Guanjun Tao

Photodegradation kinetics and byproducts identification of the Aflatoxin B1 in aqueous medium by ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry

A photodegradation study of Aflatoxin B(1) (AFB(1)) in water solution was performed under UV irradiation at different AFB(1) initial concentrations and UV irradiation intensities. The effect of UV intensity on the AFB(1) photodegradation ratio is dominative, when compared with AFB(1) initial concentration. The photodegradation of AFB(1) was proved to follow first-order reaction kinetics (R(2) > or = 0.99). Three photodegradation products, i.e. P(1) (C(17)H(14)O(7)), P(2) (C(16)H(14)O(6)) and P(3) (C(16)H(12)O(7)), were identified on the basis of low mass error and high matching property by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF MS), and the degradation pathway was proposed. This study first reports the appearance of these photodegradation products and the proposed degradation pathway in aqueous media.

High pressure homogenization processing, thermal treatment and milk matrix affect in vitro bioaccessibility of phenolics in apple, grape and orange juice to different extents

The effects of high pressure homogenization processing (HPHP), thermal treatment (TT) and milk matrix (soy, skimmed and whole milk) on the phenolic bioaccessibility and the ABTS scavenging activity of apple, grape and orange juice (AJ, GJ and OJ) were investigated. HPHP and soy milk diminished AJs total phenolic bioaccessibility 29.3%, 26.3%, respectively, whereas TT and bovine milk hardly affected it. HPHP had little effect on GJs and OJs total phenolic bioaccessibility, while TT enhanced them 27.3-33.9%, 19.0-29.2%, respectively, and milk matrix increased them 26.6-31.1%, 13.3-43.4%, respectively. Furthermore, TT (80 °C/30 min) and TT (90 °C/30 s) presented the similar influences on GJs and OJs phenolic bioaccessibility. Skimmed milk showed a better enhancing effect on OJs total phenolic bioaccessibility than soy and whole milk, but had a similar effect on GJs as whole milk. These results contribute to promoting the health benefits of fruit juices by optimizing the processing and formulas in the food industry.

Outer membrane defect and stronger biofilm formation caused by inactivation of a gene encoding for heptosyltransferase I in Cronobacter sakazakii ATCC BAA‐894

Aims:  To investigate the role of lipopolysaccharide (LPS) structure in the stability of outer membrane and the ability of biofilm formation in Cronobacter sakazakii.

Effect of Six Chinese Spices on Heterocyclic Amine Profiles in Roast Beef Patties by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry and Principal Component Analysis

The effects of Chinese spices on the profiles of 17 heterocyclic amines (HAs) from seven HA categories were investigated in roast beef patties using Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) and principal component analysis. Three groups of HAs, imidazopyridines (PhIP, DMIP, and 1,5,6-TMIP), imidazoquinoxalines (MeIQx and 4,8-DiMeIQx), and β-carbolines (harman and norharman), were detected and quantified in all of the samples. The results demonstrated that the total HA and imidazopyridine profiles could clearly be affected by 1% pricklyash peel (14.1 ± 0.76 and 6.06 ± 0.32 ng/g), chilli (41.0 ± 0.01 and 23.0 ± 0.52 ng/g), and cumin (59.9 ± 2.44 and 31.1 ± 3.06 ng/g), in comparison with control values of 21.8 ± 2.40 and 14.3 ± 2.04 ng/g, respectively. The difference was only significant (p < 0.05) for cumin. The imidazoquinoxaline profile was significantly (p < 0.05) affected by 1% pricklyash peel (0.57 ± 0.05 ng/g) and cumin (2.36 ± 0.20 ng/g) compared to the control (1.16 ± 0.11 ng/g). The β-carboline profile was only markedly (p < 0.05) affected by 1% cumin (26.4 ± 0.82 ng/g) compared to the control (6.26 ± 0.26 ng/g). In general, pricklyash peel inhibited HA formation, whereas star anise, fennel, cumin, chilli, and black pepper promoted HA formation. The findings could facilitate the selection of spices in meat processing to minimize HA formation.

Identification of phospholipids classes and molecular species in different types of egg yolk by using UPLC-Q-TOF-MS

Egg phospholipids (PLs) are currently the products of greatest commercial interest with major area of importance in various fields. Therefore, in this study, duck, hen and quail egg yolk PLs were isolated by solvent extraction with chilled acetone precipitation, and subsequently separated and identified by using ultra-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Egg PLs were separated on hydrophilic interaction liquid chromatography (HILIC) with ethylene bridged hybrid (BEH) column by gradient elution using acetonitrile/ammonium formate as a mobile phase, and detected by mass spectrometry (MS) under electrospray ionization in positive and negative ion mode. Structural characterizations of 57 molecular species of egg yolk PLs were identified based on MS/MS fragment ion information and elemental composition in MassLynx 4.1 software. The obtained results showed that phosphatidylcholine (16:0-18:1), phosphatidylethanolamine (18:0-20:4), phosphatidylinositol (18:0-18:2), phosphatidylserine (18:0-18:2), sphingomyelin (d18:1/16:0) and lysophosphatidylcholine (16:0) were the predominant species among the different classes of egg yolk phospholipids.

Effect of simulated processing on the antioxidant capacity and in vitro protein digestion of fruit juice-milk beverage model systems

The effects of simulated processing (pH adjustment and thermal treatment) on the antioxidant capacity and in vitro protein digestion of fruit juice-milk beverage (FJMB) models consisting of whey protein (WP), and chlorogenic acid (CHA) or catechin (CAT) were investigated. Results indicated that CAT was more susceptible to processing than CHA, and showed a significant (p < 0.05) decrease in ABTS and FRAP after sterilization (121°C/10 min) and pH adjustment to 6.8. WP addition had different effects (none, masking, synergetic effect) on the antioxidant activity of FJMB. Pasteurization (63°C/30 min) and pH adjustment (pH 3.7 or pH 6.8) had either non-significant or slight effects on FJMBs antioxidant capacity, while sterilization significantly (p<0.05) increased or decreased its ABTS and FRAP depending on the different models. In vitro digestion of WP in FJMB was obviously (p < 0.05) inhibited by phenolics to varying degrees, and little influenced (p>0.05) by pasteurization, whereas sterilization initially accelerated WP digestion but did not change its overall digestibility.

Dynamic high pressure microfluidization-assisted extraction and bioactivities of Cyperus esculentus (C. esculentus L.) leaves flavonoids.

The aim of this work was to study the effect of dynamic high pressure microfluidization (DHPM) on extracting total flavonoids from Cyperus esculentus L. (C. esculentus L.) leaves and to evaluate the antioxidant activity and antibacterial property of these flavonoids. In all the assays, pretreatment with DHPM was found to not only efficiently improve the yield of total flavonoids but also strengthen the antioxidant activity of the total flavonoids. C. esculentus L. leaves flavonoids had pronounced antioxidant activity in vivo that could significantly elevate the content of superoxide dismutase (SOD) without increasing the malondialdehyde (MDA) levels, and could also improve total antioxidant capacity in mice with a dose-dependent fashion. C. esculentus L. leaves flavonoids inhibited the growth of both Gram positive and Gram negative bacteria while no obvious inhibitory effect on Penicillium and Aspergillus could be observed. Our studies indicate that flavonoids from C. esculentus L. leaves can be taken as a natural antioxidant and bacteriostatic substance in food and pharmaceutical industry.

Analysis of phospholipids in Schizochytrium sp. S31 by using UPLC-Q-TOF-MS

Phospholipids are the main constituent of cell membranes and play multiple roles in cells, in forming the permeability barrier, supporting matrix, surfaces for many catalytic processes, and precursors of signal processing and macromolecular synthesis. Hydrophilic interaction (HILIC) ultra-performance liquid chromatography (UPLC) coupled with quadrupole time of flight (Q-TOF) mass spectrometry (MS) was used to analyze the composition of phospholipids from Schizochytrium sp. S31. Phosphatidyl-cholines, -ethanolamines, -inositoles, and -glycerol, and phosphatidic acid were separated by using an acetonitrile/ammonium formate gradient mobile phase. The structures of 70 phospholipids were identified by LC-MS/MS measurements in negative ion mode. The main phospholipid in Schizochytrium sp. S31, phosphatidylcholine, accounted for 49.8% of the total phospholipids, and the major phospholipid fatty acids were C16 : 0 and DHA.

Inhibitory profiles of chilli pepper and capsaicin on heterocyclic amine formation in roast beef patties

The inhibitory profiles of chilli pepper and capsaicin, as well as their relationship to the formation of heterocyclic amines (HAs) in roast beef patties were investigated using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combined with principal component analysis (PCA). HAs including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-1,6-dimethylimidazo[4,5-b]pyridine (DMIP), 2-amino-1,5,6-trimethylimidazo[4,5-b]pyridine (1,5,6-TMIP), 2-amino-3-methyl-3H-imidazo[4,5-f]quinoxaline (IQx), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (4,8-DiMeIQx), 1-methyl-9H-pyrido[3,4-b]indole (harman) and 9H-pyrido[3,4-b]indole (norharman) were detected and quantified in beef patties. Different levels of chilli pepper and capsaicin had different inhibitory profiles on HA formation, but had no significant (P>0.05) effect on the texture of the patties. Furthermore, all levels of chilli pepper and capsaicin reduced total HA and PhIP concentrations dose-dependently, with the highest inhibitions of 80% and 98% at 2mg of capsaicin. Moreover, capsaicin inhibited all HAs more than chilli pepper, implying that ingredients other than capsaicin in chilli pepper may promote the formation of HAs. These results could be useful for the reduction of HA, during food processing procedures, by spices.

Characterization of a New Flavone and Tyrosinase Inhibition Constituents from the Twigs of Morus alba L.

The twigs of Morus alba L. were found to show strong tyrosinase inhibition activity, and the responsible active components in the extract were further investigated in this study. A flavone, named morusone (1), and sixteen known compounds 2–17 were isolated from M. alba twigs and their structures were identified by interpretation of the corresponding ESI-MS and NMR spectral data. In the tyrosinase inhibitory test, the compounds steppogenin (IC50 0.98 ± 0.01 µM), 2,4,2′,4′-tetrahydroxychalcone (IC50 0.07 ± 0.02 µM), morachalcone A (IC50 0.08 ± 0.02 µM), oxyresveratrol (IC50 0.10 ± 0.01 µM), and moracin M (8.00 ± 0.22 µM) exhibited significant tyrosinase inhibition activities, much stronger than that of the positive control kojic acid. These results suggest that M. alba twig extract should served as a good source of natural tyrosinase inhibitors for use in foods as antibrowning agents or in cosmetics as skin-whitening agents.