Study On The Nutrition And Flavor Characteristics Of Lactic Acid Bacteria Fermented Kiwifruit And Its Breads

In this study,3 strains of ?-glucosidase-producing Lactic acid bacteria(LAB)strains,Pediococcus pentosaceus J28,Lactobacillus harbinensis M12 and M24,isolated from Qu starter were used to ferment kiwifruit substrate,which was used as an ingredient in bread making.The fermentation characteristics of fermented kiwifruit substrates were analyzed.Furthermore,the effects of adding fermented kiwifruit substrate on dough characteristics and baking,nutritional,flavor and storage characteristics of bread were explored.The main research findings and conclusions were as follows:In the kiwifruit substrate matrix,the 3 LAB strains adapted well as confirmed by cell counts of 8.14,8.10 and 8.03 Log CFU/m L for J28,M12 and M24,respectively,after 15.5 h of fermentation at 27.5?.?-glucosidase enzyme activities were 55.1 U/L,51.1 U/L and 48.4 U/L,respectively.The carbohydrate,citric acid,malic acid and quinic acid content significantly decreased in all kiwifruit substrates(KF-J28,KF-M12 and KF-M24)after fermentation by LAB strains.However,lactic acid and acetic acid content increased(p< 0.05).Soluble dietary fiber(SDF)and insoluble dietary fiber(IDF)contents increased and decreased by 41.32%,34.41%and 29.67% and 29.46%,26.27% and 24.44%,respectively,in KF-J28,KF-M12 and KF-M24,after fermentation.In addition,after LAB fermentation,the total phenol content and total flavonoid content of kiwifruit substrates significantly increased by 13.41?30.81% and 5.40%?37.41%,respectively.However,the content of vitamin C decreased.At the same time,the antioxidant activity significantly increased(p<0.05)before and after LAB fermentation of substrate by J28,M12 and M24.However,the highest total phenol,total flavonoid content and antioxidant capacity was observed in KF-J28.In addition,the content of large and small molecular weight peptides,reduced and increased,respectively.The SPME-GC-TOF/MS analysis were used to analyze volatile compounds.For the first time,?-angelica lactone,furfuryl acetate,?-apigenene and pantolactone were found in kiwifruit.The total types and total peak area of volatile flavor compound in the fermented kiwifruit group was higher than the control.After LAB fermentation,the acid,ester,alcohol and terpene content increased,with the most increase observed in ester content.The KF-J28 group has the highest type and content of volatile flavor compound.Dough characteristics results showed that compared with dough containing unfermented fruit(KFD),the free sulfhydryl and disulfide bond content reduced and increased by6.47%?15.58% and 15.29%?22.51%,respectively,while ??amylase activity and ??amino nitrogen content increased by 13.51%?14.86% and 4.94%?18.63%,respectively,in dough prepared with fermented fruit(KFD-J28,KFD-M12 and KFD-M24).Rheology and microstructure of the dough revealed that addition of fermented kiwifruit reduced viscoelasticity of dough and improved the processing performance of dough.In addition,use of fermented kiwifruit promoted the extension of gluten network structure and improved the gas production and gas holding capacity of dough.Among them,the gluten network structure in dough from KFD-J28 group greatly resulting in significantly improved gas production and gas holding capacity of dough.LAB fermented kiwifruit effectively improved the baking and nutritional properties of kiwifruit bread.Among them,LAB J28 fermented kiwi bread(KFB-J28)had the most significant effect,as its texture characteristics and sensory evaluation were close to or higher than wheat bread(WB).In terms of bread baking quality,compared with unfermented kiwi bread(KFB),specific volume of fermented kiwi bread,KFB-J28,KFB-M12 and KFB-M24 increased by 18.59%,17.03% and 8.22%,while the hardness decreased by 11.58%,10.17%and 8.2%,respectively.Image J and sensory analysis found that the KFB-J28 core capsule organization was more uniform,and its overall acceptability was the highest.For the nutritional characteristics of bread,the total phenols,total flavonoids and antioxidant capacity of the five types of bread were as follows,WB <KFB <KFB-M24 <KFB-M12 <KFB-J28.Compared with KFB,protein digestibility and total amino acid content of fermented kiwifruit bread increased significantly(p<0.05),and KFB-J28 had superior amino acid characteristics.Fermented kiwifruit effectively improved the flavor characteristics of bread.The most significant effect was observed in KFB-J28 bread.The odor and taste characteristics of bread measured by electronic nose and electronic tongue and analyzed by PCA showed that addition of fermented and unfermented kiwifruit significantly affected the overall taste and odor characteristics of bread.The overall taste characteristics of the three groups of fermented kiwi bread were not significantly different,but KFB-J28 and the other two groups of breads containing fermented kiwi bread were largely different in flavor and smell.After LAB fermentation,the bitterness and astringency were reduced.In terms of flavor,45,51,74,70 and58 volatile flavor substances were detected in WB,KFB,KFB-J28,KFB-M12 and KFB-M24,respectively.The content of volatile flavor substances in fermented kiwi bread(KFB-J28,KFBM12 and KFB-M24)were 1.38?1.46 and 1.21?1.28 times higher than that of WB and KFB,respectively.Studies on storage characteristics showed that adding fermented kiwifruit delayed the increase rate of bread hardening,starch recrystallization and aging enthalpy,and reduced water loss.Among breads prepared with fermented kiwifruit,the hardness of KFB-J28 bread during the same storage period was generally lower,and the recrystallization,aging and water loss rate are lower.