Freeze-thaw Storage Research Articles

Effects of arabinoxylan extracted from vinegar residue on physicochemical and structural properties of gluten proteins obtained from freeze-thaw wheat dough.

Arabinoxylan is commonly used as a hydrocolloid in frozen dough to improve the texture and the sensory qualities of the products. The effects of vinegar residue arabinoxylan (VRAX) on the secondary structures and microstructures of gluten proteins during freeze-thaw storage were studied, and the underlying mechanism governing these effects was clarified. The results revealed that VRAX improved the textural properties of gluten proteins, but had a negative impact on their viscoelasticity. Additionally, the addition of VRAX increased the number of disulfide bonds and also improved the freezing tolerance of the gluten proteins. It was found that the enthalpy of the gluten proteins decreased by 19.78% following VRAX addition. As a result of the use of VRAX, the freezing procedure resulted in reduced formation of ice crystals, protecting the gluten network structure and preserving the dough's elasticity. The network structure of gluten proteins after VRAX treatment was more ordered and integrated relative to that of frozen blank control gluten proteins. Overall, the freeze-thaw stability of the gluten proteins was enhanced by VRAX. These results suggest that VRAX has potential as an effective cryoprotectant in frozen dough. © 2024 Society of Chemical Industry.

Impact of xanthan gum on gluten microstructure and bread quality during the freeze-thaw storage

Xanthan gum (XG) is commonly used as a hydrocolloid in frozen dough to improve the texture and the sense quality of the products. The effects of XG on the molecular weight, secondary structure, microstructure of gluten and bread quality during freeze-thaw storage were studied. As results showed, XG and gluten formed more compact complexs through electrostatic interactions, which relieved the destruction of side chain molecules for gluten. XG protected the molecular weight of gluten proteins from 2 × 106 Da–108 Da. FTIR showed that XG-gluten mixtures had more α-helices (28.98%) and less intermolecular β-sheets (9.45%) compared with gluten. The secondary structure of XG-gluten remains unchanged under freeze-thaw treatment from 0 to 60 days. However, when the time reached 120 days, there was a decrease in α-helices (11.85%) and β-turns (6.28%) accompanied an increase by β-sheets (19.13%). CLSM revealed that XG gradually migrated to the centre with moisture after freeze-thaw storage, thereby protecting the gluten network. So the bread, prepared from XG-gluten mixtures, possessed superior colour, volume and visible pore proportion than bread without XG. Overall, the freeze-thaw stability of the gluten was enhance by XG under freeze-thaw treatment from 0 to 90 days.

Analyzing the storage stability of diesel emulsified fuels: a comparative standpoint

ABSTRACT The storage stability of a diesel emulsified fuel plays a crucial role in its commercial application and carries forward its environment-friendly advantage of lowering nitrogen oxides and particulate matter emissions. This article compares storage stability aspects of hydrous ethanol-diesel-Al2O3 nano (HEDA) and hydrous ethanol-diesel-Al2O3 nano-Pemulen TR-2 (HEDAP) emulsified fuels via various stability tests (visual inspection, heat storage test, centrifuge test, pH test, density, and viscosity measurements) under freeze-thaw storage condition. The production cost analysis was made to find their commercial suitability. Stability test results found higher storage stability of HEDA fuel, compared to that of HEDAP fuel. A heterogeneous mixing of Pemulen TR-2 and its weaker hydrogen bonding with other compounds could be major factors to lower the stability of HEDAP fuel. The stability of both fuels decreased with an increase in the water proportion. HEDA fuel production cost estimation was found to be lower than HEDAP fuel and slightly higher compared to diesel, which was a good sign of its commercial applicability. The powder X-ray diffraction analysis reported 41.28 nm average crystallites size of Al2O3 nanoparticles. HEDA emulsified fuel showed better storage stability along with a lower production cost in comparison with the HEDAP fuel.

Measuring Lipid Transfer Protein Activity Using Bicelle-Dilution Model Membranes.

In vitro assessment of lipid intermembrane transfer activity by cellular proteins typically involves measurement of either radiolabeled or fluorescently labeled lipid trafficking between vesicle model membranes. Use of bilayer vesicles in lipid transfer assays usually comes with inherent challenges because of complexities associated with the preparation of vesicles and their rather short "shelf life". Such issues necessitate the laborious task of fresh vesicle preparation to achieve lipid transfer assays of high quality, precision, and reproducibility. To overcome these limitations, we have assessed model membrane generation by bicelle dilution for monitoring the transfer rates and specificity of various BODIPY-labeled sphingolipids by different glycolipid transfer protein (GLTP) superfamily members using a sensitive fluorescence resonance energy transfer approach. Robust, protein-selective sphingolipid transfer is observed using donor and acceptor model membranes generated by dilution of 0.5 q-value mixtures. The sphingolipid transfer rates are comparable to those observed between small bilayer vesicles produced by sonication or ethanol injection. Among the notable advantages of using bicelle-generated model membranes are (i) easy and straightforward preparation by means that avoid lipid fluorophore degradation and (ii) long "shelf life" after production (≥6 days) and resilience to freeze-thaw storage. The bicelle-dilution-based assay is sufficiently robust, sensitive, and stable for application, not only to purified LTPs but also for LTP activity detection in crude cytosolic fractions of cell homogenates.

Effect of Xanthan Gum on the Freeze-Thaw Stability of Wheat Gluten

The effect of xanthan gum on the freeze-thaw stability of wheat gluten was evaluated during a 60-day storage period at −18 °C with thawing every 5 days for 4 h at 25 °C. The physicochemical and rheological properties of wheat gluten-xanthan gum mixtures with multiple scales were analyzed. In the control samples (wheat gluten without xanthan gum), the molecular weight by size-exclusion chromatography-multiple angle laser light scattering (SEC-MALLs), content of free SH groups measured by UV/VIS spectrophotometry, and the hole sizes in the wheat gluten network structure shown by SEM increased as the freeze-thaw storage time increased, while the surface hydrophobicity index (H0) decreased. For the wheat gluten-xanthan gum mixtures, more disulfide bonds were preserved and numerous small pores in the wheat gluten structure were observed. Meanwhile, the sample with 0.225% xanthan gum (w/w) had the lowest content of free SH groups. The wheat gluten-xanthan gum mixtures had more α-helixes than the control samples with the same freeze-thaw storage time. Rheological analysis showed that the wheat gluten-xanthan gum mixtures had higher elasticity and viscosity than the control samples. Overall, the addition of xanthan gum improved the freeze-thaw stability of the wheat gluten network.

Fabrication and Characterization of Quinoa Protein Nanoparticle-Stabilized Food-Grade Pickering Emulsions with Ultrasound Treatment: Effect of Ionic Strength on the Freeze-Thaw Stability.

The development of multilayered interfacial engineering on the emulsion freeze-thaw properties has recently attracted widespread attention, because of the essential freeze-thaw storage process in some emulsion-matrix food products. In this research, we studied the role of salt concentration on the freeze-thaw properties of quinoa protein (QPI) nanoparticles-stabilized Pickering emulsions. The QPI nanoparticles (particle concentration c = 2%, w/v) with increasing particle size and surface hydrophobicity ( H0) were fabricated by ultrasound treatment at 100 W for 20 min, by varying the NaCl addition (salt concentrations, 0-500 mM). The sonicated QPI nanoparticles with increasing salt concentrations showed higher β-sheet structure contents and stronger hydrophobic interactions, which were attributed to the decreasing charged groups and particle aggregation by electrostatic interactions. As compared to the sonicated QPI nanoparticles-stabilized Pickering emulsions ( c = 2%, oil fraction φ = 0.5) without salt accretion, the emulsions with salt accretion exhibited better freeze-thaw properties after three freeze-thaw circulations, which might be mainly caused by the generation of gel-like three-dimensional structure and multilayered network at the droplets' interface with smaller droplet sizes. Increasing the salt concentration progressively enhanced the freeze-thaw properties of sonicated QPI nanoparticles-stabilized Pickering emulsions probably due to the inhibit formation of ice crystal by the "salting-out" effects. The results of this study would provide great significance to investigate the role of salt concentration in the freeze-thaw properties of protein-stabilized Pickering emulsions.

A LC–MS/MS method for the determination of stachyose in rat plasma and its application to a pharmacokinetic study

A sensitive, simple and rapid analytical method based on a liquid chromatography–tandem mass spetrometry (LC–MS/MS) has been established and validated for the determination of stachyose in rat plasma. Plasma samples were prepared by protein precipitation with acetonitrile. Separation of stachyose and nystose (internal standard, IS) was achieved using acetonitrile-water (55:45, v/v) as the mobile phase at a flow rate of 1ml/min for 6min on an Asahipak NH2P-50 4E column with an Asahipak NH2P-50G 4A guard column. Detection and quantification were conducted by LC–MS/MS method in the negative ion mode using multiple reaction monitoring (MRM) transitions at m/z [M–H]− 665.4→383.1 for stachyose and 665.5→485.0 for IS, respectively. The method was linear over the concentration ranges of 100–30000ng/ml with a lower limit of quantification (LLOQ) of 100ng/ml. The intra- and inter- day precision were all within 8.7% and the accuracy ranged from 97.2–108.4% and 98.3–102.4%, respectively. Stability studies indicated that stachyose was stable under short-term, long-term and three freeze-thaw storage conditions. The method was successfully applied to a pharmacokinetic study involving pulmonary administration of micronized Rehmannia glutinosa oligosaccharides (RGOS) to rats.

IGF-I Improves Mitochondrial Membrane Potential during Hypothermic Storage of Canine Spermatozoa

ABSTRACTThe aim of study was to evaluate the effects of insulin-like growth factor I (IGF-I) on canine sperm function during cooled and freeze-thaw storage. Extenders supplemented with different IGF-I concentrations (0, 100 and 200 ng/ml) were added to canine spermatozoa, and the sperm samples were stored at 4°C for 48 hr or freeze-thawed. Sperm motility, morphology, plasma-membrane integrity (PMI) and mitochondrial membrane potential (MMP) were evaluated. IGF-I had no effect on PMI or morphology during cooling and freeze-thawing. However, IGF-I alleviated the reduction in progressive motility and MMP caused by cooled storage and led to an improvement in MMP after freeze-thawing. In conclusion, IGF-I can be helpful to maintain progressive motility of canine spermatozoa during hypothermic storage via increased MMP.

Effect of NaCl and sugar on physicochemical properties of flaxseed polysaccharide-potato starch complexes

To investigate the effect of salt and sugar on the physicochemical properties of flaxseed polysaccharide- potato starch (FG-PS) complexes we measured pasting, gelling, swelling properties, and freeze-thaw stability by methods of rapid viscosity analysis, texture analysis, centrifugation, and freeze-thaw storage, respectively. In the presence of NaCl, the pasting temperature, peak viscosity, final viscosity, breakdown value, and swelling power of FG-PS complexes increased as the NaCl level increased. The hardness of FG-PS complexes gradually reduced with increasing NaCl level. Syneresis of FG-PS complexes was the lowest with addition of high levels of NaCl. These results indicate that both starch-salt and hydrocolloid-salt interactions might govern the physicochemical properties of FG-PS complexes in the presence of NaCl. In the presence of sugar, an increase in pasting temperature, peak viscosity, final viscosity, breakdown value, and gel hardness of FG-PS complexes was observed with increasing added level of sucrose and glucose, while swelling power and syneresis decreased.

Factors affecting production of metal powder by electric arc atomization : C.Dodan et al. (University of Gaziantep, Gaziantep, Turkey.)

A sensitive, simple and rapid analytical method based on a liquid chromatography–tandem mass spetrometry (LC–MS/MS) has been established and validated for the determination of stachyose in rat plasma. Plasma samples were prepared by protein precipitation with acetonitrile. Separation of stachyose and nystose (internal standard, IS) was achieved using acetonitrile-water (55:45, v/v) as the mobile phase at a flow rate of 1 ml/min for 6 min on an Asahipak NH2P-50 4E column with an Asahipak NH2P-50G 4A guard column. Detection and quantification were conducted by LC–MS/MS method in the negative ion mode using multiple reaction monitoring (MRM) transitions at m/z [M–H]− 665.4 → 383.1 for stachyose and 665.5 → 485.0 for IS, respectively. The method was linear over the concentration ranges of 100–30000 ng/ml with a lower limit of quantification (LLOQ) of 100 ng/ml. The intra- and inter- day precision were all within 8.7% and the accuracy ranged from 97.2–108.4% and 98.3–102.4%, respectively. Stability studies indicated that stachyose was stable under short-term, long-term and three freeze-thaw storage conditions. The method was successfully applied to a pharmacokinetic study involving pulmonary administration of micronized Rehmannia glutinosa oligosaccharides (RGOS) to rats.