Xian-Bing Xu

Inhibitory effect of sugarcane molasses extract on the formation of Nε-(carboxymethyl)lysine and Nε-(carboxyethyl)lysine

Molasses, the main byproduct of sugar production, is a well-known source of phenolic compounds. In this study, the effect of sugarcane molasses extract on the formation of Nε-(carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) was investigated in glucose-lysine model reaction systems. Results showed that sugarcane molasses extract significantly and dose dependently inhibited the formation of CML and CEL in model reaction systems. The antiglycation activities of sugarcane molasses extract were not only brought about by its antioxidant activities but also associated with its trapping abilities of reactive carbonyl species, such as glyoxal (GO) and methylglyoxal (MGO), the key intermediate compound for the formation of CML and CEL. Besides, the presence of sugarcane molasses extract effectively reduced the extent of browning. The present study emphasized the potential health effects of sugarcane molasses and the possibility of using byproducts as effective ingredients to reduce dietary Maillard reaction end products.

Simultaneous determination of glyoxal, methylglyoxal and diacetyl in beverages using vortex-assisted liquid–liquid microextraction coupled with HPLC-DAD

The detection of α-dicarbonyl compounds including glyoxal (GO), methylglyoxal (MGO) and diacetyl (DA) levels in beverages could be effectively used to evaluate the degree of sugar degradation. In this study, a rapid and inexpensive clean-up method called vortex-assisted liquid–liquid microextraction (VALLME) instead of the expensive solid phase extraction method was successfully applied to purify beverages (tea drinks, soft drinks and carbonated drinks) containing α-dicarbonyl compounds after derivatization with o-phenylenediamine. The clean-up samples were analyzed by using a high-performance liquid chromatography-diode array detector (HPLC-DAD). The matrix effects were corrected by using an internal standard (3,4-hexanedione). The limits of quantitation (LOQs) ranging from 22.3 μg L−1 to 22.7 μg L−1 for GO, from 6.4 μg L−1 to 6.7 μg L−1 for MGO and from 5.4 to 6.2 μg L−1 for DA were observed for standards spiked into tea drinks, soft drinks or carbonated drinks. In addition, the developed method exhibited excellent linearity (R2 > 0.99) for GO (recovery rates, 85.0–108.0%), MGO (recovery rates, 90.8–113.0%) and DA (recovery rates, 93.8–109.3%). The contents of GO (ranging from 265.8 to 9899.8 μg L−1), MGO (<319.7 μg L−1), and DA (<298.6 μg L−1) were accurately quantified in fifteen beverage samples. VALLME as an inexpensive, rapid and valid technique improved the HPLC-DAD determination of GO, MGO and DA in drinks.

Comparative Study of the Effect of Glucosamine and Free Ammonium on 4-Methylimidazole Formation

The effect of glucosamine analogues (glucosamine and acetylglucosamine) and free ammonium on the formation of 4-methylimidazole (4-MeI) was investigated in the caramel model reaction systems. Methylglyoxal (MGO) was detected after derivatization by high-performance liquid chromatography with a diode array detector (HPLC-DAD). 4-MeI in the Maillard reaction was tested using a high-performance cation exchange chromatography coupled with APCI-MS (HPCEC-MS). The levels of pyrazines tested by gas chromatography (GC) coupled with MS were applied to mark the condensation reaction between dicarbonyls and free ammonium. Results showed that the formation of 4-MeI and its precursor MGO was inhibited in glucosamine analogue model reaction systems. Besides, the results from pyrazines and brown intensity in glucosamine analogues model reaction systems indicated that glucosamine analogues mainly underwent the reaction of intra-intermolecular polymerization into melanoidins rather than the degradation reaction into MGO. Using glucosamine analogues to produce the caramel color with a low level of 4-MeI was applicable.

The effect of pH and amino acids on the formation of methylglyoxal in glucose‐amino acid model system

BACKGROUNDnMethylglyoxal (MGO) as a α-dicarbonyl compound not only affects food flavor and color but also contributes to the loss of nutrition and the generation of toxic compounds. The study was carried out using a glucose-amino acid model system with incubation at 120 °C to investigate the effect of amino acids and pH on the formation of MGO. MGO derivative (2-methylquinoxaline) was detected by high-performance liquid chromatography with a diode array detector. Changes in glucose, amino acids and products such as acetic acid were tested using high-performance anion exchange chromatography with an electrochemical detector or an electrical conductivity detector.nnnRESULTSnLysine and glycine had higher reactivity to form MGO and melanoidins than arginine and proline. More acetic acid was produced and a higher consumption of arginine was observed in glucose-arginine solution. Moreover, higher pH significantly accelerated the formation of MGO.nnnCONCLUSIONnAmino reactivity and pH were two important factors affecting the formation of MGO in the Maillard reaction.

Non-destructive analysis of caviar compositions using low-field nuclear magnetic resonance technique

Caviar is one of the most popular and expensive animal products in world trade. Water, fat and protein contents are key chemical compositions, and account for the majority of mass of caviar. In this study, the performance of a rapid, accurate analysis of water, fat and protein analysis was reported in caviar and raw sturgeon eggs through low-field 1H nuclear magnetic resonance (LF-NMR) relaxometry combined with partial least-squares regression (PLSR) models. For caviar, the correlation coefficients (Rcv2) of water, fat and protein were 0.9930, 0.9698 and 0.9783 with root mean square error of cross-validation (RMSECV) of 0.0760, 0.0308 and 0.0566, respectively. For raw sturgeon eggs the Rcv2 were 0.9932, 0.9592 and 0.9770, and the RMSECV were 0.1098, 0.0878 and 0.0917, respectively. Besides, a LF-NMR and principal component analysis (PCA) combined method also was developed to discriminate the caviar and raw sturgeon eggs based on the hydrogen protons originating from different environments with various salt concentrations.

Isotope dilution HPLC-MS/MS for simultaneous quantification of acrylamide and 5-hydroxymethylfurfural (HMF) in thermally processed seafood

The objective of this study was to develop an accurate, robust and rapid HPLC-MS/MS-based method capable of quantifying acrylamide and 5-hydroxymethylfurfural (HMF) simultaneously. A Phenomenex Synergi Fusion-RP C18 column (50mm×2.5mm, 2μm) was used, and the MS/MS instrument was operated in multiple reaction monitoring mode. The isotope dilution method was used to correct for the matrix effect from samples. This method demonstrated low limits of quantification (2.12ng/mL for acrylamide and 4.86ng/mL for HMF) and excellent linearity (R2>0.999). This method also demonstrated excellent quantification accuracy, precision, and recovery (87-110%). Using the method developed, target analytes were quantified in 14 thermally-processed seafood samples. Resulting concentrations ranged from 5.58 to 50.35μg/kg for acrylamide, and from 12.54 to 2276.44μg/kg for HMF. The proposed isotope dilution HPLC-MS/MS method is a valid and rapid technique for simultaneous analysis of acrylamide and HMF in seafood.

Promotion effect of sulfite on deoxyosones and 4-methylimidazole in caramel model system

In this study, hydrogen-deuterium (H/D) exchange experiment was carried out to reveal the promotion effect of sulfite on the formation of deoxyosones and 4-methylimidazole (4-MeI) in the Maillard reaction. Glucose-ammonium (40mmol/L, pH 7.4 in PBS) model systems with different levels of sulfite were incubated at 110°C for 2h. Alpha-dicarbonyls were detected after derivatization by a high-performance liquid chromatography with a diode array detector (HPLC-DAD). 4-MeI in the Maillard reaction was tested using a high-performance anion exchange chromatography with an electrochemical detector (HPAEC-ED). The H/D exchange ratios of hexose (fructose, glucose and mannose) were tested by HPAEC-MS. Results showed that the aldo-enol transition of enediol was promoted by sulfite, which promoted the formation of deoxyosones and 4-MeI. In addition, the oxidation reaction of enediols was inhibited by the antioxidant sulfite, which caused the inhibition of osones formation in the Maillard reaction.

Isotope dilution quantification of 5-hydroxymethyl-2-furaldehyde in beverages using vortex-assisted liquid–liquid microextraction coupled with ESI-HPLC-MS/MS

Vortex-assisted liquid–liquid microextraction (VALLME) is a fast and simple pretreatment method, which has been applied for the clean-up of beverages containing caramel color. Herein, a reversed-phase C18 column (50 mm × 2.5 mm, 2 μm) was used, and the MS/MS instrument was operated in the multiple reaction monitoring mode for the sensitive and selective detection of 5-hydroxymethyl-2-furaldehyde (HMF). The matrix effect and detection stability were corrected using the isotope dilution method. This method demonstrated low limit of quantification (0.3 μg L−1) and excellent linearity (R2 = 0.999). The recovery rates of HMF ranged from 87.5% to 101.0% in carbonated drinks and from 85.1% to 98.7% in soft drinks. The content of HMF was quantified in thirteen beverage samples, ranging from 0.2 to 14.8 mg L−1. In conclusion, the VALLME coupled with the HPLC-ESI-MS/MS method is a valid and rapid technique for isotope dilution quantification of HMF in beverages.

Isotope dilution determination for the trace level of 4(5)-methylimidazole in beverages using dispersive liquid-liquid microextraction coupled with ESI-HPLC–MS/MS

In this study, a rapid and reliable pretreatment method called dispersive liquid-liquid microextraction (DLLME) was developed for the determination of 4(5)-methylimidazole (4-MeI) in beverages. The clean-up samples were analyzed by a high performance liquid chromatography coupled with triple quadrupole mass spectrometer (HPLC-MS/MS) using a reversed-phase C18 column (250u202fmmu202f×u202f4.6u202fmm, 5u202fμm). The matrix effects and the fault of DLLME operation were corrected by the isotope dilution technique. The developed method exhibited the limit of quantification (0.3u202fμgu202fL-1) and excellent linearity (R2u202f=u202f0.999). In addition, the recovery values of 4-MeI in carbonated beverage were ranging from 102.60% to 113.22%, in soft drinks were ranging from 103.24% to 108.85%. The content 4-MeI was detected in thirteen beverage samples treated with DLLME and solid phase extraction method (SPE) (ranging from 6.4 to 165.5u202fμgu202fL-1). The consistent result of 4-MeI content detected by DLLME and SPE method concluded that the established method on the basis of DLLME was rapid, robust and accurate for the trace 4-MeI determination in beverages.

Presence of Fluorescent Carbon Nanoparticles in Baked Lamb: Their Properties and Potential Application for Sensors

The presence of nanoparticles in food has drawn much attention in recent years. Fluorescent carbon nanoparticles are a new class of nanostructures; however, the distribution and physicochemical properties of such nanoparticles in food remain unclear. Herein, the presence of fluorescent carbon nanoparticles in baked lamb was confirmed, and their physicochemical properties were investigated. The fluorescent carbon nanoparticles from baked lamb emit strong blue fluorescence under ultraviolet light with a 10% fluorescent quantum yield. The nanoparticles are roughly spherical in appearance with a diameter of around 2.0 nm. Hydroxyl, amino, and carboxyl groups exist on the surface of nanoparticles. In addition, the nanoparticles could serve as a fluorescence sensor for glucose detection through an oxidation-reduction reaction. This work is the first report on fluorescent carbon nanoparticles present in baked lamb, which provides valuable insight into the physicochemical properties of such nanoparticles and their potential application in sensors.