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Gewählte Master / Diploma Thesis:

Lisa Heinzle (2016): Nährmedienoptimierung für den Nachweis käsereischädlicher Clostridien in Milch.
Master / Diploma Thesis - Institut für Lebensmittelwissenschaften, BOKU-Universität für Bodenkultur, pp 124. UB BOKU obvsg

Data Source: ZID Abstracts
Abstract:
One big issue in hard cheese manufacturing is the avoidance of the so-called late-blowing effect, a characteristic cheese defect. This quality degradation is evoked by the germination of clostridial endospores during the cheese ripening process. Their fermentation products butyrate and gas lead to strong off-flavours and unwanted cracks and holes making the affected cheeses unpalatable. Due to the major product damage, cheese producers face high economic losses. Therefore, the ability to detect clostridial spores in raw milk prior to cheese production is important. The aim of this thesis is the optimization of a nutritional medium for the microbial detection of cheese damaging Clostridium spp. in milk. Based on a literature research, the species Cl. butyricum, Cl. sporogenes, Cl. beijerinckii and Cl. tyrobutyricum were selected as test strains, whereas the focus was on Cl. tyrobutyricum as presumptive main cause for late-blowing. After creating a reference strain library and the preparation of spore suspensions, growth-experiments with various media compositions were conducted within different testing systems. In the Bioscreen-C apparatus, changes of the optical density of the inoculated media was measured, whereas in the BacTrac-system, which is based on alterations of impedance, the matrix milk could already be included in the experiments. Finally, higher sample throughputs and faster results were achieved in a microtiterplate system with a colour indicator for growth-detection. After the definition of a basic formula, two additives for inhibition of accompanying microbiota, especially Bacillus spp. and Paenibacillus spp. were established during the experiments. Moreover, the pH of the media was optimized. The improved formula made it possible to finally detect cheese damaging Clostridia in spiked UHT-milk within 48 hours.

Beurteilende(r): Domig Konrad

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