Robert Mackenzie believes his family farms location, surrounded by the coastlines of the Moray, Cromarty and Dornoch firths and sheltered by the north west Highlands, is what gives Cullisse Highland Rapeseed Oil its particular, buttery taste, chosen by chefs from London to Singapore.

The farms position also gives way to good growing conditions for the crop, which is too far north to feel the effects of flea beetle and avoids most disease issues, with slugs the only real setback, according to Mr Mackenzies brother Peter, who manages the farming side of the operation.

The brothers prefer to keep variety choice under wraps, commenting only that it requires careful selection to create a flavoursome oil with good colour.

Mr Mackenzie says: Varieties are mostly developed for traits like higher yields and most are not selected on taste. Rapeseed that goes for bulk refining is just a blend of a lot of varieties, which is processed at really high temperatures and undergoes a bleaching process, creating a mutual flavour.

Some varieties we have tried made a much darker and cloudier oil or can be much more industrial tasting. When youre cold pressing, youre trying to select a variety thats going to give a nicer flavour. The problem is these varieties then go out of fashion and seed companies drop them. We have probably only got one to two years left of the variety we are growing, unless we just use farm saved seed but that can be problematic over time. We may need to do some trials and select a new variety soon.

Alongside wheat, potatoes, spring and winter barley, the farm grows around 80 hectares of oilseed rape, of which about 100 tonnes goes into its own-brand cold pressed oil, while the rest is sold on the open market.

Buttery Mr Mackenzie says: Chefs like our oil because they say its buttery and grassy-tasting, a bit like peas or asparagus but not all varieties have that. Some can be quite bitter. Theres obviously the varietal difference but also the climatic difference too. We have a longer, cooler, growing season that creates this flavour, whereas German oils tend to have a much more peppery flavour as a result of their shorter, hotter growing season.

The cold pressing process also retains the flavour of the crop, resulting in a healthy oil with a thicker consistency.

To make a standard vegetable oil its refined at a very high temperature with a chemical called Hexane which extracts all the oil from the seed and the colour is then neutralised. With cold pressing youre not getting every drop of oil out of the seed but as its a gentler process, youre retaining that colour and you get that nuanced flavour.

Mr Mackenzies inspiration for the cold pressing process was an unusual one, stemming from his involvement with Farm Africa while studying agriculture at university.

We liked the idea of Scottish rural communities supporting rural communities in Africa, so did some fundraising events. I went out to see some of their work in Kenya and visited a village that had been given a cold press to crush sunflower seeds. All the local smallholders would bring their seeds for crushing and they could then sell the oil at market. It was a simple process and much more crude than our sophisticated equipment. I wondered why we werent doing it with rapeseed.

The company now donates 20p from every litre sold to Farm Africa.

The business pressing facility started life in a shipping container but is now housed in a converted granary.

They can now press 1t a day, equating to around 400 litres of oil and 600kg of by-product which is fed to the farms suckler herd or sold to neighbouring farms.

For the oil itself, 60% of Cullisses market is retail, through farmers markets, shows and independent retailers, while the remainder goes to the food service industry.

However, like many food businesses, the Covid-19 pandemic has meant it has been a tough year.

When the pandemic hit all the restaurants closed and the market disappeared. We do a lot of food service to London and normally we have pallet-loads going down there every few weeks, but we had nothing over winter as London shut down. Our first load this year went last week (late April), so things are starting to pick up again, he says.