Changes of Some Physicochemical Properties of Yoghurt made from ${\beta}$-Galactosidase-treated Commercial Milks

${\beta}$-Galactosidase 처리 시유로 제조한 요구르트의 이화학적 성분 변화

  • Lee, In-Seon (Department of Dairy Science, Sungkyunkwan University) ;
  • Kim, Sang-Hee (Department of Dairy Science, Sungkyunkwan University) ;
  • Ha, Jae-Ho (Korea Food Research Institute) ;
  • Kang, Kook-Hee (Department of Dairy Science, Sungkyunkwan University)
  • Published : 1989.12.01

Abstract

This study was carried out to hydrolyze lactose in commercial milk by ${\beta}-galactosidase$ from Kluyveromyces fragilis and to compare some physicochemical properties of yoghurts made from control and lactase-treated commercial milks. Quantitative analysis of sugars was performed by gas liquid chromatograph (GLC) on trimethylsilyl (TMS) derivatives. In commercial milk, 94.6% of lactose was hydrolyzed after 2 hours incubation at $40^{\circ}C$ with 6.0 units/ml of ${\beta}-galactosidase$. pH, titratable acidity and viable cell number of yoghurt made from lactase-hydrolyzed (LH) commercial milk were 4.1, 1.04% and $6.5{\times}10^8/ml$ of Str. thermophilus, $8.9{\times}10^8/ml$ of L. bulgaricus after 8 hours incubation at $40^{\circ}C$, respectively, The total contents of amino acid were 2.63% in control and 2.19%. in LH yoghurt. The total contents of free amino acid were 26.95 mg% in control and 17.55mg% in LH yoghurt. Analysis of free fatty acids resulted in that the contents of short chain fatty acids in LH yoghurt were a little higher than those in control. Both in control and LH yoghurt, the palmitic acid content was highest and that was followed by oleic and myristic acid.

Keywords

${\beta}$-galactosidase;yoghurt;lactose intolerance