In many packaged food products, a plastic barrier is used to protect the foods from mechanical, microbial, and chemical damage. However, the materials used let through some oxygen, which can also food to spoil. There are materials which provide better gas barrier properties, but many of these are problematic for the environmental or non-transparent, so they are rarely used.

Byeong-Su Kim, Yonsei University, Seoul, Republic of Korea, Dongyeop X. Oh, Korea Research Institute of Chemical Technology, Ulsan, and University of Science and Technology, Daejeon, both Republic of Korea, and colleagues have created an optically transparent and renewable gas barrier coating. The material, which the researchers call a  “crab-on-a-tree” coating, combines chitin nanowhiskers (CNWs)—found in crabs—and cellulose nanofibers (CNFs)—which are found in various trees.

The researchers created the coating via a layer-by-layer (LbL) method using a spray coater. A layer of polyethylene terephthalate (PET) was added to the top, and the layers were then hot-pressed to produce the finished coating. The combination of crystalline nanomaterials and thin films in the coating results in a flexible film with excellent barrier properties. The coating showed an oxygen transmission rate of less than 0.5 mL m^–2 per day and maintains its performance when exposed to mechanical stress or moisture.

• Crab-on-a-Tree: All Biorenewable, Optical and Radio Frequency Transparent Barrier Nanocoating for Food Packaging,
  Taehyung Kim, Thang Hong Tran, Sung Yeon Hwang, Jeyoung Park, Dongyeop X. Oh, Byeong-Su Kim,
  ACS Nano 2019, 13, 3796–3805.
  https://doi.org/10.1021/acsnano.8b08522