Skate with cocoa - a taste of paradise?

As he judges a post-Blumenthal Masterchef, John Walsh asks if some gastronomic combinations are scientifically wrong

Take this forkful of roast lamb and put it in your mouth. How does it compare with the last few plates of roast lamb you've tasted? Is it dry, moist, savoury, sweet? Would it be improved by mint sauce, cranberry sauce, apple sauce, horseradish sauce? Would it have been improved if the cook had had the wit to roast it with rosemary, or tarragon, or dill or garam masala? Would you have preferred to eat it in a "trio" with some lamb sweetbreads and a roundel of braised lamb shoulder with apricots? Have you tried eating lamb with all these things, and have you a good memory for past flavours? And do you actually care tuppence about any of this?

Of course you do. You must. To discriminate between one flavour and another is the mark of a civilised person. Caring about the taste of what we eat every day is the basis of the whole worldwide foodstuffs industry. The billion-dollar restaurant industry is predicated on the human desire to consume food with ever more intense and/or sophisticated flavours. Creating dishes that emphasise the taste of ingredients is the craft of the good cook; being able to do so consistently, quickly, and with visual flair is the mark of the good chef. But are our judgements about what tastes "good" or "bad" wholly subjective? Have we trained ourselves to think only some foods "go with" other foods – or are there hard and fast rules we can make about which flavours are, as it were, allowed to mate with others? How can we tell what our taste buds are telling us? How do we know if we have taste about taste?

The question has additional urgency if you happen, like me, to be a restaurant critic. As with most other critics, you are not trained for this role. But when you eat three courses at a new restaurant, drink the house red wine and write your assessment complete with stars-out-of-five, how do you justify your opinions? What do you know that other eaters don't?

Tonight, on Masterchef: the Professionals, I can be seen tasting forkfuls of venison and salmon and celeriac mash and confidently voicing the opinion that this is under-seasoned, that doesn't taste of much, and these flavours should never be seen together. But how do I know I'm (or my co-judges in the show, Tracey MacLeod and Charles Campion) right? If we say this lamb is "correctly" cooked, what criteria are we applying?

Luckily there are cooking gods around whom we can ask. They're called Michel Roux Jr and Gregg Wallace, long-term Masterchef judges, and their opinion is taken as law by the quaking (and often, tonight, weeping) contestants. Gregg and Michel tell each other with such conviction that a dish has been done right or wrong, there seems no room for doubt. When a contestant on tonight's show decides to serve up "quail chocolate cake," explaining, several times, that he's an exponent of "mad cooking", the judges treat him kindly, offer to take his pulse, and finally utter the words: "Quail and chocolate – no!" Do we like that certainty of approach? It's autocratic. It's doctrinaire. It makes up the rules. It's a subjective opinion, masquerading as the Objective Truth.

I suspect that we arrive at the Objective Truth about food through opposition. I'm a connoisseur of gastronomic abominations. There's no getting round the basic revulsion I felt, in a restaurant in Gloucestershire, at putting in my mouth a starter that combined jellified crayfish soup, boiled-until-mushy sweetcorn and a froth of sweet coconut. I'm still trying, after a year or so, to forget my folly in trying sanguinaccio, a regional Italian dish from Abruzzo, in a London restaurant: sweet pâté of pig's blood and chocolate on sourdough bread. It tasted like an intense chocolate pudding, until a whisper of animal fat began to squeak in protest at the back of your throat, and your gag reflex starts up ...

I remember a one-man-band restaurant in Avignon, where the chef-patron-waiter (highly recommended by friends) offered us just one main course for dinner: skate with fennel sauce. That sounded OK. It was a change from black butter sauce, which has accompanied skate in the last 2,748 restaurants I've been to. The aniseedy quality of fennel goes well with most fish – many French anglers flavour their bait with anise oil because their victims are attracted to it. The skate duly arrived. It looked fine, as did the lightly cooked fennel beneath it. What did not look fine was the spindrift of brown dust that had been liberally shaken over the plates just before serving. It was cocoa powder. The combination was horrible, wrong in taste, wrong in texture, wrong in flavour, bringing a touch of elevenses cappuccino into pointless intercourse with the briny Atlantic.

What was the chef thinking? That because one sweet-shop flavour (liquorice) went with skate, a nice bit of chocolate might give it more of a zing? When he cleared the plates away, and saw the quantity of uneaten fish, I tried to ask:"What were you thinking?" in my O-level French. It came out as "Qu'est-ce que vous penserez, monsieur?" And his reply was: "Je pense que certaines personnes n'en savent rien sur le gout."

Some people know nothing about taste. That's an interesting phrase. Because having taste isn't an accomplishment, or something you know about; it's a sense, shared by all humans. Restaurant critics need a halfway-reliable palate, despite the way it's been trashed by Famous Grouse and Marlboro Lights down the years. We may not have perfect pitch about food, the way piano tuners have about pianos. But we know, from the experience of several hundred restaurant meals, that many things taste OK, some things taste absolutely gorgeous, and far too many things taste either of nothing, or of something hideously misconceived in the kitchen.

There's nothing new about hideous gastronomic misconceptions. We may be amazed by the sophistication of the ancient Greeks, their eager embrace of their trading partners' cuisines, from Persia and Macedonia to India, their invention of the three-course meal (bread with fishy relishes; spit-roasted beef, pork, wild boar, mutton, goat or hare; then cakes and sweetmeats, fresh fruit and nuts) and their connoisseurship of wine, even in the 4th century BC. But we still cannot fathom what they were doing serving up oysters, sea-urchins and shrimps fried in honey.

Fish in honey? What a disgusting thought. It reminds you of those dishes – Liver in Lager, Saveloy on a Bed of Lychees, Pork Cyst – cooked up in The Regret Rien, the cod-French restaurant owned by Timothy Spall's monstrous character Aubrey in Mike Leigh's film Life is Sweet. We may have laughed at the awfulness of Aubrey's menu, but we laugh uncomfortably today; for what seemed risible in 1991, the year the film was released, now sounds likely to join the delights in store at Heston Blumenthal's The Fat Duck restaurant in Bray: snail porridge, bacon-and-egg ice cream.

Even the most celebrated cooks have proved surprisingly fallible in their judgements. Mrs Beeton, whose 1,112-page Book of Household Management contained the information that drinking iced water (especially after strenuous sport) was potentially fatal, and that pasta should be boiled in water for one hour and 45 minutes. Her successor as national foodie bossyboots, Fanny Cradock, was a glint-eyed combination of harpy, grande dame and howling snob, whose credentials as a food expert often seemed suspect. Not just her fondness for offal (veal brains cooked in cream, kidneys flambéed in brandy and smelling strongly of alcoholic wee) but her eccentric love for food colouring. Green Cheese Ice Cream – vanilla ice-cream with melted Gruyère cheese, dyed green with vegetable colouring – was a favourite, if only with her.

We know pretty well which food doesn't go with which. Are we sure we know what foods go together in blissful harmony? If we're lucky we do. If we're lucky, we've experienced the made-for-each-other taste of cold roast lamb and mango chutney, of Yorkshire pudding and beef jus, of chicken and tarragon, of roasted duck breast with cherries, of toast and Gentleman's Relish, of corn flakes with sliced banana, of honeydew melon with ground ginger, of gin and tonic, of vino santo and cantucci biscuits, and can agree that yes, there are convergences of flavour in the world that satisfy a deep internal human longing – that are right and true.

In the novel The Debt to Pleasure, John Lanchester's gourmet hero Tarquin Winot identifies a spiritual communion:

" ... lamb and apricots are one of those combinations which exist together in a relation that is not just complementary but that seems to partake of a higher order of inevitability – a taste which exists in the mind of God. These combinations have the quality of a logical discovery: bacon and eggs, rice and soy sauce, Sauternes and foie gras, white truffles and pasta, steak-frites, strawberries and cream, lamb and garlic, Armagnac and prunes, port and Stilton, fish soup and rouille, chicken and mushrooms; to the committed explorer of the senses, the first experience of any of them will have an impact comparable with an astronomer's discovery of a new planet." Winot's litany of tastes (though he pinched the final sentiment from Jean Anthelme Brillat-Savarin, who wrote, in The Physiology of Taste: "The discovery of a new dish confers more happiness on humanity than the discovery of a new star") appears as the epigraph of a new book, The Flavour Thesaurus: pairings, recipes and ideas for the creative cook. Its author, Niki Segnit, spent three years identifying 99 flavours under 16 headings, from Roasted (chocolate, coffee, peanut) to Floral Fruity (raspberry, fig, rose, blueberry, coriander seed, vanilla, white chocolate) and boldly goes about classifying – no, suggesting – what goes well with what.

She distinguishes between the five qualities that your taste buds can identify – sweetness, saltiness, sourness, bitterness and umami, which is broadly speaking savouriness – and the flavours detected mainly by our sense of smell. It's in the contrast of tastes and flavours that the magic of gastronomy lies, and, like a maverick Auntie Mame of the kitchen, Ms Segnit matchmakes some startlingly different ingredients: garlic with coffee, cabbage with apple, shellfish with celery, Brussels sprouts with dried cranberries.

Can we, thanks to Ms Segnit, confidently say, in the future, that to eat X and Y together will bring bliss and joy to the taste buds, but to combine W and Z in your bruised and put-upon mouth will induce only tears and a gag reflex? Can we finally tell chefs all over the country: "Stop that! We have incontrovertible proof here that venison medallions and Bird's Instant Custard do not belong on the same plate"? Can we say, "Look here – there are rules about taste and flavour to follow at last"?

If only. But Ms Segnit does not supply a list of combinations that are anathema to the human spirit. And she doesn't even claim to be prescriptive about her happy pairings. Her book is celebratory of happy food marriages, not condemnatory of dodgy liaisons.

In the end it comes down to a trade-off between the ambition of chefs to serve something more creative and satisfying than seared meat with two vegetables – after all, the Greeks were doing that, 2,400 years ago – and the sense to know when two or three flavours are perfect company and any more is a crowd. In the post-Blumenthal universe, chefs will go on pushing the envelope of fancy cuisine, piling flavour on flavour until the main ingredient in the dish gets lost in the ruck. In tonight's Masterchef, one of the contestants spouts admirable sense about cooking ("I'm not going to complicate things. I'm not mixing 'n' matching. I don't marry up odd flavours – that's not the way to treat food") before knocking up a gallimaufry of roasted rabbit in a red wine sauce together with celeriac fondant, langoustine and black pudding – all of which completely mug and overwhelm the hapless bunny.

That's why, I'm afraid, the world still needs the much-reviled, spoilt, world-weary, taste-jaded restaurant critic. Who else is going to call time on pretentious, misconceived, overambitious cooking, that drags oysters and peaches onto the same plate, or introduces crab to Marmite? Just look at the faces of the food critics on Masterchef tonight. Watch as they eye up the combination of essences on the end of their forks, hoping, against all likelihood of success, that this time they'll find the gastronomic Nirvana that's eluded them for so long.

'Masterchef: The Professionals' is on BBC2, 8pm