Characterization of the key flavor compounds in cream cheese by GC-MS, GC-IMS, sensory analysis and multivariable statistics.

The aroma types of cream cheese affect its commercial value and consumer acceptability. However, the types of volatile substances and sensory characteristics of cream cheese at different fermentation stages are still unclear. Therefore, in this study, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) were used to analyze the volatile substances in cream cheese fermentation. Orthogonal partial least squares discriminant analysis (OPLS-DA), odor activity value (OAV), relative odor activity value (ROAV) and variable projection importance (VIP) were used to identify the characteristic flavor substances in cream cheese fermentation. Finally, the relationship between key flavor substances and sensory characteristics was determined by partial least squares (PLS) analysis. A total of 34 and 36 volatile organic compounds were identified by HS-SPME-GC-MS and HS-GC-MS, respectively, and 14 characteristic flavor substances were found, based on VIP, ROAV and OAV models. Combined with sensory analysis and flavor substance changes, it was found that the cream cheese fermented for 15 d had the best flavor and taste. This study reveals the characteristics and contribution of volatile substances in cream cheese at different fermentation stages, which provides new insights into improving flavor and quality control.

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.

Effects of Reducing Sugars on the Structural and Flavor Properties of the Maillard Reaction Products of Lycium barbarum Seed Meal.

Lycium barbarum seed meal contains a variety of bioactive compounds, but the use of L. barbarum seed meal in the food industry is rare. This study aimed to evaluate the effect of reducing sugars on the structural and flavor properties of the Maillard reaction products (MRPs) of the Lycium barbarum seed meal hydrolysate (LSH). The results showed that the flavors and tastes of the MRPs were affected by reducing sugars. In comparison to oligosaccharides, monosaccharides were more suitable for the development of MRPs with good sensory qualities. The structural characteristics of L. barbarum seed meal precursor MRPs were also affected by reducing sugars. The MRPs produced with the participation of monosaccharides had higher ultraviolet absorption and browning than the MRPs produced with oligosaccharides. The molecular weights of the MRPs were found to be 128-500 Da and 500-1000 Da. Compared to the MRPs made from other sugars, xylose-meridian products (X-MRPs) had a stronger meaty flavor. The mellowness and continuity of the MRPs made from monosaccharides were superior to those made from oligosaccharides. The MRPs formed by L. barbarum seed meal exhibited the characteristics of umami and meat flavor. MRPs with better flavors may be used to develop new types of seasoning salts.

Gut modulatory effects of flaxseed derived Maillard reaction products in Sprague-Dawley rats during sub-chronic toxicity.

Our study aimed to understand the effects of Maillard reaction products (MRPs) intake on intestinal health, in vitro digestion, and fermentation metabolites in Sprague-Dawley (SD) rats. MRPs promoted the digestion of pepsin, but was not conducive to the subsequent in vitro digestion of trypsin. MRPs ingestion increased the propionate in intestine, but it could not change the branched-chain fatty acids (BCFAs) and short-chain fatty acids (SCFAs). However, MRPs ingestion led to an increase in the Lactobacillus abundance in gut. In the high-dose groups, the abundance of genes in partial amino acid and monosaccharide metabolism increased, while in lipid metabolism decreased compared with the middle dose groups. Therefore, the absorption of MRPs was lowered than that of protein and carbohydrates. Through functional predictive analysis, our study could reveal the effects of long-term intake of MRPs on intestinal health in SD rats.

Analysis of key precursor peptides and flavor components of flaxseed derived Maillard reaction products based on iBAQ mass spectrometry and molecular sensory science.

Flaxseed derived Maillard reaction products (MRPs) have typical meaty flavor, but there is no report on comparison of their amino acids and peptides reactivity. The peptides and amino acids of flaxseed protein hydrolysates were separately collected by G-15 gel chromatography. Taste dilution analysis (TDA) showed that peptides-MRPs had high umami, mouthfulness, and continuity enhancement. Further, LC-MS/MS revealed that flaxseed protein hydrolysates consumed 41 peptides after Maillard reaction. Particularly, DLSFIP (Asp-Leu-Ser-Phe-Ile-Pro) and ELPGSP (Glu-Leu-Pro-Gly-Ser-Pro) accounted for 42.22% and 20.41% of total consumption, respectively. Aroma extract dilution analysis (AEDA) indicated that formation of sulfur-containing flavors was dependent on cysteine, while peptides were more reactive than amino acids for nitrogen-containing heterocycles. On the other hand, 11 flavor compounds with flavor dilution (FD) ≥ 64 were identified for flaxseed derived MRPs, such as 2-methylthiophene, 2-methyl-3-furanthiol, furfural, 2-furfurylthiol, 3-thiophenethiol, thieno[3,2-b] thiophene, 2,5-thiophenedicarboxaldehyde, 2-methylthieno[2,3-b] thiophene, 1-(2-methyl-3-furylthio)-ethanethiol, 2-methylthieno[3,2-b] thiophene, and bis(2-methyl-3-furyl)-disulfide. In addition, we further demonstrated the flavors formation mechanism of flaxseed derived MRPs.

Aromatic effects of immobilized enzymatic oxidation of chicken fat on flaxseed (Linum usitatissimum L.) derived Maillard reaction products.

To control the oxidation in chicken fat by immobilized lipoxygenase (LOX), Maillard reaction products (MRPs) with chicken flavor were prepared and analyzed for flavor mechanism. >50% activity of immobilized LOX was retained after repeated use for five times or five weeks. The oxidized chicken fats were prepared by thermal, free LOX, and immobilized LOX treatments. After addition of chicken fats, Maillard reaction produced more aliphatic aldehydes and alcohols (126.0-839.5 ng/g and 493.5-2332.4 ng/g, respectively) which resulted in noticeable enhanced reaction, but the content of sulfur compounds such as thiols and thiophenes decreased significantly (870.8-1233.9 ng/g and 1125.0-2880.3 ng/g, respectively), and the structure of sulfur compounds could easily form alkyl side chains. However, there was no significant difference in sensory and flavors between oxidized chicken after treatments, which may be related to oxidized degree. The mechanism was proposed or aromatic effects of oxidized chicken fat on flaxseed derived MRPs.

Acute, genetic and sub-chronic toxicities of flaxseed derived Maillard reaction products.

In present study, the acute, genetic, and sub-chronic toxicities of flaxseed derived Maillard reaction products (MRPs) were investigated. Acute toxicity results showed that the 50% lethal dose (LD50) of MRPs in rats was >15.0 g/kg body weight (BW); whereas, the 50% effective dose (ED50) of MRPs was 12.3 g/kg BW. Ames test demonstrated that the back-mutation colonies for MRPs addition of 5,000 µg/dish was positive, which displayed certain mutagenicity. There were no significant differences in micronucleus rate and sperm deformity rate among different dose groups. The sub-chronic toxicity confirmed that less than 0.75 gMRPs/kg BW intake did not affect weight, food intake, mortality, gross pathology, histology, hematology, and serum biochemistry. The obtained results can provide an imperative reference on the safety of a meat flavoring agents.

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.

Three Novel ACE Inhibitory Peptides Isolated From Ginkgo biloba Seeds: Purification, Inhibitory Kinetic and Mechanism.

Alcalase, dispase, trypsin, and flavourzyme were used to hydrolyze the extracted Ginkgo biloba seeds protein isolate (GPI). The Ginkgo protein hydrolyzates (GPHs) with the maximum degree of hydrolysis (DH) and ACE inhibitory activity were selected, and ultra-filtered to obtain components with different molecular weights (MW) (<1 kDa, 1-3, 3-5, and 5-10 kDa). The components with MW of <1 kDa showed better ACE inhibition (IC50:0.2227 mg/mL). Purification and identification by Sephadex G-15 gel chromatography and LC-MS/MS conferred three new potential ACE inhibitory peptides [TNLDWY (non-competitive suppression mode), IC50: 1.932 mM; RADFY (competitive inhibition modes), IC50:1.35 mM; RVFDGAV (competitive inhibition modes), IC50:1.006 mM]. Molecular docking depicting the inhibitory mechanism for ACE inhibitory peptides indicated that the peptides bound well to ACE and interacted with amino acid residues at the ACE active site.