| Lactic acid bacteria play a dominant and decisive role in the formation of traditional sour dough flavor,and will greatly affect the quality of steamed bread.The research focuses on flavor differences from sour dough in different regions,and the microbial communities of lactic acid bacteria from sourdough from different regions was comprehensively revealed by combination of high-throughput sequencing and culture-dependent methods.Effects of lactic acid bacteria on volatile flavor compounds of sour dough were preliminarily analyzed and the dominant strains were selected as starter cultures for steamed bread production compared to the traditional sourdoughs.This study provides a theoretical basis for the industrialization of traditional steamed bread and it's a great significance to promote the industrialization of staple food.The following are main results.(1)The flavor characteristics of the sourdough in the Northwest District of China.Two sourdoughs,one from Gansu Province and another from Xijiang area,were sampled for the present study.Compared to yeast-based steamed bread,sourdough-based steamed bread is superior in hardness,adhesiveness,flexibility and chewiness.Sourdough-based steamed bread has better surface area fraction,average diameter and density of stomata than yeast-based steamed bread.Sourdough contributed rich flavor compounds to steamed bread,but significant difference in volatile flavor substances took place between the two sourdoughs.(2)Diversity and structural characteristics of microbial flora in sourdough from different sources.A total of 19 strains of lactic acid bacteria were isolated from Gansu sourdough sample,in which Lactobacillus plantarum and Pediococcus pentosus were dominant species,accounting for 42.11% and36.84%,respectively.A total of 16 strains of lactic acid bacteria were isolated from Xinjiang sourdough sample,in which Lactobacillus plantarum was the dominant species,accounting for 75.00%.Highthroughput sequencing further confirmed such results.All alpha diversity indices were lower in Xingjiang sourdough than in Gansu sourdough.It is clear that the species diversity from Gansu sourdough is more abundant.The difference coefficient between Xingjiang sourdough was 0.023,indicating that no difference in species diversity was observed.The value of the dissimilarity coefficient between Xingjiang and Gansu sourdoughs was 0.232,indicating that a significant difference in species diversity between them occurred.Lactobacillus plantarum strain 2-2 produced the most acidity and grew fast in Gansu sourdough,and Lactobacillus plantarum strain 18 showed the best acid activity and growth performance in Xinjiang sourdough.Compared to the acid-production ability of different strains during the fermentation process of sourdough dough,Lactobacillus plantarum strains were regarded as the strongest acid producer.(3)Flavor characteristics of different lactic acid bacteria fermentation dough.The comparison of dough fermented with dominant strains and traditional sourdoughs was made.It was seen that the dough fermented with Lactobacillus plantarum strains was significantly superior in elasticity and chewability to other fermented doughs.the steamed buns fermented by Lactobacillus plantarum strain 2-2 is smaller in its stomata size,larger in density,and softer in internal taste.The volatile profiles of sourdoughs were similar,but individual volatile compounds between the sourdoughs of Gannsu and Xingjiang regions were detected.These results point out that the differences in the microflora and the dominant strains lead to the difference in the quality of steamed breads from region to region.In summary,this work systematically analyzed the flora structure of sourdough in Xinjiang and Gansu regions.It provides a theoretical basis and technical support for the use of dominant lactic acid bacteria blend cultures to the processing of traditional steamed bread.Of course,our work should provide a new insight for the transformation of the old sourdough to industrial production. |
PDF Full Text Request