Effect of Drawing Temperature at a Freezer and Overrun on De-emulsified Fat of Ice Cream.

Abstract

Ice cream having characteristic texture is produced by freezing amix in an o/w emulsified state by a freezer. We have investigatedthe effect of drawing temperature at the freezer and overrun on de-emulsifiedfat. Ice cream consisting of vegetable fat 9.0%, M.S.N.F. 9.5% andtotal solids 38.0% was prepared by freezing the mix in a CREPACOcontinuous freezer. Conditions were varied as follows. The drawingtemperature at the freezer was -3.5-degrees-C, -4.5-degrees-C or-5.5-degrees- C, the overrun was 40%, 70%, 100% or 130%, and themix flow rate was 65l/h. The particle size distribution of the fatglobules was measured by a Laser diffraction particle size analyzer.The fat de-emulsification rate was determined by the difference ofthe particle size distribution of the fat globules that were measuredin ice cream mix and ice cream solution prepared by diluting icecream at 5-degrees-C approximately -10-degrees-C with 5 volumes ofdeionized water. Melting resistance was examined by the meltdownmethod. The fat de-emulsification rate increased in proportion todecreased drawing temperature, and the melting resistance improved.The fat de-emulsification rate increased in proportion to higheroverrun, and the milting resistance improved. Dryness of ice creamincreased in proportion to decreased drawing temperature and higheroverrun. The particle size distribution of fat globules changed inproportion to the increased fat de- emulsification rate; fat globulesof below 1.2 mum decreased and the distribution of globules of from3 to 4 mum and 8 to 15 mum was unusually increased.