Jingyang Yu

Controlled formation of flavor compounds by preparation and application of Maillard reaction intermediate (MRI) derived from xylose and phenylalanine

An effective method for preparing Maillard reaction intermediate (MRI) derived from xylose (Xyl) and phenylalanine (Phe) in aqueous medium was proposed in this study. Maillard reaction products (MRPs) were prepared by Maillard reaction performed under stepwise increase of temperature, and cysteine was added as an indicator. The formation conditions of MRI generated from Xyl and Phe were determined through MRPs browning analysis. The MRI prepared under the determined formation conditions was purified using RP-HPLC, and characterized using UPLC-ESI-mass spectra and NMR. The molecular mass (297.1 Da) and formula (C14H19O6N) were proposed. The capacity of flavor formation of heated MRI was evaluated through GC-MS. Results showed that flavor compounds were formed during the subsequent heat treatment, and MRI could be a great potential substitute of MRPs in preparation of fresh process flavors. Therefore, controlled formation of process flavors could be achieved by preparation and application of MRI.

Direct determination of 3-chloro-1,2-propanediol esters in beef flavoring products by ultra-performance liquid chromatography tandem quadrupole mass spectrometry

A sensitive ultra-performance liquid chromatography tandem quadrupole mass spectrometry (UPLC-TQ-MS) method coupled with amino solid-phase extraction was developed for the direct determination of 3-chloro-1,2-propanediol (3-MCPD) esters which were firstly detected in the natural beef flavoring products. The analyzed 3-MCPD esters in this paper contain three monoesters and six diesters. The validation data indicated that the proposed method provided good linearity, repeatability and sensitivity. The method showed a good linearity within the range of 40–200 μg kg−1 for monoesters and 20–100 μg kg−1 for diesters with the determination coefficients (R2) ranging from 0.9912 to 0.9993. The limits of detection (LODs) for monoesters and diesters of 3-MCPD were in the range of 0.04–5.0 μg kg−1 and 0.13–16.0 μg kg−1, respectively. The method accuracy was confirmed by higher sample recovery which ranged from 80.5 to 113.7%. The repeatability expressed as intra-day precision ranged from 0.8 to 9.9% and inter-day precision varied from 2.8 to 13.8%. The validated method was successfully applied for determination of 3-MCPD esters in beef flavoring products.

Mechanism of Formation and Stabilization of Nanoparticles Produced by Heating Electrostatic Complexes of WPI–Dextran Conjugate and Chondroitin Sulfate

Protein conformational changes were demonstrated in biopolymer nanoparticles, and molecular forces were studied to elucidate the formation and stabilization mechanism of biopolymer nanoparticles. The biopolymer nanoparticles were prepared by heating electrostatic complexes of whey protein isolate (WPI)-dextran conjugate (WD) and chondroitin sulfate (ChS) above the denaturation temperature and near the isoelectric point of WPI. The internal characteristics of biopolymer nanoparticles were analyzed by several spectroscopic techniques. Results showed that grafted dextran significantly (p < 0.05) prevented the formation of large aggregates of WD dispersion during heat treatment. However, heat treatment slightly induced the hydrophobicity changes of the microenvironment around fluorophores of WD. ChS electrostatic interaction with WD changed the fluorescence intensity of WD regardless of heat treatment. Far-UV circular dichroism (CD) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopies confirmed that glycosylation and ionic polysaccharide did not significantly cause protein conformational changes in WD and ChS (WDC) during heat treatment. In addition, hydrophobic bonds were the major molecular force for the formation and stabilization of biopolymer nanoparticles. However, hydrogen bonds slightly influenced their formation and stabilization. Ionic bonds only promoted the formation of biopolymer nanoparticles, while disulfide bonds partly contributed to their stability. This work will be beneficial to understand protein conformational changes and molecular forces in biopolymer nanoparticles, and to prepare the stable biopolymer nanoparticles from heating electrostatic complexes of native or glycosylated protein and polysaccharide.

Effect of Temperature on Flavor Compounds and Sensory Characteristics of Maillard Reaction Products Derived from Mushroom Hydrolysate

Maillard reaction products (MRPs) were prepared from mushroom hydrolysate (MH) by heating with d-xylose and l-cysteine at various temperatures (100 °C–140 °C) for 2 h at a pH of 7.4. The sensory characteristics of MH and MRPs were evaluated by panelists and volatile compounds were analyzed by GC/MS. Additionally, partial least squares regression (PLSR) was performed to analyze the correlation between quantitative sensory characteristics and GC/MS data. GC/MS results revealed that higher reaction temperature resulted in more nitrogen and sulfur containing compounds in MRPs while alcohols, ketones and aldehydes were the major flavor compounds obtained in MH. PLSR results showed that 3-phenylfuran and 2-octylfuran were the compounds responsible for the caramel-like flavor; 1-octen-3-ol, (E)-2-octen-1-ol and geranyl acetone were significantly and positively correlated to mushroom-like flavor, whereas, 2-thiophene-carboxaldehyde, 2,5-thiophenedicarboxaldehyde and 3-methylbutanal positively affected MRPs meat-like attribute. Overall, 125 °C was identified as the optimal temperature for preparing MRPs with abundant volatile compounds and favorable sensory characteristics; the concentration of free amino acids and 5′-GMP, which are associated with the umami taste, in MRPs derived under 125 °C were 3 to 4 times higher than those in MH.

Investigating the optimum conditions for minimized 3-chloropropane-1,2-diol esters content and improved sensory attributes during savory beef flavor preparation

In this study, the effects of enzymatic hydrolysis of tallow and addition of sodium chloride (NaCl) were evaluated on the formation of 3-monochloropropane-1,2-diol (3-MCPD) esters and sensory characteristic of beef flavors. The enzymatic hydrolysis condition had significant effects on 3-MCPD mono/di-esters formation during the beef flavor preparation. Considering the safety and sensory characteristics of beef flavors, the optimal enzymatic hydrolysis conditions were selected as: lipase concentration 75U/g tallow, tallow concentration 80% (w/v) and pH 7.0 at 47.5°C for 9.5h. Using the optimal enzymatic hydrolysis conditions, no 3-MCPD monoesters were detected and 3-MCPD-diesters concentration was strongly dependent on NaCl concentration and its addition moment (before or after thermal reaction) at different temperatures. In conclusion, beef flavor was prepared using the optimal hydrolysis conditions and heated at 110°C for 100min, then 10% NaCl was added when the system was cooled to 60°C.