomass strengthofChlorella sorokiniana BTA 9031 was0.955g L-1 . The fatty acid methyl esters (FAME) determinedsubsequentlyacid transesterification was observed to contain fatty acids suitable for biodiesel production.

L-leucine methyl ester stimulates insulin secretion and islet glutamate dehydrogenase

1983 ◽  
Vol 245 (4) ◽  
pp. E338-E346 ◽  
Author(s):  
P. Knudsen ◽  
H. Kofod ◽  
A. Lernmark ◽  
C. J. Hedeskov
Keyword(s):  
Insulin Secretion ◽  
Methyl Ester ◽  
Glutamate Dehydrogenase ◽  
Insulin Release ◽  
Methyl Esters ◽  
Tumor Cell Line ◽  
Fold Increase ◽  
Inhibitory Effect ◽  
Amino Acid Derivative ◽  
Mouse Pancreatic Islets

Column perifusion of collagenase-isolated mouse pancreatic islets was used to study the dynamics of insulin release in experiments lasting for several hours. The methyl esters of L-leucine and L-arginine were synthesized. Whereas L-arginine methyl ester (L-arginine OMe) had no effect, L-leucine OMe stimulated the release of insulin. The effect of L-leucine OMe was maximal at 5 mmol/liter. Whereas the Km for glucose-stimulated insulin release was unaffected by 1 mmol/liter L-leucine OMe, the maximal release of D-glucose was increased by the amino acid derivative that appeared more effective than L-leucine. L-Leucine OMe was also a potent stimulus of insulin release from the perfused mouse pancreas. In the presence of 10 mmol/liter L-glutamine, 1 mmol/liter L-leucine OMe induced a 50- to 75-fold increase in insulin release. A similar stimulatory effect was also observed in column-perifused RIN 5F cells, a cloned rat islet tumor cell line. A twofold increase in islet glutamate dehydrogenase activity was induced by 5 mmol/liter L-leucine OMe, a larger effect than that of L-leucine (P less than 0.02), whereas L-arginine OMe had a small inhibitory effect. We conclude that L-leucine OMe is a potent stimulus of insulin secretion and that its effect on the beta-cells may be exerted by activating islet glutamate dehydrogenase.

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