On the Role of Starchy Grains in Ice Nucleation Processes

Little is known about the role of starchy food on climate
change
processes like ice nucleation. Here, we investigate the ice nucleation
efficiency (INE) of eight different starchy food materials, namely,
corn (CO), potato (PO), barley (BA), brown rice (BR), white rice (WR),
oats (OA), wheat (WH), and sweet potato (SP), in immersion freezing
mode under mixed-phase cloud conditions. Notably, among all these
food materials, PO and BA exhibit the highest ice nucleation efficiency
with ice nucleation temperatures as high as −4.3 °C (T50 ∼ −7.0 ± 0.5 °C)
and −6.5 °C (T50 ∼
−7.2 ± 0.2 °C), respectively. We also explore the
effect of environmentally relevant physicochemical conditions on ice
nucleation efficiency, including different pH, temperature, UV/O3/NOx exposure, and various cocontaminants.
The change in shape, size, surface properties, hydrophobicity, and
crystallinity of materials accounted for the altered INE. The increase
in shape, size, and hydrophobicity of the sample generally reduces
the INE, whereas an increase in crystallinity enhances the INE of
the sample under our experimental conditions. The results suggest
that environmentally relevant concentrations slightly alter INE, indicating
their role as catalysts in environmental matrices. The outcome of
studies on the ice nucleation properties of these food-containing
aerosols might help in the physicochemical understanding of other
biomolecule-induced ice nucleation, which is still an underdeveloped
research area.