Maomao Zeng

Interactions of milk α- and β-casein with malvidin-3-O-glucoside and their effects on the stability of grape skin anthocyanin extracts

The interactions of α- and β-casein with malvidin-3-O-glucoside (MG), the major anthocyanin in grape skin anthocyanin extracts (GSAE), were examined at pH 6.3 by fluorescence, fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy. The binding constant (KS), binding force and effects of the interactions on the caseins conformation and GSAE stability were investigated. The results showed that α- and β-casein bound with MG via hydrophilic (van der Waals forces or hydrogen bonding) and hydrophobic interactions, respectively. α-Casein had a slightly stronger binding affinity toward MG than β-casein, with respective KS values of 0.51×10(3)M(-1) and 0.46×10(3)M(-1) at 297K. The secondary structures of α- and β-casein were changed by MG binding, with a decrease in α-helix and an increase in turn for α-casein and no change in α-helix and a decrease in turn for β-casein. The casein-anthocyanin interaction appeared to have a positive effect on the thermal, oxidation and photo stability of GSAE.

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.

Modification of soy protein hydrolysates by Maillard reaction: Effects of carbohydrate chain length on structural and interfacial properties

This study investigated the effects of carbohydrate chain length on the structural and interfacial properties of the Maillard reaction conjugates of soy protein hydrolysates (Mw>30 kDa). The covalent attachment of sugars to soy peptides was confirmed by amino acid analysis and examination of the Fourier-transform infrared spectra. The results suggested that the emulsion stability of the conjugates increased as the length of the carbohydrate chains increased. The surface activity measurement revealed that the soy peptide-dextran conjugates were closely packed and that each molecule occupied a small area of the interface. It was further confirmed that the soy peptide-dextran conjugates formed a thick adsorbed layer at the oil-water interface, as observed in the confocal laser scanning micrographs. The interfacial layer of soy peptides was rheologically complex with broad linear viscoelastic region and strong elastic modulus, and the soy peptide-dextran conjugates might form multilayer adsorption at the interface. This study suggested that the improved surface properties of the soy peptide-dextran conjugates were a result of the strong membrane formed by the closely packed molecular and multilayer adsorption at the interface, which provided steric hindrance to flocculation.

Effects of the size and content of protein aggregates on the rheological and structural properties of soy protein isolate emulsion gels induced by CaSO 4

The effects of the size and content of soy protein isolate (SPI) aggregates on the rheological and textural properties of CaSO4-induced SPI emulsion gels were investigated. Considerable differences in the rheological, water-holding, and micro-structural properties were observed. The gels with larger and/or more SPI aggregates showed substantial increase in the elastic modulus and had lower gelation temperatures. Creep data suggested that the size of the SPI aggregates contributed more to the elastic modulus, whereas the increase of aggregate content enhanced the elastic modulus and viscous component of the gels. The water-holding capacity was markedly enhanced (p<0.05) with the increase in both the size and content of SPI aggregates. Confocal laser scanning microscopy and scanning electron microscopy showed that larger and/or more SPI aggregates resulted in more homogeneous networks with smaller oil droplets. These insights provide important information for the product development in relation to soy protein-stabilized emulsions and emulsion gels.

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.

Complexation of bovine β-lactoglobulin with malvidin-3-O-glucoside and its effect on the stability of grape skin anthocyanin extracts

The binding interaction between bovine β-lactoglobulin and malvidin-3-O-glucoside (MG), the major anthocyanin in grape skin anthocyanin extracts (GSAE), was studied at pH 6.3 using fluorescence, Fourier transform infrared and circular dichroism spectroscopy. The binding constant (KS), binding force and effect of the interaction on the β-lactoglobulin conformation and GSAE stability were investigated. The results indicated that β-lactoglobulin complexed with MG mainly via hydrophobic interaction with KS of 0.67×10(3)M(-)(1) at 297K. The secondary structure of β-lactoglobulin was changed by MG binding, with a decrease in α-helix, turn and random coil and an increase in β-sheet. Bovine whey protein effectively prevented the color fading and degradation of anthocyanin in the GSAE solution during the thermal treatment (80°C/2h), H2O2 oxidation (0.005% H2O2/1h) and photo illumination (5000lx/5d). The whey protein-anthocyanin complexation appeared to have a positive effect on the thermal, oxidation and photo stability of GSAE.

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.

Controlled Release of Fluidized Bed-Coated Menthol Powder with a Gelatin Coating

We estimated the release properties of fluidized bed-coated menthol powder by static headspace analysis and by relating the release properties and the properties of the coating. Powder was spray-dried onto different coating materials such as gelatin, an oil-gelatin emulsion, modified starch, and Aquacoat® ECD in a fluidized bed system, and then submerged in water at 37°C with a shearing force. The release properties of encapsulated menthol powder were estimated over 15 min compared with spray-dried powder. The microencapsulation efficiency of menthol powders was determined, as well as the density, surface tension, viscosity, and powder contact angle of coating materials. The gelatin emulsion was found to be a potential coating material for controlling menthol release from the coating powder and high microencapsulation efficiency (90.44%) achieved; 60% of the menthol powder was released after 11 min. These results indicate that the solubility and integrity of the coating is important to the success of the fluidized bed-coating process for controlled release of flavor from this degradation-activated release system.

Preheated milk proteins improve the stability of grape skin anthocyanins extracts

The effects of casein and whey proteins, preheated at 40-100°C and 45-60°C for 15min, respectively, on color loss and anthocyanins degradation in grape skin anthocyanins extracts (GSAE) at pH 3.2 and 6.3 were evaluated. Preheating milk proteins effectively improved their protective effects against color loss and anthocyanins degradation in GSAE solutions during thermal treatment (at 80°C for 2h), H2O2 oxidation (0.005% H2O2 for 1h) and illumination (at 5000lx for 5 d). Whey proteins and casein, preheated at 50°C and 60°C for 15min, respectively, demonstrated the optimal protective effects. However, preheated whey proteins had a better protective effect on the thermal, oxidation and photo stability of GSAE, decreasing the thermal, oxidative and photo degradation of anthocyanins in GSAE 71.59%, 32.22% and 56.92% at pH 3.2 and 54.91%, 22.89% and 46.68% at pH 6.3, respectively.

Chemical components of cold pressed kernel oils from different Torreya grandis cultivars.

The chemical compositions of cold pressed kernel oils of seven Torreya grandis cultivars from China were analyzed in this study. The contents of the chemical components of T. grandis kernels and kernel oils varied to different extents with the cultivar. The T. grandis kernels contained relatively high oil and protein content (45.80-53.16% and 10.34-14.29%, respectively). The kernel oils were rich in unsaturated fatty acids including linoleic (39.39-47.77%), oleic (30.47-37.54%) and eicosatrienoic acid (6.78-8.37%). The kernel oils contained some abundant bioactive substances such as tocopherols (0.64-1.77mg/g) consisting of α-, β-, γ- and δ-isomers; sterols including β-sitosterol (0.90-1.29mg/g), campesterol (0.06-0.32mg/g) and stigmasterol (0.04-0.18mg/g) in addition to polyphenols (9.22-22.16μgGAE/g). The results revealed that the T. grandis kernel oils possessed the potentially important nutrition and health benefits and could be used as oils in the human diet or functional ingredients in the food industry.