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Castritius S.,Research and Teaching Institute for Brewing in Berlin VLB Berlin | Kron A.,Mannheim University of Applied Sciences | Schafer T.,Mannheim University of Applied Sciences | Radle M.,Mannheim University of Applied Sciences | Harms D.,Research and Teaching Institute for Brewing in Berlin VLB Berlin
Journal of Agricultural and Food Chemistry | Year: 2010

A new approach of combination of near-infrared (NIR) spectroscopy and refractometry was developed in this work to determine the concentration of alcohol and real extract in various beer samples. A partial least-squares (PLS) regression, as multivariate calibration method, was used to evaluate the correlation between the data of spectroscopy/refractometry and alcohol/extract concentration. This multivariate combination of spectroscopy and refractometry enhanced the precision in the determination of alcohol, compared to single spectroscopy measurements, due to the effect of high extract concentration on the spectral data, especially of nonalcoholic beer samples. For NIR calibration, two mathematical pretreatments (first-order derivation and linear baseline correction) were applied to eliminate light scattering effects. A sample grouping of the refractometry data was also applied to increase the accuracy of the determined concentration. The root mean squared errors of validation (RMSEV) of the validation process concerning alcohol and extract concentration were 0.23 Mas% (method A), 0.12 Mas% (method B), and 0.19 Mas% (method C) and 0.11 Mas% (method A), 0.11 Mas% (method B), and 0.11 Mas% (method C), respectively. © 2010 American Chemical Society.


Castritius S.,Research and Teaching Institute for Brewing in Berlin VLB Berlin | Bussing S.,Research and Teaching Institute for Brewing in Berlin VLB Berlin | Geier M.,Research and Teaching Institute for Brewing in Berlin VLB Berlin | Falkenstein M.,Steinfurth Mess Systeme GmbH | Harms D.,Research and Teaching Institute for Brewing in Berlin VLB Berlin
European Food Research and Technology | Year: 2015

To satisfy the requirements regarding a precise analytical method for carbonated beverages, a sample preparation method to selectively and efficiently remove dissolved carbon dioxide (CO2) from carbonated beverages is presented in this work. The key element of this development is a membrane module with semipermeable hollow fibre membranes. The CO2 permeates in the membrane module as the sample stream flows through the membrane into a stripping gas stream. A specifically developed phase splitter induces a two-phase flow (gas and liquid) of the beverage sample, which results in an accumulation of the dissolved CO2 in the gas phase. In addition to the development of the membrane decarbonation unit and the significant parameters, an extensive study comparing the unit with common decarbonation techniques has been carried out. More than 96 % of the CO2 was removed from the carbonated sample, resulting in a residual CO2 concentration of <0.1 g/L in the decarbonated sample. © 2015, Springer-Verlag Berlin Heidelberg.


Baumjohann N.,Research and Teaching Institute for Brewing in Berlin VLB Berlin | Harms D.,Research and Teaching Institute for Brewing in Berlin VLB Berlin
Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment | Year: 2015

During storage, acetaldehyde migration from polyethylene terephthalate (PET) bottles can affect the quality of mineral water even in the low µg l−1 range negatively, as it features a fruity or plastic-like off-flavour. For a sensitive and fast analysis of acetaldehyde in mineral water, a new analysis method of 2,4-dinitrophenylhydrazine (DNPH) derivatisation followed by HPLC-electrospray tandem mass spectrometry (ESI-MS/MS) was developed. Acetaldehyde was directly derivatised in the mineral water sample avoiding extraction and/or pre-concentration steps and then analysed by reversed-phase HPLC-ESI-MS/MS using multiple reaction monitoring mode (MRM). Along with method development, the optimum molar excess of DNPH in contrast to acetaldehyde was studied for the mineral water matrix, because no specific and robust data were yet available for this critical parameter. Best results were obtained by using a calibration via the derivatisation reaction. Without any analyte enrichment or extraction, an LOD of 0.5 µg l−1 and an LOQ of 1.9 µg l−1 were achieved. Using the developed method, mineral water samples packed in PET bottles from Germany were analysed and the correlation between the acetaldehyde concentration and other characteristics of the samples was evaluated illustrating the applicability of the method. Besides a relationship between bottle size and CO2 content of the mineral water and acetaldehyde migration, a correlation with acetaldehyde migration and the material composition of the bottle, e.g. recycled PET, was noted. Investigating the light influence on the acetaldehyde migration with a newly developed, reproducible light exposure setup, a significant increase of the acetaldehyde concentration in carbonated mineral water samples was observed. © 2015 Taylor & Francis.


PubMed | Research and Teaching Institute for Brewing in Berlin VLB Berlin
Type: Evaluation Studies | Journal: Journal of agricultural and food chemistry | Year: 2010

A new approach of combination of near-infrared (NIR) spectroscopy and refractometry was developed in this work to determine the concentration of alcohol and real extract in various beer samples. A partial least-squares (PLS) regression, as multivariate calibration method, was used to evaluate the correlation between the data of spectroscopy/refractometry and alcohol/extract concentration. This multivariate combination of spectroscopy and refractometry enhanced the precision in the determination of alcohol, compared to single spectroscopy measurements, due to the effect of high extract concentration on the spectral data, especially of nonalcoholic beer samples. For NIR calibration, two mathematical pretreatments (first-order derivation and linear baseline correction) were applied to eliminate light scattering effects. A sample grouping of the refractometry data was also applied to increase the accuracy of the determined concentration. The root mean squared errors of validation (RMSEV) of the validation process concerning alcohol and extract concentration were 0.23 Mas% (method A), 0.12 Mas% (method B), and 0.19 Mas% (method C) and 0.11 Mas% (method A), 0.11 Mas% (method B), and 0.11 Mas% (method C), respectively.


PubMed | Research and Teaching Institute for Brewing in Berlin VLB Berlin
Type: Journal Article | Journal: Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment | Year: 2015

During storage, acetaldehyde migration from polyethylene terephthalate (PET) bottles can affect the quality of mineral water even in the low g l(-1) range negatively, as it features a fruity or plastic-like off-flavour. For a sensitive and fast analysis of acetaldehyde in mineral water, a new analysis method of 2,4-dinitrophenylhydrazine (DNPH) derivatisation followed by HPLC-electrospray tandem mass spectrometry (ESI-MS/MS) was developed. Acetaldehyde was directly derivatised in the mineral water sample avoiding extraction and/or pre-concentration steps and then analysed by reversed-phase HPLC-ESI-MS/MS using multiple reaction monitoring mode (MRM). Along with method development, the optimum molar excess of DNPH in contrast to acetaldehyde was studied for the mineral water matrix, because no specific and robust data were yet available for this critical parameter. Best results were obtained by using a calibration via the derivatisation reaction. Without any analyte enrichment or extraction, an LOD of 0.5 g l(-1) and an LOQ of 1.9 g l(-1) were achieved. Using the developed method, mineral water samples packed in PET bottles from Germany were analysed and the correlation between the acetaldehyde concentration and other characteristics of the samples was evaluated illustrating the applicability of the method. Besides a relationship between bottle size and CO2 content of the mineral water and acetaldehyde migration, a correlation with acetaldehyde migration and the material composition of the bottle, e.g. recycled PET, was noted. Investigating the light influence on the acetaldehyde migration with a newly developed, reproducible light exposure setup, a significant increase of the acetaldehyde concentration in carbonated mineral water samples was observed.


PubMed | Research and Teaching Institute for Brewing in Berlin VLB Berlin
Type: Evaluation Studies | Journal: Journal of agricultural and food chemistry | Year: 2012

A new approach for the determination of the attenuation limit of beer samples using the specific fingerprint region of middle-infrared (MIR) spectroscopy in combination with multiple regression by partial least-squares (PLS) was developed using an attenuated total reflectance (ATR) module. A specific spectral region between 1200 and 800 cm(-1) was identified as highly informative for the quantification of the limit of attenuation. The absorptions in this region are induced by vibrational bands of ethanol (1080, 1040, and 880 cm(-1)) and dissolved extract, in majority maltotriose (1160-1140 and 1040-980 cm(-1)). The multivariate calibration results in a root mean squared error of calibration (RMSEC) of 0.40% and a validation procedure with independent samples results in a root mean squared error of validation (RMSEV) of 0.50%. A repeatability test, concerning the precision of the developed MIR method as well as the reference method, was analyzed using Students t test. The test has shown no significant difference between the two random samples.

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