The Effect Of Natural Compound Strain Fermentation On The Quality Of The Dough

Mianpi is a snack which is widely popular in Northwest region of China due to its unique flavor and rich nutritional value. Using wheat flour as raw material, the production of Mianpi has four steps:kneading into dough, washing gluten, fermenting and steaming. Fermentation is the key step, during which yeasts and lactic acid bacteria are used to improve the quality of Mianpi. However, it is susceptible to external factors which will have an adverse effect on the quality of Mianpi.In order to analyze the microbial flora in fermentation broth, the traditional microbial isolation and culture techniques were used to isolate and identify the dominant strains. Besides, the scanning electron microscope (SEM), X-ray diffraction (XRD), rapid viscosity analysis (RVA), texture properties and sensory evaluation were also used to analyze the changes of starch structure and the quality of Mianpi during fermentation. The conclusions were list as following:(1) During fermentation, the number of yeast is 4.26-6.85 log10 CFU mL-1, lactic acid bacteria is 6.00-7.93 log10 CFU mL-1, so lactic acid bacteria played the important role during fermentation.(2) The study identified the isolated lactic acid bacteria and yeasts, and the results confirmed that the Saccharomyces cerevisiae and Lactobacillus plantarum were the dominant yeast and lactic acid bacteria during fermentation, which was consistent with relevant studies.(3) After fermentation, the starch granules became smaller, bumpy with several pores in surface. Besides, the crystal signal was weakened and the viscosity was decreased, which may be results of microbial gas production and acid hydrolysis.(4) According to sensory evaluation, the sample of M2 fermented for two days had the best quality, and at this moment, the number of yeast was 5.00 log10 CFU mL-1 and the lactic acid bacteria was 7.07 log10 CFU mL-1. The ratio of the two kinds of microorganisms was 1:100, which provides reference to development of the complex fermentation agent.(5) The study used four indexes, including hardness, springing, cohesiveness and chewiness to evaluate the textural properties of Mianpi. Besides, the fermentation index of F2 (pH of 3.12, TTA of 1.76 and viscosity of 42.50 mpa·s) could provide guidence for future production, and the texture properties of M2 (hardness of 6303?6420, cohesiveness of 0.88?0.94, springing of 1.41 and chewiness of 8186?8326) could provide reference for production and quality control of Mianpi.