Spray freezing has many existing and potential applications in the food and pharmaceutical industries, and provides an option for further freeze-drying. Complex microstructures are generated within drops during spray-freezing via the formation of ice crystals. The size and number of these crystals is influenced by the cooling conditions, which includes slip velocity. A high power, high resolution phase Doppler anemometer (PDA) system has been used to measure the size and axial velocity of individual droplets passing locations vertically below the spray nozzle in a spray-freezing chamber. The PDA receiver was positioned at a scattering angle of 70 degrees to ensure collection of scattered light due to first order refraction only. Droplet size distributions were normalised with respect to the total number of data samples detected. Not all data samples were accepted by the PDA validation software for size and velocity measurements. Dropping the chamber temperature (from +20 degrees C to -60 degrees C) and increasing the distance from the nozzle (from 38 mm to 220 mm) both increased the data rejection rate, although increases were smaller at distances greater than 100 mm and temperatures less than -22 degrees C. We postulate that data rejection is caused by the formation of ice crystals within the drops as they freeze, which modifies light transmission through the droplet and therefore the first order refracted scattered light. Freezing times predicted from a drop freezing model are similar to those probed in the PDA experiments with hydraulic nozzles, suggesting that PDA can potentially be used as a non-invasive probe for drop freezing.