In the foodie world, the debate about Scotland's oil can only mean one thing: rapeseed.
Touted as a healthier alternative to imported olive oil because it contains 10 times the level of omega-3 and half the saturated fat, it also ticks the right boxes in terms of being a locally grown product with a low carbon footprint.
The industry in Scotland has expanded dramatically over recent years since the launch of Ola, the first Scottish rapeseed oil, in 2008 and there are now at least seven artisan brands being produced on farms across the country – mostly in the north and east, although the latest to launch is on the Isle of Arran. Generally, the colour of this edible Scottish oil is a distinctive bright yellow, and flavours range from buttery to nutty to grassy, depending on the variations in terroir.
It's inevitable that, as the industry matures and develops, more questions are being raised about the accuracy of claims about the oil being "100% pure" and "rich in omega-3".
In terms of the latter, a new benchmark has been established this week by biochemist Dr Jane McKenzie of Queen Margaret University in Edinburgh. She was asked to analyse Black & Gold cold-pressed oil from East Lothian to establish its nutritional content for marketing purposes, with specific regard to its omega-3 levels.
Dr McKenzie says there's a problem in the way omega-3 is marketed, because it can be cancelled out if omega-6 levels are too high. "Everyone claims their oil is rich in omega-3 but it's not the total amount that matters; what's important is the balance between omega-3 and omega-6 fatty acids."
She was able to confirm that the balance between omega-3 and omega-6 acids in the East Lothian oil conformed to the World Health Organisation's guidelines.
She also found – to her surprise – that the level of antioxidants in rapeseed oil matched that of olive oil and, crucially, that neither of the attributes in rapeseed oil was destroyed while cooking at high temperatures, whereas they begin to break down when olive oil is heated.
This original research now means Scottish cold-pressed rapeseed oil is probably superior to extra virgin olive oil in health terms.
Research is also under way at Glasgow Caledonian University to analyse Stark cold-pressed rapeseed oil, made from plants grown on Arran from Ayrshire seeds. It's an expensive business at £1500 per sample, but producer Ewan Stark says it's worth it in terms of marketing his product in an increasingly competitive market.
He is keen to discover whether west-coast oil, produced from spring crops, has any unique nutritional properties. Most east-coast oils, he says, are from winter crops.
Another challenge to rapeseed oil's ascendency in the Scottish foodie firmament comes from the investigative food writer and Sunday Herald columnist, Joanna Blythman. She insists that, after tasting UK-grown rapeseed oil, she remains underwhelmed and prefers the green delights of imported extra-virgin olive.
"I actively dislike the flavour: dry, bitter sometimes, at best neutral," she told me last week. She also believes it to be an environmentally unfriendly crop because it takes lots of nitrate fertilisers to grow it.
"Also," she said, "most seeds are pre-treated with neonicotinoid pesticides, the kind that are killing off bees."
But Gregor Mackintosh, founder of Mackintosh of Glendaveny from Aberdeenshire, Scotland's largest producer of cold-pressed rapeseed oil with outlets in 64 Tesco and 43 Asda stores in Scotland, and another significant supermarket contract in the pipeline, vigorously disputes this.
"If pest controls are used at all they are heavily monitored to meet national standards and are nothing compared to those used on carrots, potatoes or other mainstream crops," he says.
"Every crop seed is pre-treated, and it cuts out so many problems further down the line that might require a huge chemical input to sort them out. And by the time it comes to harvest, there's hardly any trace of neonicotinoid left."
Stark, an agronomist from Dundee, adds that neonicotinoid is only harmful to bees if they come into contact with the seed, which is unlikely because they are in the ground.
"Pre-treatment will have no effect on daughter crops," he said.
Lynn Mann of Supernature in Midlothian argues that using spring varieties of rapeseed, as she does, helps reduce the growing season and cut down on the need for chemical pest control over the winter.
But it might not be as clear-cut as it appears. John Sorrie of Ola, near Inverurie, says he uses bee-friendly sprays on his homegrown seeds and plants – but hints that not every grower is so ethical.
Like the oil itself, this debate is set to run and run.
cate.devine@theherald.co.uk
Twitter: @CateDvineWriter
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