Effects Of Different Sourdoughs On The Quality Of Potato Steamed Bread And The Preparation Of Composite Starter

As one of the important products of Potato Staple Food Strategy in China,potato steamed bread has been circulated in the market at present,but it still needs improvemnets regarding taste,texture,and flavor.Sourdough is a traditional starter composed of many different microbes.Interactions of various microorganisms in sourdough can effectively improve the quality of fermented products.In this study,five kinds of traditional Chinese sourdough(CTS1 to CTS5)were taken as the research objects,the nutritional components and microbial diversity of CTSs were comprehensively analyzed by various physical and chemical analysis methods,as well as high throughput sequencing technology.The best CTS for potato steamed bread was screened by statistical analysis based on the quality comparison of potato dough and steamed bread fermented by different CTSs.Finally,taking the selected sourdough as the research object,the dominant microbes were isolated and preliminary compounded,and the effects of different compounding ratios on the quality characteristics of potato steamed bread were compared and studied.This study aims at providing theoretical support for the application of composite starter in the production of potato steamed bread.The main results are as follows:(1)The crude protein,total starch,dietary fiber in five CTSs were 8.15~14.38%,65.58~77.26%,0.87~3.62%,respectively.Their pH ranged from 3.82 to 6.22.CTS1 showed the highest total polyphenol content(0.22 mg CAE/g DW)and CTS5 had the best antioxidant activity(2.94 ?g TE/mg DW).The bacteria in sourdough were mainly Pediococcus and Lactobacillus,while the fungi were mainly Wickerhamomyces and Saccharomyces.CTS1 showed the highest abundance and diversity of bacterial flora(ACE:102.16,Chao1:101.6;Simpson:0.34,Shannon:1.39).The highest abundance of fungi was CTS2(ACE: 121.84,Chao1: 116.60),and the highest diversity of that was CTS5(Simpson: 0.31,Shannon: 1.47).(2)Among the five kinds of sourdough,CTS1 had the best rheological properties,and the pH of 30% potato dough fermented by that was lowest(4.31).The sourdough fermentation could degrade the protein of potato dough in different levels,and CTS1 had the best ability.There were significant differences regarding the specific volume,height-diameter ratio,color and texture of different sourdough potato steamed bread(SPSB),while CTS1 and CTS4 showed better characteristics than commercial yeast.Sourdough fermented steamed bread have richer flavor components than their commercial yeast counterparts.Although there are significant differences in volatiles content,alcohol and aldehyde are dominant,and their relative odor activity values are higher.Sourdough fermentation decreased the content of protein,dietary fiber,mineral elements and antioxidant activity of 30% potato steamed bread,but the content of resistant starch was higher(27.41%~44.07%)and the predicted glycemic index was lower(65.93~72.43).(3)CTS1 was the most suitable sourdough for making 30% potato steamed bread.The isolated dominating yeast was Saccharomyces cerevisiae,while the primary lactic acid bacteria species was identified as Lactobacillus plantarum.Amount of Saccharomyces cerevisiae that suitable to make composite starter was between 1-2%,as they resulted in the highest dough height and gas production(14.4~18.9 mm;617~853 mL).For Lactobacillus plantarum,the suitable addition amount was 0.5% to 2% because of the relatively high lactic acid production(3.32~4.83 mg/g).By comparing the technological characteristics of potato steamed bread made by different composite starters,the ideal ratio of Saccharomyces cerevisiae to Lactobacillus plantarum was set as 0.5% to 1.5% as the resulted potato steamed bread had the highest specific volume(2.24 mL/g).In summary,sourdough is rich in nutrients and diverse in microbial composition.It can be used as a starter to improve the quality characteristics of potato steamed bread and the improvement effect depends on the varieties of specific sourdough.The composite starter based on sourdough has great potential in the industrial production of potato steamed bread.