Flax fibres fight fungi

In the early 20th century, New Zealand’s flax industry was a significant money earner, supplying fibre for the world’s rope and linen trade, but the advent of non-renewable synthetic fibres made the more labour-intensive natural version all but redundant. Now, new research has uncovered a hitherto unknown property of our native flax Phormium tenax (harakeke). It has potentially valuable anti-fungal properties.

Research into stabilising flax fibres in old cloaks

The finding was made during research on how to prevent the deterioration of some of New Zealand’s oldest Māori cloaks. In a press release, Victoria University of Wellington’s Associate Professor of Chemistry Dr Gerald Smith says his team was trying to find ways of stabilising the flax fibres in old cloaks, which become brittle after exposure to light and humidity over time.

“As well as finding a way of halting this deterioration, we also found that the enhanced resistance some harakeke have to fungal growth means it could ultimately find new uses in conservation and textiles — as well as in packaging that would prevent food from spoiling.”

Flax fibres produce anti-fungal compound

The researchers discovered that the harakeke fibres produce a chemical compound called coumarin, a fragrant substance that we can smell in freshly cut grass that has anti-fungal properties and repels pests.

Dr Smith says that they also identified the presence of a number of metal ions in the flax fibres, which could also be contributing to its anti-fungal properties. “We know the anti-fungal properties are there, but we don’t yet fully understand the chemistry or how to control or enhance those properties.”

Potential for innovative products

Dr Smith says the research has the potential to lead to a range of innovative new products.

“One possibility is the development of innovative textiles that are protected from fungal attack by natural, environmentally-friendly means. Another is the development of packaging for food such as fruit, which spoils easily.

“Many existing anti-fungal treatments are harmful both to health and the environment, so there is strong demand for effective, natural and volatile anti-fungal agents that we can use in food storage.”

Applications are also anticipated in the museum sector for storing and protecting heritage items.

Problem of ‘vinegar syndrome’ in museums

Experimenting on different varieties of flax supplied by Landcare Research from New Zealand’s national collection, Dr Smith says they found that harakeke has a particularly high content of a type of sugar polymer called hemi-cellulose, which results in the production of acetic acid causing deterioration of fibres.

“It’s known as ‘vinegar syndrome’ and is a menace in the museum environment – because as well as accelerating damage on the item producing it, it is volatile and can float off and affect other exhibits. Another big problem we found is with fibres that were dyed black. The dye was usually made from a mud rich in iron salts, called paru, which also contains acidic materials.”

As part of her Victoria University master’s project, Te Papa Conservator Rangi Te Kanawa worked with Dr Smith to develop a treatment for the affected fibres. The treatment, which is sprayed on, uses sodium alginate and zinc acetate to bind the harakeke fibres together, neutralising the acid and slowing the deterioration.

As well as the spray being used on cloaks at Te Papa, it is now also being used by conservators in other museums overseas.