Old varieties of apples, bananas and onions are part of a UK study to potentially give consumers products with "significantly" higher levels of nutrients, it has been announced.

A consortium including Royal Botanic Gardens, Kew, and Cranfield University, assembled by consumer goods firm Unilever, will examine "pre-domesticated" varieties of plants which have been changed relatively little by breeding and could contain higher nutrient levels.

It follows research by Unilever which found that the Egremont Russet variety of apple contains up to 10 times more of a phytonutrient than some modern varieties - thought to be one example of older plant varieties being richer in nutrients and fibre.

Unilever said it hoped that the study, co-funded by the Technology Strategy Board, would result in new products containing ingredients from plants that currently have little use within the food industry.

The three-year study will also attempt to identify older and more nutritious varieties of mangoes and tea.

Dr Mark Berry, based at Unilever's research and development laboratories in Bedford who is leading the consortium, said: "The plants we eat today like fruits and vegetables have often been bred and selected on their weight-based yield per acre of land, and not necessarily on the nutrient content of the produce.

"This research looks to turn this approach on its head. Perhaps a better strategy for human health, not to mention sustainable agriculture, would be to buy plants not based on their weight, but on their nutrient content.

"It's fascinating to contemplate that these pre-domesticated varieties have remained relatively unchanged for thousands of years. We'll be going back in time to identify the plants from yesteryear that our ancient ancestors would have eaten, with a view to potentially reintroducing them into our diet."

Professor Monique Simmonds from Royal Botanic Gardens, Kew, said: "This project provides us with an exciting opportunity to investigate, with scientists at Cranfield University and Unilever, the chemistry of under-utilised plants and older varieties of some of our favourite fruits.

"It enables us to increase our knowledge about the diversity of phytochemicals in these plants and whether their diversity has decreased during domestication. In an age when we are losing so much of our biodiversity due to changes in land use we can also evaluate the loss in phytochemical diversity that could have a negative impact on our health."

Professor Leon Terry from Cranfield University added: "The new project brings together the expertise of three internationally recognised UK-based organisations with the collective view that a paradigm shift is required whereby ingredients are selected on their health-promoting properties.

"Although fruit and vegetable-based products like smoothies are widely available, few contain the benefits of naturally high health-promoting phytochemical content from older cultivars. This is because the varietal selection of fruit and vegetables supplied by the fresh produce industry today has been increasingly centred on their products' price, size, visual appearance, storage potential and yield."