Effects Of Silver Carp Muscle Hydrolysates On The Quality And Aroma Characteristics Of Frozen Dough Steamed Bread

Steamed bread is a traditional staple food in most parts of China.Frozen dough technology promotes the industrialization of steamed bread products.Nevertheless,the quality of frozen dough will gradually deteriorate during the frozen storage.Currently,the efficient cryoprotectant is a critical factor to improve the quality of frozen dough products.The previous research showed that silver carp muscle hydrolysates(SCMH)had good cryoprotective activity on yeast and there are no research reports that SCMH as a cryoprotectant was applied in frozen dough steamed bread.Therefore,this paper added SCMH to frozen dough on the basis of previous research and studied the quality and aroma of frozen dough steamed bread as well as exploring its potential antifreeze mechanism of SCMH on yeast.The specific research contents and results are as follows:(1)The changes of moisture content,proof time of dough and specific volume,texture,internal structure of steamed bread subjected 0～6 freeze-thaw cycles were analyzed with SCMH,and trehalose group and the blank group was used as a reference.SCMH and trehalose could mitigate the changes of moisture content and proof time of dough and texture,internal structure,sensory quality of steamed bread during freeze-thaw.After 6 freeze-thaw treatment,the proof time of dough with SCMH 137 min,which of the SCMH and trehalose group was significantly less than that of the blank group(167 min);The specific volume of steamed bread with SCMH was 1.91 mL/g,which of the SCMH was significantly higher than that of the blank group(1.66 mL/g).The hardness,adhesion and chewiness of steamed bread with SCMH were significantly lower than that of the blank group(P<0.05).Furthermore,the color of steamed bread was indenpent on SCMH.However,SCMH had a positive impact on the overall sensory quality of steamed bread after freeze-thaw treatment.Therefore,SCMH had a good cryoprotective effect on frozen dough steamed bread(2)The changes of survival rate,viable cell rate,fermentation ability and growth curve,cell microstructure and transcriptome of yeast when yeast suspension with SCMH was subjected 0～6 freeze-thaw cycles were analyzed,and trehalose was used as a reference.The results showed that the survival rate and gas production capacity of yeast gradually decreased with the increase of the number of freeze-thaw cycles;After 6 freeze-thaw treatment,the yeast survival rate,viable cell rate,the gas production capacity of yeast in dough and sugar liquid with SCMH were 12.2%,40.7%,473 mL·kg-1·h-1 and 167 mL·L-1·h-1,which of the SCMH group was higher than that of the blank group(0%,0%,287 mL·kg-1·h-1 and 67 mL·L-1·h-1).The growth curve results showed the lag phase of yeast wtih SCMH was prolonged by 4 h,while that of the blank group was prolonged by 10 h,and the OD600 value at the stationary phase was only 50%of that the SCMH group.Scanning electron microscopy observed that the surface of yeast cells was wrinkled,sticky and perforated after freeze-thaw treatment,the addition of SCMH and trehalose obviously protected the integrity of cell structure.Transcriptomic analysis indicated that the cryoprotective mechanism of SCMH on yeast was related to promote the expression of fatty acid,glycerol,amino acid and ribosome anabolism in yeast intracellular.After freeze-thaw treatment,ELO2 and ELO3 of fatty acid anabolism with SCMH was up-regulated to contribute to yeast to accumulated unsaturated fatty acids in yeast cells and enhance the fluidity of cell membrane.Furthermore,the up-regulation of relevant genes of anabolic pathway and the down-regulation of genes of catabolic pathway of glycerol,phenylalanine,tyrosine,tryptophan,histidine,arginine and lysine indicated that SCMH increased the expression of glycerol and these amino acids to paly a cryoprotective role.(3)Electronic nose and GC-MS were used to analyse the effects of SCMH on the odor of dough and steamed bread.Electronic nose analysis suggested that the odor characteristics of dough before and after fermentation changed greatly not before and after fermentation but after processing into steamed bread and the addition of SCMH had a significant effect on odor characteristics.GC-MS analysis showed the main volatile compounds in the SCMH included 1-penten-3-alcohol(22.88%),cis-2-penten-1-alcohol(5.78%),2,3-butanediol(32.05%),3,5-octadiene-2-one(2.79%),thioacetic acid(10.43%),O-decyl hydroxylamine(2.82%)and p-xylene(5.74%).The typical fishy compounds in SCMH were hardly detected in steamed bread.Moreover,the variety and content of aroma compounds of the dough and steamed bread with SCMH also increased.The content of 2,3-butanediol,3-Methylthiopropanol,phenylethanol,isoamyl alcohol and 3-hydroxy-2-butanone increased most significantly.This study revealed the effect and mechanism of SCMH on the quality and aroma characteristics of frozen dough steamed bread,and provided a theoretical basis for application of SCMH to improve the quality of frozen dough steamed bread.