Improvement on Physical Properties of Pullulan Films by Novel Cross‐Linking Strategy

Pullulan based films possess several advantages, including high transparency, low toxicity, good biodegradability, good mechanical properties, and low oxygen permeability, are preferable for food packaging. The application of pullulan films on food packaging, however, has inherent disadvantage of high water solubility. In this study, glutaraldehyde and glycerol were used as the cross‐linking reagent and the plasticizer respectively to improve water resistance and physical properties of the pullulan films. Effects of cross‐linking degree on physical properties, including water absorptions, swelling behaviors, water vapor permeability and tensile strengths of films were evaluated. FTIR results demonstrated that the pullulan films were successfully cross‐linked by glutaraldehyde. The tensile strength of pullulan films could be enhanced significantly (P < 0.05) when glutaraldehyde was between 1% and 5% (w/w); nevertheless, the amount of glutaraldehyde above 20% (w/w) led to films brittleness. With the addition of glycerol as a plasticizer enhanced the extensibility of films as well as the hydrophilicity, resulting in higher water vapor permeability.     

Effect of bioactive compounds in lactobacilli-fermented soy skim milk on femoral bone microstructure of aging mice

BACKGROUND: Soy skim milks fermented with lactobacilli contain various phytochemicals such as isoflavones and peptides. We used lactobacilli‐fermented soy skim milk as a nutritional supplement for 6 weeks to investigate its anti‐osteoporosis effect in 13‐month‐old female BALB/c aging mice. Freeze‐dried powder of soy skim milk fermented by Lactobacillus paracasei subsp. paracasei NTU 101 (NTU 101F) and L. plantarum NTU 102 (NTU 102F) were used in this study. RESULTS: The trabecular bone volumes in mice fed NTU 101F and NTU 102F increased by a factor of 3.48 and 2.16 compared with control values, respectively. The network density and thickness of distal metaphyseal trabecular bone in mice fed with NTU 101F and NTU 102F milks were significantly denser than that of control mice; moreover, the NTU 101F group had the largest resting area ratio and smallest resorbing area compared with other groups. The beneficial effect may due to isoflavones as well as higher amounts of polysaccharide and peptide in NTU 101F milk. CONCLUSION: The results suggest that dietary supplement with fermented soy skim milk can attenuate aging‐induced bone loss in BALB/c mice and possibly lower the risk of osteopenia or osteoporosis in aging. Copyright © 2011 Society of Chemical Industry     

Cream formation in a semifermented tea

The formation of cream in Paochung tea, a popular semifermented tea, which undergoes a lesser degree of enzymic oxidation during manufacture, was investigated at various extraction temperatures, extraction times, pHs and leaf/water ratios. The primary components of Paochung tea cream were catechins (30%), caffeine (20%) and protein (16%). (−)-Epigallocatechin gallate and (−)-epicatechin gallate were the major catechins precipitated during creaming, constituting 19% and 5% of the tea cream respectively. The amount of tea cream produced and its composition were influenced by extraction temperature and pH. The tea leaf/water ratio determined the amount of tea cream formed but did not affect the cream composition. Catechins were considered to be the key component in tea cream. They interacted with caffeine and protein to induce tea cream formation. © 1999 Society of Chemical Industry     

Expression and purification of goat lactoferrin from Pichia pastoris expression system

ABSTRACT:  The recombinant goat lactoferrin (rGLF) was expressed in the methylotropic yeast Pichia pastoris using pGAPZαC vector, GAP as promoter, and Zeocin as the selective marker. After transformation of the GLF-pGAPZαC into Pichia pastoris X-33 expression host, the GLF-pGAPZαC vector was integrated into the GAP promoter locus of Pichia pastoris X-33 chromosome. The rGLF was expressed and secreted into the broth using α-factor preprosequence. SDS-PAGE and PAS staining analysis indicated that the rGLF could be purified to electrophoretic homogeneity by heparin-Sepharose 6 Fast Flow affinity chromatography and glycosylated by the expression host. The yield of purified rGLF was approximately 2.0 mg/L of culture broth. The N-terminal sequence was identical to the native goat lactoferrin (nGLF). The iron-binding behavior, papain-inhibiting property, and thermal stability of the purified rGLF were comparable to nGLF. This is the 1st report of intact goat lactoferrin expression using the P. pastoris system.     

The determination of zeolite crystal diffusivity by gas chromatography—II. Experimental

Experimental results are reported for the adsorption of propane and n-butane in a column packed with Linde 5A zeolite crystals, and methane, propan n- and iso-butane in a column packed with silicalite crystals. The adsorption equilibrium constant K and crystal diffusivity D_c, we obtained at different temperatures in the range 100–300°C, for each sorbate and packing and the heat of adsorption and diffusional activation energ were determined.The results show that in order to separate the effects of K and the pressure drop, the latter must be independently estimated by a suitable correla     

Dephytinisation of rice bran and manufacturing a new food ingredient

Rice bran was extruded at 130 °C and a screw speed of 140 rpm for 20 s to inactivate lipase and prevent lipid oxidation. Although the extrusion process induced further complex formation between phytic acid and protein as well as between phytic acid and starch, nearly 94% of phytic acid in the extruded rice bran could still be removed by solid/liquid extraction conducted at 25 °C for 30 min using hydrochloric acid at pH 2 as solvent and a solvent/rice bran ratio of 15. After the extract had been neutralised and phytic acid removed, it was added back to the rice bran solid to replenish the nutritional and functional components of the solid. The mixture was then dried in a drum dryer to yield a powdered product. The dephytinised rice bran product contained most of the protein, fat, dietary fibre and B vitamins and more than 50% of the oryzanol originally present in the raw rice bran. © 2001 Society of Chemical Industry     

Process Characteristics of Hydrolysis of Chitosan in a Continuous Enzymatic Membrane Reactor

ABSTRACT: Crude enzyme from Bacillus cereus NTU-FC-4 was used to hydrolyze chitosan of 66% deacetylation in a membrane reactor, operated at 45 °C and pH 5, to continuously produce chitooligosaccharides. Major oligomers in the product from the reactor were chitobiose, chitotriose, chitotetraose, chitopentaose, and chitohexaose. When the membrane reactor was operated at an enzyme/substrate ratio of 0.2 (unit/mg) and residence time of 100 min, it reached steady state in 2.5 h. The system could be operated for 15 h and still maintained a stable product composition. When the volume replacement exceeded 2.5, the productivity of the membrane reactor became higher than that of the batch reactor, and the difference between them became even greater when the volume replacement was further increased. The apparent Michaelis constant (K_m) for the enzyme in the membrane reactor was 18.8 mg/mL, but the apparent K_m was 5.4 mg/mL for the batch reactor, suggesting that the affinity of the enzyme for chitosan was lower in the membrane reactor compared with the enzyme in the batch reactor. The estimated values of apparent V_max were 0.18 and 0.20 mg reducing sugar/mL/min for the enzyme in the membrane reactor and in the batch reactor, respectively, indicating that the enzyme activity was not greatly altered when used in the membrane reactor.     

Antioxidant properties and protein compositions of porcine haemoglobin hydrolysates

Porcine haemoglobin hydrolysates were prepared through hydrolysis by Alcalase followed by Flavourzyme, and their protein compositions were analyzed using Sephadex G-50 gel filtration chromatography. The antioxidant activities, including reducing power, ferrous ion chelating ability, and DPPH radical scavenging activity, of the hydrolysates were evaluated. The results showed that the hydrolysates of haemoglobin exhibited low reducing powers, but high ferrous ion chelating abilities and DPPH radical scavenging activities. The hydrolysate, obtained through hydrolysis by 2% Alcalase for 4 h and followed by 1% Flavourzyme for 6 h, had the highest ferrous ion chelating ability of 63.54% at a concentration of 5.0 mg/mL. The hydrolysate, obtained through hydrolysis by 2% Alcalase for 4 hrs, had the highest DPPH radical scavenging activity of 41.94% at a concentration of 5.0 mg/mL. According to the results of protein composition analysis, we divided the hydrolysates into three groups, including high molecular weight (MW) group (Group I), medium MW group (Group II), and low MW group (Group III). The reducing power and ferrous ion chelating ability of the hydrolysates were significantly and positively correlated to the relative amount of Group I, and negatively correlated to the relative amount of Group III. This study revealed that the antioxidant activities of porcine haemoglobin hydrolysates were dependent on their protein compositions. The high MW protein fraction (Group I) was responsible for the high reducing power and ferrous ion chelating ability of the hydrolysate.     

Mechanical and dynamic properties of graft polyurethane/allyl novolac resin simultaneous interpenetrating network

Two series of polyurethane (PU)/allyl novolac resin simultaneous interpenetra ing networks (SINs) were synthesized. The PU components were prepared by reacting 4,4′-diphenyl methane diisocyanate with poly(tetramethylene oxide) (PTMO), whose molecular weight range was 600–700 (for convenience, this polymer was called UT1), 900–1050 (UT2) and 1900–2100 (UT3), respectively. The phenolic resin component was synthesized by substituting the hydroxy groups of the phenolic resin with the allyl group. To prove that the alkene group can be applied as a binding element between the networks to improve the network compatibility, trimethylol propane monoally ether (TMPME) with a double bond was chosen as the PU chain extender in one series of the PU/allyl novolac resin SINs (designated TUT1, TUT2 and TUT3 for different molecular weights of PTMO used as PU soft segments). After a detailed study of the thermal, mechanical, and dynamic properties and morphology, the extent of phase mixing of the graft PU/allyl novolac resin SINs (TUT series SINs) was significantly improved over that of UT series SINs. This result is consistent with the loss tangent shift in dynamic mechanical analysis measurements and with transmission electron microscope micrographs. The mechanical properties of the graft SINs (TUT series) were lower than those of the original SINs (UT series) because TMPME with bulky structure was used as the chain extender of PU.     

Comparison of primary and secondary aminosilance coupling agents in anhuydride-curde epoxy fiberglass composites

Fourier transform infrared spectroscopy (FT-IR) has been utilized to investigate the interfacial chemical bonding at the interfaces of the aminosilanes and the nedic methyl anhydiride cured epoxy matrix in fiber-reinforced composites. It is found that the nedic methyl anhydride can react with γ-aminopropyltriethoxysilane (APS) and N-methylaminoproplytrimethoxysilane (MAPS). In comparing the relative reactivities of two coupling agents to the epoxy resin, the secondary aminosilance has a higher reactivity than the primary aminosilance. An elevated temperature is required for the copolymerization to take place between the silane and the epoxy resin. The results indicate that covalent bonds form at the coupling agents. The molecular structure of the interface in MAPS treated fiberglass reinforced composites is different from that of the APS treated fiber composites. In addition, an accelerated copolymerization initiated by the coupling agent treated surface is also found in the resin interphase which may be important in determining the mechanical properties of the composites.