News about Britain's brewing industry is usually bad news. The wondrous diversity of our home-grown beers gets whittled down steadily. Regional independents shut their doors or are bought. Ale sales drop while lager sales (boring!) rise steadily. That's all the more reason to applaud Tesco's Beer Challenge.

The Beer Challenge runs every spring and autumn, and aims to find a new brew that's appropriate to the season. Breweries wanting to enter devise their recipe, make it in a small batch, and send it in for preliminary judging. From that, finalists are chosen in two categories: small brewer (fewer than 10,000 barrels) and large. Finalists are subjected to a blind tasting by a panel comprising both Tesco buyers and outsiders. I was one of the outsiders this year, and it was a fascinating exercise. I'd never tasted so many beers blind before.

Overall quality was good, though a few bottles (I don't know whose) possessed precious little character. This being the spring session, the beers needed to be "refreshing", and some met that criterion only in the sense that water is refreshing.

Both the two winning beers, I'm pleased to say, got high marks from me. And they had two things in common apart from good taste: they're bottle conditioned, and they make use of additional flavourings. From the 150-year-old Cornwall brewery St Austell, the flavourings in Clouded Yellow were vanilla, cloves and maple syrup. Clouded Yellow was first produced for a Celtic beer festival last December. Roger Ryman, head brewer, says: "We wanted to throw the rule book out and make a one-off just for this event."

They "unleashed the shackles" and came up with a wheat beer, which proved to be very popular, especially with women. "When the festival finished we had some left over, and for the Tesco Challenge we gassed it up and put it in bottles. It was almost accidental."

With the small brewer winner, Hop Back's Crop Circle, I spotted instantly its flavour of coriander seeds - that inimitable, citrus nuttiness cutting cleanly through the tangy attack of three different hops. Mind you, Hop Back has some experience of adding eastern-style flavours to its beers: its earlier Taiphoon uses lemongrass. And it has excelled in making fresh-tasting pale ales since its beginnings in 1987, when it brewed initially just to supply the local Wyndham Arms in Salisbury. I think Crop Circle is more successful. Coriander takes well to the brew kettle, as you know if you've drunk any of the Belgian white beers in which it's an essential ingredient.

Both beers will be exclusive to Tesco for six months, and arrive shortly. If the experience of other brewers is replicated, they will sell like hotcakes - and Tesco will keep them on if they sell well enough. If you're looking to match them with food, Crop Circle may be the better bet. Clouded Yellow is more of an apéritif.

Tesco's initiative is part of a movement among the supermarkets to promote a good range of brews. But if you want access to the smaller breweries, specialists are still best. In Leicester, the mail order list from The Bottle Store (tel: 0116 2707744) always makes for appetising reading. In London, The Beer Shop (tel: 020 7739 3701) claims to sell the UK's biggest selection of bottled brew.

There's also, although it makes patronising assumptions about larger brewers, not all of whom can be dismissed as mere technicians - think of Fuller's, Young's and Caledonian. Nonetheless, beerstalker makes a good list focusing on micro breweries. Or, failing that, just pop into Tesco.