In extreme heat, ice packs are essential for delivery boxes. Recently, reusable cooling packs made of gel have also been introduced. However, they are useless if the plastic packaging tears and melts. Scientists have developed a coolant that maintains its shape without allowing water to form when melted. Not only can it be reused when frozen, but it also biodegrades without plastic components, making it environmentally friendly.
A research team led by Professor Gang Sun and Dr. Jiahan Zou from the University of California, Davis, presented their findings on the development of "jelly ice," which is reusable and biodegradable using gelatin, at the annual meeting of the American Chemical Society (ACS) held in Washington, D.C., on the 18th.
Gelatin is a hydrogel that solidifies in water like a jelly. In other words, water is trapped between the particles that are linked together in a mesh. It is also referred to as a "solid substance" due to its solid nature.
Professor Sun began his research after hearing a question from Professor Luxin Wang of the university's Department of Food Science. Professor Wang noted that seeing melted ice creating water in the seafood display at supermarkets made him think it could spread pathogens and contaminate the display. The jelly ice developed by Professor Sun alleviated Professor Wang's concerns. While it freezes into a solid like regular ice, it does not create messy water when it melts.
The research team stated that the idea for jelly ice came from the process of freezing tofu. Professor Sun said, "Frozen tofu retains water inside, but when thawed, it releases water," adding that "we attempted to solve this problem using gelatin, another material."
Gelatin is a protein derived from collagen found in tendons or cartilage, making it safe for the human body. Additionally, it is a polymer material made of long chains that form a hydrogel with tiny holes capable of trapping water molecules.
Test results showed that in jelly ice, water remained trapped within the holes during the phase change process from liquid to solid ice and back to liquid. The research team first published their findings on jelly ice in 2021 in the journal of the American Chemical Society and has since continued to improve the production method. They reported that they can now produce jelly ice composed of 90% water in a single step.
Jelly ice can be washed with water or bleach and can be frozen and melted freely by changing temperatures. Jelly ice shakes and compresses like jelly at room temperature, but it does not leak water. When cooled below 0 degrees Celsius, it becomes a solid again.
Dr. Zou stated, "Compared to regular ice of the same shape and size, jelly ice has a cooling efficiency that can reach up to 80% in terms of the amount of heat it can absorb during the phase change process," adding that "on the other hand, it is reusable and can maintain its heat absorption capacity even after multiple freezing and thawing cycles, making it superior to regular ice."
The research team announced that they can create jelly ice in sheet forms weighing 0.45 kg (1 pound), similar to commercially available large cooling packs. However, without external packaging, it can be customized into any shape and has the advantage of being biodegradable. They added that it is made entirely of natural ingredients, and when placed in a pot, it decomposed and helped promote tomato growth.
Professor Sun stated that while jelly ice was initially developed for food preservation, it could also be used for transporting pharmaceuticals, blood, and biological samples in biotechnology research. It has the advantage of being usable in areas where water is scarce, making it difficult to produce ice. However, the research team noted that large-scale production trials are necessary before commercialization.
References
ACS Fall 2025, https://acs.digitellinc.com/live/35/session/560625
ACS Sustainable Chemistry & Engineering (2021), DOI: https://doi.org/10.1021/acssuschemeng.1c06309