Exopolysaccharides (EPS) produced by lactic acid bacteria can be used as natural stabilizers in fermented milk. The ability of EPS to modulate viscosity has not been correlated to their concentration but rather to their structure and their interactions with other milk compounds. The development of a product with desirable characteristics requires knowledge of the EPS structure–function relationship. The aim of this study was to compare the influence of various EPS structures on the gel formation and rheological/physical properties (firmness, apparent viscosity, elastic modulus, syneresis) of fermented milk. Three Streptococcus thermophilus—HC15 (control); 0131 (neutral, flexible, branched EPS); 2104 (anionic, stiff, linear EPS)—and four Lactobacillus delbrueckii subsp. bulgaricus—210R (control); 11842 (neutral, flexible, branched EPS); 702074 (neutral, flexible, branched EPS); 291 (neutral, stiff, branched EPS)—were compared. Strains were grown at 42 °C in skim milk until pH reached 4.6. Gel formation and elastic modulus were modified by the anionic and linear EPS from strain 2104 as compared with the other strains. Higher values for apparent viscosity, firmness and whey retention were obtained with strains 0131, 2104 and 291 producing EPS with linear or few branching and high molecular weight. This work showed that the gel formation and rheological/physical properties of fermented milk are modified by the structural characteristics of EPS, especially negative charge, flexibility, degree of branching and molecular weight. This study contributes to a better understanding of the EPS structure–function relationship in view to provide tools to develop fermented products with desirable characteristics.

摘要 乳酸菌产生的胞外多糖(EPS)是发酵乳中天然的稳定剂○ EPS调解黏度的能力与EPS的浓度无关,而与EPS的结构和EPS与乳成分相互作用的程度有关○ 因此将EPS用于乳制品中首先要了解EPS结构与功能之间的关系○ 本文对比了不同EPS结构对发酵乳凝胶的形成和流变/物理特性(硬度、表观粘度、弹性模量、收缩作用)的影响○ 选择了不同来源的EPS进行了比较,其中3株Streptococcus thermophilus中HC15 (对照组)、0131(产中性、柔软、分枝EPS)、2104 (产阴离子、硬的、线性EPS),4株Lactobacillus delbrueckii subsp. Bulgaricus中210R (对照组)、11842 (产中性、柔软、分枝EPS)、702074 (产中性、柔软、分枝EPS), 291 (产阴离子、硬的、线性EPS)○ 所有菌株在脱脂乳中培养(42 °C)到pH4.6○ 用菌株2104所产的阴离子和线性的EPS来修正凝胶形成和弹性模量,并与其他菌株进行对比,能够产生线性或者少量分枝及高分子量EPS的菌株0131、2104和291所产生的EPS具有较高的表观粘度、硬度和乳清保持力○ 本研究结果表明通过调整EPS的结构特性,如负电荷、弹性、分枝度和分子量,可以改变发酵乳的凝胶形成和流变/物理特性○ 因此,基于EPS结构与功能之间的关系,将有助于发酵乳制品的质量改善○