Yana Zhao

Mechanical properties and solubility in water of corn starch-collagen composite films: Effect of starch type and concentrations

This study investigated the possibility of enhancing the properties of collagen with three different maize starches: waxy maize starch, normal starch, and high amylose starch. Scanning electron microscopy images revealed that starch-collagen films had a rougher surface compared to pure collagen films which became smoother upon heating. Amylose starch and normal starch increased the tensile strength of unheated collagen films in both dry and wet states, while all starches increased tensile strength of collagen film by heating. Depending upon the amylose content and starch concentrations, film solubility in water decreased with the addition of starch. DSC thermograms demonstrated that addition of all starches improved the thermal stability of the collagen film. Moreover, X-ray diffraction results indicated that except for high amylose starch, the crystallinity of both starch and collagen was significantly decreased when subject to heating. FTIR spectra indicated that intermolecular interactions between starch and collagen were enhanced upon heating.

Performance of high amylose starch-composited gelatin films influenced by gelatinization and concentration.

In order to study the impact of starch in film performance, high amylose corn starch was composited in gelatin films under different gelatinization conditions and, in high and low concentrations (10 and 50wt.%). It was found that hot water gelatinized starch (Gel-Shw) increased film mechanical strength and was dependent upon the starch concentration. The addition of an alkali component to the starch significantly enhanced the swelling of the starch granules and expedited the gelatinization process. Incorporation of starch, especially the alkalized starch (Sha), into the gelatin films decreased film solubility which improved its water resistance and water vapor permeability (WVP). Multiple techniques (DSC, TGA, FT-IR, and XRD) were used to characterize the process and results, including the crosslinking of the dissolved starch molecules and the particles formed from gelatinized starch during retrogradation process, which played an important role in improving the thermal stability of the composited gelatin films. Overall, the starch-gelatin composition provides a potential approach to improve gelatin film performance and benefit its applications in the food industry.

Characterization of Se-enriched Pleurotus ostreatus polysaccharides and their antioxidant effects in vitro

Selenium-enriched polysaccharides have become a major research focus owing to their high anti-oxidant activities. Selenium-enriched Pleurotus ostreatus polysaccharide (Se-POP) and the native polysaccharide (POP) were obtained by hot water extraction from fresh fruiting bodies of P. ostreatus with or without selenium. Se-POP and POP had similar average molecular weights (0.95×104Da and 0.94×104Da, respectively). Se-POP was mainly composed of fucose, rhamnose, arabinose, galactose, glucose, and xylose, similar to the composition of POP, but in different molar ratios. In an FT-IR analysis, in comparison to POP, two new absorption peaks at 941cm-1 and 1048cm-1 were observed due to COSe and SeO bonds. In vitro study of DPPH, hydroxyl, and ABTS free radicals, Se-POP had a stronger antioxidant capacity than that of POP. Compared to POP, Se-POP had a superior ability to reduce hydrogen peroxide (H2O2)-induced oxidative stress and apoptosis in murine skeletal muscle (C2C12) cells. In general, selenium in Se-POP contributed to high antioxidant and biological activities. Se-POP acts as a potent antioxidant and has the ability to prevent oxidation via reactive oxygen species (ROS) and free radicals in humans. These results suggest that Se-POP is a candidate dietary supplement for functional foods.

Effects of Pig Skin and Coconut Powder Mixture on Gelling and Rheological Properties of Composite Gel Prepared with Squid Myofibrillar Protein and Lard

Abstract The effects of the mixture of pig skin (PS) and coconut powder (CP) on the gelling and rheological properties of composite gel prepared with squid myofibrillar protein (MP) and lard were studied. The addition of PS and CP gel had significantly improved the water-holding capacity (WHC) and gelling properties of MP-Lard composite gel. Besides, composite gels with an adequate amount of PS and CP gel had a better texture and higher whiteness. The SDS-PAGE results showed that the presence of PS and CP gel did not affect the coagulated proteins in composite gels. The three-dimensional network structures of composite gels containing PS and CP gel were more compact and homogeneous. In general, the mixture of PS and CP could enhance the gel quality of MP-Lard composite gel and it could be used as a fat substitute in surimi products.

Seleno-short-chain chitosan induces apoptosis in human breast cancer cells through mitochondrial apoptosis pathway in vitro

ABSTRACT Seleno-short-chain chitosan (SSCC) was a synthesized chitosan derivative with the molecular weight of 4826.986 Da. The study is aimed to investigate cytotoxicity of SSCC on human breast cancer MCF-7 and BT-20 cells and explore apoptosis-related mechanism in vitro. The MTT (3- [4,5-Dimethylthiazol-2-yl]-2, 5-diphenylterazolium bromide) assay showed that SSCC exhibited significantly cytotoxic effects on MCF-7 and BT-20 cells in a dose- and time-dependent manner, and the effective inhibitory concentration was 100 μg/ml and 200 μg/ml, respectively. Apoptosis assay of these two kinds of cells was determined by Hoechst 33,342/PI and Annexin V-FITC/PI double staining. The cell cycle assay showed that SSCC triggered S and G2/M phase cell cycle arrest in MCF-7 cells and S phase cell cycle arrest in BT-20 cells in a time-dependent manner. Further studies demonstrated that SSCC led to the generation of reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential (MMP) in these two kinds of cells. N- acetyl-L cysteine (NAC), as a radical scavenger, significantly inhibited the generation of ROS and decreased the apoptosis of MCF-7 and BT-20 cells. Moreover, the expression of mitochondrial apoptosis-related proteins was detected by western blot assay. SSCC up-regulated the expression of Bax, down-regulated the expression of Bcl-2, subsequently increased the release of cytochrome c from mitochondria to cytoplasm, and activated the cleavage of caspase-9 and −3, which finally induced apoptosis in MCF-7 and BT-20 cells in vitro. Consequently, these data indicated that SSCC could induce apoptosis of MCF-7and BT-20 cells in vitro by mitochondrial pathway.

Fabrication of acid-swollen collagen fiber-based composite films: Effect of nano-hydroxyapatite on packaging related properties

ABSTRACT Acid-swollen collagen fibers and nano-hydroxyapatite were used to develop a biodegradable film. At 4 wt% of hydroxyapatite or below, collagen fiber formed acceptably homogeneous films, with hydroxyapatite dependent increase in opacity and color. Hydroxyapatite addition significantly improved tensile strength of the composite films along with an observable decrease in elongation. Furthermore, the film’s water vapor and oxygen barrier property were enhanced. Additionally, thermal stability of the films was improved. Scanning electron microscope images showed adding hydroxyapatite caused the composite films a coarser and uneven surface. Collagen fiber-hydroxyapatite composite film provides the potential to apply as a novel material for food packaging.