Abstract
Edible films and coatings based on biopolymers to protect and extend the shelf life of food and medicine can be functionalized, by applying a holographic marker on the coating surface for marking products or sensing storage conditions. In this work, holographic markers were prepared on the surface of thin biopolymer coatings based on starch, gelatin, agar and also starch/gelatin and starch/agar blends by the nanoimprint method from a film-forming solution. The morphology of the surface of holographic markers using optical microscopy in reflection mode was examined, as well as the reasons for its formation using an analysis of the flow curves of film-forming solutions. It was found that the surface morphology of the marker strongly depends on the composition, consistency index of film-forming solution and miscibility of the components. It was shown that the starch/agar film-forming solution at the ratio of 70/30 wt.% has a low consistency index value of 21.38 Pa·s0.88, compared to 64.56 Pa·s0.67 for pure starch at a drying temperature of 30 °C, and the components are well compatible. Thus, an isotropic morphology of the holographic marker surface was formed and the value of diffraction efficiency of 3% was achieved, compared to 1.5% for the marker made of pure starch. Coatings without holographic markers were analyzed by tensile strength and water contact angle, and their properties are highly dependent on their composition.
Highlights
One of the urgent directions in the development of new packaging materials is the creation and study of non-toxic, biocompatible, biodegradable and edible packaging [1]
The aim of this work was to study the surface morphology formation processes of the edible coatings with a holographic marker based on potato starch, gelatin, agar and starch/gelatin and starch/agar blends on their diffraction efficiency, as well as mechanical strength and wettability
Coatings are prepared from the film-forming aqueous starch/fish gelatin in the presence of glycerol, that the solubility of the starch film decreases from solutions based on potato starch, gelatin, agar, as well as starch/gelatin and starch/agar blends, 46.56% to 30.19% when mixed with gelatin in a ratio of 3:1 [35]
Summary
One of the urgent directions in the development of new packaging materials is the creation and study of non-toxic, biocompatible, biodegradable and edible packaging [1]. Such packaging usually consists of biopolymers, blends thereof, as well as biocomposites and can be functionally and active [2] These materials are used for extending the shelf life of food and drugs, creating forms of drug delivery and partially solving the problem of environmental pollution by non-biodegradable packaging waste [3]. An edible holographic marker gives the visual multicolor optical effects on the surface of food products without using dyes This technology can be used for decoration of food products [4,5], the marking of food and pharmaceutical products [6] and for monitoring storage conditions, due to the sensitivity of the markers to humidity and temperature [7,8]
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