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Open AccessArticle

Heterogeneous Freezing of Liquid Suspensions Including Juices and Extracts from Berries and Leaves from Perennial Plants

1
Institute of Material Chemistry, TU Wien, 1060 Vienna, Austria
2
Faculty of Physics, Aerosol Physics and Environmental Physics, University of Vienna, 1090 Vienna, Austria
*
Author to whom correspondence should be addressed.
Atmosphere 2019, 10(1), 37; https://doi.org/10.3390/atmos10010037
Received: 18 December 2018 / Revised: 7 January 2019 / Accepted: 13 January 2019 / Published: 17 January 2019
(This article belongs to the Special Issue Ice Nucleation in the Atmosphere)
Heterogeneous ice nucleation in the atmosphere is not fully understood. In particular, our knowledge of biological materials and their atmospheric ice nucleation properties remains scarce. Here, we present the results from systematic investigations of the ice nucleation activity of plant materials using cryo-microscopy. We examined berry juices, frozen berries, as well as extracts of leaves and dried berries of plants native to boreal regions. All of our samples possess reasonable ice nucleation activity. Their ice nucleating particle concentrations per unit of water volume vary between 9.7 × 105 and 9.2 × 109 cm−3 when examined within temperatures of −12 to −34 °C. Mean freezing temperatures ranged from −18.5 to −45.6 °C. We show that all samples contained ice nuclei in a size range below 0.2 µm and remain active if separated from coarse plant tissue. The results of examining ice nucleation properties of leaves and dry berry extracts suggests that their ice-nucleating components can be easily suspended in water. Sea buckthorn and black currant were analyzed using subtilisin (a protease) and urea. Results suggest proteinaceous compounds to play an important role in their ice nucleation activity. These results show that separation between ice nucleation particles stemming from microorganisms and those stemming from plants cannot be differentiated solely on proteinaceous features. Further oxidation experiments with ozone showed that black currant is highly stable towards ozone oxidation, indicating a long atmospheric life time. View Full-Text
Keywords: biological ice nucleation; heterogeneous ice nucleation; ice-nucleating macromolecules; ice-nucleating particles; cold hardiness biological ice nucleation; heterogeneous ice nucleation; ice-nucleating macromolecules; ice-nucleating particles; cold hardiness
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Felgitsch, L.; Bichler, M.; Burkart, J.; Fiala, B.; Häusler, T.; Hitzenberger, R.; Grothe, H. Heterogeneous Freezing of Liquid Suspensions Including Juices and Extracts from Berries and Leaves from Perennial Plants. Atmosphere 2019, 10, 37.

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    Doi: http://doi.org/10.5281/zenodo.2542064
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