Scientists have found that seaweed is rich in a variety of polysaccharides, which can be stretched into thin films after forming gels. Its good flexibility makes it have the potential to be used as plastic wrap. Seaweed plastic wrap can be cooked with the wrapped food or eaten directly. If it is accidentally thrown into nature by people, as long as it is in contact with enough water for more than 2 hours, it will decompose into organic matter, enter the soil and blend into nature.

Intern reporter Zhou Qianying

Open the refrigerator with a hungry stomach, take out a rice ball or hamburger wrapped in plastic wrap, throw it directly into the microwave to heat it, and can't wait to take a bite of the food still wrapped in plastic wrap, chew it with relish, and while tasting the food, you seem to have tasted a hint of the sea...

This seemingly nonsensical plot in the movie is a real scene in life. All this is thanks to the new environmentally friendly plastic wrap developed with seaweed as raw material - seaweed plastic wrap.

Recently, the website of the British "New Scientist" weekly reported a research result of the team of Kelan Ward of the University of Leeds in the UK in the field of seaweed cling film. The team used a brown algae called Sargassum to produce a cling film that can be safely used to wrap moist foods such as fresh-cut fruits.

So, how is seaweed cling film produced? What is unusual? With these questions, the Science and Technology Daily reporter interviewed Professor Xu Jiachao and Associate Professor Wang Lei of the School of Food Science and Engineering of Ocean University of China to unveil the "mystery" of seaweed cling film.

Natural, environmentally friendly and widely available

Plastic is the result of industrial civilization. It brings convenience to mankind while also bringing endless troubles and disasters. At present, the plastic cling films on the market cannot be degraded. If they are buried in the soil, the plasticizers in the plastic will penetrate into the soil and water, and eventually enter the human body with water and plants. At the same time, plastic molecules can also enter the human body and cause harm to the human body.

Nowadays, small seaweed can be transformed into a new type of environmentally friendly cling film, which provides a new possibility for solving plastic pollution.

There are many types of seaweed, with a total of more than 20,000 species, and almost all marine plants can be classified as algae. Seaweed has huge development potential, and the active substances in it can be developed into medicines, functional foods, and cosmetics. Now, small seaweed can also be made into cling film.

Scientists have found that seaweed is rich in a variety of polysaccharides, such as alginate, agar, carrageenan, etc. These polysaccharides can be extended into thin films after forming gels, and their good flexibility makes them have the potential to make cling film. Conventional plastic cling film will be discarded after one use, while seaweed cling film can be cooked or eaten directly with the wrapped food. In addition, it takes 200-1000 years for an ordinary plastic bag to be completely degraded, and if seaweed cling film is accidentally thrown into nature by people, as long as it is in contact with enough water for more than 2 hours, it will decompose into organic matter, enter the soil and blend into nature.

However, not all seaweed is suitable for cling film. Wang Lei told reporters: "At present, the cling film made of alginate in brown algae has better performance. In addition, carrageenan and agar in red algae, including other terrestrial plant gums, can be made into films directly or through compounding."

Try to replace plastic with seaweed products

Seaweed is a widely used natural resource. For a long time, in order to better benefit human life and solve the environmental pollution problems caused by plastics, Chinese and foreign scientists have been conducting innovative research on replacing plastics with seaweed products.

Indian scientists grind dried seaweed into particles, remove impurities from it, and then heat it in a specific container to finally get real gel. This gel can be made into seaweed films of different thicknesses, and even if it is as thin as a cicada's wing, it will not be easily damaged.

Indonesia is also a major seaweed producer. One of its start-ups has taken advantage of local seaweed production to launch a packaging material made of seaweed that can not only be eaten directly, but also be 100% biodegradable.

In addition to these countries, China has also conducted innovative research on seaweed cling film and has long been committed to the research on the utilization of harmful seaweed biomass.

The scientific research team led by Xu Jiachao invented the patented edible and fully biodegradable seaweed food cling film. Compared with traditional cling film, the biggest advantage of this cling film is that it is highly safe, has no plasticizers and no carcinogens, can achieve 100% biodegradation within 6-12 months, and will not cause pollution to the environment.

Based on many years of research experience on marine organisms, Xu Jiachao found that alginate in kelp is a good raw material for making cling film. "Algin is a natural anionic polysaccharide that can react with Ca^2+ to form a denatured gel calcium alginate. When a large amount of Ca^2+ is present, it will combine with the alginate molecules to form a tight "egg box" mesh-like denatured gel structure, which has good film-forming properties." Xu Jiachao introduced that because calcium alginate is a strong gel, the calcium alginate film formed is too brittle and has poor toughness, and is not easy to fold and curl, which limits its practical use. For this reason, they developed a dual-ion denatured gel technology, which can improve the flexibility and mechanical properties of the calcium alginate film.

Xu Jiachao's team also promoted the development of fully biodegradable seaweed mulch. According to statistics, China's 580 million mu of film-covered land is suffering from serious damage from "white pollution". Xu Jiachao's team prepared the Enteromorpha that caused ecological disasters on the Qingdao coast into a fully biodegradable seaweed mulch, which can effectively replace traditional plastic mulch and resolve the problem of "white pollution".

In addition to plastic wrap and mulch, seaweed can also be made into tableware. The team led by Academician Yu Shuhong of the University of Science and Technology of China extracted a food-grade Sargassum cellulose nanofiber (SCNF) from Sargassum industrial waste. SCNF forms SCNF hydrogel after calcium ion cross-linking. The team prepared SCNF hydrogel into a Sargassum cellulose-based structural material with high strength and high thermal stability. This structural material has good processability and food safety, and can be processed into tableware of different shapes.

Large-scale promotion requires many hurdles

Plastic substitutes made from seaweed show a very broad market prospect. At present, many companies around the world are promoting plastic substitutes such as straws, tableware, and packaging bags made from seaweed, and are continuously expanding the production scale of seaweed biomaterials.

"The Chinese cling film market is nearly 20 billion yuan. The launch of seaweed cling film will greatly change people's lives." Wang Lei said, "The development of seaweed cling film can strongly stimulate the development of seaweed breeding and processing industries, and can create huge economic value. In addition, it can also solve the "white pollution" problem caused by plastic products, and has good ecological, economic and social benefits."

However, if seaweed cling film wants to be promoted on a large scale, it still faces many problems that need to be solved.

Like all degradable materials, high cost is also one of the bottlenecks restricting the development of seaweed cling film. At present, traditional plastic cling film still occupies the mainstream market. A large part of the reason is that the price of seaweed cling film is too high, making it difficult to promote. When people buy it, they prefer lower-priced plastic cling film.

"In addition, the difficulty in the research and development of seaweed cling film is that this type of cling film is relatively thick, and its ductility and toughness need to be improved, so it is necessary to continue to increase investment in scientific research; at the same time, the production machinery and production lines required for the industrialization of seaweed cling film are not yet perfect. To solve these problems, equipment development and basic research need to be carried out simultaneously, so as to achieve the common development of the entire industry chain." Xu Jiachao said.

At present, their research on seaweed cling film has made breakthrough progress in the laboratory stage. Despite the difficulties in the transformation of scientific and technological achievements, Xu Jiachao is still full of confidence in the market application of seaweed cling film. He said that after the launch of this technology, it will greatly benefit and change people's social life. He hopes to unite enterprises and all walks of life to promote the industrialization of the project as soon as possible.

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