Development of a natural plant-based preservative for delicatessen products
Master's thesis at the Berlin University of Applied Sciences, Faculty V - Life Sciences and Technology
Consumers increasingly expect food without additives and E-numbers that tastes good, has a long shelf life and is safe. The industry is responding with innovative new processes, technologies and ingredients. The aim of the project was to develop a natural plant-based preservative from pak choi(Brassica rapa subsp. Chinensis) for delicatessen products. The variety used, "Arax", is characterised by an intense red colouring of the leaves. In addition to antimicrobial secondary plant compounds, it also contains health-promoting polyphenolic compounds.
Pak Choi offers foundation
The pak choi plants were grown in the greenhouse in culture trays under exclusion of daylight. Different radiation spectra were set under LED lighting to investigate the effects on plant growth. The "global radiation" variant was in the field at the same time.
Optical differences between the different irradiation variants were already visible during cultivation. In the radiation spectrum with exclusively blue and red LED light, the red colouration of the leaves was most intense, the high-energy radiation triggered an increased formation of protective pigments in the plant.
After harvesting on the 28th day after sowing, the fresh mass was determined and the samples were then dried and powdered. Extracts were obtained from the powders using various solvents.
Analytical tests on the cultivation variant with blue-red spectrum showed the highest concentrations of the three lead substances: Total polyphenols, flavonoids and anthocyanins.
A dark red component in the radiation increased the fresh mass and the total polyphenol content per culture tray was 13% higher than with the blue-red radiation.
For the microbiological investigations, a food matrix was prepared into which either pak choi extract or powder was introduced. Depending on the concentration, an at times dramatic optical change in the matrix was observed due to the violet inherent colouring of the pak choi.
Various tests were carried out to assess the inhibitory effect. In surface tests, a certain inhibitory effect was found against selected bacteria. In the delicatessen matrix itself, the inhibitory effect could not be proven, as a large proportion of the microorganisms could not be detected there. However, test results indicate that pak choi extract in the delicatessen matrix inhibits the growth of the mould Aspergillus niger.
Berlin University of Applied Sciences (formerly: Beuth University of Applied Sciences Berlin), Faculty V - Life Sciences and Technology
Master's thesis Franziska Schulz 2019
Food Technology (LT), Laboratory for Food Technology - Product Development,
Project leader: Prof. Dr. Simone Peschke
Horticultural Phytotechnology (GPT), Greenhouse Laboratory: Prof. Dr. Claus Bull