Bioplastic food packaging from brown seaweed alginate

Abstract

Brown macroalgae provide abundant biomass and contain gel-forming polysaccharides, their use of which are interesting as potential material in the production of biodegradable plastic for food packaging.In this research, bioplastic films suited for different applications were developed, such as food coating and edible wrapping, as well as conventional films. Experiments were conducted to explore the best methodology to use, and a base mixture of alginate-water solution containing a few other compounds, was developed. Three different types of commercial sodium alginate powder were used, all of which originated from Norway, and had known characteristics. The effect of incorporating these alginates was compared in the finished films, along with combinations of other compounds added, giving variance in color and texture.The focus of the study was on working out a mixture for a strong film. The preparation parameters time and screw speed were optimized and standardized for all samples, while temperature was slightly lowered for thicker solutions, as they required prolonged heating. All films were evaluated for strength, flexibility, adhesiveness and homogeneity, and out of those tested, 33 films were then selected for further characterization.Mechanical properties were measured with a TA-HD plus texture analyzer, 5 samples for each film. Other measured parameters of the films included thickness, color and water activity. The results were used for comparison between the films of this study. The thickest film was 0.49 mm, it had stable water activity (AW), good flexibility and was fairly transparent. This film contained two of the alginates supporting good mechanical properties in the study, and had tensile strength of 0.67 MPa, elongation-at-break was 147 % and toughness 0.09 MJ/m3. The type of water solvent, as well as one of the substances used in this formulation, distinguished it from most other films. Texture measurements can result in great difference of values, related to equipment and measuring methods used, therefor a comparison with plastic films on the market, measured under same conditions, is needed. To give some approximation to these measurements, values from one sample test of a thin transparent commercial plastic sheeting (commonly used for vegetable or flower wrapping) were 0.12 MPa, 119 % and < 0.00 MJ/m3 for tensile strength, elongation-at-break and toughness respectively.Principal Component Analysis (PCA) on data from all measurements, showed clear relation between thickness and overall film strength. Pearson’s analysis showed strong positive correlation for thickness to strength (r=0.802) and toughness (r=0.708) but intermediate to breaking strain (r=0.461). Toughness and breaking strain had also positive correlation (r=0.754). Near infrared spectroscopy (NIR) and microscopic evaluation of the films were performed as well.The results from this project are a promising opportunity among new trends in food packaging. Next steps will be further development of few selected films and upscaling to manufacturing of thin, safe and biodegradable films.