Quality Promotion Of The Bran-enriched Steamed Bread With Mixed Strains From Sourdoughs

The species of strains is one of the main factors affecting the quality of steamed bread.The strains of Yeast(YCY5-2 Saccharomyces cerevisiae,NCBI accession number KX197410)and Lactobacillus(ZKL10-4,Lactobacillus crustorum,NCBI accession number KX197413)isolated from different sourdoughs which was the main source of the fermentation strains.They were applied in tartary buckwheat bran steamed bread initially,clarified the proportion of mixture and fermentation process.But it was not study the quality promotion mechanism,fermentation mechanism and the storage characteristics fermented with mixed strains.Moreover,whether the other bran bread(such as wheat bran steamed bread and oat bran steamed bread)have the same effect as tartary buckwheat bran steamed bread was not study.In this paper,the affectation of different strains on the quality of tartary buckwheat bran bread were studied.And then,the effects of mixed strains on the quality and the metabolic process of tartary buckwheat bran were studied.Finally,it was studied the effect of mixed strains on the quality of different bran bread and the changes in storage process.The results are as follows:1.Respectively used Saccharomyces cerevisiae and Lactobacillus crustorum mixed strains(KF),Angel instant dry yeast and Lactobacillus crustorum mixed strains(KAL),Saccharomyces cerevisiae(KYY)and Angel instant dry yeast(KA)to ferment the buckwheat bran steamed bread,then compared with their basic nutrient composition,specific volume,texture,sensory scores,antioxidant properties and volatile flavor components.It showed the lowest starch content(70.28±0.61 g/100g)and the highest protein content(8.66±0.01 g/100g)in KF group.The specific volume of KF(2.62±0.067 m L/g)was significantly higher than other groups.In total physical structure,the textural properties and the sensory score of KF group was the best.The scores was:KF(82.9)>KYY(78.9)>KAL(76.3)>KA(72.0).In antioxidant properties,the total flavonoids(137.71±6.894 mg Rutin/100g),total phenolics(2592.25±55.280 mg GAE/100g),DPPH,ABTS+,scavenging ability,[OH],O2-and total reducing ability of KF were higher than that of KAL,KYY and KA.In flavor compounds,the KA,KAL,KYY and KF groups were distinguish detected in 54,51,60 and 79 flavor components,and the content of aldehydes,furanes,hydrocarbons,alkanes,phenols,ethers and ketones which in the KF group were higher than the relative levels of KA,KAL,KYY;except the highest content of alcohol in KYY group.Furthermore,it also were detected four special esters(nonanolactone methacrylate,ethyl palmitate,cyclopentadecanolide,ethyl oleate).The results showed that the fermentation of Saccharomyces cerevisiae and Lactobacillus crustorum could significantly improve the quality of tartary buckwheat bran streamed bread,and the quality of steamed bread ferment with Saccharomycescerevisiae was good as well.2.Studied and analyzed the four strains fermented tartary buckwheat bran doughs in the process of metabolic changes.The fermentation activity of KF(1.870±0.070)and KYY(1.777±0.011)was highest at 5th hour,it was significantly higher than the KA and KAL,(p<0.05).The total number of yeast colonies showed an increasing tendency firstly,and then stabled.While the lactic acid bacteria colonies increased firstly and then decreased.During the process of dough fermentation,the trend of the pH was decreased,but the TTA was increased steadily.The glucose content of the doughs with different strains increased firstly and then decreased.At the late stage of fermentation,the content of glucose in the sample KF(0.654±0.040 mg/g)was the lowest which followed by KYY(0.790±0.027 mg/g).At the beginning of fermentation,there was almost no lactic acid and acetic acid,then the content of lactic acid and acetic acid increased as the fermentation progressed.The amino acid content increased firstly and then decreased in KA samples,but it decreased at first,and then increased,decreased at last in the KF,KYY and KAL groups.The overall tendency was increased firstly and then decreased.The content of total flavonoid(278.27±6.01 mg Rutin/100g)and total phenolics(2616.42±10.01 mg GAE/100g)in KF were the highest at the later period of fermentation,it was 1.57 times,1.35 times higher than that of KA dough respectively;Changes of rutin and quercetin contents tendency in KF and KA samples were the same.The rutin content decreased at first,and then increased;while the content of quercetin increased continuously.The rutin and quercetin in KF samples(35.02±1.90 mg/100 g,247.11±11.89 mg/100g)was significantly higher than that of the KA sample(18.12±1.01mg/100 g,210.72±10.90 mg/100g).3.Used Saccharomyces cerevisiae and Lactobacillus crustorum mixed strains fermented wheat bran steamed bread(MF)and oat bran steamed bread(YF),and used angel dry yeast fermented wheat bran steamed bread(MA)and oat bran steamed bread(YA)as comparisons.Through compared the basic nutritional content,specific volume,texture analysis,sensory assessment and antioxidant activity.The affection of starch and protein content in wheat bran and oat bran bread was the greatest in mixed stains group.The specific volume of the MF sample(2.247±0.047 mL/g)was the highest,and had significant differences with other samples;the specific volume of the YF sample was also higher than the YA.The MF samples had the lowest hardness and the best elasticity,the sensory scores were :MF(88.1)>YF(87.2)>MA(81.4)>YA(80.9).The DPPH scavenging ability,[?OH] and total reducing power of YF,MF samples were significantly higher than YA and MA samples,respectively.The total phenol content in YF samples(321.27±6.966 mg GAE/100g)was the highest,and the content of flavonoids in MF samples(40.53±1.654 mg Rutin/100g)was the highest.Therefore,the mix strains of Saccharomyces cerevisiae and Lactobacillus crustorum can not only improve the quality of tartary buckwheat bran steamed bread,but also enhance the application of wheat bran steamed bread and oat bran steamed bread.4.Used Saccharomyces cerevisiae and Lactobacillus crustorum complex strains fermented wheat bran steamed bread,oat bran steamed bread and buckwheat bransteamed bread respectively,stored at 25? and 4?,compared the six bran steamed bread in moisture content,gelatinization,texture traits,starch recovery and microbial changes:(1)During the storage of different bran steamed bread at 25?,the moisture content of steamed bread showed a decreasing tendency firstly,and then increased gradually.At the 120 th hour,the moisture content of YA was the highest(43.64±1.02)%.With the storage time last long,the texture traits of all samples were increased significantly and the compressive relaxation were decreased obviously.At the 96 th hour of storage,their texture traits were:KA>YA>MA>YF>MF>KF,the compressive relaxation were:KA<MA<YA<MF<YF<KF.The degree of gelatinization was decreased in the storage.During the storage,the enthalpy ?H increased gradually;all samples of the aging enthalpy were not detected at 0h;but the amylopectin increased rapidly at0-36 th hour,the trend was stabled after 36 h.The ?H value was KF<MF<YF<YA<MA<KA when they stored for 96 h.The starch aging of tartary buckwheat bran steamed bread fermented with mixed strains was the lowest.The total number of colonies and lactic acid bacteria in the steamed bread were the highest in the pre-storage period,and there was an increasing trend in the later storage period.The total number of colonies was 6.0 Log cfu/g at 72 th hour,but the total number of colonies in the tartary buckwheat bran bread was within 6.0 Log cfu/g,and the microbial proliferation rate decreased gradually after 72 h.(2)The moisture content and gelatinization value of different bran steamed bread stored at 25? were the same as 4?.With the increasing of storage time,the texture traits of the steamed bread increased significantly,the compressive relaxation were significantly reduced in the 4 days of storage,and the trend of decreasing was slower after 4 days.The total number of colonies,lactic acid bacteria and mold showed an increasing tendency after 8 days.The E.coli was not detected during storage period.At the twelfth day of storage,the total number of colonies in tartary buckwheat bran steamed bread(1.5±0.1 Log cfu/g)was significantly lower than that of other bran steamed bread,and the molds were less than 2.3 Log cfu/g.The results showed that quality changes of tartary buckwheat bran bread was the smallest,followed by wheat bran steamed bread fermented with mixed strains,when stored at 4? and 25?.It claimed the bran bread fermented with mixed strains can be maintain a better storage properties.