Characterization of a fermented dairy, sour cream: Lipolysis and the release profile of flavor compounds.

Lipolysis and flavor development during fermentation of sour cream were studied by evaluating the physicochemical changes, sensory differences and volatile components. The fermentation caused significant changes in pH, viable count and sensory evaluation. The peroxide value (POV) decreased after reaching the maximum value of 1.07 meq/kg at 15 h, while thiobarbituric acid reactive substances (TBARS) increased continuously with the accumulation of secondary oxidation products. The Free fatty acids (FFAs) in sour cream were mainly myristic, palmitic and stearic. GC-IMS was used to identify the flavor properties. A total of 31 volatile compounds were identified, among which the contents of characteristic aromatic substances such as ethyl acetate, 1-octen-3-one and hexanoic acid were increased. The results suggest that lipid changes and flavor formation in sour cream are influenced by fermentation time. Furthermore, flavor compounds may be related to lipolysis such as 1-octen-3-one and 2- heptanol were also observed.

GC-MS and GC×GC-ToF-MS analysis of roasted / broth flavors produced by Maillard reaction system of cysteine-xylose-glutamate.

Maillard reaction products (MRPs) with roasted/broth flavors were prepared and analyzed for the resulting flavor differences. The identification of volatile compounds in MRPs was carried out by GC-MS and GC × GC-ToF-MS. A total of 88 compounds were identified by GC-MS; 130 compounds were identified by GC × GC-ToF-MS, especially acids and ketones were identified. Principal component analysis (PCA) was used to visualize the volatile compounds, and the roasted/broth flavors were differentiated. The contents and types of pyrazines were more in roasted flavors; thiol sulfides and thiophenes were more in broth flavors. All in all, the differences in volatile compounds producing roasted/broth flavors were studied through the cysteine-xylose-glutamate Maillard reaction system, which provided a theoretical basis for the future use of Maillard reaction to simulate meat flavor.

Enzymatic hydrolysis of flaxseed (Linum usitatissimum L.) protein and sensory characterization of Maillard reaction products.

We aimed to simplify the enzymolysis process for flaxseed protein hydrolysates production as Maillard reaction products (MRPs) to generate different flavor characteristics. More than 50% activity of immobilized enzymes (Alcalase and Flavourzyme) was retained after repeated use. Subsequently, after five weeks, the activities of the immobilized enzymes were also observed to be higher after storage at 4 °C. The optimum conditions for production of flaxseed protein hydrolysates using sequential enzymatic hydrolysis were as follow: 3,000 U/g of Alcalase at 60 °C and pH 8.0 for 2 h and 120 U/g of Flavourzyme at 50 °C and pH 6.5 for 2 h. Partial least squares regression analysis revealed that resulting peptides with the molecular weight (MW) higher than 1,000 Da could improve the mouthfulness and stability in umami soup; whereas, peptides with MW of 128-1,000 Da mainly contributed to the generation of meat-like flavor compounds with a significant effect on umami taste and bitterness.