Freeze Drying of Fermented Milk Prepared from Milk and Fruit Juices

유유와 과즙으로 만든 발효유의 동결건조

  • Ko, Young-Tae (Department of Foods and Nutrition, Duksung Women's University) ;
  • Oh, Mi-Hwa (Department of Foods and Nutrition, Duksung Women's University)
  • 고영태 (덕성여자대학교 식품영양학과) ;
  • 오미화 (덕성여자대학교 식품영양학과)
  • Published : 1998.12.01

Abstract

Fermented milk was prepared from milk or mixture of milk and apple juice/grape juice, and it was freeze dried. pH change and growth of Lactobacillus acidophilus (KCTC 2182) during freeze drying were studied. The effects of freeze drying on sensory evaluation and volatile aroma compounds in freeze dried sample or reconstituted sample were also studied. Freezing and freeze drying did not affect pH of fermented milk. Number of viable cells of L. acidophilus was markedly reduced during freezing or freeze drying. When number of viable cells in original fermented milk was considered as 100%, survival ratio of viable cells after freezing was $64.5{\sim}85.2%$ and that after freeze drying was $10.0{\sim}21.1%$. When sensory properties of original fermented milk prepared from juice-milk (ratio 15:35) were compared with those of freeze dried/reconstituted sample, sensory properties of original sample were better than those of freeze dried/reconstituted sample. Ethanol, diacetyl, butanol and acetoin were detected in all of original samples and freeze dried/reconstituted samples while acetone was detected in samples containing high amount of grape juice. Volatile aroma compounds in original fermented milk were reduced during freeze drying. L. acidophilus produced ethanol, diacetyl and acetoin during fermentation.

Keywords

fermented milk;Lactobacillus;apple juice;grape juice;freeze drying