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 a mix in an o/w emulsified state by a freezer. We have in vestigated the effect of drawing temperature at the freezer and overrun on de-emulsified fat. Ice cream consisting of vegetable fat 9.0%, M.S.N.F. 9.5% and total solids 38.0% was prepared by freezing the mix in a CREPACO continuous freezer. Conditions were varied as follows. The drawing temperature at the freeze was -3.5°C, -4.5°C or -5.5°C, the overrun was 40%, 70%, 100% or 130%, and the mix flow rate was 65l/h. The particle size distribution of the fat globules was measured by a Laser diffraction particle size analyzer. The fat de-emulsification rate was determined by the difference of the particle size distribution of the fat globules that were measured in ice cream mix and ice cream solution prepared by diluting ice cream at 5°C-10°C with 5 volumes of deionized water. Melting resistance wasexamined by the meltdown method. The fat de-emulsification rate increased in proportion to decreased drawing temperature, and the melting resistance improved. The fat de-emulsification rate increased in proportion to higher overrun, and the milting resistance improved. Dryness of ice cream increased in proportion to decreased drawing temperature and higher overrun. The particle size distribution of fat globules changed in proportion to the increased fat de-emulsification rate; fat globules of below 1.2μm decreased and the distribution of globules of from 3 to 4μm and 8 to 15/μm was unusually increased.