Paper-based food packaging materials are widely used, renewable, and biodegradable. Because of its porous structure, paper has poor or no barrier performance against grease, water vapor, water, and volatile organic compounds. Moreover, recycled paperboard can be a source of organic residuals that are able to migrate into packed food. Two different types of paperboard produced from primary and secondary cellulosic fibers were coated using renewable materials, such as alginate and chitosan, and comprehensive barrier measurements showed multifunctional barrier properties of these two biomaterials. Both paper substrates were successfully coated using a draw-down coater, and the measured air permeability of the coated samples was 0 mL•min −1 . Grease resistance was improved, while it was possible to reduce water vapor transmission, the migration of mineral oil saturated hydrocarbons and mineral oil aromatic hydrocarbons (MOSH/MOAH), and the permeation of volatile compounds for both paper substrates when compared with uncoated substrates. Wettability and water absorptiveness of chitosan-and alginate-coated papers were found to be substrate-dependent properties, and could be significantly affected by bio-based coatings. In summary, industrially produced paperboard was upgraded by coating it with the naturally biodegradable biopolymers, alginate and chitosan, thus achieving extraordinary barrier performance for various applications within the packaging industry.
Chitosan is a versatile biopolymer with many interesting functionalities. Its effects on the barrier and mechanical properties of single- or double-coated fibre-based packaging papers in dependence on the applied drying regime were successfully tested. Our investigations revealed chitosan to be a highly robust biopolymer, since the different drying regimes did not alter its contribution to the development of strength and barrier properties of the coated packaging papers. These properties showed a stronger influence of the applied coat weights than of the different drying regimes. The effect of chitosan coatings were quantified by measuring tensile strength (TS), burst strength (BS) and tensile energy absorption (TEA). These revealed that TS, BS and TEA of the coated papers increased significantly. Moreover, the chitosan-coated papers were less permeable against water vapor and air. High grease resistance was observed for double-coated papers, irrespective of the drying regimes. The coated paper surface showed a more hydrophilic character, resulting in lower contact angles and higher water absorption properties. In this study, industrially produced chitosan has been proven to be a renewable, robust biopolymer that can be utilized as an additive to increase strength and the barrier properties of fibre-based materials.
We present a rapid
method based on 2D thin layer chromatography
(TLC) for the simultaneous separation and quantification of organic,
lipophilic extractives occurring in lignocellulosic biorefineries.
The separation is based on alkaline followed by acidic elution for
a 2D separation of the different compound classes (sterols, fatty
alcohols, fatty acids, and resin acids). Staining with Nile Blue A
and subsequent scanning and image analysis of the plates provides
quantitative information on the concentration of each compound class.
Correlation coefficients between 0.92 (abietic acid, resin acid) and
0.98 (β-sitosterol, sterol) are determined in these experiments.
Besides the analysis of the composition, this procedure indicates
the relative polarity as the acidity or basicity of the constituents.
TLC results of an industrial lipophilic extractives sample correlate
with state-of-the-art GC × GC–MS measurements with differences
being in the range between 0.5 (fatty alcohols) and 6% (resin acids),
respectively.
The current demand to cut back on the use of plastic materials has brought a major boost to the search for bio-based alternatives. Not only are plastic bags and primary food packaging under scrutiny here, but also those materials used as functional barriers to reduce, for example, the migration of mineral oil hydrocarbons (MOH) from recycled paper and board packaging. Most of the barriers now in use are synthetic, often have only moderate barrier functionalities and in addition reduce the environmentally-friendly character of cellulose-based materials. Against this background, bio-based polymers have been evaluated in terms of their functional barrier properties. Chitosan was found to be among the best performers in these materials. In this study, the behavior of a lab-made chitosan acetate film was compared with conventionally produced polymer films. The two-sided migration experiment described recently was used to determine the barrier properties of the tested materials. This not only allowed to test the intrinsic migration of the films and the permeation through them, but also to simulate real packaging situations by using a recycled paper as donor for MOH. The migrated fractions were determined using gas-chromatography-based techniques. While the conventionally produced polymer films showed only moderate barrier function, excellent results were seen for the biopolymer. It reduced the migration from the recycled paper to not detectable, singling it out as a good alternative to conventional materials.
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