Effect of phenolic compounds on protein cross-linking and properties of film from fish myofibrillar protein

The effects of several phenolic ocmpounds (caffeic acid, catechin, ferullic acid and tannic acid) at various concentrations (1, 3 and 5% based on protein) on cross-linking and properties of film from myofibrillar proteins of bigeye snapper (Priacanthus tayenus) were investigated. Among all phenolic compounds used, tannic acid exhibited the highest cross-linking ability on myofibrillar protein as evidenced by higher decrease in free amino groups with coincidentally lower band intensity of myosin heavy chain (MHC). In addition, the extent of protein cross-linking increased with increasing concentration of phenolic compounds. Addition of phenolic compounds could enhance mechanical properties of the resulting films. As phenolic compounds content increased, Young's modulus (E) and tensile strength (TS) of the films increased, while their elongation at break (EAB) decreased (P<0.05), suggesting stronger and stiffer film structure. At the same concentration used, tannic acid rendered the film with higher mechanical properties, compared to others. Phenolic compounds decreased film transparency and affected color of the films differently, depending on types and concentrations used. Films from myofibrillar proteins with and without polyphenol generally had the excellent barrier properties to UV light at the wavelength of 200-800nm. Therefore, it could potentially be used as inner packaging material for high-fat foods to prevent the lipid oxidation and thus prolonging the shelf-life of foods during storage.     

Properties,Microstructure and Heat Seal Ability of Bilayer Films Based on Fish Gelatin and Emulsified Gelatin Films

Bilayer films prepared by the lamination of fish gelatin film (GF) and its corresponding emulsified film (EF) with different thickness ratios (7:3, 5:5 and 3:7) were characterized. Bilayer films had the similar tensile strength (TS) to EF (p > 0.05) but showed lower elongation at break (EAB) (p < 0.05). All bilayer films showed the lower water vapor permeability (WVP) but higher oxygen permeability (OP) than GF. Bilayer films had varying ΔE* (total color different), where the highest value was observed in that laminated with higher thickness ratio of EF (p < 0.05). Lower light transmission and higher transparency value were obtained for bilayer films, compared to GF (p < 0.05). Based on scanning electron microscopic (SEM) cross-section micrographs, all bilayer films consisted of two layers. Differential scanning calorimetric (DSC) analysis revealed that the bilayer films had the higher glass transition temperature (T _g) than GF but lower than EF. All bilayer films were heat sealable, however their seal strength and seal efficiency were lower than those of GF (p < 0.05). Therefore, the thickness ratios of GF and EF had a marked effect on the mechanical and barrier properties as well as heat sealing ability of resulting bilayer films.     

Characterization of porcine plasma protein-based films as affected by pretreatment and cross-linking agents

The effects of pretreatment and cross-linking agents on properties of porcine plasma protein-based film were investigated. Based on sodium dodecyl sulfate polyacrylamide gel electrophoresis and solubility study, porcine plasma protein-based film was stabilized mainly by hydrogen bond, while film with pretreatment (pH 10 and heated for 30 min) contained hydrogen bond and hydrophobic interaction. The incorporation of glyoxal or caffeic acid resulted in the increase in protein cross-links stabilized by both disulfide and non-disulfide covalent bonds. Nevertheless, the prior oxygenation had no marked impact on the property of film added with caffeic acid. α-Chymotrypsin was more effective than pepsin in hydrolysis of films. Greater thermal stability with an increase in the melting point was observed in film incorporated with caffeic acid, indicating a greater degree of cross-linking. The coincidental increase in initial temperature of film degradation was noticeable. The FTIR spectra revealed the intermolecular interaction between protein molecules as indicated by the shift of amide-I peak.     

Characteristics of film based on protein isolate from red tilapia muscle with negligible yellow discoloration

The properties of film from fish protein isolate (FPI) prepared by prior washing followed by alkaline solubilization process (ASP) from red tilapia muscle were monitored during the storage of 20 days at 50% RH and 25°C, in comparison with those of films from washed mince. Lipid, heme iron and non-heme iron contents in FPI were decreased by 98.8, 36.8 and 91.9%, respectively in comparison with those of washed mince (p<0.05). Films from FPI had higher tensile strength (TS) and elongation at break (EAB) than those from washed mince for both pH (3 and 11) used for film preparation (p<0.05). Film from FPI at pH 3 showed the highest TS, while that from washed mince at pH 11 had the lowest TS (p<0.05). Nevertheless, films from FPI had higher WVP than those from washed mince for both pH used (p<0.05). At the same pH used for film preparation (3 or 11), films from FPI showed the lower TBARS values than those from washed mince (p<0.05). Nevertheless, films from both FPI and washed mince had the higher TBARS values when pH 3 was used for film preparation, compared with pH 11 (p<0.05). Among all films, those from FPI prepared at pH 3 had the highest transparency and no yellow discoloration was observed during the storage of 20 days, in comparison with other films (p<0.05). Conversely, film from washed mince prepared at pH 3 had the higher increase in b*-value and ΔE*-value than other films. Therefore, FPI could serve as a potential material for film preparation with lower contents of lipid and prooxidants, thereby preventing the yellow discoloration of the fish myofibrillar protein-based film during extended storage.     

Antennal and behavioral responses of Cis boleti to fungal odor of Trametes gibbosa

Cis boleti (Coleoptera: Ciidae) preferentially colonizes fungi from the genus Trametes that are known as important wood decomposers. The aim of our research was to investigate if C. boleti uses the chemical volatile composition of its fungal host, Trametes gibbosa, as a key attraction factor. Therefore, the T. gibbosa fruiting body volatiles were analysed by using gas chromatography-mass spectrometry, with parallel electroantennographic detection (GC-MS/EAD) using adults of C. boleti. Furthermore, we examined the behavioral responses of C. boleti to the T. gibbosa volatile compounds. The dominant component of the T. gibbosa fruiting body bouquet was 1-octen-3-ol. Other volatiles, like the aldehydes hexanal, nonanal, and (E,E)-2,4-decadienal and the terpene alpha-bisabolol, were present in minor quantities. 1-Octen-3-ol was released with a ratio of the (R)- and (S)-enantiomers of 93:7, respectively. Electroantennography (EAG) employing C. boleti antennae yielded consistently dominant responses to 1-octen-3-ol. GC-EAD and EAG responses to pure standard compounds showed that C. boleti also perceived other host fungal volatiles. A highly significant attraction to 1-octen-3-ol was observed in behavioral tests. Female beetles were significantly attracted to the (S)-(+)- enantiomer at 10 times lower doses than male beetles. Our finding is the first direct proof that ciid beetles use 1-octen-3-ol as a key cue for host finding.     

Effect of Melanin-Free Ink on Mechanical Properties and Yellow Discolouration of Protein Film from Washed Sardine Mince

The effect of the melanin-free ink (MFI) at different concentrations (0, 0.1, 0.2, 0.3 and 0.4 gL^?1 of film forming solution (FFS)) on the properties and yellow discolouration of films from washed sardine mince was studied. Tensile strength (TS) of the film increased with increasing MFI concentration (P < 0.05). Conversely water vapour permeability (WVP) of films decreased as the concentration of MFI increased (P < 0.05). Fourier transform infrared (FTIR) spectra of films showed a slight shift to lower wavenumber of amide-B band of film added with MFI, indicating protein cross-linking. The microstructure showed slightly rough surface of the films when amount of MFI increased. However, cracks in the films were much decreased when MFI at higher levels was incorporated. Films added with MFI had lower thiobarbituric acid reactive substances (TBARS) value, indicating the lowered lipid oxidation. The addition of MFI also decreased the yellow discolouration but increased the transparency of film in a dose-dependent manner.     

Properties of film from splendid squid (Loligo formosana) skin gelatin with various extraction temperatures

Properties of film from splendid squid (Loligo formosana) skin gelatin extracted at different temperatures (50-80°C) were investigated. Tensile strength (TS) and elongation at break (EAB) of films decreased, but water vapour permeability (WVP) increased (P<0.05) as the extraction temperature increased. Increase in transparency value with coincidental decrease in lightness was observed with increasing extraction temperatures. Electrophoretic study revealed that degradation of gelatin became more pronounced with increasing extraction temperatures. As a consequence, their corresponding films had the lower mechanical properties. FTIR spectra of obtained gelatin films revealed the significant loss of molecular order of the triple helix. Thermogravimetric analysis indicated that F80 exhibited the higher heat susceptibility and weight loss. Loosen structure was observed in film prepared from gelatin with increasing extraction temperatures. Thus, the temperature used for gelatin extraction from splendid squid skin directly affected the properties of corresponding films.     

Effect of pH on the properties of protein-based film from bigeye snapper (Priacanthus tayenus) surimi

The effects of the pH and protein content on the properties and compositional changes of protein-based films from bigeye snapper (Priacanthus tayenus) surimi were investigated. Tensile strength of bigeye snapper surimi films prepared at the acidic (pH 3) and alkaline (pH 11) conditions were not significantly different (P > 0.05). Nevertheless, elongation at break of films prepared at pH 3 was higher than that at pH 11 (P < 0.05). The acidic and alkaline conditions had no effect on water vapor permeability of the films obtained. However, the film prepared at acidic condition was more yellowish than that prepared at alkaline pH. Protein content influenced the mechanical properties and color of films.     

Properties and Characteristics of Multi-Layered Films from Tilapia Skin Gelatin and Poly(Lactic Acid)

Multi-layered films based on tilapia skin gelatin and poly(lactic acid) (PLA) were characterized, in comparison with the control gelatin and PLA films. Three different layers of multi-layered films (PLA/Gelatin/PLA) were visualized by scanning electron microscopic (SEM) analysis. The synergetic effect of lamination was evidenced by the increased mechanical properties (P < 0.05). Multi-layered films had higher water vapor barrier property and water resistance, compared to control gelatin film (P < 0.05). Gelatin films showed increased lightness (L*) with coincidental decrease in total color difference (?E*) in the presence of PLA layers (P < 0.05). Transparency and solubility of films decreased with increasing ratio of PLA (P < 0.05). In addition, multi-layered films showed the enhanced hydrophobicity and thermal stability as evidenced by increased water contact angle and degradation temperature, respectively. Thus, PLA/Gelatin/PLA multi-layered film with improved water vapour barrier property could serve as bio-degradable packaging material for wider applications.     

Properties and microstructure of protein-based film from round scad (Decapterus maruadsi) muscle as affected by palm oil and chitosan incorporation

The properties of protein-based film prepared from round scad (Decapterus maruadsi) muscle in the absence and the presence of palm oil and/or chitosan were investigated. Films added with 25% palm oil (as glycerol substitiution) had the slight decrease in water vapor permeability (WVP) and elongation at break (EAB) (p < 0.05). WVP and tensile strength (TS) of films increased but EAB decreased when 10–40% chitosan (as protein substitution) was incorporated (p < 0.05). Hydrophobic interactions and hydrogen bonds, together with disulfide and non-disulfide covalent bonds, played an important role in stabilizing the film matrix. The a* and b*-values increased with increasing chitosan levels (p < 0.05). Films added with chitosan were less transparent and had the lowered transmission in the visible range. The incorporation of 25% palm oil and 40% chitosan yielded the films with the improved TS but decreased water vapor barrier property. Apart from film strengthening effect, chitosan inconjunction with Tween-20 most likely functioned as the emulsifier/stabilizer in film forming solution containing palm oil.