产胞外多糖乳酸菌的筛选及其对羊酸乳品质特性的影响

Screening of Exopolysaccharide-producing Lactic Acid Bacteria and Their Influences on the Quality Characteristics of Fermented Goat Yogurt

摘要:

目的利用乳酸菌分泌的胞外多糖（exopolysaccharides，EPS）增强羊酸乳的质构特性与凝胶性能，以缓解其乳清析出问题，提升羊酸乳品质。方法从传统发酵蔬菜中筛选出5株能够产EPS的乳酸菌，测定不同乳酸菌发酵菌对羊酸乳微观结构、质构特性及流变行为的影响。结果经16S rDNA鉴定，菌株S4、N4、S1、C1、C4为植物乳植杆菌（Lactiplantibacillus plantarum），其中菌株C1、C4具备产黏特性。相较于非产黏植物乳植杆菌S4、N4、S1，产黏植物乳植杆菌C1、C4发酵制备的羊酸乳凝胶网络更致密、网络间隙更小，且具有更高的硬度、内聚性、浓稠度和黏度。相较于非产黏植物乳植杆菌S1，产黏植物乳植杆菌C1、C4发酵的羊酸乳弹性模量更高，可有效减轻剪切应力对羊酸乳凝胶体系的破坏作用。持水性和低频核磁共振（LF-NMR）结果表明，产黏植物乳植杆菌C4发酵的羊酸乳持水能力更优，持水率达（58.37±1.66）%，T₂₃为（167.16±13.14）%。结论产黏植物乳植杆菌可显著提升羊酸乳的持水性与黏度，改善羊酸乳的综合品质。

Abstract:

Objective This study used the exopolysaccharides (EPS) secreted by lactic acid bacteria to enhance the textural and gel properties of fermented goat yogurt, aiming to alleviate syneresis and improve the yogurt quality. Method Five EPS-producing strains of lactic acid bacteria were isolated from traditionally fermented vegetables. The influences of fermentation with different lactic acid bacteria strains on the microstructure, textural properties, and rheological behavior of fermented goat yogurt were studied. Result Strains S4, N4, S1, C1, and C4 were identified by 16S rDNA sequencing as Lactiplantibacillus plantarum, among which strains C1 and C4 showed EPS-producing capability. The fermented goat yogurt samples prepared with strains C1 and C4 capable of producing EPS showed denser gel network with smaller gaps, higher hardness, higher cohesiveness, higher consistency, and higher viscosity than those prepared with strains S4, N4, and S1 without the capability of producing EPS. Compared with the fermentation with strain S1, the fermentation with strains C1 and C4 enhanced the modulus of elasticity of fermented goat yoghurt, which reduced the damage caused by shear stress to fermented goat yoghurt. Water-holding capacity and low-frequency NMR (LF-NMR) results showed that the fermented goat yogurt prepared with Lactiplantibacillus plantarum C4 exhibited higher water-holding capacity, with the water-holding rate of (58.37±1.66)% and T₂₃ value of (167.16±13.14)%. Conclusion This study suggests that EPS-producing Lactiplantibacillus plantarum can significantly enhance the water-holding capacity and viscosity of fermented goat yogurt, thus improving the comprehensive quality of fermented goat yoghurt.