Comparative Studies On Fermentation Properties About Regional Characteirstic Sourdough Steamed Breads And Their Preferred Lactobacillus

Steamed bread fermented by traditional sourdough is very popular amomg consumersbecause of its good taste and unique flavor. Lactobacillus (LABs) plays an important role intaste and flavor formation. There are a lot of traditional characteristic sourdoughs in China.However, the study about different traditional sourdough is narrow and the application ofstrains isolated from traditional sourdoughs is very limited. In this paper, characteristicsourdoughs from wheat cultivation&steamed bread consuming area as research objects,studies have been focused on sorudough qualities and their products qualities. Then LABsmicroorganisms in excellent traditional sourdough and their effects on qualities of wheatsteamed bread and buckwheat steamed bread were explored. The main contents and results asfollows:1. We collected six samples from Shandong, Henan and Hebei and explored the qualitiesof their fermentation activities, acid production capacities and their products’ specific volume,texture and sensory evaluation. Fermentation activity and acid production capacity resultsshowed that sourdoughs from Qingdao Shandong, Zhumadian Henan and Xingtai Hebei hadhigher fermentation activity (2.01,1.96and1.95respectively) and moderate acid productionrate. There were significant difference on specific volume and texture among these traditionalsteamed breads. Zhumadian and Xingtai had larger specific volume (2.52mL/g and2.51mL/g rspectively). Sensory evaluation showed that Zhumadian and Xingtai had higher scorein appearance, skin color, flavor and overall acceptability. The total score was Xingtai(87.45)>Zhumadian (87.18)>Qingdao (84.81)>Baoding (84.42)>Nanyang (83.97)>Jining(81.16). Sourdoughs collected from Zhumadian and Xingtai highlighted superior potential forfermenting the steamed bread.2.The flavor compounds of steamed breads made by these traditional sourdoughs wereanalysed by GC-MS. The results showed that steamed breads made by sourdoughs fromdifferent origins demonstrated significantly difference in flavor types and contents. Althoughunique flavor profiles with compounds such as esters, aldehydes and alkenes detected in eachsample, the abundance of total substance was Zhumadian> Xingtai> Nanyang> Qingdao>Jining> Baoding. Steamed breads made by Zhumadian and Xingtai sourdoughs detectedmore unique flavour substracts including acetic acid-methyl-1-butyl, octyl aldehyde, hexylacetate,2,3-dihydro-furanone, caprylic acid.3. LABs was isolated from Zhumadian Henan and Xingtai Hebei sourdoughs.5representative LABs were rescreened by producing acid and flavor. They were used forfermenting steamed breads. The results showed that different LABs fermentation had differenteffects on specific volume, texture and sensory score of steamed bread. Strain ZL6and XL3improved these qualities significantly. By16S rDNA indentification, the results showed ZL6belonged to Lactobacillus brevis, XL3belonged to the genus of Lactobacillus planetarium.4. The preferred ZL6, XL3and LP Biogreen300were applied to wheat and buckwheatmatrix for studing their growth and acid production ability in different matrices and the effectsof different LABs fermentation on wheat and buckwheat steamed breads qualities. The results showed that three LABs grew well in both of the matrix. Sourdough significantly improvedthe gas retention capacity and holding capacity, increased the steamed breads specific volume.For wheat dough, ZL6behaved better than LP and XL3in improving dough height Hm, gasretention R, texture and increasing the sensory score. While for buckwheat dough, LP andXL3improvement were more pronounced. LABs fermentation could significantly enhancethe DPPH and ABTS radical scavenging capacity of wheat and buckwheat dough and theirsteamed bread. The amount of addition was ZL6> XL3> LP. Heating would decrease thesteamed breads’ antioxidant activity significantly. while LABs fermentation, particularly ZL6and XL3, could improve this situation. Analysis the hardness, moisture migration andamylopectin retrogradation enthalpy of steamed bread during storage, we found that LABsfermentation could delay the hardening rate and suppress amylopectin recrystallization ofsteamed bread. ZL6in delaying the wheat steamed bread staling worked better than LP andXL3, whlie LP and XL3were more obvious in buckwheat system.5. The impacts of different LABs fermentation on wheat and buckwheat steamed breadflavor characteristics were investigated by GS-MS. The results showed that LABsfermentation increased both the total content and flavor compounds types. Compared tocommon wheat steamed bread, the total amount of flavor compounds of wheat steamed breadincreased53.11%,61.06%and56.92%respectively after adding LP, ZL6XL3fermentedsourdough. For buckwheat steamed bread, the total amount of flavor increased24.16%,36.29%and26.70%respectively. Introduction of sourdough significantly increased the content ofethyl esters, acid-2-hydroxy ethyl caprylate, ethyl formate, heptyl ester of ethanol,2-methyl-pentyl alcohol,2/3-methyl butanol, pentanol,1-hexanol, acetic acid,3-methyl-butyric acid, caproic acid, caprylic acid, aldehydes and ketones compounds such as3-hydroxy-2-butanone, furfural,2-heptenal. The use of wheat sourdough bread also facilitatedthe generation of lactone compound including5-phenyl-2(3H)-furanone and5-butyl-2(3H)-furanone. For ordinary buckwheat bread, including nonyl ketone,2-nonenal.