Colour

Science programme: Sensory & consumer science

Colour in fruit is a primary driver for first-time consumer selection. Good, rich colour is associated in consumers’ minds with health benefits. In fact, many of the compounds producing colour are antioxidants, which do have proven health benefits.

Colour in fruit derives from anthocyanins (from orange to reds, blues and blacks), carotenoids, (reds, oranges, yellows), and chlorophylls (greens). The compounds are independent of each other and their ratios determine specific colour. There are over 500 anthocyanins alone, and the sheer number of colouring compounds means studies on fruit colour are complex. Another challenge for scientists is to produce fruit with good colour without over-ripeness.

Understanding of plant pigments is the province of analytical biochemists, who work with plant breeders, plant physiologists and molecular biologists to produce the required colour in fruit.

Current projects at HortResearch focus on selecting novel colours in apple and kiwifruit, both in skin and flesh. A highlight of this work was the gold colour in ZESPRI™ GOLD kiwifruit, which led to a scientific paper on its carotenoid composition. The paper describes our understanding of the gold colour and how its green chlorophyll is masked. Work is also being carried out on avocado oil to determine how much lutein it contains in comparison with olive oil.

Other work on berries focuses on co-pigmentation and how anthocyanins combine with other phenolics.

The team’s chief capability is the high-throughput analysis of plant pigments. Essentially the work is lab-based with a small amount of field work.

Collaborations in work on colourful fruit phytochemicals have taken place with another Crown Research Institute, Crop & Food Research, on molecular control of anthocyanins, and with scientists at the University of Bologna in Italy, who are examining the determination of colour in kiwifruit flesh.