While the British jingoism angle covered in other answers is definitely an important one, I think it’s worth considering the context in which the speech was delivered to get the full picture.
The speech was delivered by Truss at the Conservative Party conference in 2014 - when she was serving as Secretary of State for Environment, Food, & Rural Affairs in David Cameron’s coalition government. This needs to be seen, then, in the context of appealing to the Conservative Party membership in the hope of their continued support, as well as a pitch to the country as a whole - given a General Election was right around the corner.
In the same speech, she attacks both Labour and the EU - note that this speech took place two years before the Brexit referendum;
The amount of British food we consumed and produced went down and the last Labour government tied our farmers up in red tape. They wasted £600 million on fines to the EU and left us with the worst bovine TB problem in Europe.
The fact is Labour don’t care about the countryside. They think we can’t grow enough of our own food. They think it’s fine to outsource it. Well, they are wrong.
She goes on to promote British agriculture and food production;
I want our children to grow up knowing the taste of a British apple, of Cornish sardines, of Herefordshire pears, of Norfolk turkey, of Melton Mowbray pork pies and, of course, of black pudding.
Under a Conservative government, Britain will lead the world in food, farming and the environment. In a fortnight, I’m going to Paris to the world’s largest food trade fair and I will be bigging up British products.
So yes, the thrust of the sound bite linked is a jokey jibe at France based on their good reputation for producing cheese; but linked to promoting British agriculture - part of her job description as DEFRA Secretary. The speech also needs to be seen in the wider context of being a speech to the Tory Party faithful (hence the jingoism), rather than a serious policy speech, as well as taking place less than a year before a General Election.