植物乳杆菌YW11胞外多糖对酸乳加工特性的影响

Processing Properties of Yogurt Affected by the Exopolysaccharide Produced by Lactobacillus plantarum YW11

研究植物乳杆菌YW11胞外多糖(exopolysaccharide,EPS)对酸乳发酵过程中菌株生长、产酸速率和微流变特性,以及产品质构和风味特性的影响,结果表明,不同添加量(0.05、0.15、0.25 mg/g)的EPS对发酵过程菌株(保加利亚乳杆菌、嗜热链球菌)的生长和产酸速率无明显影响。添加EPS对发酵过程中样品的弹性指数(elasticity index,EI)、宏观黏度指数(microviscosity index,MVI)和流动性指数(fluidity index,FI)具有不同的影响,随着EPS添加量的增加,EI逐渐降低,MVI升高,而FI无明显变化。不同添加量的EPS均可提高酸乳的持水力,其中以EPS-0.25组样品的持水力最大,达57.93%;随着EPS添加量的增加,酸乳的硬度降低,最低值为10.08 g;黏力增加,最大值为9.57 g;而内聚性变化不大,在0.45~0.48之间。添加EPS使酸乳中蛋白交联结构增强,蛋白颗粒更小,网络结构中存在较大孔隙结构。添加适量的EPS能够促进酸乳风味物质如醛类、酸类和酯类等化合物的形成。本研究有助于进一步了解植物乳杆菌EPS对酸乳加工特性的影响,并基于EPS的应用提升酸乳品质。

The effect of the exopolysaccharide(EPS)from Lactobacillus plantarum YW11 on microbial growth,acid production rate and microrheological properties during yogurt fermentation and the texture and flavor characteristics of the final product was studied.The results showed that there was no significant effect of different concentrations(0.05,0.15 and 0.25 mg/g)of the EPS on the growth of Lactobacillus bulgaricus and Streptococcus thermophilus or acid production rate during the fermentation process.Addition of the EPS had different effects on the elasticity index(EI),microviscosity index(MVI)and fluidity index(FI)of yogurt during fermentation;with increasing addition of the EPS,the EI decreased gradually,the MVI increased,whereas the FI did not change significantly.The water-holding capacity of yoghurt could be improved by adding different amounts of the EPS,reaching the maximum of 57.93%at an EPS concentration of 0.25 mg/g.With increasing addition of EPS,the hardness of yoghurt decreased to the lowest value of 10.08 g,the viscosity increased to the highest value of 9.57 g,while the cohesiveness changed little,varying between 0.45 and 0.48.Addition of EPS enhanced the cross-linked structure of proteins in yoghurt,made the protein particles smaller,and produced larger pores in the network structure.Addition of an appropriate amount of the EPS could promote the formation of flavor compounds such as aldehydes,acids and esters.The results of this study will be helpful for further understanding the effect of L.plantarum EPS on the processing characteristics of yogurt,and the application of the EPS to improve yoghurt quality.