Study on the optimization of sourdough starter with high activity

Objective: This research aimed to study the preparation of standardized and stable sourdough starter, to explore the effects of different drying processes and protective agents on the survival rate of sourdough, and examine its storage activity. Methods: A variety of fruits were selected to prepare sourdough, the fermentation process was studied, and the strains were isolated and identified by ITs and 16s gene sequencing in the database. The optimum scheme was obtained by selecting the drying process, sample state and protectant formulation with the activity after drying and storage activity as indexes. Results: It was found that the bread prepared with grape sourdough had the best specific volume, porosity and hardness. On this basis, the drying survival rate and storage activity were used as indexes to study the combination of drying protectants. Finally, two better protective agent formulations were obtained by orthogonal experiment: ① Freeze-dried the dominant pure bacterial solution, skim milk 35%, maltodextrin 7.5% and trehalose 25%, and the drying survival rate was about 93%. ② Spray dried sourdough germ whole, skim milk 35%, maltodextrin 10% and trehalose 15%, and the drying survival rate was about 90%. Conclusion: It was found that the storage activity of the spray-dried starter decreased rapidly, while that of the freeze-dried starter was slower.