A bright summer's morning backstage in the Bake Off tent and in one corner a petite, dark-haired woman called Faenia Moore is carefully shelling a boiled egg. The show's chief home economist is so precise, so focused, it's obvious this is a vital part of her duties. "This?" she says, looking down at the egg. "This is Paul's breakfast." Conspiratorially she leans in and stage whispers: "He's on a bit of a health kick, staying away from the carbohydrates and all that."

From left, Sue Perkins, Mary Berry and Paul Hollwood. Photograph: Phil Fisk

Paul Hollywood is trying to stay off the carbs? Oh dear. He might have come to the wrong place. On the day I arrive, the Bake Off team are near the beginning of the new 10-part series, and the contestants are furiously working their way through a signature bake, another minor miracle of flour, fat and eggs and a few other things besides. Carb-light it ain't.

The contestants may be sweating but the technical team that makes sure everything works is a model of calm. One side of the backstage area is a makeshift television studio gallery, from which the director can monitor the six cameras constantly working out in the tent, a producer at his side. The other side is the preparation kitchen, where the contestants may never step. Taped to the fridge is a list of the 10 technicals and showstoppers, complete with photos (none of which I am allowed to reveal). Just in case a contestant does stumble in here, it's folded over down the middle to hide the list of technicals.

Food researcher Becca Watson. Photograph: Phil Fisk

The team back here is led by Faenia, a veteran of Great British Menu, who has been on this show since series one. With her is Georgia May, as blonde as her colleague is dark, who has worked on Food and Drink and The Great British Food Revival. There's also food researcher Becca Watson, who has worked with the Hairy Bikers and Lorraine Pascale, and who is tasked with making sure Paul and Mary's choice of technical recipe is achievable. The idea had been that I should help out back here but the reality is that this is the proverbial finely oiled machine. The last thing they need is a pair of clumsy hands; they give me a washing-up bowl and some dirty spoons.

Who can blame them? Almost the entire team has long experience of the show. I am literally superfluous to requirements. Sue Perkins wanders in from the floor and stares over the shoulder of Becca, who is testing a forthcoming technical recipe. "Sue's a very good baker," Becca says. Sue nods slowly. "I made a treacle cake back here recently. Basically I annoy the shit out of them. Or help out as I call it." She tells me she made brownies for the crew during one previous shoot. "Although essentially when I'm in here I'm asking one question which is what is this and how can I eat it?"

A little later Mary Berry comes in to consult with Becca, a vision in her floral bomber jacket. Together they huddle over Becca's bench, studying the list of ingredients for next week's technical. "We couldn't really do it without her brilliant research work," Mary says. Becca laughs. "Now we're five series in, the challenge is to find recipes that are hard enough and intricate enough."

Mel Giedroyc. Photograph: Phil Fisk

Before shooting even begins the contestants have to come up with the 10 signature and showstopper bake recipes they would need if they made it all the way to the final. Those are studied by Chloe Avery, the food producer responsible for all the edible aspects of the show. Each episode takes two days to shoot, but the three-strong home economics team start work a full two days before that, gathering ingredients. (The "home economist" job title is an anachronistic hangover from postwar attempts to bring rigour and respectability to school cookery lessons; the TV job has little to do with economics and absolutely nothing to do with the home.)

"Basically we're in charge of everything to do with the food and the equipment," says Georgia. Before the series begins they check the ovens by preparing a dozen Victoria sponge mixes. "We mark each one, then get a runner to stand at each station with their cake mix so we can be sure they've all gone into the oven at the same time and can be properly tested." Likewise, they have to make sure they're all level. "We just have to be certain we're fair."

Then there are the ingredients. "We've got to make sure the contestants are happy. They can specify what brand of a product they want, we have to get it and then de-brand it for screen." What's more, contestants can make requests right up to the start of each round. "Sometimes they'll be awake in the middle of the night and they'll have decided that, oh, figs will be the thing that will make their bake." Accordingly each morning of the competition a runner is positioned from first light outside the nearest big supermarket, ready to receive a shopping list.

Behind the scenes of the Great British Bake Off. Photograph: Phil Fisk

Whichever retailer gets the full Bake Off shop should be very happy indeed: the volumes are impressive. During series four, the bakers worked their way through 200kg of flour, 150kg of sugar, 90kg of butter, 80kg of chocolate, 2,000 eggs and 35 litres of double cream. They used 21 different types of flour and generated 208 hours of washing up. "We actually get excited when contestants start getting knocked out because we think it means less work," says Georgia. "But weirdly it never works out that way." With the signature bake under way and the technical this afternoon, she is now busy preparing ingredients for the showstopper tomorrow, laboriously debranding packs of butter. "Last year [winner] Frances Quinn had a showstopper that required 150 ingredients. It filled the whole of that table," she says, pointing to a trestle. "We did a chocolate showstopper and that alone used 50 kilos of the stuff."

For a while they discuss the challenges they've faced back here. Both of them say ingredients have become more available since they started. "I remember a few series back, someone wanted freeze-dried raspberries so I had to pick them out of a box of Special K one by one," Georgia says. "Now you can buy those almost anywhere." Nibbed pistachios became a fetish last year. Things like that, they say, they've often had to buy mail order. And then there are the climactic conditions. "It's always hot when we're dealing with chocolate which needs cool weather," says Georgia. "And cold when we're trying to prove bread."

Part of Faenia's job is to go out on to the floor during each round and spot what's going on with the bakers. "For example if I can see somebody's meringues are failing, I'll feed that back to the producers so Mel or Sue can be sent over for a chat. It's about the story." I ask them if they get emotionally involved. Becca says no. "I keep myself to myself back here." Georgia admits to being less detached. "You can see people losing it because the bake hasn't gone very well and you do feel for them." But don't you ever think, look, it's just a bloody cake? "No, because we know how much it matters to them." Clearly these women know their baking. So Faenia, how do you think you'd do in Bake Off? She thinks seriously about it. Clearly she would describe herself as a contender. "Though I don't think I'd win. I'm just not geeky enough. These people truly love baking."

Photograph: Phil Fisk

At which point Paul Hollywood sticks his gloriously salt-and-peppered head into the prep kitchen, with an expectant look on his face. "I tucked your eggs in behind the thyme bush," Faenia says pointing back to the set. He reappears a moment later complaining he can't find them. With a gentle sigh Faenia follows him back out, only to return a moment later. Someone had moved them. All is fine. Paul Hollywood has his breakfast. The contestants are coming to the end of their signature bake. The latest round of The Great British Bake Off is clearly in very good hands.