The former Great British Bake Off judge said she sniffs food and uses it if it smells ok.
Berry, 82, said her mother gave her plenty of tips about cooking and running a home, which feature in her new book.
"I was brought up in the war and things were quite difficult. The garden was an enormous help then," Berry told the Cheltenham Literature Festival.
"There were no freezers but those sort of tips I got from my mother about using things up.
"And also to use my nose. I don't do sell-by dates but I have to confess if there is a pot of cream I just lift the lid and smell it.
"If it's all right, I have it. You do have to be careful if it is meat and keep within the dates."
She also revealed she shops in Waitrose regularly as it is the nearest supermarket to her home and picks up the £10 dinners with wine from Marks and Spencer.
Berry said leaving the Great British Bake Off after it switched to Channel 4 from BBC1 was not a hard decision to make.
"It wasn't difficult at all because Mel and Sue and I, and Paul too, were a real team," she said.
"When we heard that Bake Off was moving over to Channel 4, I thought the BBC commissioned the programme and I've had seven wonderful years.
"The stars of the show are the bakers, it is the most wonderful show, it has a format. I thought I would stay with the BBC and Mel and Sue said exactly the same.
"There is no way that the BBC have enough of your money, they couldn't afford the amount of money Channel 4 was offering and, as I say, I had seven smashing years.
"Of course it is going on and is a great programme. If I could have chosen anyone to take my place, I would have chosen Prue Leith."
She admitted to watching the new series, which is now hosted by Noel Fielding and Sandi Toksvig.
"I have watched some of it," she said.
"I don't have quite the same interest because I am not seeing what we are all up to. It's doing really well and it will still go on exactly the same. I have got things up my sleeve..."
She said she was thrilled the hit show spawned a new generation of bakers and it was lovely that children shared pictures with her of what they had made.
Berry also revealed she has been filming a new TV show for BBC, called Classic, which will be broadcast next year.
"It is so lovely to do a show in a proper kitchen," Berry said.
"I have been doing next year's programme and that's lovely because it is in a proper kitchen, with all my own things around me and everything works.
"It is very similar to Everyday. It is called Classic and we do a lot of outside broadcasts for it. It was great fun.
"The recipes I have been doing I hope are you can say 'oooh and arrrrgh' about.
"They are assembled quickly, not too many ingredients and we trial the recipes out time and time again until they are perfect and easy for you to do.
"I go quite slowly to explain things. I hope you enjoy it because I enjoyed do it a lot."
Berry said she was comfortable with fame and said everyone she meets was so nice and complementary about her books and TV shows.
"It has got everyone cooking and baking and I am very proud of that. There is nothing better than on a wet day and get cooking and get baking," she said.
But she has no plans to retire.
"Would you retire if you had such an exciting fun life as I'm having? I having an absolute ball and the BBC are being so generous to me," she said.
"I have no intention of retiring and my husband Paul has done that for me."
