Water resistance and mechanical properties of low methoxy-pectin nanocomposite film responses to interactions of Ca2+ ions and glycerol concentrations as crosslinking agents.

To achieve a low methoxy-pectin nanocomposite film with maximum resistance to water and acceptable mechanical properties, the interactions of different glycerol concentrations and Ca2+ ions in both steps of crosslinking on the swelling degree (SD) and mechanical properties of prepared films were investigated using response surface methodology (RSM). Accordingly, quadratic second-order models were fitted to the SD and tensile strength responses; while the cubic model demonstrated a good relation between independent variables and elongation at break respectively. As a compromise between water resistance and mechanical properties of the prepared films, the use of 0.5% Ca2+, 0.75% Gly1 and 7.5% Gly2 is suggested as the optimum condition. Generally, crosslinking of pectin polymer with Ca2+ cations in the second step along with incorporation of nanocellulose into pectin film led to the formation of more flexible and completely water insoluble pectin nanocomposite film in comparison to the other polymers crosslinked with Ca2+ cations.

Preparation and characterization of a novel bionanocomposite edible film based on pectin and crystalline nanocellulose.

In this study, for the first time, the edible pectin film was reinforced by crystalline nanocelullose (CNC). The incorporation of three levels of CNC (2, 5 and 7% w/w) on mechanical, thermal and water vapor barrier properties of pectin-based biodegradable film were investigated using solution casting evaporation method for film preparation. The optimum result was obtained through the nanocomposite film with 5% CNC in terms of mechanical and water vapor properties as the tensile strength increased up to 84% and water vapor permeability decreased by 40%. However, analysis of thermal properties indicated no significant effect of CNC on glass transition temperature. X-ray diffraction (XRD) studies illustrated a positive correlation between the degree of crystallinity and the CNC level. Moreover, AFM images presented good dispersion of CNC in the pectin matrix suggesting appropriate interaction between the filler and matrix, which is in agreement with mechanical consequences. According to the overall results, the reinforcement of pectin film with 5% CNC compared to other strengthening strategies had a higher effect and therefore it could be introduced as a good candidate for the development of strong, completely biodegradable and renewable food packaging material.

Furanic compounds and furfural in different coffee products by headspace liquid-phase micro-extraction followed by gas chromatography-mass spectrometry: survey and effect of brewing procedures.

In this study, the levels of furan, 2-methylfuran, 2,5-dimethylfuran, vinyl furan, 2-methoxymethyl-furan and furfural in different coffee products were evaluated. Simultaneous determination of these six furanic compounds was performed by a head space liquid-phase micro-extraction (HS-LPME) method. A total of 67 coffee powder samples were analysed. The effects of boiling and espresso-making procedures on the levels of furanic compounds were investigated. The results showed that different types of coffee samples contained different concentrations of furanic compounds, due to the various processing conditions such as temperature, degree of roasting and fineness of grind. Among the different coffee samples, the highest level of furan (6320 µg kg⁻¹) was detected in ground coffee, while coffee-mix samples showed the lowest furan concentration (10 µg kg⁻¹). Levels in brewed coffees indicated that, except for furfural, brewing by an espresso machine caused significant loss of furanic compounds.

Determination of polycyclic aromatic hydrocarbons in smoked fish samples by a new microextraction technique and method optimisation using response surface methodology.

Microwave-assisted extraction coupled with dispersive liquid-liquid microextraction as a recently introduced method was applied to determine polycyclic aromatic hydrocarbons in Iranian smoked fish. The results showed that the interaction of hydrolysing solution volume with ethanol ratio, volumes of extracting and disperser solvent is significant in the obtained model. Optimized conditions were: a hydrolysing solution volume 10 ml with 50% ethanol, a pH of 5, and extracting and disperser solvent volumes of 150 and 500 µl respectively. The level of 16 polycyclic aromatic hydrocarbons (PAHs) was determined in 80 smoked fish consisting of four species. The contamination of benzo[a]pyrene in all samples except three was below the European Commission's maximum level of 2 µg kg(-1) for smoked fish, while the ∑4 PAHs (benzo[a]pyrene, chrysene, benzo[a]anthracene and benzo[b]fluoranthene) were between 3 and 12 µg kg(-1) wet weight in all samples. Of the species examined, Hypophthalmichthys molitrix had the highest PAHs (∑16).