Effect of freezing temperature and warming rate on dendrite break-up when freezing ice cream mix

Small ice crystals are critical to ice cream quality and shelf life. In a scraped-surface freezer, ice crystals nucleate on the wall where the temperature is the coldest. The scraper blade then transports these crystals, in a layer of slush, to the warmer bulk zone of the freezer. Understanding the formation of ice crystals in a scraped-surface freezer will aid in retaining small ice crystals in ice cream. By freezing and warming thin layers of ice cream mix on a temperature-controlled microscope slide, it was found that warmer freezing temperatures gave more elongated and slightly larger crystals with a wider size distribution. Warming the crystals faster produced smaller or rounder ice crystals, depending on the residence time. These results suggest that, other variables being equal, freezers designed to quickly warm the scraped slush layer from its wall temperature to the bulk temperature may produce ice cream with smaller ice crystals.