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

Abstract

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.

Surfaces of silver birch (<i>Betula pendula</i>) are sources of biological ice nuclei: in vivo and in situ investigations

“…Particles that trigger higher freezing temperatures are referred to as ice-nucleating particles (INPs) (Vali et al, 2015). Among these are mineral dusts (Broadley et al, 2012;Zolles et al, 2015), soot (DeMott, 1990;Gorbunov et al, 2001) and biogenic particles (Pöschl et al, 2010), and when airborne they have the potential to affect cloud glaciation and consequently weather and climate (Lohmann, 2002;Mishchenko et al, 1996;Forster et al, 2007;Baker, 1997). The land surface is a major contributor to global aerosols (Fröhlich-Nowoisky et al, 2016;Pöschl, 2005;Després et al, 2012;Jaenicke, 2005).…”

Ice Nucleation Activity of Alpine Bioaerosol Emitted in Vicinity of a Birch Forest

“…This may be due to the larger time lag between the rain event and sampling or because relative humidity was lower on UA5 compared to UA4. Regarding the freezing temperature, high number concentrations of IN were found to be active around −20 • C, which is similar to the freezing temperatures of silver birch extracts (Betula pendula) [3,38] and some extracts from frost resistant vegetation (e.g., black currant (Ribes) and sea buckthorn (Hippophae)) [53]. In a recent study, we proposed that INMs of Betula pendula can be washed off the trees' surface during rainfall events [38].…”

Hippophae Rhamnoides L. Botanical, Medicinal, Traditional, and Current Use of Plant and Fruits: A Review

“…Due to its high lipid content, the freezing point of unfiltered juice can be as low as -18.5 degrees. This juice is a very important advantage for storage, as it can maintain its liquid form even at sub-zero temperatures Table 3 90 .…”