Laboratory Chemistry / Food Chemistry

Food chemistry deals with the ingredients of food and their changes. The focus is on the chemical analysis of the composition of food as well as changes during processing and storage. In addition, purity, quality and safety are tested and assessed. In the laboratory, students learn the most important classical-conventional determination methods and detection methods for essential food components in practice.

In addition to the possibility of using conventional chemical examination procedures, modern, conclusive methods of food analysis can of course also be used in the laboratory. These include physical-chemical or biochemical analytical procedures such as high-performance liquid chromatography (e.g. for the analysis of sugars), gas chromatography (e.g. for the analysis of aromatic substances) or SDS electrophoresis (for the analysis of proteins). The Chemistry / Food Chemistry Laboratory is an interdisciplinary laboratory: There are internal cooperations, for example with the Bioprocess Engineering or the Raw Materials Science and Sensory Laboratory.

In the Chemistry / Food Chemistry laboratory, students of the Food Technology programme (B.Sc.) complete the compulsory practicals for the Food Chemistry and Biochemistry modules as well as the compulsory elective module Food Analysis.

By first getting to know the classical determination methods of food chemistry, the students should develop a good basic understanding of food analysis in this laboratory practical. With the conventional techniques, they learn the principle behind the modern technique. The focus is on chemical-analytical detection methods of the main components of food. Different experiments are carried out for this purpose: For example, the saponification number, the acid number and the iodine number are to be determined to characterise fats and oils; the fatty acid distribution is to be determined with the help of gas chromatography. In another experiment, the aim is to apply nitrogen determination according to Kjeldahl's method and thus determine the total protein content of food. Using thin-layer chromatography, the students learn to detect and determine amino acids. How to determine the content of reducing sugars in a sample with the reductometric method according to Luff-Schoorl, the students also learn in a practical exercise.

In the biochemistry module, students get an overview of important food components including their biochemical reactions during ripening, production and storage. The focus of this practical course is on analytical methods to provide an understanding of biochemical food analysis. Here, the students carry out investigations on dyes and browning reactions, e.g. on caramelisation, the Maillard reaction or enzymatic browning, learn about separation procedures such as gel electrophoresis and enzymatic methods, for example the enzymatic hydrolysis of lactose or the determination of enzyme activity.

In the compulsory elective module food analysis, selected chromatographic, spectroscopic and biochemical methods are dealt with. Practical exercises on (bio-) chemical analyses are carried out with the help of modern instrumental analytics.

Within the framework of a thesis, analytical questions can be processed, documented and evaluated according to scientific principles.

Since the Chemistry Laboratory is an interdisciplinary laboratory, sugar analyses, for example, are carried out with the help of HPLC (high-pressure liquid chromatography) in cooperation with the Bioprocess Engineering Laboratory. HPLC is often used when individual components of a mixture - in this case different sugars - are to be separated and thus identified. The determination of sugars and carbohydrates is of great importance in food analysis, as it is necessary for the correct declaration of nutritional values. This is also important in view of the fact that there are more and more people with intolerances such as fructose or lactose intolerance. The scientists in the Raw Materials Science and Sensory Laboratory in the Chemistry Laboratory use HPLC to test the fructose content in products, for example.

Gas chromatography (GC) as an important analytical method for organic compounds is also used for research purposes in order to be able to make the most objective statements possible about the smell of food. For example, in cooperation with the Bioprocess Engineering Laboratory, volatile substances that are produced during fermentation - among other things during beer production - are separated and quantified.

• High-pressure liquid chromatograph with DAD detector or RI detector for the separation of substances as well as identification and quantification via standards; also for the analysis of non-volatile substances.
• Gas chromatograph with FID (liquid injection, headspace, SPME) for separating mixtures into individual chemical compounds (only applicable for components that are gaseous or can be vaporised)
• UV-VIS photometer: This spectroscopic method uses the electromagnetic waves of ultraviolet (UV) and visible (VIS) light for quantitative analyses (e.g. enzymatic content determination of sugars).
• SDS-PAGE electrophoresis is used for the analysis of proteins. It is an analytical method for separating mixtures of substances according to molecular mass in an electric field.
• Kjeldahl digestion and distillation unit to determine the nitrogen and thus the protein content.
• Rotary evaporator for precipitating substances from solids - by evaporating the solvent - e.g. for dissolving out fat from chocolate
• Ultrasonic bath for degassing e.g:_CO2 from fruit juices (by ultrasonic vibrations in a liquid)
• Vacuum filtration unit for separating or cleaning a medium, usually a suspension
• Ultrapure water system: Ultrapure water contains virtually no foreign substances, such as minerals. It is used for chemical analysis.
• Centrifuge to separate solids from liquids, e.g. milk into fat layer and skimmed milk.
• Analytical balance: The most sensitive balance in the laboratory allows the exact weighing of only 1 milligram of substance.