EVALUATION OF FROSTGARD AS AN ANTIFREEZE, INHIBITOR OF ICE NUCLEATORS, AND CRYOPROTECTANT ON PINOT-NOIR LEAF TISSUE

Laboratory procedures were developed to determine the effectiveness of Frostgard (FG). Specific experiments tested its antifreeze, anti-ice nucleation, and cryoprotection properties in grapes. The freezing poin t of water was related to the amount of impurities in the water and le ss with FG concentration. FG at 1% (v/v) depressed the ice nucleation temperature (INT) of water solutions by 1-degrees-C. Also, FG depresse d INT of ice nucleation active (INA) bacterial suspensions in addition to kill the bacteria. The anti-ice nucleation properties were also te sted on fluorophlogopite, an inorganic ice nucleator. FG required the presence of ice nucleators to effectively depress INT, possibly by bin ding to active nucleation sites. FG at 0.25% (v/v) reduced the freezin g injury to grape leaf disks by 21% to 25% at -2-degrees-C. At lower t emperatures there was no protection. Our results suggest that the prac tical significance of the cryoprotectant nature of FG is very limited.