Barnard is under no illusions about what she needs to do to make PepsiCo the outright leader in both categories. Quaker's Oatso Simple brand is PepsiCo's only entrant in the top 20 UK cereal brands, and the entire Quaker brand is still worth less than Kellogg's Special K. Tropicana may dominate juices, but PepsiCo's PJ smoothie brand, which Bernard also oversees, is still worth only a quarter of Innocent and its Copella brand has yet to reach its full potential.
Hence PepsiCo's decision to step up the pressure this year. In February it invested £15m to relaunch its Quaker brand, which included new-look packaging and products. It has also embarked on a major advertising campaign that switches Quaker's focus to the cholesterol-lowering property of oats. Barnard says this is a major change of direction for the brand.
"We've always sold Quaker on its health attributes but have been much more generic about the goodness of oats," she says. "Consumers understand that oats are good for you but don't know why. Part of the challenge marketers face is that there are so many good things to say about oats, and the temptation is to talk about all of them. Instead, we've picked cholesterol as the main area to go for."
The new adverts, which focus on the fact that by the age of 35 more than one in two people has high cholesterol, are a stark change from the company's previous campaign, which featured children's TV character Windy Miller.
But while using Windy helped raise the profile of the brand, Barnard admits that it didn't effectively address health issues in the same way that its rivals Weetabix, Kellogg and Nestlé have.
"Windy Miller was a fun campaign and generated interest and visibility around the brand but it is difficult to talk about serious health issues with a plasticine character. In the past we have assumed that consumers understood more than they did.
"Many brands talk about cholesterol but only to people who know they've got a problem. The number of people who know they have high cholesterol is very small." Barnard highlights the fact that 60% of her sales force have raised cholesterol.
The time is ripe for Quaker to take a step up in the cereals category. Consumer interest in health is at an all-time high and Barnard believes that no other brand is better placed to capitalise on this.
"Quaker has been about in the UK for 100 years and my best analogy is that it's a bit like a Victorian terrace," she says. "Nobody ripped out all the original windows and fireplaces. It was left untouched in the seventies and eighties. We've got a brand that hasn't been messed around with and its heritage is still intact. From a marketing point of view this is our biggest asset. We don't have to re-invent our brand and move into new territory."
Tropicana's heritage is another weapon in Barnard's armoury. The business has doubled in the past three years and the juice has moved from being a niche product with a south east London bias to a premium mass-market juice. The company has been innovating with new fruits with the launch of Pomegranate Blend and Cranberry Blend last month, and is open to bringing new flavours to the market, but only if it can guarantee sufficient supply.
"Never a week goes by without opening the papers and reading about some new fruit with more antioxidants than the last," she says. "But we've got to be able to have a quality product that we can supply.
"Most of the time when you see these weird and wonderful fruits they are from a couple of trees in the Brazilian rainforest, but being able to consistently source the correct quality and quantity is no mean feat. Once we have secured this, we want to bring them to consumers who have adventurous tastes."
PepsiCo is employing this tactic with its PJs brand, which will benefit from the addition of four functional flavours to the portfolio in May. One of the new flavours, Rainforest Acai, is already available in the US as part of California-based Naked Juice Company's business.
PepsiCo bought the business from private equity company North Castle Partners at the end of last year, and Barnard says more of Naked's US flavours will be added to the PJs range.
So how does she handle the fact that, even though PJs grew an impressive 100% in value last year, it is still playing catch-up with Innocent, which soared 168% in the same period?
"Innocent is a tough competitor and I have a huge amount of respect for the business. I think PJs can play a different role within smoothies. PJ consumers tend to be slightly younger and there's more of a male/female mix.
"Innocent is quite a female brand and targets much older people. We think we can open PJs up to a wider audience. Bringing out more functional drinks will enable us to stand for something different."
And does she foresee a time when PJs could overtake Innocent? "At the moment both businesses are growing but at some point the smoothies market will normalise. The market is still small - household penetration is only 10% and Innocent is expensive. But there is room for two successful brands."
She is more concerned about bolstering Quaker and Tropicana's position, and has ambitious plans for both. "I see Quaker as a growth driver. The vision on the 10-year horizon is to be number one in healthy cereals, which requires it to be worth about £250m. It's ambitious but the timing is right."
And what about Tropicana? "It is the crown jewel in our company and offers the biggest opportunity," she says. "Could we double Tropicana again? I don't see any reason why not. Making sure we steer Tropicana to another three years of success will be what defines me."n
Q&A What is your career background?
I will have been with PepsiCo for 10 years this summer. I spent the first seven years working with Walkers in sales and when we restructured the business I took on the role of general manager for Quaker and Tropicana.
What's a typical day like?
Busy, but I don't think there is a typical day. We have a broad portfolio so I am effectively running five businesses - cereals, Tropicana, Snack-a-Jacks, Copella and PJs - and each are businesses in their own right and need care and attention. My role is incredibly diverse. One day I might be figuring out activity for the next quarter, and I could be working on longer-term strategic planning the next. Tropicana is a global business so I also work closely with our partners in North America and around the world.
What has been your biggest success at PepsiCo?
It was the change we made in 2005 to start advertising Tropicana as a premium brand. That really put it on the path of success. Before this, PepsiCo had concentrated on giving the brand mass appeal and the biggest switch was to push the premium message. This was a different approach and convincing the business it was the right one was pretty tough but it is now the way we manage Tropicana in all other markets around the world.
Which of your brands offers up the biggest challenge?
My sleeping giant is Copella. We haven't really cracked the code yet on how we promote it in the way we did with Tropicana. The consumer base is narrow and incredibly loyal. We will get there but it's the one I need to address. There is no reason why Copella can't be a £100m brand.