Lactobacillus casei HS4胞外多糖对发酵乳组织结构和流变特性的影响（英文）

Effect of Exopolysaccharide Produced by Lactobacillus casei HS4 on Microstructure and Rheological Properties of Fermented Milk

研究干酪乳杆菌(Lactobacillus casei)HS4所产乳酸菌胞外多糖(exopolysaccharide,EPS)及其对发酵乳微观结构和流变性的影响。通过Sephadex G-50柱纯化得到两种类型的EPS,分别命名为HS4-1-EPS和HS4-2-EPS。HS4-1-EPS主要由葡萄糖组成,峰面积为0.940。HS4-2-EPS主要由葡萄糖和甘露糖组成,峰面积比为0.3830.364。红外光谱结果显示,HS4-1-EPS和HS4-2-EPS均为杂多糖。分别采用干酪乳杆菌HS4、嗜热链球菌-保加利亚乳杆菌(1:1)复合菌株以及复合菌株添加纯化EPS制成的不同发酵乳作为样品,通过测定流变特性及微观结构观察,研究补充纯化EPS和原位EPS对发酵乳流变特性及微观结构的影响。结果显示,其在4℃贮存期间显示出不同的流变特性及微观结构。基于扫描电镜下样品的微观结构,可以推知,EPS的类型和空间阻挡效应与发酵乳的流变性质相关。

This study aimed to investigate the exopolysaccharide (EPS) of Lactobacillus casei HS4 and its effect on the microstructure and rheological properties of fermented milk. Two fractions of EPS, named as HS4-1-EPS and HS4-2-EPS, were obtained by size exclusion chromatography on a Sephadex G-50 column. HS4-1-EPS was mainly composed of glucose with a peak area of 0.940. HS4-2-EPS was mainly composed of glucose and mannose with a peak area ratio of 0.383:0.364. Fourier transform infrared (FT-IR) spectroscopy revealed that HS4-1-EPS and HS4-2-EPS were both heteropolysaccharides. The rheological properties and microstructure of three fermented milks made respectively with a mixed starter culture of Streptococcus thermophilus and Lactobacillus bulgaricus (1:1) in the presence and absence of the purified EPS and a monoculture of L. casei HS4 were observed to determine the effect of supplementation of the purified EPS versus in situ EPS on the rheological properties of fermented milk. These fermented milks showed different rheological properties during storage at 4 ℃. Based on the microstructure observation, we concluded that the type and space barrier effect of EPS correlated with the rheological properties of fermented milk.