Stephan Walch

Dr. Stephan Walch

Chemisches und Veterinäruntersuchungsamt Karlsruhe
orcid

Research Focus & Metrics

Academic Career Length

15Years (2012-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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21 December 2018 in Toxics
Verified
Journal Article
Open access
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Dirk W. LachenmeierDirk W. Lachenmeier
Dirk W. Lachenmeier
Steffen SchwarzSteffen Schwarz
Steffen Schwarz
JTJan C. Teipel
Jan C. Teipel
MHMaren Hegmanns
Maren Hegmanns
TKThomas Kuballa
Thomas Kuballa
CBCarmen Breitling-Utzmann
Carmen Breitling-Utzmann
The four heat-induced coffee contaminants—acrylamide, furfuryl alcohol (FA), furan and 5-hydroxymethylfurfural (HMF)—were analyzed in a collective of commercial samples as well as in Coffea arabica seeds roasted under controlled conditions from very light Scandinavian style to very dark Neapolitan style profiles. Regarding acrylamide, average contents in commercial samples were lower than in a previous study in 2002 (195 compared to 303 µg/kg). The roasting experiment confirmed the inverse relationship between roasting degree and acrylamide content, i.e., the lighter the coffee, the higher the acrylamide content. However, FA, furan and HMF were inversely related to acrylamide and found in higher contents in darker roasts. Therefore, mitigation measures must consider all contaminants and not be focused isolatedly on acrylamide, specifically since FA and HMF are contained in much higher contents with lower margins of exposure compared to acrylamide.

4 January 2020 in Foods
Verified
Journal Article
Open access
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AOAlex Okaru
Alex Okaru
ASAndreas Scharinger
Andreas Scharinger
TRTabata Rajcic de Rezende
Tabata Rajcic de Rezende
JTJan C. Teipel
Jan C. Teipel
TKThomas Kuballa
Thomas Kuballa
Dirk W. LachenmeierDirk W. Lachenmeier
Dirk W. Lachenmeier
Monitoring coffee quality as a means of detecting and preventing economically motivated fraud is an important aspect of international commerce today. Therefore, there is a compelling need for rapid high throughput validated analytical techniques such as quantitative proton nuclear magnetic resonance (NMR) spectroscopy for screening and authenticity testing. For this reason, we sought to validate an 1H NMR spectroscopic method for the routine screening of coffee for quality and authenticity. A factorial experimental design was used to investigate the influence of the NMR device, extraction time, and nature of coffee on the content of caffeine, 16-O-methylcafestol (OMC), kahweol, furfuryl alcohol, and 5-hydroxymethylfurfural (HMF) in coffee. The method was successfully validated for specificity, selectivity, sensitivity, and linearity of detector response. The proposed method produced satisfactory precision for all analytes in roasted coffee, except for kahweol in canephora (robusta) coffee. The proposed validated method may be used for routine screening of roasted coffee for quality and authenticity control (i.e., arabica/robusta discrimination), as its applicability was demonstrated during the recent OPSON VIII Europol-Interpol operation on coffee fraud control.

1 April 2018 in Food Chemistry
Verified
Journal Article
Closed access
TKThomas Kuballa
Thomas Kuballa
THThomas Hausler
Thomas Hausler
AOAlex Okaru
Alex Okaru
MNMaria Neufeld
Maria Neufeld
KAKennedy Abuga
Kennedy Abuga
Dirk W. LachenmeierDirk W. Lachenmeier
Dirk W. Lachenmeier

13 March 2023 in Psychoactives
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Journal Article
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Dirk W. LachenmeierDirk W. Lachenmeier
Dirk W. Lachenmeier
CSConstanze Sproll
Constanze Sproll
SWStephan Walch
Stephan Walch
In the European Union (EU), cannabidiol (CBD) products extracted from Cannabis sativa L. require pre-marketing authorisation under the novel food regulation. Currently, 19 CBD applications are being assessed by the European Food Safety Authority (EFSA). During the initial assessment of the dossiers, the EFSA Panel on Nutrition, Novel Foods, and Food Allergens (NDA) identified several knowledge gaps that need to be addressed before the evaluation of CBD can be finalised. The effects of CBD on the liver, gastrointestinal tract, endocrine system, nervous system, psychological function, and reproductive system need to be clarified. The contribution of this research is to provide an evidence-based assessment of the potential risks associated with CBD products, and to provide recommendations for risk management in the European Union while awaiting the finalisation of novel food applications. The available literature allows for a benchmark dose (BMD)–response modelling of several bioassays, resulting in a BMD lower confidence limit (BMDL) of 20 mg/kg bw/day for liver toxicity in rats. Human data in healthy volunteers showed increases in the liver enzymes alanine aminotransferase and aspartate aminotransferase in one study at 4.3 mg/kg bw/day, which was defined by the EFSA NDA panel as the lowest observed adverse effect level (LOAEL). The EFSA NDA panel recently concluded that the safety of CBD as a novel food cannot be assessed, resulting in a so-called clock stop for the applications until the applicants provide the required data. The authors suggest that certain CBD products still available on the EU market as food supplements despite the lack of authorisation should be considered “unsafe”. Products exceeding a health-based guidance value (HBGV) of 10 mg/day should be considered “unfit for consumption” (Article 14(1) and (2)(b) of Regulation No. 178/2002), while those exceeding the human LOAEL should be considered “injurious to health” (Article 14(1) and (2)(a) of Regulation No 178/2002).

24 September 2020 in Foods
Verified
Journal Article
Open access
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JTJan C. Teipel
Jan C. Teipel
THThomas Hausler
Thomas Hausler
KSKatharina Sommerfeld
Katharina Sommerfeld
ASAndreas Scharinger
Andreas Scharinger
SWStephan Walch
Stephan Walch
TKThomas Kuballa
Thomas Kuballa
Due to legal regulations, the rise of globalised (online) commerce and the need for public health protection, the analysis of spirit drinks (alcoholic beverages >15% vol) is a task with growing importance for governmental and commercial laboratories. In this article a newly developed method using nuclear magnetic resonance (NMR) spectroscopy for the simultaneous determination of 15 substances relevant to assessing the quality and authenticity of spirit drinks is described. The new method starts with a simple and rapid sample preparation and does not need an internal standard. For each sample, a group of 1H-NMR spectra is recorded, among them a two-dimensional spectrum for analyte identification and one-dimensional spectra with suppression of solvent signals for quantification. Using the Pulse Length Based Concentration Determination (PULCON) method, concentrations are calculated from curve fits of the characteristic signals for each analyte. The optimisation of the spectra, their evaluation and the transfer of the results are done fully automatically. Glucose, fructose, sucrose, acetic acid, citric acid, formic acid, ethyl acetate, ethyl lactate, acetaldehyde, methanol, n-propanol, isobutanol, isopentanol, 2-phenylethanol and 5-(hydroxymethyl)furfural (HMF) can be quantified with an overall accuracy better than 8%. This new NMR-based targeted quantification method enables the simultaneous and efficient quantification of relevant spirit drinks ingredients in their typical concentration ranges in one process with good accuracy. It has proven to be a reliable method for all kinds of spirit drinks in routine food control.

26 May 2023 in F1000Research
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Journal Article
Open access
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Dirk W. LachenmeierDirk W. Lachenmeier
Dirk W. Lachenmeier
SHStephanie Habel
Stephanie Habel
BFBerit Fischer
Berit Fischer
FHFrauke Herbi
Frauke Herbi
YZYvonne Zerbe
Yvonne Zerbe
CSConstanze Sproll
Constanze Sproll
Cannabidiol (CBD)-containing products are widely marketed as over the counter products, mostly as food supplements. Adverse effects reported in anecdotal consumer reports or during clinical studies were first assumed to be due to acid-catalysed cyclization of CBD to psychotropic Δ 9tetrahydrocannabinol (Δ 9THC) in the stomach after oral consumption. However, research of pure CBD solutions stored in simulated gastric juice or subjected to various storage conditions such as heat and light with specific liquid chromatographic/tandem mass spectrometric (LC/MS/MS) and ultra-high pressure liquid chromatographic/quadrupole time-of-flight mass spectrometric (UPLC-QTOF) analyses was unable to confirm THC formation. Another hypothesis for the adverse effects of CBD products may be residual Δ 9THC concentrations in the products as contamination, because most of them are based on hemp extracts containing the full spectrum of cannabinoids besides CBD. Analyses of 362 hemp-based products of the German market (mostly CBD oils) confirmed this hypothesis: 39 products (11%) contained Δ 9THC above the lowest observed adverse effect level (2.5 mg/day). Hence, it may be assumed that the adverse effects of some commercial CBD products are based on a low-dose effect of Δ 9THC, with the safety of CBD itself currently being unclear with significant uncertainties regarding possible liver and reproductive toxicity. The safety, efficacy and purity of commercial CBD products is highly questionable, and all of the products in our sample collection showed various non-conformities to European food law such as unsafe Δ 9THC levels, hemp extracts or CBD isolates as non-approved novel food ingredients, non-approved health claims, and deficits in mandatory food labelling requirements. In view of the growing market for such lifestyle products, the effectiveness of the instrument of food business operators' own responsibility for product safety and regulatory compliance must obviously be challenged, and a strong regulatory framework for hemp products needs to be devised.