Material Evolutionary Pattern And Regulation Of Fermented Goat Milk

Fermented goat milk is a high-quality protein source that meets consumer demands in the post-epidemic era in terms of speciality cuisine,household consumption and medical needs.However,the development of the goat milk industry is currently constrained by imbalanced flavors,which stem from the synergistic effect of short and medium chain free fatty acids and substances such as aldehydes,ketones,and alcohols.Balancing flavor and enhancing nutrition are the foundation for enhancing the core competitiveness of goat milk products and consolidating the long-term healthy development of the industry.Therefore,fermentation models combining various processing technologies were designed to systematically regulate the flavor and nutritional quality of goat milk during the fermentation by tracking the material evolution under each mode and analyzing the response of fermentation-assisted technologies and product quality.A data matrix of 1298 metabolites was constructed based on untargeted metabolomics analysis of goat milk before and after fermentation to investigate the response of goat milk system during fermentation.After statistical and chemometric analyses,significant difference substances were screened,and mapping pathways were integrated.It was found that fermentation accumulated polyunsaturated fatty acids and amino acids such as tyrosine,tryptophan,and proline in the final product through amino acid metabolism,TCA cycle and lipid oxidation metabolism,which improved the nutritional quality and bitterness perception of goat milk.Accumulated bitter compounds（L-methionine,tyrosine,valine）and stinky compound（decanoic acid）reduced the flavor quality and consumer acceptability of fermented goat milk.Design a combined browning goat milk fermentation model to introduce caramel flavor and browning to improve the flavor quality of fermented goat milk.Analysis of various goat milk samples before and after brown fermentation using biomimicry techniques and sensory evaluation,revealed that browning reduced sample brightness and increased consumer preference.Subsequent fermentation improved the brightness,and reduced the perception of astringency,bitterness and sweetness.Furthermore,based on the intelligent hybrid z-score standardization-principal components algorithm-multimodal denoising autoencoder,fused the biomimetic and spatial multi-omics data of brown goat milk and brown goat yogurt,and it was clear that the fermentation process significantly improved the flavor and nutritional quality through the tricarboxylic acid cycle-urea cycle-glycolysis composite pathway.Based on the lipid profile of goat milk samples collected before and after fermentation by high-throughput quantitative lipomics,488 lipid molecules were identified.144 lipid molecules with significant differences were mapped to multiple databases,revealing that fermentation up-regulated the content of polar lipids（sphingomyelins,phosphatidylcholines,phosphatidylethanolamines and simple Glc series）and neutral lipids（tiradylglycerols and diradylglycerols）through glycerophospholipid metabolism and sphingolipid metabolism.Subsequently,a fermentation model combined with magnetic field was designed to selectively regulate the neutral lipid content in fermented goat milk samples.Lipidome evolution of goat milk during traditional and magnetic field enhanced fermentation was comprehensively identified and quantified,and it was found that compared with the traditional mode,the content of tiradylglycerol in magnetic field enhanced fermentation decreased from 1752.47 to 784.78 μg mL^-1 and diradylglycerol from 60.36 to 24.89 μg mL^-1.Magnetic field enhanced fermentation also increased the ceramide content and decreased saturated fatty acid content.After statistical and chemometric analysis of lipid molecules under different fermentation modes,146 significantly different lipids were screened,and it was clear that magnetic field mainly regulated glycerophospholipid metabolism,sphingolipid metabolism,linoleic acid metabolism,α-linolenic acid metabolism,glycosylphosphatidylinositol-anchor biosynthesis,glycerolipid metabolism and arachidonic acid metabolism pathways control the neutral lipid accumulation of fermented goat milk.Integrating the above results,a fermentation model combined with magnetic field and browning was designed to realize the systematic regulation of flavor and nutritional quality.The casein-glucose simulation system was designed to clarify the inhibition mechanism of magnetic field on browning.The UV absorption and modified proteomics analysis were performed on the simulation system and actual samples with and without magnetic field.It was found that magnetic field treatment could down-regulated the glycosylation of simulation system and actual samples by inducing protein aggregation,on the premise of not reducing sensory expectations,masking the glycosylation sites,changing the accessibility of lysine and arginine,and to avoid the formation of late glycosylation end products.Based on chemometrics,statistical analysis and bioinformatics,the comprehensive data set of metabolomics and proteomics was further processed to clarify that the mechanism of magnetic field enhancing the flavor of brown goat yogurt samples and reducing neutral lipid accumulation was the directional regulation of glycerophospholipid-sphingolipid metabolism,amino acid metabolism,TCA cycle pathway and other energy metabolism related biological events.In summary,this study focuses on fermented goat milk and characterizes the impact of fermentation models combined with different processing technologies on its flavor and nutritional quality.Through spatial multi-omics techniques,the evolution mechanism of fermented goat milk substances was analyzed,and it was clarified that the goat milk fermentation model combined with magnetic field and browning is an effective method for achieving systematic regulation of flavor and nutritional quality.These results can provide important scientific basis for effectively regulating the flavor and nutritional quality of fermented goat milk,and have important reference value for the optimization and development of new technologies in goat milk processing.