Release of active compounds from agar and agar–gelatin films with green tea extract

Active biodegradable films based on agar and agar–fish gelatin were developed by the incorporation of green tea aqueous extract to the film forming solution. The effect of the partial replacement of agar by fish skin gelatin as well as the addition of the green tea extract on the physical properties of the resultant films was evaluated. Special attention was given to the release of antioxidant and antimicrobial compounds from the agar film matrices with and without gelatin. Agar–gelatin films were less resistant and more deformable than agar films. The inclusion of green tea extract decreased tensile strength and elongation at break in both agar and agar–gelatin films. Water vapour permeability and water resistance was not affected either by the replacement of agar by gelatin or the addition of green tea extract, but the water solubility noticeably increased in the films containing green tea extract. The presence of gelatin in the agar–green tea matrix film hindered the release of total phenolic compounds, catechins and flavonols in water. As a consequence, the antioxidant power released by the films was lower in the case of films containing gelatin. However, the antimicrobial activity of the films was not affected by the presence of gelatin.     

Effects of gelatin origin,bovine-hide and tuna-skin,on the properties of compound gelatin–chitosan films

With the purpose to improve the physico-chemical performance of plain gelatin and chitosan films, compound gelatin–chitosan films were prepared. The effect of the gelatin origin (commercial bovine-hide gelatin and laboratory-made tuna-skin gelatin) on the physico-chemical properties of films was studied. The dynamic viscoelastic properties (elastic modulus G′, viscous modulus, G″ and phase angle) of the film-forming solutions upon cooling and subsequent heating revealed that the interactions between gelatin and chitosan were stronger in the blends made with tuna-skin gelatin than in the blends made with bovine-hide gelatin. As a result, the fish gelatin–chitosan films were more water resistant (∼18% water solubility for tuna vs 30% for bovine) and more deformable (∼68% breaking deformation for tuna vs 11% for bovine) than the bovine gelatin–chitosan films. The breaking strength of gelatin–chitosan films, whatever the gelatin origin, was higher than that of plain gelatin films. Bovine gelatin–chitosan films showed a significant lower water vapour permeability (WVP) than the corresponding plain films, whereas tuna gelatin–chitosan ones were only significantly less permeable than plain chitosan film. Complex gelatin–chitosan films behaved at room temperature as rubbery semicrystalline materials. In spite of gelatin–chitosan interactions, all the chitosan-containing films exhibited antimicrobial activity against Staphylococcus aureus, a relevant food poisoning. Mixing gelatin and chitosan may be a means to improve the physico-chemical performance of gelatin and chitosan plain films, especially when using fish gelatin, without altering the antimicrobial properties.     

Identification of active compounds from Aurantii Immatri Pericarpium attenuating brain injury in a rat model of ischemia–reperfusion

Ischemic stroke is caused by brain injury due to prolonged ischemia by occlusion of cerebral arteries. In this study, we isolated active compounds from an ethanol extract of Aurantii Immatri Pericarpium (HY5356). We first showed by DNA fragmentation assay that HY5356 improved human hepatocellular carcinoma cells (HepG2) under hypoxic conditions by inhibiting apoptosis. When HY5356 was fractionated with dichloromethane (MC), ethyl acetate (EA) and n-butanol (BU), the MC fraction improved cell viability at the lowest concentration (100 μg/ml). Intraperitoneal injection of HY5356 (200 mg/kg) or the MC fraction (200 mg/kg) to rats prior to occlusion attenuated brain injury significantly in a rat model of ischemia–reperfusion. Adopting cell viability under hypoxic conditions as an activity screening system, we isolated nobiletin and tangeretin as active compounds. The results suggest that intake of Aurantii Immatri Pericarpium containing nobiletin and tangeretin as active compounds might be beneficial for preventing ischemic stroke.     

Effect of homogenization conditions on properties of gelatin–olive oil composite films

Gelatin–olive oil composite films were prepared through emulsification to improve water barrier ability of gelatin-based films. The effects of homogenization conditions of film-forming dispersions (FFD) on lipid droplets distributions in the FFD and films were evaluated and compared. Some selected physical properties, e.g., water vapor permeability (WVP), microstructure of the films were also evaluated. The rotor–stator homogenizer provided a lower energy input and so the largest particles were observed in the related FFD and films. These films exhibited excellent water barrier ability, but poor mechanical resistance, extensibility and transparency. The microfluidizer provided the FFD with lower and narrower particle size distributions, promoting mechanical resistance, extensibility and transparency of the films. The physical properties of the emulsified films were dependent on the special microfluidization pressure or cycle used, e.g., the WVP of the films decreased upon increasing microfluidization pressure or cycle. The present results indicated that the microfluidizer can be used to modulate lipid droplets in the FFD, thus films’ properties.     

Copper release from nano‑copper/polypropylene composite films to food and the forms of copper in food simulants

The influences of temperature, exposure time, different types of polypropylene (PP), (3-Aminopropyl) triethoxysilane (KH550) used as coupling agent, sterilizing conditions on copper migration from nano‑copper/PP composite films into food/ food simulants were explored. Results showed that copper migrated more easily from polypropylene (PPH) films with a maximum rate of 34.51%, compared to those from copolymer polypropylene (PPR) and block copolymer polypropylene (PPB) to 3% acetic acid (w/v). Gamma (γ) irradiation could significantly increase the copper migration (P < 0.05). Different forms of copper were found in different simulants. Copper crystals were found in 10% ethyl alcohol and identified by scanning electron microscopy and energy dispersed analysis of X-rays (SEM-EDX). The hydroxylation (%) of nano‑copper/PP films was less than 100%. These films had certain antioxidant and antimicrobial properties which could extend the shelf life of packaged food. The migration amount of copper into rice vinegar was the largest, with a maximum of 0.65 mg/ kg.Industrial relevanceAlthough nanomaterials are potentially beneficial for food packaging, migration of nanoparticles to the packaged food can be harmful to the human body. Therefore, it is very important to determine the presence and characterize the morphology of nanoparticles in food. In this paper, we have developed a new and effective packaging material containing nanoparticles and have explored the migration form and morphology in food simulants. In conjunction with the results of current study, nano‑copper/PP packaging material can be suggested for maintaining the product quality and has commercial potential.     

Characterization of the key odor-active compounds in steamed meat of Coilia ectenes from Yangtze River by GC–MS–O

In this study, the key odor-active compounds in the steamed meat of Coilia ectenes from Yangtze River were isolated by headspace monolithic material sorptive extraction and analyzed by gas chromatography–mass spectrometry–olfactometry (GC–MS–O). A total of 49 volatile compounds were identified and quantified in the extract. The results of gas chromatography–olfactometry analysis combined with odor activity value showed that trimethylamine (fishy, ammonia-like), 3-methylbutanal (dark chocolate), decanal (green, oily), hexanal (green), (Z)-4-heptenal (fishy, boiled potato) and benzaldehyde (bitter almond) were the key odor-active compounds contributing primarily to the overall aroma of steamed Coilia ectenes meat. Among them, trimethylamine and (Z)-4-heptenal were the most potent odor-active compounds on the basis of their detection frequency at high odor intensities.     

Study of the retention and release of n-hexanal incorporated into soy protein isolate–lipid composite films

This work deals with the study of the kinetic of aroma release, which had been previously incorporated into soy protein isolate (SPI)–lipid composite films. The aim was to determine the influence of type and amount of lipidic material on aroma (n-hexanal) release and retention, as well as the apparent diffusion coefficients. To carry out this study it have been employed SPI-based films containing two SPI:LIPID ratios (1:0.25 and 1:0.5), and two types of lipids, oleic acid (OA) and beeswax (BW), in OA:BW ratios 100:0, 70:30, 50:50, 30:70 and 0:100. The measurements were performed by a gas chromatography technique. The films that showed more retention were SPI:LIPID 1:0.5 100% BW and control film. Concerning release rate, films containing BW as unique lipid material gave the lowest aroma release rate. Apparent diffusion coefficients (D_app) of all films are in the same order of magnitude (10⁻¹⁵ m² s⁻¹). D_app decreases when BW increases in the film matrix and when oleic acid amount decreases. In conclusion, for encapsulating n-hexanal, SPI-BW films demonstrated the best performances, followed by control film (without lipids).     

Rheological evaluation of gelatin–xanthan gum system with high levels of co-solutes in the rubber-to-glass transition region

Effects of moisture content, xanthan gum (XG) addition, and glucose syrup (GS):sucrose ratio on the gelation of gelatin-XG systems with high levels of co-solutes were investigated in the rubbery and the glass transition regions. Frequency sweep tests were performed between 0.1 and 100 rad and the storage (G′) and loss (G″) moduli of the system were measured in the temperature range of 60 to −15 °C. The onset of glass transition region increased with decreasing moisture content. The time–temperature superposition yielded master curves of G′ and G″ as a function of timescale of measurement. G″ and G″ were superimposed with the horizontal shift factor a_T, which was temperature dependent according to the Williams–Landel–Ferry (WLF) equation. Glass transition temperature (T_g) of the samples were determined by dynamic mechanical analysis (DMA) from the peak of tan δ. T_g decreased with XG addition. The energy of vitrification of samples with XG increased compared to samples containing only gelatin. Relaxation spectra of the samples were calculated from rheological measurements using the first and second approximations. The Rouse theory was more closely followed with the second approximation.     

Development of a solid phase microextraction protocol for the GC–MS determination of volatile off-flavour compounds from citral degradation in oil-in-water emulsions

The conditions for headspace solid phase microextraction (HS-SPME) analysis of volatile off-flavour compounds in citral emulsion were determined. Type of SPME phase (65 μm PDMS/DVB, 100 μm PDMS and 75 μm CAR/PDMS), adsorption temperature and salt concentration were significant factors affecting total peak area in the gas chromatogram and optimised in one factor experiments. Then, adsorption temperature (30–50 °C), adsorption time (20–40 min), and salt concentration (0–6 M) were studied to develop HS-SPME condition for obtaining the highest extraction efficiency. PDMS/DVB in 65 μm was the optimum fiber because of high adsorption efficiency and good reproducibility. The optimal condition was adsorption at 50 °C for 40 min and 6 M salt added to sample. Good Linearity, high recovery, good reproducibility and low limit of detection (LOD) for all off-odour compounds according to the optimised SPME conditions indicated that the SPME procedure was applicable for the analysis of the degraded citral products in headspace volatile of emulsion.     

Mechanical spectra and calorimetric evaluation of gelatin–xanthan gum systems with high levels of co-solutes in the glassy state

Mechanical properties of gelatin–xanthan gum (XG) mixtures with high levels of co-solutes were examined by dynamic mechanical analysis (DMA). The mechanical spectra of the samples were modeled according to the Williams–Landel–Ferry (WLF) equation/free-volume theory, which requires an entropic lightly cross-linked network. For the α dispersion, E′ and E′′ superposed with the horizontal shift factor a_T, which was temperature-dependent according to the WLF equation; no other secondary dispersion mechanism was detected. The addition of XG to gelatin networks with high levels of co-solutes changed the glass transition temperature (T_g) and kinetics of glass transition and glassy states. In the glassy state, the WLF equation was unable to follow progress in the mechanical properties, which were better described by the Andrade equation. The calorimetric measurements of the gelatin–XG systems were made using a modulated temperature differential scanning calorimetry (MTDSC) to improve the determination of T_g. The samples were exposed to two cooling and heating cycles to provide a controlled recent thermal history in the temperature range of 40 °C to −70 °C. The T_g values of the samples were determined from the second heating cycle in the reversing heat signal. The calorimetric T_g values increased with increasing glucose syrup:sucrose ratio due to increased crosslinking, whereas mechanical T_g decreased with increased XG content due to network formation.     

Edible films made from blends of manioc starch and gelatin – Influence of different types of plasticizer and different levels of macromolecules on their properties

The interest in the development of edible and biodegradable films has increased because it is every day more evident that non-degradable materials are doing much damage to the environment. In this research, bioplastics were based on blends of manioc starch (native and modified) and gelatin in different proportions, added of glycerol or sorbitol, which were used as plasticizers. The objective was to study the effect of two different plasticizers, glycerol and sorbitol, and different concentrations of starch and gelatin on the barrier (water vapor permeability – WVP), mechanical (tensile strength and elongation at break), physicochemical (solubility in water and in acid) and physical properties (opacity and thickness) of the obtained bioplastics samples. As a result, all of them showed transparency and resistance to tensile strength, as well as increasing in thickness values and in the WVP, as the gelatin content increased in the formulations. Finally, all results for tensile strength and elongation at break obtained for those samples plasticized with sorbitol were better than those plasticized with glycerol.     

On the release of volatile acids from wood-based panels – chemical aspects –

Wood-based panels release different amounts of volatile organic acids, which depend, among other factors, on the binder used. The volatile acids released from the boards can be measured using the flask method following the principle of measuring the formaldehyde release according to EN 717-3. Particleboards bonded with alkaline curing phenol-formaldehyde resins (PF-boards) release higher amounts of acetic and lower amounts of formic acid compared to those boards bonded by acid curing urea-formaldehyde reins (UF-resins) or binders based on polymeric diphenylemethandiisocyanates (PMDI). This has been explained by the equilibrium reaction between sodium hydroxide in PF-resins and volatile acids, which leaves less free formic acid than free acetic acid to emanate from the boards. Increasing the binder content in the boards also leads to an increase in the over all amount of sodium hydroxide in the boards. Accordingly, less free acids are left, which could be released from the boards. Fibres made by the chemo-thermo-mechanical process (CTMP) using sodium hydroxide and sodium sulphite as pulping agents release less formic acid than those made by the thermo-mechanical pulping (TMP). This behaviour was also attributed to the equilibrium reaction between the alkali in CTMP-boards and the volatile acids.