Cellulose nanocrystal dispersions protect tree fruits from cold damage
B. Arnoldussen, J. Alhamid , C. Mo, X. Zhang, P. Wang, Q. Zhang, M. Whiting
Cold damage to reproductive buds or flowers is a perennial concern to tree fruit producers. Indeed, cold damage has caused more economic losses to crops in the US than any other weather hazard. The potential losses (yield reductions to complete crop failure) from cold damage are predicted to increase with variable weather patterns resulting from climate change. Cellulose nanocrystals (CNC) represents a new generation of renewable nano-biomaterials, with many unique physical and chemical properties, including their low thermal conductivity. Our team has developed a process for creating CNC dispersions that can be sprayed onto trees, forming a thin (ca. 25µm-40µm) and durable insulating film around the surface of the buds. Thermal image analyses revealed that apple (Malus domestica Borkh) and sweet cherry (Prunus avium L.) flower buds treated with 3% CNC dispersions lose 16.5% less thermal energy into the environment in cold conditions than untreated buds. Analyses of internal freezing events in apple with digital scanning calorimetry showed that buds coated in 3% CNC exhibited lethal freezing at a temperature 3.2°C and 5.5°C lower than the untreated control 1 and 3 days after application, respectively. Large-scale field trials using commercially available electrostatic sprayers showed that CNC-treated (2.5%) reproductive buds were hardier by ca. 5.8°C, a level of protection that lasted up to 7 days post application. The results of this work suggest that CNC dispersions can effectively protect reproductive buds from cold damage and may represent a novel means for fruit growers worldwide to reduce losses.