Jörg Hau

Acrylamide from Maillard reaction products

The discovery of the adventitious formation of the potential cancer-causing agent acrylamide in a variety of foods during cooking has raised much concern, but the chemical mechanism(s) governing its production are unclear. Here we show that acrylamide can be released by the thermal treatment of certain amino acids (asparagine, for example), particularly in combination with reducing sugars, and of early Maillard reaction products (N-glycosides). Our findings indicate that the Maillard-driven generation of flavour and colour in thermally processed foods can — under particular conditions — be linked to the formation of acrylamide.

Food chemistry: Acrylamide from Maillard reaction products

The discovery of the adventitious formation of the potential cancer-causing agent acrylamide in a variety of foods during cooking has raised much concern, but the chemical mechanism(s) governing its production are unclear. Here we show that acrylamide can be released by the thermal treatment of certain amino acids (asparagine, for example), particularly in combination with reducing sugars, and of early Maillard reaction products (N-glycosides). Our findings indicate that the Maillard-driven generation of flavour and colour in thermally processed foods can — under particular conditions — be linked to the formation of acrylamide.

MyHits: improvements to an interactive resource for analyzing protein sequences

The MyHits web site (http://myhits.isb-sib.ch) is an integrated service dedicated to the analysis of protein sequences. Since its first description in 2004, both the user interface and the back end of the server were improved. A number of tools (e.g. MAFFT, Jacop, Dotlet, Jalview, ESTScan) were added or updated to improve the usability of the service. The MySQL schema and its associated API were revamped and the database engine (HitKeeper) was separated from the web interface. This paper summarizes the current status of the server, with an emphasis on the new services.

Determination of the plant growth regulator chlormequat in food by liquid chromatography–electrospray ionisation tandem mass spectrometry

A confirmatory method for the determination of trace levels of chlormequat in a variety of different food matrices was developed. It entails a single clean-up step over a solid-phase cation exchange resin and subsequent liquid chromatography-electrospray ionisation tandem mass spectrometry using a stable isotopically labelled internal standard. Mass spectral acquisition was done in selected reaction monitoring mode, selecting the transitions from both the 35Cl and the 37Cl isotope of chlormequat. Recoveries after extraction and clean-up, determined with radio-labelled chlormequat and averaged over the spiking range (16-65 microg kg(-1)) in four different commodities, were within 88-96%, with a coefficient of variation better than 8%. The method can be applied to pears, pear juice concentrates, fruit purées, and cereal products, with typical limits of detection for chlormequat estimated at 2-5 microg kg(-1). A survey of different food commodities revealed that chlormequat was detectable--albeit at very low levels--in many of the food samples analysed, with the highest concentration recorded in pears purchased in Switzerland and of South African origin (5.5 mg kg(-1)). Measurements were also conducted on two LC-MS instruments and demonstrate the versatility and robustness of the method and its applicability to instruments of different ion source design.

Characterisation of modified whey protein in milk ingredients by liquid chromatography coupled to electrospray ionisation mass spectrometry.

Whey proteins are an important ingredient in the food industry. We have investigated the protein composition of commercial whey samples by liquid chromatography coupled to electrospray ionisation mass spectrometry on a time-of-flight instrument. We found that industrial whey protein contains a multitude of different modifications, ranging from almost native proteins through different degrees of glycosylation and oxidation up to almost completely oxidised forms. The information obtained allows characterisation of the influence of industrial processing on protein modifications and classification of whey protein-based ingredients or milk powders from different suppliers.

Glucuronidation of the Green Tea Catechins, (-)-epigallocatechin-3-gallate and (-)-epicatechin-3-gallate, by Rat Hepatic and Intestinal Microsomes

The flavonoids (-)-epigallocatechin-3-gallate (EGCg) and (-)-epicatechin-3-gallate (ECg) are major components of green tea and show numerous biological effects. We investigated the glucuronidation of these compounds and of quercetin by microsomes. Quercetin was almost fully glucuronidated by liver microsomes after 3 h, whereas ECg and ECGg were conjugated to a lesser extent ([Formula: See Text] and [Formula: See Text] respectively). The intestinal microsomes also glucuronidated quercetin much more efficiently than ECg and EGCg. Although the rates were lower than quercetin, intestinal microsomes exhibited higher activity on the galloyl group of ECg and EGCg compared to the flavonoid ring, whereas hepatic glucuronidation was higher on the flavonoid ring of EGCg and ECg compared to the galloyl groups. The low glucuronidation rates could partially explain why these flavanols are present in plasma as unconjugated forms.

Practical approach to archival and retrieval of analytical data in the laboratory.

Todays analytical laboratory uses a large number of different instruments that are connected in networks. Together with increasing automation, data are produced at a rate that can easily reach gigabytes per month, which generates the problem of systematic archival. In addition, working under Good Laboratory Practice requires that archival of raw data be performed in such a way that they can be readily retrieved upon request, even years later. While systematic archival of data is already performed in most laboratories, it is the retrieval of saved information that is often far from straightforward. This paper describes a simple but systematic approach for both archival and retrieval of data files and related electronic documents. It consists of an unambiguous scheme for the naming of electronic files, an efficient backup strategy, a simple database holding information about any data acquired, and a convenient interface to this database that can be accessed from any workplace while assuring restricted access. The system is capable of handling several databases concurrently and is used in our facility to archive data from several workgroups. The use of freely available software such as the Linux operating system made it possible to implement a fast and stable solution at exceptionally low cost.

Acrylamide from Maillard reaction products: Food chemistry

The discovery of the adventitious formation of the potential cancer-causing agent acrylamide in a variety of foods during cooking has raised much concern, but the chemical mechanism(s) governing its production are unclear. Here we show that acrylamide can be released by the thermal treatment of certain amino acids (asparagine, for example), particularly in combination with reducing sugars, and of early Maillard reaction products (N-glycosides). Our findings indicate that the Maillard-driven generation of flavour and colour in thermally processed foods can — under particular conditions — be linked to the formation of acrylamide.