Publications by authors named "Jan Fritsche"

14 Publications

  • Page 1 of 1

A DNA microarray for the authentication of giant tiger prawn (Penaeus monodon) and whiteleg shrimp (Penaeus (Litopenaeus) vannamei): a proof-of-principle.

Anal Bioanal Chem 2021 Aug 11;413(19):4837-4846. Epub 2021 Jun 11.

Department of Safety and Quality of Milk and Fish Products, Max Rubner-Institut (MRI), Hermann-Weigmann-Str. 1, 24103, Kiel, Germany.

This proof-of-principle study describes the development of a rapid and easy-to-use DNA microarray assay for the authentication of giant tiger prawns and whiteleg shrimp. Following DNA extraction and conventional end-point PCR of a 16S rDNA segment, the PCR products are hybridised to species-specific oligonucleotide probes on DNA microarrays located at the bottom of centrifuge tubes (ArrayTubes) and the resulting signal patterns are compared to those of reference specimens. A total of 21 species-specific probes were designed and signal patterns were recorded for 47 crustacean specimens belonging to 16 species of seven families. A hierarchical clustering of the signal patterns demonstrated the specificity of the DNA microarray for the two target species. The DNA microarray can easily be expanded to other important crustaceans. As the complete assay can be performed within half a day and does not require taxonomic expertise, it represents a rapid and simple alternative to tedious DNA barcoding and could be used by crustacean trading companies as well as food control authorities for authentication of crustacean commodities.
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http://dx.doi.org/10.1007/s00216-021-03440-2DOI Listing
August 2021

Effect of reduction of sodium content on the microbial ecology of Edam cheese samples.

AMB Express 2021 Feb 16;11(1):28. Epub 2021 Feb 16.

Departments of Microbiology and Biotechnology, Max Rubner-Institut, Hermann-Weigmann-Str. 1, 24103, Kiel, Germany.

Sodium intake is a major risk factor for non-communicable diseases. Consequently, reformulation of cheeses such as Edam to contain less sodium may contribute to lowering disease risk. However, sodium is essential for cheese manufacture, influencing starter culture bacteria activity and abundance during fermentation. This study aimed to assess the microbial diversity of reformulated Edam cheese samples with a reduced sodium content using culture-independent technique. The microbial diversity of samples produced using simple sodium reduction, as well as by substituting salt with a mineral salt compound containing potassium, were analysed in comparison to regular control Edam samples during manufacture and the subsequent 6-week ripening period using 16S rDNA metagenomics. In addition, a challenge test using Listeria (List.) innocua as a surrogate species for List. monocytogenes was performed. Reducing sodium content did not influence the microbiological composition of reformulated samples in comparison to that of regular samples. The starter culture bacteria dominated the microbial diversity and no increase in spoilage or potentially pathogenic bacterial growth was detected, including that of List. innocua. From a microbiological perspective, it can be concluded that lowering sodium content in Edam samples without affecting the microbial composition is achievable through simple sodium reduction and through implementation of a mineral salt replacement approach.
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http://dx.doi.org/10.1186/s13568-021-01188-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7886953PMC
February 2021

Developing an Automatic Color Determination Procedure for the Quality Assessment of Mangos () Using a CCD Camera and Color Standards.

Foods 2020 Nov 21;9(11). Epub 2020 Nov 21.

Institute for Food Chemistry, Hamburg School of Food Science, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany.

Color is one of the key sensory characteristics in the evaluation of the quality of mangos () especially with regard to determining the optimal level of ripeness. However, an objective color determination of entire fruits can be a challenging task. Conventional evaluation methods such as colorimetric or spectrophotometric procedures are primarily limited to a homogenous distribution of the color. Accordingly, a direct assessment of the mango quality with regard to color requires more pronounced color determination procedures. In this study, the color of the peel and the pulp of the mango cultivars "Nam Dokmai", "Mahachanok", and "Kent" was evaluated and categorized into various levels of ripeness using a charge-coupled device (CCD) camera in combination with a computer vision system and color standards. The color evaluation process is based on a transformation of the RGB (red, green, and blue) color space values into the HSI (hue, saturation, and intensity) color system and the Natural Color Standard (NCS). The results showed that for pulp color codes, 0560-Y20R and 0560-Y40R can be used as appropriate indicators for the ripeness of the cultivars "Nam Dokmai" and "Mahachanok". The peels of these two mango cultivars present two distinct colors (1050-Y40R and 1060-Y40R), which can be used to determine the fruit maturity during the post-ripening process. However, in the case of the cultivar "Kent", peel color detection was not an applicable approach for determining ripeness; thus, the determination of the pulp color with the color code 0550-Y20R gave promising results.
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http://dx.doi.org/10.3390/foods9111709DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7700315PMC
November 2020

Microbial composition of sweetness-enhanced yoghurt during fermentation and storage.

AMB Express 2020 Jul 25;10(1):131. Epub 2020 Jul 25.

Department of Microbiology and Biotechnology, Max Rubner-Institut, Hermann-Weigmann-Str. 1, 24103, Kiel, Germany.

The reformulation of dairy products to contain less added sugar can contribute to reducing sugar consumption, thereby reducing the risk of non-communicable diseases. The objective of this study was to investigate the microbial ecology of reformulated yoghurt, which was produced using bi-enzymatic modification of lactose to increase its sweetness by a factor of 2-3. Ultimately, this reformulation strategy could reduce the amount of added sugar needed for equal sweetness of the end product. The bi-enzymatic modification relied on utilisation of a β-galactosidase enzyme to convert the milk sugar lactose to galactose and glucose, followed by the enzymatic conversion of the glucose moiety to fructose using a glucose isomerase. The microbial ecology of reformulated yoghurt produced with two mixed starter culture preparations containing either Streptococcus (S.) thermophilus and Lactobacillus (Lb.) delbrueckii or S. thermophilus, Lb. acidophilus and Bifidobacterium sp. strains, was analysed during fermentation and cool storage using 16S rRNA based metagenomics. None of the yoghurt samples showed a significant difference in microbial composition between sweetness-enhanced and regular milk at all sampling time points during manufacture and storage of yoghurt. However, a significant difference between the microbiota of inoculated milk before and after fermentation was observed. In both types of yoghurt, the starter culture genera dominated the microbial ecology at the end of fermentation as expected, reducing the possibility of growth of potentially pathogenic or spoilage bacteria possibly resulting from a changed carbohydrate spectrum.
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http://dx.doi.org/10.1186/s13568-020-01069-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7381539PMC
July 2020

[Fix the Supply Side! Demand Stimulus Will Not Cure What Ails].

Wirtschaftsdienst 2020 22;100(4):266-271. Epub 2020 Apr 22.

2Wirtschafts- und Sozialwissenschaften, Universität Hamburg, Welckerstr. 8, 20354 Hamburg, Deutschland.

The explosion of Covid-19 cases is looming in Germany. The German Society for Epidemiology has warned that the number of cases could soon overshoot the capacity of the healthcare system. This may be true even if Germany follows the 'flatten-the-curve'- approach to reduce infection rates. A suppression of the virus remains the best solution for the crisis. Supply will suffer as long the virus persists. Until then, demand side measures will not cure the epidemic. Coordinated measures for business that ensure compliance and European debt instruments may be part of a strategy to solve the crisis.
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http://dx.doi.org/10.1007/s10273-020-2630-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7174817PMC
April 2020

Design of a user-friendly and rapid DNA microarray assay for the authentication of ten important food fish species.

Food Chem 2020 May 19;311:125884. Epub 2019 Nov 19.

Max Rubner-Institut (MRI), Department of Safety and Quality of Milk and Fish Products, Hermann-Weigmann-Str. 1, Kiel 24103, Germany. Electronic address:

Seafood is particularly susceptible to the substitution of species. In order to guarantee authentic seafood products, seafood processors and traders must perform self-checks on the authenticity of imported and purchased goods. However, the conventional Sanger sequencing of PCR products for the authentication of seafood species is time-consuming and requires advanced infrastructure. DNA microarrays (DNA chips) with species-specific oligonucleotide probes represent a rapid alternative to sequencing-based species authentication. So far, though, only DNA microarrays for the authentication of land vertebrate species have achieved market success. In this work, a user-friendly DNA microarray assay was developed for the authentication of ten important food fish species that can be performed in four to five hours from start to end. The assay was tested with authenticated specimens from 67 different fish species, and by comparing the probe signal patterns all target species and even closely related non-target species could be distinguished.
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http://dx.doi.org/10.1016/j.foodchem.2019.125884DOI Listing
May 2020

Correction to: Chemometric tools for the authentication of cod liveroil based on nuclear magnetic resonance and infrared spectroscopy data.

Anal Bioanal Chem 2019 10;411(26):7051

Federal Research Institute of Nutrition and Food, Department of Safety and Quality of Milk and Fish Products, Max Rubner-Institut, Hermann-Weigmann-Strasse 1, 24103, Kiel, Germany.

The article Chemometric tools for the authentication of cod liver oil based on nuclear magnetic resonance and infrared spectroscopy data, written by Editha Giese, Sascha Rohn and Jan Fritsche.
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http://dx.doi.org/10.1007/s00216-019-02122-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6834727PMC
October 2019

Chemometric tools for the authentication of cod liver oil based on nuclear magnetic resonance and infrared spectroscopy data.

Anal Bioanal Chem 2019 Oct 10;411(26):6931-6942. Epub 2019 Aug 10.

Federal Research Institute of Nutrition and Food, Department of Safety and Quality of Milk and Fish Products, Max Rubner-Institut, Hermann-Weigmann-Strasse 1, 24103, Kiel, Germany.

Cod liver oil is a popular dietary supplement marketed as a rich source of omega-3 fatty acids as well as vitamins A and D. Due to its high market price, cod liver oil is vulnerable to adulteration with lower priced vegetable oils. In this study, H and C nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and gas chromatography (coupled to a flame ionization detector) were used in combination with multivariate statistics to determine cod liver oil adulteration with common vegetable oils (sunflower and canola oils). Artificial neural networks (ANN) were able to differentiate adulteration levels based on infrared spectra with a detection limit of 0.22% and a root mean square error of prediction (RMSEP) of 0.86%. ANN models using H NMR and C NMR data yielded detection limits of 3.0% and 1.8% and RMSEPs of 2.7% and 1.1%, respectively. In comparison, the ANN model based on fatty acid profiles determined by gas chromatography achieved a detection limit of 0.81% and an RMSEP of 1.1%. The approach of using spectroscopic techniques in combination with multivariate statistics can be regarded as a promising tool for the authentication of cod liver oil and may pave the way for a holistic quality assessment of fish oils. Graphical abstract.
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http://dx.doi.org/10.1007/s00216-019-02063-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6834736PMC
October 2019

Recent Developments and Digital Perspectives in Food Safety and Authenticity.

Authors:
Jan Fritsche

J Agric Food Chem 2018 Jul 11;66(29):7562-7567. Epub 2018 Jul 11.

Department of Safety and Quality of Milk and Fish Products, Federal Research Institute of Nutrition and Food , Max Rubner-Institut , Hermann-Weigmann-Straße 1 , 24103 Kiel , Germany.

Food safety is of fundamental importance for the food processing industry, food retailers and distributors, and competent authorities because of its potentially direct impact on the health of consumers. Next to the prevention of microbiological, chemical, and physical hazards, increasing efforts are currently made to combat risks associated with food fraud or food authenticity. Food safety management systems nowadays comprise food safety, food defense, and food fraud prevention measures, trying to cope with the increasing complexity and globalization of the food supply chains. Future digital opportunities include the prediction of food safety and food authenticity issues by handling structured and unstructured data retrieved from various sources and origins to ensure the health of consumers and to minimize economical losses.
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http://dx.doi.org/10.1021/acs.jafc.8b00843DOI Listing
July 2018

Determining quality parameters of fish oils by means of H nuclear magnetic resonance, mid-infrared, and near-infrared spectroscopy in combination with multivariate statistics.

Food Res Int 2018 04 16;106:116-128. Epub 2017 Dec 16.

Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Department of Safety and Quality of Milk and Fish Products, Hermann-Weigmann-Strasse 1, 24103 Kiel, Germany. Electronic address:

Fish oil is becoming increasingly popular as a dietary supplement as well as for its use in animal feed, which is mainly due to its high contents of the health promoting omega-3 fatty acids. However, these polyunsaturated fatty acids are highly susceptible to oxidation, which results in a decrease of the fish oil quality. This study investigated the potential of H NMR, FT-MIR, and FT-NIR spectroscopy in the quality assessment of fish oils. A total of 84 different fish oils, of which 22 were subjected to accelerated storage with varying temperature and light exposure, were used to develop models for predicting the peroxide value (PV), the anisidine value (AnV), and the acid value (AV). Predictions were based on comprehensive spectroscopic data in combination with Artificial Neural Networks (ANN) as well as Partial Least Squares Regression (PLSR). The best ANN model for PV was obtained from NMR data, with a predictive coefficient of determination (Q) of 0.961 and a Root Mean Square Error of Prediction (RMSEP) of 1.5meqOkg. The combined MIR/NIR data provided the most reliable ANN model for AnV (Q=0.993; RMSEP=0.74). For AV, the ANN model based on the MIR data yielded a Q of 0.988 and an RMSEP of 0.43mgNaOHg. In most cases, the accuracy of the ANN models was superior to the respective PLSR models. Variable selection and data dimensionality reduction turned out to improve the performance of the ANN models in some cases. The application of H NMR, FT-MIR, and FT-NIR spectroscopy in combination with ANN can be considered very promising for a rapid, reliable, and sustainable assessment of fish oil quality.
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http://dx.doi.org/10.1016/j.foodres.2017.12.041DOI Listing
April 2018

Mitigation strategies for ester bound 2-/3-MCPD and esterified glycidol in pre-fried breaded and frozen fish products.

Food Chem 2018 Apr 14;245:196-204. Epub 2017 Oct 14.

Department of Safety and Quality of Milk and Fish Products, Max Rubner-Institut, Federal Research Institute for Nutrition and Food, Hermann-Weigmann-Str 1, 24103 Kiel, Germany. Electronic address:

Pre-frying of chloride-containing raw materials (e.g., breaded frozen fish products) can lead to the formation of fatty acid esters of 2-monochloropropane-1,3-diol, 3-monochloropropane-1,2-diol (MCPD-E), and glycidol (G-E). The aim of the present study was to identify relevant parameters for the formation of these process contaminants during the pre-frying. Secondly, several mitigation approaches have been investigated. The major proportion of the MCPD-E and G-E in the fish products resulted from the pre-frying oil absorbed, while the temperature and the heating period of the pre-frying oil showed the strongest impact. A significant reduction of the MCPD-E content in the pre-frying oil was achieved by filtering-off solid breading particles. Additionally, the G-E content decreased resulting from the use of adsorbent materials. Moreover, the analyses of total polar material and the color intensity of the pre-frying oil are suggested as screening methods for estimating the MCPD-E and G-E contents in the fish products.
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http://dx.doi.org/10.1016/j.foodchem.2017.10.076DOI Listing
April 2018

Assessment of the oxidative stability of conventional and high-oleic sunflower oil by means of solid-phase microextraction-gas chromatography.

Int J Food Sci Nutr 2012 Mar 19;63(2):160-9. Epub 2011 Aug 19.

Hochschule für Angewandte Wissenschaften, Lohbrügger Kirchstraße 65, D-21033 Hamburg, Germany.

Headspace-solid-phase microextraction-gas chromatography (HS-SPME-GC) was used to identify in total 74 volatile lipid oxidation compounds altogether in thermally stressed conventional and high-oleic sunflower (HOSF) oil samples (in accelerated storage conditions for 14 days at 80°C). Out of the volatile compounds identified, six volatile compounds were selected as marker compounds for the assessment of lipid oxidation of sunflower (SF) and HOSF oils due to their low odour threshold values and fatty-rancid odour impression. Additionally, other oxidation parameters such as fatty acid composition, peroxide value (PV), anisidine value and tocopherol and tocotrienol composition were determined. Multivariate statistical methods (principal component analysis and agglomerative hierarchical cluster analysis) were applied to identify sensitive oxidation marker compounds. Preliminary results revealed that hexanal, E-2-heptenal, E-2-decenal and E,E-2,4-nonadienal were the most suitable in differentiating HOSF and SF oil varieties from each other and SF samples with differing oxidative properties. Differentiation of SF samples according to their volatile compound composition was done in accordance with the results from the well-known oil quality parameters (e.g. PV or fatty acid composition). In conclusion, the combination of volatile compound analysis with HS-SPME-GC and multivariate statistical methods provides a sensitive tool in differentiating conventional SF and HOSF oils by means of volatile lipid oxidation marker compounds.
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http://dx.doi.org/10.3109/09637486.2011.609158DOI Listing
March 2012

Attitudes and perceptions of AIDS clinical trials group site coordinators on HIV clinical trial recruitment and retention: a descriptive study.

AIDS Patient Care STDS 2007 Aug;21(8):551-63

Univeristy of California at Los Angeles, Department of Infectious Diseases, Los Angeles, California, USA.

HIV-seropositive blacks, Hispanics, women of all ethnicities, and injection drug users (IDUs) have low rates of clinical trial participation. The opinions of research nurses and study coordinators as potential facilitators and barriers to access to clinical trials may contribute to this disparity. Study coordinators and research nurses from the adult AIDS Clinical Trials Group (ACTG) clinical trials units responded to an anonymous computer-based survey comprising multiple choice questions and clinical scenarios. Descriptive statistics were used to determine frequencies of responses. Recruitment rates of blacks, Hispanics, women and IDUs were mostly rated appropriate compared with the geographic region demographics. Most sites ranked white men as being the most interested in clinical trials. Sites rated their most effective interactions were with white men. Respondents felt they were less likely to enroll individuals who had missed previous clinical appointments or did not speak English. Perceptions that IDUs, Hispanics, blacks, and, to a lesser extent, women had less interest in clinical trials participation than white males may affect recruitment of the targeted populations. Interventions to improve interactions with targeted populations and to remove logistical and language barriers may improve the diversity of clinical trial participants.
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http://dx.doi.org/10.1089/apc.2006.0173DOI Listing
August 2007

Gas chromatographic analysis of infant formulas for total fatty acids, including trans fatty acids.

J AOAC Int 2002 Jan-Feb;85(1):86-94

U.S. Food and Drug Administration, Office of Nutritional Products, Labeling and Dietary Supplements, Washington, DC 20204, USA.

Twelve powdered and 13 liquid infant formulas were analyzed by using an extension of AOAC Official Method 996.01 for fat analysis in cereal products. Samples were hydrolyzed with 8 N HCl and extracted with ethyl and petroleum ethers. Fatty acid methyl esters were prepared by refluxing the mixed ether extracts with methanolic sodium hydroxide in the presence of 14% boron trifluoride in methanol. The extracts were analyzed by gas chromatography. In powdered formulas, saturated fatty acid (SFA) content (mean +/- SD; n = 12) was 41.05 +/- 3.94%, monounsaturated fatty acid (MUFA) content was 36.97 +/- 3.38%, polyunsaturated fatty acid (PUFA) content was 20.07 +/- 3.08%, and total trans fatty acid content was 1.30 +/- 1.27%. In liquid formulas, SFA content (mean +/- SD; n = 13) was 42.29 +/- 2.98%, MUFA content was 36.05 +/- 2.47%, PUFA content was 20.65 +/- 2.40%, and total trans fatty acid content was 0.88 +/- 0.54%. Total fat content in powdered formulas ranged from 4.4 to 5.5 g/100 kcal and linoleic acid content ranged from 868 to 1166 mg/100 kcal. In liquid formulas, total fat content ranged from 4.1 to 5.1 g/100 kcal and linoleic acid content ranged from 820 to 1100 mg/100 kcal. There were no significant differences between powdered and liquid infant formulas in concentrations of total fat, SFA, MUFA, PUFA, or trans fatty acids.
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August 2002
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