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Interactions of the flavoring compounds hexyl acetate (HxAc), heptyl acetate (HpAc), linalyl formate (LiFo), linalyl acetate (LiAc), geraniol, linalool, limonene, and myrcene with soy protein isolate (SPI) were estimated in pH 3.0, 6.0, and 9.0 aqueous solutions using headspace solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS). The binding capacity of HxAc, HpAc, LiFo, LiAc, geraniol, and linalool increased in the pH of the medium from 3 to 9. For limonene and myrcene, an unexpected increase in headspace concentration or a "salting-out" effect was observed. Between pH 3 and 9, better accessibility to the primary hydrophobic sites as a result of a modification to the protein's flexibility was observed. PRACTICAL APPLICATIONS: SPME method is a technology of dynamic adsorption for flavors. The lowest level of lead be practicably detected in food as low as the practiced concentration of flavors (0.01-0.1 mM) in our study. At low concentrations of flavors, it is close to the actual flavor's concentration of food. In the previous studies, the technology, such as equilibrium dialysis, headspace-gas phase which need higher concentration of flavors (>0.2 mM). The interaction between flavors and protein has a different binding law at high and low concentrations. As we produced the acid fruit soy protein milk beverage, the off-flavors present in the beverage were due to the change in the interaction between denature SPI and flavors. The present work is aimed at paving the way for further research to elucidate flavor imbalances in acid fruit soy protein milk beverage.

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An alkaline extractable arabinoxylan (HBAX-25) was fractionated from crude arabinoxylan (HBAX) obtained optimally in hull-less barley (Hordeum vulgare L. var. nudum Hook. f.) bran. Molecular properties and structural characterization of HBAX-25 were investigated thoroughly based on chemical composition of 8.31% (w/w) moisture and 87.57% (w/w) sugar with specifically few proteins (1.08%, w/w) and high arabinoxylans (82.46%, w/w). Data from monosaccharide composition indicated that HBAX-25 mainly consisted of arabinose (30.13 mol%) and xylose (51.55 mol%) with A/X ratio of 0.58, representative for arabinoxylans, which coincided with FT-IR results and was corroborated by methylation and NMR analyses, i.e., a relatively low-branched arabinoxylan composed of un-substituted (1,4-linked ß-D-Xylp, 71.19%), mono-substituted (1,3,4-linked ß-D-Xylp, 14.78%) and di-substituted (1,2,3,4-linked ß-D-Xylp, 10.76%) xylose units as backbone via ß-(1→4) linkages, with six possible branches or individuals included. Hence, a structural basis of HBAX-25 was established, which could have potential in food and other value-added applications capable of interpreting their physicochemical, functional and technological characteristics.

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The interactions between flavors (hexyl acetate [HxAc], heptyl acetate [HpAc], linalyl formate [LiFo], linalyl acetate [LiAc], geraniol, linalool, limonene and myrcene) and soy protein isolate (SPI) were investigated, the influence of flavors structure and preheated SPI (PSPI) were determined by using headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) technology. For HxAc and HpAc, the binding of SPI and the flavors decreased in the order nature > 80 °C > 90 °C > 100 °C PSPI, for LiFo, LiAc, geraniol, and linalool, nature < 80 °C < 90 °C < 100 °C PSPI. For limonene and myrcene, an increase in headspace concentration or "salting out" effect was noticed. The NSPI (nature SPI) and PSPI of 80 °C showed two class binding sites for HxAc and HpAc. These results serve as a foundation for further investigation into the effect of preheating of SPI on its ability to bind to flavor-inducing compounds.

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The effects of xanthan gum on the release of strawberry flavor compounds in formulated soy protein isolate (SPI) beverage were investigated by headspace gas chromatography (GC). Seven strawberry flavor compounds (limonene, ethyl hexanoate, (Z)-3-hexenyl acetate, ethyl 2-methylbutanoate, ethyl butanoate, (Z)-3-hexen-1-ol and diacetyl) could be detected by GC and hence analyzed the gas-matrix partition coefficients (K). The release of flavor compounds was restrained in SPI and/or xanthan gum solution. The retention of (Z)-3-hexen-1-ol, limonene and diacetyl significantly changed (p<0.05) with increasing xanthan gum concentrations. Presence of any other esters led to suppression of the release of ester compounds in water and SPI solution. The less-volatiles (γ-decalactone, methyl cinnamate, hexanoic acid, 2-methyl butyric acid and furaneol) accelerated the release of ester compounds to some extent in different matrices. The above results demonstrated that presence of SPI and xanthan gum could bring about an imbalance in the strawberry flavor.

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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-, ß-, γ- and δ-isomers; sterols including ß-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.

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This paper reports on the elucidation of the possible mechanism for forming the putty structure of hyaluronan (HA) at low pH (2.5) using rheological methods. Oscillation and stress relaxation tests on a series HA putty samples containing various concentrations of salt indicated that ionic forces were not the driving force for their formation, but hydrogen bonds were responsible for driving two or more HA molecular chains together to form a three dimensional network. Our results indicated/confirmed that the carboxyl group of the glucuronic acid and acetamido group of N-acetylglucosamine moieties on two neighboring HA chains are involved in the formation of the intermolecular hydrogen bonding, which lead to the formation of the putty at pH 2.5.

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A new method was developed for quantitative determination of the viscoelastical characteristics of hyaluronic acid (HA) putty (formed at pH 2.5) using a stress relaxation approach. A concept of entanglement network numbers (ENN) was applied to provide a quantitative measure for the strength of HA putty. Based on the new approach, the relationship between ENN and HA concentration was established. The new approach was successfully applied to evaluate the effect of temperature, urea concentration and pH on putty strength as well as estimate the effects of glucose, ß1-3-linked D-glucuronic acid and ß1-4 linked D-N-acetylglucosamine, on the ENN of HA solutions quantitatively. The ENN established in the current study can be extended to other non-cross linked hydrogels, i.e. they are formed by hydrogen bonds, ionic interactions or other non-covalent bonds.

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BACKGROUND: Fatty acids are essential components in cell membranes of bacteria, and they determine the different structures of lipids and lipid A. Therefore, fatty acids are good targets for development of rapid and reliable methods for differentiation of bacteria. RESULTS: Here we report fatty acid distributions in three different bacteria-Escherichia coli, Francisella novicida and Bacillus subtilis-studied by using gas chromatography-tandem mass spectrometry. Different fatty acid profiles were observed in the three bacteria. Hydroxyl fatty acids were observed in E. coli and F. novicida, but not in B. subtilis. Carbocyclic fatty acids were observed in E. coli but not in F. novicida or B. subtilis. Methyl-branched fatty acids were observed in B. subtilis but not in E. coli or F. novicida. Although saturated and unsaturated fatty acids were all observed in the three bacteria, their chain lengths and distribution patterns were different. CONCLUSION: The results indicate that the fatty acid profile in a given bacterium is highly specific, and gas chromatography-tandem mass spectrometry is a rapid and sensitive method for the identification or detection of bacteria.

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A rapid and simple method was developed for the determination of volatile flavor compounds (VFCs) in soy sauce by head space solid-phase microextraction (HS-SPME) coupled to capillary gas chromatography-mass spectrometry (GC-MS). Five types of SPME fibers, including 85 microm PA, 100 microm PDMS, 75 microm CAR/PDMS, 65 microm PDMS/DVB, 50 microm DVB/CAR/PDMS were investigated. Three parameters for HS-SPME in terms of adsorption time, salt concentration, and extraction temperature were optimized. Adsorption time tested in this study were 20, 40 and 60 minutes; the salt concentrations were 180, 210, 250, 270 and 300 g/L; and extraction temperatures were 25, 35, 45, 55 and 65 degrees C. The concentrations of the compounds were calculated based on their relative peak areas to the internal standard of 2-octanol. An 85 microm PA fiber, adsorption time of 40 min, a temperature of 45 degrees C and NaCl concentration of 250 g/L were selected as th optimum conditions. This optimized method was applied to evaluate a real sample. As a result, 97 compounds in a soy sauce sample were isolated and identified successfully. The results showed that alcohols, carboxylic acids, esters and phenols were the major VFCs of soy sauce. The most important groups of volatile compounds in the soy sauce sample were ethanol, hexadecanoic acid, phenylethyl alcohol and 2,3-butanediol. In addition, some oxo-compounds and heterocyclic compounds were also found. The average relative standard deviation of the relative peak area was 12.1%, and the recoveries were 79.9% - 109.6%. The method is simple, fast and accurate with high reproducibility, high sensitivity and low cost.

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