DETERMINATION OF ICE CRYSTAL SIZE DISTRIBUTIONS IN FROZEN DESSERTS

Formation of the ice crystal size distribution during manufacture of frozen desserts plays an important role in determining textural characteristics. A crystal size distribution with a large mean size and wide variation results in a coarse product. A new methodology has been developed to characterize the ice crystal size distribution accurately. An optical microscope was used to produce photomicrographs of ice crystals in frozen products. The microscope was housed in a refrigerated glove box, which provided excellent temperature control and allowed samples to be analyzed at various stages of manufacture. The photomicrographs were analyzed using a digitizing board connected to a microcomputer. Several ice cream and ice milk formulations were analyzed to test the methodology. Ice crystal size was inversely related to the total solids of the formulations. Ice crystal size also increased substantially between draw and hardening and during the first 7 wk of storage at -20-degrees-C. Further frozen storage did not result in any significant change in crystal size. These results agree with previous data and with theoretical considerations.