Secrets of the past may not be the only valuable knowledge held by some of New Zealand’s oldest Māori cloaks.
While researching the properties of harakeke (native flax) to find ways of stabilising the flax fibres in the cloaks before an exhibition at Te Papa last year, Associate Professor of Chemistry Gerald Smith discovered potentially beneficial anti-fungal properties in their fibres.
Gerald believes this natural resistance could be used, in the long term, for new innovations such as treatments to preserve old books and papers, textiles that are protected from fungal attack by environmentally-friendly means or natural packaging for food that spoils easily, such as fruit.
These new possibilities arose from research for a Master’s project by Rangi Te Kanawa, a Conservator at Te Papa.
She developed a treatment to bind together deteriorating harakeke fibres, which become brittle over time after exposure to light and humidity, and her treatment was used on some of the cloaks in the exhibition.
While examining the fibres, Gerald and Rangi found that harakeke produced coumarin, a fragrant chemical compound that can be smelled in the aroma of freshly cut grass. Coumarin has anti-fungal properties and also repels pests.
They also identified the presence of a number of metal ions in the fibres, which could be contributing to its anti-fungal properties too. However, not all of the properties identified in harakeke fibres had such potential.
Harakeke was found to have a particularly high content of a type of sugar polymer called hemicellulose, which results in the production of harmful levels of acetic acid.
“This evolution of acetic acid is known as the vinegar syndrome, because of its vinegary smell. It 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,” says Gerald.
More recently, Gerald has shown that potentially damaging hydrogen peroxide is produced by decomposing harakeke fibres.
“It’s a balancing act. We need to learn how to control the chemical reactions taking place to bring out the desirable, anti-fungal properties, and limit the undesirable effects of things like acetic acid and peroxide.”