If a farmer's wife can't tackle her addiction to supermarkets, who can? Jo Ewart Mackenzie challenges her mother-in-law to survive a week without Tesco ... and support her local suppliers

YOU might expect the kitchen of a farmer's wife to be stocked with fresh-laid eggs, milk from local cows, breads and jams crafted from home-grown crops. Not so the larder of Roz Mackenzie. Her immaculate fridge contains two kinds of fruit juice, several varieties of cheese, sliced ham from the deli counter, lettuce, tomatoes, cucumber, leeks, eggs, cream, milk, fillet steak, steak mince, a pack of puff pastry, chicken breasts and various condiments. Elsewhere there are potatoes, carrots and frozen peas. There are fresh rolls every day with bread every other day. Roz also has fresh fruit including bananas, apples and occasionally grapes, and always has a plentiful supply of chocolate.

All of it has been sourced from her favourite supermarket. Raised on a farm and the mother of a fourth-generation farmer (my husband), Roz lives in rural Inverness-shire. In her heart, my mother-in-law knows she should buy meat from the local butcher, bread and cheese from the farmers' market, and fruit and veg from the farm shop. But she has become so accustomed to supermarket shopping that the very idea of seeking out local produce seems daunting.

Each week, Roz spends around £65 on food for herself and my father-in-law. According to a study by the New Economic Foundation, for every £10 spent in the supermarket, £12 is generated in the local economy. For every £10 spent via a local vegetable box scheme, the equivalent local gain is £24.

With this in mind, I have decided to challenge my mother-in-law to spend a week shopping exclusively at local independent shops to see if she could taste the difference. "But I don't really go to the supermarket that often," Roz says earnestly.

Don't get me wrong. My husband and I dine very well indeed when we eat with my in-laws, but like so many people with hectic work, family and social schedules, Roz has become almost impervious to the wealth of fresh seasonal produce on her doorstep because Tesco appears to provide everything she needs.

Roz also lives just outside one of Scotland's "Tesco towns" - Inverness - where more than 50% of all food purchases are from that chain. In this respect, Inverness is second only to Perth, where some 60% of the grocery spend goes to the supermarket giant. Inverness has two superstores, one mammoth Tesco Extra and a proposed fourth store. It is increasingly difficult not to shop with the country's biggest supermarket chain. Or is it?

From an environmentalist's perspective, it has become too easy in today's 24/7 supermarket shopping culture for consumers to forget about the climate-changing costs of convenience - which is attributable in no small part to food miles and aggregate farming - and the decimation of the high street and the rural economy.

To help Roz on her way to a clearer conscience and a lower carbon footprint, I prepare a list of 10 shops in and around Inverness she could use instead of visiting the supermarket, including delis and farm shops, plus an organic box scheme. After two uncharacteristic shopping-free days, Roz finally ventures out to nearby Bogbain Farm Shop for a few provisions.

"I was really impressed with the range," she says afterwards. "The shop was excellent. However, I was looking for milk and cream - they didn't sell milk and they only had a gallon of cream, which was far too much for me. So the shop manager, who was very helpful, offered to pour some into a smaller container for me. While he was doing that, I bought some eggs, honey, bacon and a steak pie."

Roz spent £14.09. She would go back, though suggests: "It would be better if they stocked milk - and smaller cartons of cream - and they did say their cheese supplier, Connage Highland Dairy, is going to start doing that. It's certainly handy for me because it's on my way home."

Capitalising on her guarded enthusiasm, I suggest she joins me at a farmers' market. A study by the University of Essex found that for every kilo of produce purchased at a farmers' market, 187g of CO2 is emitted. The equivalent produce bought at a nearby supermarket generates 431g of CO2.

At 9.30am the following Saturday, we arrive at the Inverness Farmers' Market and I pull a slightly overwhelmed Roz into the queue for the Ullapool Bakery. Having bought rolls and pastries from her local baker yesterday (£4.24), she plumps for two loaves from the artisan bakery.

At Speyside Organics she buys a large chicken and some lamb mince; sausages and bacon from Brackla Farm; and a chunk of nine-month matured Sweet Milk cheese from Wester Lawrenceton Dairy. By the time we reach two stalls laden with colourful vegetables, Roz has really got into her stride and stocks up on romanesque broccoli, Rooster potatoes, carrots, onions, salad leaves and leeks.

Roz's shop comes to £26.25 and the total distance her food has travelled to point of purchase comes to approximately 170 miles. The contents of her usual supermarket basket clocks up a staggering 26,900 food miles, and that's assuming that the apples and butter come over on the same flight.

"This will last me all week!" Roz exclaims with some surprise as we pile our booty into the car after an hour's leisurely shopping. "But I still need milk," she points out. I've forgotten to take some of our own milk from my husband's dairy to her. Roz sets off for a nearby deli and comes back with a four-litre carton of Highland Fresh. "I couldn't get parked and they only had semi-skimmed," she says reproachfully, "and it cost £1.65 - isn't that quite expensive?"

"I don't know. How much is it in Tesco?" I ask.

"I've no idea!" she confesses. "I never look at the price of things in the supermarket. I think most people don't; you just go round putting things in your trolley, and they're so crafty the way they move things so that you pass more food on the way - usually half of which you don't even need."

Despite the fact the "big four" chains - Tesco, Asda, Morrison and Sainsburys - now control around 80% of the UK's £97 billion annual grocery spend, the Competition Commission recently found supermarkets not guilty of damaging small independent retailers. The commission has even recommended a review of planning to enable more competition between supermarkets.

A few days after the farmers' market visit, my husband and I are invited for a roast-chicken dinner. As she prepares the meal, Roz raves about the local produce. "The difference in the quality of the vegetables and potatoes is amazing," she says. "These potatoes are so fluffy and full of flavour. When I buy potatoes from the supermarket, there's a certain sameness to the taste - their bread too. The sunflower seed and honey loaf from the market is absolutely delicious, so moist.

"I also notice that the local meat is a bit fattier, but in a good way; there's much more taste to it."

Now that she has completed the challenge, does Roz intend to make more use of her local shops?

"Definitely," she says. "I'm going to organise a vegetable box. I thought the farmers' market was fantastic, I could get everything I needed there and the wonderful produce inspired me to cook more."

And the supermarket?

"I'll only go to the supermarket now for basic supplies, say once a month," she asserts. "I haven't been to Tesco for about 10 days and I haven't missed it. This has been a real eye-opener. I had no idea there was so much local produce out there."

Having successfully shaken Roz out of her supermarket-shopping stupor, however, I can't help wondering how long this enthusiasm for buying local will last. "As long as I don't go for a paper, then I'll be fine," she surmises.

"Why?" I ask suspiciously, knowing full well that she buys a newspaper every day. "Where do you get your paper?"

"Tesco," she replies.

www.scottishfarmersmarkets.co.uk www.localfoodworks.org www.hilocalfood.net www.scottishfoodguide.com