New biodegradable food packaging from cellulose and sweetcorn stalks offers best of both worlds

Researchers in China have highlighted the possibilities offered by a new form of biodegradable food packaging made of a mix of sweetcorn stalk material and cellulose nanofibres

The suggestion from the scientists is that using nanofibres of cellulose, or plant fibre, along with corn straw cores (CSC), part of the sweetcorn stalk, combines the positive characteristics of both materials.

Writing in the journal Food Hydrocolloids, they said that CSC has been identified as a potential biodegradable form of food packaging thanks to, for example, its resistance to ultraviolet light and water vapour.

However, it also has drawbacks, among them a lack of mechanical strength, poor resistance to microorganisms and poor water resistance.

In an effort to overcome some of these limitations, the researchers decided to develop composite materials made up of cellulose nanofibres and CSC.

After testing their novel nanocomposites, the researchers said that they had “good mechanical properties” and acted as effective barriers to water vapour. The materials were also good UV barriers and were able to block bacteria too.

The nanocomposites, essentially, offer the best of both worlds, namely the UV and water vapour barrier properties of the CSC, coupled with the improved mechanical strength and bacteria resistance of cellulose nanofibres.

Developing novel biodegradable food packaging materials is important because the pressure to increase plastic production for the sector remains high.

Other research has indicated that demand for food packaging, much of which is not biodegradable, is increasing by just over 7% a year.

Key among the various packaging materials used, the scientists note, are polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET) and polyamide (PA).

“They are widely used due to good mechanical properties, transparency and mature craftsmanship,” the authors said in their study.

“However, a variety of them are not able to be degraded and effectively recycled, which brings about some extraordinarily serious environmental problems.

“Not only that, the price of traditional plastic materials is gradually raised by the shortage of petroleum resources.

“For these reasons, the development of new-generation packaging materials has caused concern of the world-wide researchers.”

While there are already biodegradable petroleum-based packaging materials used for food packaging, among them PBAT, the researchers note that there are non-biodegradable components associated with these materials that result in the production of plastic waste.

For the production of the novel materials described in the new paper, sweetcorn stalks are readily available, with the researchers describing them as “by far the most readily available crop residue”.

Other parts of the corn straw stalk are useful too, with the cortex, an outer tissue layer, being used for animal feed, fibre for the paper industry and the production of biomass ethanol. The cortex of corn straw is also used for the production of active ingredients for industry.

Up to now, there have been a few studies looking at using corn straw cores, according to the researchers.

However, cellulose nanofibres, they note, have been used widely in recent years, not least because they are easily available, biodegradable and non-toxic.

Uses have included paper production, the creation of composite materials, edible films and packaging, the scientists wrote in their paper.

The scientists involved in the study are from several institutions. Nine of them are based at the Department of Materials Science and Engineering at the Beijing Institute of Technology in the Chinese capital.

A further two researchers are from the School of Materials Science and Engineering at the North University of China in the city of Taiyuan, while one scientist is at the China North Chemical Research Academy Group in Beijing.

The new study, published online in May, is titled Corn straw core/cellulose nanofibres composite for food packaging: Improved mechanical, bacteria blocking, ultraviolet and water vapour barrier properties.

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