According to Huffman et al. (2013) a burst of biological ice nuclei (IN) can be found over woodlands during and after rain events. The origin of these particles can be e.g. bacteria (e.g. Pseudomonas syringae), fungi (e.g. Fusarium acuminatum spores), and (decayed) plant litter. B. Pummer et al. (2012) report that both pollen and pollen washing water from plants originating from the northern timberline show ice nucleation activity. These facts suggest that other parts of the plants might also act as IN due to their cold protection and cold tolerance mechanisms. Hence investigations were done concerning the ice nucleation activity of other biological materials. On the one hand, further parts of plants (mainly berries and berry juices) from the northern timberline were investigated. On the other hand, investigations were done on both water-interacting and structural polysaccharides, like pectin and chitin, as well as chemical modifications of these polysaccharides. Additionally, altering experiments were done for selected carbohydrate samples to see if treatment with ozone has any influence on the freezing properties of water. ATR-FTIR spectroscopy was done to see if the ozone treatment influences the freezing properties.