You may not have heard of his Swiss company, Givaudan, but you will certainly have sampled its range in your breakfast cereals, ice creams, herbal teas, biscuits, cake-mixes, soups and chewing-gums - indeed, anywhere a manufacturer might add flavourings to enhance a foodstuff's taste. Today Givaudan's formulations go into one in every five of the world's artificially flavoured foods; and although the company will not name its customers, you can safely assume that it supplies most of the big names.

This morning's challenge for Hefti is to develop an innovative grapefruit flavour, followed by a new synthesis of lime and, if he has time, a modern variety of mandarin. He knows the optimal amount of trans-2-hexenal that will enhance a sweet's apple flavouring - and that, by reformulating the recipe with added heptyl acetate, he can turn apple into pear. The secret is what he calls 'creative appraisal' of the flavours provided by nature: although a real banana comprises around 225 volatile flavour components, Hefti can engineer an artificial alternative using just nine ingredients, although some formulations will need up to 70. A kilogram of the recipe - vanillin, ethyl butyrate, isoamyl acetate, benzyl acetate, eugenol, phenethyl alcohol, isoamyl isovalerate, cis-3-hexenol, all mixed into a solvent - will flavour 5,000 litres of drinks. Even if it lacks the fresh fruit's nuances, the result is impressively familiar to anyone who has ever tasted a banana fast-food milkshake.

Some tastes are harder to synthesise - 'a good coffee flavour is tough,' Hefti admits - but he relishes the challenge. In the meantime, there are always newly discovered natural tastes and smells to reproduce, thanks to Givaudan's international expedition programme. In hot-air-balloon missions over Madagascan rainforest, botanists seek out highly flavoured 'new' molecules from plants and tree bark. Its laboratories have already copied some examples for use in children's lollipops.

But do we really need 300 varieties of factory-manufactured strawberry flavouring? You might expect your strawberry yoghurt or premium ice cream to contain at least a smidgen of fruit derivatives, but that would be to underestimate the skills of the professional flavourist (not forgetting his peers specialising in colourings and preservation). Not that the catch-all term 'flavouring' on the label is designed to arouse any suspicions about the synthetic formulations within.

Thomas Hefti's patient smile suggests that he has been put on the defensive before. It would, he explains calmly, be uneconomic for the food industry to rely solely on real strawberries; there would not be enough fresh fruit to go round, and besides, the individual berries contain far too little natural flavour to make large-scale extraction viable. What works for a cake mix might taste wrong in a child's medicine. 'And not everyone wants the same flavour,' he adds. 'Even in nature you have strawberries that are riper or greener. The foodstuff producer might want their product recognised as distinct.'

Besides, we consumers apparently want those heavily processed tastes that have become familiar. 'If a German consumer is used to eating tinned pineapple, he will expect a tinned pineapple flavour,' Hefti claims. 'But in the Philippines, they will expect pineapple flavourings to taste like fresh pineapples.' In other words, having weaned us off fresh fruit, the food industry now finds us rejecting the taste of the real thing.

Givaudan's scientists do not like the word 'artificial'. Heini Menzi, vice president for European R&D, explains that it would be helpful if this article instead used the term 'nature identical' to refer to non-natural flavourings. 'NI' chemicals, Dr Menzi explains, are identical in their molecular composition to ingredients found in nature. The difference is that they have been synthesised in the lab by a chemical process - allowing a flavour originating in a plant to be manufactured cost-effectively in vast quantities.

There can be big savings: it will cost around £4,500 to isolate a kilogram of vanillin, which flavours everything from ice cream to cola drinks, directly from vanilla beans. But in the lab it can be synthesised for less than £6 per kilogram, typically using by-products from the paper or petrochemical industries. Either way, you end up with 4-hydroxy-3-methoxybenzaldehyde, and if the marketing people insist that consumers want vitamin C in their non-natural orange-flavoured drink, it can always be added later.

What really frustrates Menzi is the perception that NI flavourings are any less wholesome. 'The public assumes that natural means healthy, that NI means dubious - and that's not true,' he says. 'All food is only chemistry, after all - but that sort of language is scary to the general public. So people become concerned, "Oh, this is artificial..." And to some extent, yes it is. But the chemist can get to the same molecule, whether he takes it physically out of the raw plant, or via synthesis. From a taste point of view, you could use either.'

Besides, he adds, naturally sourced flavours may include all sorts of undesirable residues left over from the farm: herbicides, pesticides, microorganisms, even levels of plant toxins that, he suggests, could be harmful. In a state-of-the-art plant like Givaudan's, the consumer is guaranteed a healthier end product, he suggests and if he is aware of any irony in his explanation, he does not show it.

In the vast factory where the chemistry takes shape, a short stroll from the development labs, each formulation is defined by its own intense pungent or treacle-sweet odour: burnt roast beef one moment, caramel and peardrops the next, barley soup and horseradish to follow. Two industrial robots create the more common flavours from 400 chemical compounds; around them, white-coated men mix the smaller batches by hand from among 2,500 ingredients piped down from the storage vaults. These ingredients are stored in large tubs labelled with words you rarely see on food-ingredients lists: 'Ethyl octanoate-2', 'Hexenal-2-trans', 'Pentyl-iso valerate', 'Butanol', 'Neryl acetate', 'Ethyl decanoate', 'Benzaldehyde', 'Valerolactone gamma', and occasionally a gentler, more familiar term such as orange oil or eucalyptol. The resulting formulations, stacked up in sealed plastic tubs at the loading yard, show how global this industry has become: Worcester sauce flavouring going to South Africa, tomato flavouring heading to Japan. An orange-juice flavouring, to 'improve' Slovenian OJ, is labelled 'Highly flammable, Harmful'. There is even 'black tea' flavouring destined for China.

'Humanity doesn't need a single extra flavour,' Menzi admits, 'but the market will absorb more. Each year there are one or two new chemicals that have an impact.' Advances in neuroscience, he says, will produce further innovations: 'Once we understand how we perceive sweetness, we could think of molecules with no calorific value that trigger the right neurons,' he explains.

Still, as science brings them ever-greater opportunities, Givaudan's visionaries accept that they cannot ignore the public's prejudices. 'Today you have a lot of consumers in Europe concerned about the authenticity of food,' Menzi says. 'They want authentic strawberry flavours, authentic chicken - and that puts a lot of weight on natural raw materials.' If the market demands more natural raw materials, then Menzi will supply them. But, he is at pains to point out, 'that doesn't mean that natural is any better than NI'.

Sue Dengate first knew there was something wrong with her daughter Rebecca when, as a baby, she simply refused to sleep. 'It was terrible,' Dengate says from her home in New South Wales. 'There's nothing more tiring with a baby who needs round-the-clock attention. Then, as Rebecca grew older, she was constantly restless and irritable, very difficult to discipline, and quite defiant. It was as if she entered the terrible twos and never came out.'

Only when Rebecca was 11 was she diagnosed with attention deficit hyperactivity disorder (ADHD). By systematically excluding food ingredients using the elimination diet, Sue discovered the cause of her daughter's problems. 'That diet was our magic solution,' she says. 'Within days, avoiding the foods that caused all the trouble, she was a completely different person. There are 50 additives which have been found to disrupt children's behaviour, and Rebecca had been affected by all of them. The trouble is, there are more of them being added all the time - and they're released on to the market before their effects have been properly tested.'

The experience set Dengate on a long campaign to help other families whose health had suffered because of food additives. She has written books including Fed Up and The Failsafe Cookbook , and now runs a a support group called the Food Intolerance Network. Its heart-wrenching members' newsletter, combining personal tales of despair with amateur investigative science, lists problems such as children's asthma, migraines, skin rashes and irritable bowel syndrome that are firmly blamed on an ever-growing range of commonly used additives. 'What I thought was fresh meat from my local supermarket hasn't been fresh at all,' contributes one mother in the most recent edition, after discovering that her daughter's severe asthma improved when she switched to a local butcher's steaks. 'Meat is sent to the supermarket in vacuum packs, then repacked in trays and sold as fresh. But the pack lasts the supermarket up to eight weeks, so the meat can be up to 60 days old in the vacuum pack before sold as fresh.' Another writes: 'My three-year-old daughter developed eczema at six months when I introduced solids, and by eight months she needed frequent cortisone cream.' After isolating food additives that were the cause, the eczema is almost gone.

Some of the complaints concern synthetic bread preservatives and antioxidants used to prevent rancidity in oils (reactions include asthma, depression, fatigue and learning difficulties). Others relate to 'natural' additives such as the colouring annatto yellow and flavour enhancers called ribonucleotides, that, in the concentrations used in foods, have been linked to itchy skin rashes and swollen mouths and throats in some individuals.

If any of the technologists' other planned innovations do produce unfore seen harmful effects, Sue Dengate warns, it could be decades before we isolate the cause.

Still, at least her own story has a happy ending: Rebecca, now 21, manages to control her diet rigorously, and as a result is healthy. 'And lovely,' her mother adds. 'But you know, even when we discovered what was the cause of her problems, I was left grieving for 11 years of my daughter's life that had been stolen from me. That,' she says a little sadly, 'is the major regret of my life.'

Readers of Observer Food Monthly might naively imagine that society had finally woken up to the dangers of cheap, over-processed foods, and come to place a value in knowing the provenance of what we eat; that informed opinion now considers natural, if not organic, foods to be worth paying a premium for; and that today's nutrition-led problems, from obesity to children's hyperactivity, ought to be addressed before we commit to tomorrow's genetically modified uncertainties.

But turn instead to publications with names such as Food Chemical News, Food Engineering, Food Product Design and Food Technology , and you quickly realise that the multi-billion-pound food industry has some very different priorities. In the stainless-steel world of perpetual innovation described in their pages, you can watch the vast body of food scientists striving to find ever newer ways to synthesise products to sell to us. This scientific revolution is about anything but returning to nature: today's buzzwords are superingredients and shelf-life extension, nutrigenomics and nutraceuticals, biosensors and biotechnology enhancements. It is not food we are dealing with, you quickly learn, but 'food systems' - industrialised 'solutions' designed to maximise manufacturers' investment returns while promising untold new consumer benefits. Untold benefits, that is, that the last few hundred generations have somehow done without.

The industry's annual pilgrimage this year will be to Las Vegas, where for a week in July the Institute of Food Technologists will bring together 20,000 specialists for its agenda-setting Food Expo. The five-day technical programme suggests just where the industry is heading: with keynote presentations on 'Second generation genetically modified foods', 'Advances in food irradiation research', and 'The role of edible coatings and biopolymers in food packaging', it becomes clear how far the science lab is writing tomorrow's menus.

The schedule also addresses those inconvenient little hurdles that jump up in the way of progress, with workshop topics including cost-effective responses to the obesity crisis ('Expanding Margins, Not Waistlines!'), and, with food regulation a growing menace, a symposium entitled 'The Fallacy of the Consumer's Right to Know'. As one of the speakers promises, it will help manufacturers fight all those 'nonessential' demands from consumers to know what exactly they are eating - demands stemming simply from 'curiosity, faddism and activists'.

Many of those 'faddists' who shun the technologists' advances in favour of organic produce or natural ingredients may despair at the human diet's relentless industrialisation. Yet talking to some of the delegates planning to attend the IFT expo, it becomes clear just how far today's emerging technologies are going to be sold to us on their potential health benefits. 'Nutraceutical' supplements with claimed medicinal benefits are increasingly being designed into mainstream food recipes; in the future, they may be accompanied by 'nutrigenomic' diets, custom-prescribed by doctors to minimise health risks that are highlighted by your personal DNA. Think of nutritionally enhanced eggs or chocolate, designed specifically to lower your chances of developing Alzheimer's or bone cancer. The scenario is not that far removed, considering that chemical additives such as beta apo 8'carotenal, canthaxanthin and citranaxanthin are already widely used in poultry feed to 'enhance' the colour of egg yolks.

It is no surprise that much of today's research money is spent on technologies designed to keep food 'fresher' for longer. Why bin a sliced loaf after a few days if techniques developed for Nasa can preserve it for months if not years? Why rely on pasteurisation if pathogens can be killed using gamma rays?

Since Nasa first irradiated meat 32 years ago to feed the Apollo 17 crew, the technology has persisted as one of the industry's favourite means of prolonging shelf life. Irradiation kills bacteria such as salmonella and E.coli O157, and stops vegetables from sprouting. But its opponents have used concern about chemical byproducts, and damage to vitamins and enzymes, to limit its use. So the public, warned by campaigners that the process can add potential toxins such as formaldehyde to their meat, have never quite come on board. In Britain, food regulations currently allow only herbs, spices and vegetable seasonings to be irradiated. Still, the industry continues to campaign for the technology's eventual widespread introduction.

In the meantime, its scientists have devised a whole other tool kit with which to keep foods on the shelves for longer. Their techniques range from high-pressure processing (HPP), which might blast your orange juice with pressures up to 150,000 pounds per square inch, to pulsed electric field (PEF) technology, which subjects fresh foods to bursts of high-voltage electricity. Both prevent bacteria from reproducing without destroying the food's texture or taste - so expect more of your ready-meals to be blasted and zapped in future.

Scientists at Kraft Foods, the multinational whose brands range from Philadelphia cream cheese to Kenco coffee, foresee a time soon when a food package itself will signal when its contents are no longer edible. 'We call it smart packaging,' says Manuel Marquez-Sanchez at Kraft's NanoteK consortium, an alliance of 15 universities exploring how nanotechnology can aid food production. 'With a combination of tiny sensors and activators built into it, the pack will know if something is wrong, and correct itself or warn the consumer. It might have anti-microbial properties that can detect microorganisms - which extends a food's life.'

Nanotechnology involves manipulating matter at the molecular level to create entirely new materials and microscopic machines (a nanometre, is a billionth of a metre). The food industry is already getting excited at the prospect of tiny nanotechnology robots, or 'nanobots'. 'Instead of harvesting grain and cattle for carbohydrates and protein, nanobots could assemble the desired steak or flour from carbon, hydrogen and oxygen atoms present in the air as water and carbon dioxide,' Marvin Rudolph, director of DuPont Food Industry Solutions, which advises ingredients companies, predicted breathlessly in Food Technology magazine. No need, then, to nurture such inefficient and expensive food sources as cows and plants, if new industrial processes can simply replicate their atomic structures in pre-flavoured shrink-wrapped packages. But Dr Rudolph's vision went further: 'Nanobots present in foods could circulate through the blood system, cleaning out fat deposits and killing pathogens,' he suggested. In other words, these new industrial creations could actually promise to benefit human health. How useful would that be to an industry seeking to deflect public concern over obesity?

Manuel Marquez-Sanchez, too, has big hopes for nanotechnology. By manipulating ingredients at the nano level, and storing them in 'nanocapsules', he believes that Kraft will be able to devise such treats as an interactive, customisable drink. 'The idea is that everyone buys the same drink, but you'll be able to decide its colour, flavour, concentration and texture,' he explains enthusiastically. 'Once you have a technology to design nanocapsules, based on food-grade materials, you can offer products that put the consumer in control.' Although the industry, one presumes, will wish to retain control of everything from labelling requirements and costs to the degree of prior safety testing.

Dr Marquez-Sanchez, who works from Kraft's labs in Illinois, will not say which brands of drink he is working on, but he admits that Kraft is certainly looking to bring the resulting products to market. 'It's definitely possible,' he says. To show how serious he is, he mentions a 'shake gel' that he has developed - a drink which becomes thicker or more watery according to how hard it is shaken. 'You can choose how thick you want it - and the beautiful part is that if you change your mind it's reversible.' The tiny polymers that cause the effect are not yet food grade, but that hurdle, he says, could be overcome within two years. And by using ultrasound or radio frequencies to trigger these nanocapsules, we could determine the colour, fragrance or taste of our fruit drink or wine.

The Kraft vision is not universally welcomed. Pat Mooney, executive director of the Canadian technology watchdog the ETC Group, has particular worries about the damage that nanoparticles might do to our bodies or to the wider environment - seeping into rivers as tiny pesticide particles from farmed fish, or damaging our brains as they bypass the human immune system. 'Once you get below 100 nanometres in size, all the characteristics of an element change,' he explains. 'We just don't know what it will mean for human health. Nanoparticles can enter the body's cells, and at 30 nanometres can pass the blood-brain barrier. Kraft's packaging materials and drinks-with-100-flavours could be great - but what happens to the nanoparticles you don't want when you drink a glass? Are you sure they'll pass through your body safely? And what do they do to the environment afterwards? There are big safety questions, but nobody's regulating it.'

But Marquez-Sanchez says that his job is simply to uncover the knowledge, and to leave others to decide how to use it. 'I'm a scientist,' he says. 'I used to work at the Los Alamos National Laboratory, and the knowledge developed there might be used to develop a nuclear bomb. But it might also lead to the use of cobalt-60 [in radiotherapy] to kill tumours. You have a choice.'

Few organisations have shaped food technology as much as Nasa and its well-resourced friends at the US Army's research labs at Natick, Massachusetts. The space programme is directly responsible for spin-offs such as water filters and softeners, enriched baby food, portable cooler-warmers, and freeze-dried ingredients; Nasa money has also accelerated the development of microwave ovens and irradiated food. So if today's research successfully enhances food provision in a future space mission, there is a very good chance that it will become available in supermarkets tomorrow.

The current challenge at the Johnson Space Centre in Houston, is to produce food that will still be edible years from now. Michele Perchonok, a food scientist in the Advanced Food Technology unit, has studied the emerging food-preservation techniques, from high-pressure processing and pulsed electric fields to radio-frequency sterilisation and oscillating magnetic fields. The Army, she says, has developed a sandwich that is still edible after seven years, although Dr Perchonok has not yet tasted it ('the quality isn't as good as you'd like to see,' she explains). Still, her own mission is only marginally less daunting: to ensure that food sent with the Mars mission will survive three to five years in space.

Because these new preservation techniques replace conventional high-temperature heat processing, the space crews will enjoy food that, according to Perchonok, retains more of its taste and nutrients. 'That's the fascination with these new technologies,' she says. 'We're going to have higher-quality food - and the benefits could come to consumers.' She pauses briefly. 'The question, I suppose, is do we really need food that lasts for three years?'

The food industry is always looking for new ways to push back their products' use-by dates. If there is less wastage when items are being shipped across the world, and weeks-old fruit can still appear 'fresh' at the checkout, then producers see the results in their profits. Much of the buzz today surrounds 'modified atmosphere processing' and 'active packaging', in which meat or lettuce leaves are flushed with antimicrobial gases, washed in chlorine, or wrapped in packages lined with chemicals such as butylated hydroxyanisole (BHA) or tertiary-butylhydroquinone (TBHQ) - some of which are suspected carcinogens. But it is one thing to make a bagged pre-washed salad last an extra month; will supermarkets really want 'shelf stability' of three or four years?

'It's almost intuitive for the human race to want to eat fresh food,' argues Richard Young, policy adviser to the Soil Association. 'I accept that it's been one of the great successes of agriculture in the last century to extend the range of produce we can enjoy out of season - but when you've got shelf lives going even into a second year, it seems we're moving into an area where the risks outweigh the benefits.' The big danger of the modern food industry, he adds, is 'that the rate of change is occurring on a completely different scale to anything in human evolution. And we're not giving ourselves any time to adjust to any problems that we can't yet see.'

There is way to predict the direction that food technology is likely to take: follow the money. And as more of us look to improve our health, the market is booming for 'functional' or 'nutraceutical' foods that claim to enhance our wellbeing. In Geneva last week, where the 'nutraceutical' and 'cosmeceutical' industries gathered for the Vitafoods International convention, much was made of the $6.3 billion that the sector is already said to be worth. Among the exhibitors seeking their share were the manufacturers of Xlim, 'the drink idea for figure awareness'.

But it's the multinationals who will dominate this revolution. Kellogg's has cereals and pasta containing psyllium, a grain said to help lower cholesterol; Nestlé has joined L'Oréal, to produce dietary supplements that claim to 'improve the quality of skin, hair and nails by supplying nutrients essential to their physiology'.

At the factory level, these growing demands mean finding new ways to obtain health-enhancing ingredients on an industrial scale: rather than rely on fish to produce the omega-3 fatty acids that benefit our hearts, for instance, the omega-3s can now be sourced straight from algae. But it also means introducing new health-focused marketing claims for food prod ucts that may owe more to old-fashioned hype. Will SkinCola, the new 'cellular renewal' drink marketed as 'the first skincare beverage', really promote 'beautiful clear skin' through ingredients such as 'activated oxygen and Z-Bec, a combination of zinc and vitamins'?

Julian Mellentin, who co-wrote The Functional Foods Revolution and analyses the industry for the newsletter New Nutrition Business, is sceptical of some of the more visionary claims. Beyond the new scientific findings about the benefits of naturally healthy foods (such as broccoli and wholegrains), he sees functional foods as remaining a niche area for some time.

What, though, if all these nutritional advances were combined with the genetic revolution that has finally cracked the human genome? What if your GP used your genetic profile to design you a customised diet that included nutraceuticals that could give you a longer, healthier life?

'It's not a question of whether, but when,' according to Jim Kaput, a biotechnologist at the University of California at Davis and a leading figure in the field of 'nutritional genomics', or 'nutrigenomics'. So convinced is Dr Kaput that we will one day be eating personalised foods to fight our genetic predispositions that he has become president of a Chicago biotech company called NutraGenomics.

The reason that so much dietary advice in the news appears to be contradictory, Kaput claims, is that we all respond to foods according to our own individual DNA patterns. 'The organic, vegetarian-hippy types say that if it's natural, it's good for you, and you should have it every day,' he says. 'That's not right. We're self-dosing, and we don't know how foods such as ginseng will affect us long-term. Yes, we're all going to die - but we want to live a little longer.' And science will be there to help.

'We're going to make that diet-gene connection,' Kaput says, 'linking specific nutrients to health in each individual. In 10, maybe 15 years, we'll be able to do genetic tests that will allow us to tweak your diet, so that you will be given dietary supplements according to your dietary profile. And in 25 years, if society allows it, we'll test babies at birth. Given this genotype, we'll say, here's their optimum diet for maintaining health.'

Once science has revealed our optimum diet, says Kaput, society will have to grapple with the ethics of whether the state should force us to eat the foods that will make us healthier.

Talking to a scientist such as Kaput, so enthralled by the promise of technology, it seems pointless to suggest that naturally grown, unadulterated produce seems to have served human health pretty well over the centuries. Yet does have a point when he highlights the gap between what we know about healthy eating, and what we actually choose to eat? The west's trans-fat saturated, synthetically flavoured, salt-packed fast-food diet has been incontrovertibly linked to the rise in type two diabetes and obesity - but it is something we seem unwilling to give up. Considering this government's caution over introducing a 'fat tax', it seems unlikely that its successors will wish to force us to eat greens that suit our genes.

Still, the future will not wait. Jozef Kokini, director of the Centre for Advanced Food Technology at at Rutgers University, agrees with Jim Kaput that our dietary choices will become far more 'intelligent'. 'Fifteen years ago, the idea of making food choices that are optimal for each one of us personally sounded like science fiction,' he says. 'Today it's real science. The personal diet will prevent cancer and increase your lifespan and your quality of life.'

Food science, Dr Kokini adds, is in the midst of a revolution, with 'truly an explosion' in new ideas. 'You'll find foods that are better designed in terms of health prevention attributes, oranges that will last three weeks and still be fresh, a bunch of new textures and flavours with mouthfeel you can't even conceive of.' It will, he says, be 'a very exciting time over the next 20 years, a revolution. You'll be amazed.'

And if new revenue streams follow, you can presume the food industry will enthusiastically embrace it. After all, why should science make way for naysayers such as Sue Dengate, at the Food Intolerance Network? 'What all this means is higher doses of cheaper food additives leading to more irritability, restlessness and sleep difficulties,' Dengate says in despair. 'Why can't food technologists just stop mucking around with our food supply?'