Executive Summary: Carotenoid natural dyes from horticultural wastes: Extraction with bio-solvents and application to textiles

Summary of Project and Key Findings:
This project investigated the extraction of carotenoids from horticultural by-products. Carotenoids are a group of highly coloured, non-water soluble compounds, which impart the characteristic colours of carrots, pumpkins and some other types of fruit and vegetables, and they have potential as natural dyes. This project found that carotenoids could be extracted by two bio-solvents. After some optimisation of extraction parameters, methods were developed to apply the extracts to the most important locally-grown natural fibres, wool and harakeke. Colours such as pink, purple, yellow/orange and brown were imparted to the fibres, with the colours being dependant on the particular horticultural by-product, extraction protocol and application conditions. This research complemented a parallel study into the water-based extraction and utilisation of natural dyes from local bio-resources, by extracting different compounds, with different colours, and thus broadening the colour range of locally-sourced natural dyes available to end-users.

The student who conducted the research gained experience in processing horticultural by-products, solid-liquid extraction, green chemistry, natural products chemistry, UV/visible spectroscopy, textile colouration, colour measurement and working safely in a busy chemical laboratory.

This work enhanced the value proposition of locally produced natural dyes to end-users. The ultimate goal is to benefit the local horticultural industry by having a new revenue stream and additional employment. The work also supports innovation and sustainability amongst end-users of the natural dyes, such as manufacturers of rugs, carpets, apparel, paint, and leather.