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Speaker 1: Welcome to Brainstuff from house stuff works dot com where

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Speaker 1: smart happens. Hi. I'm Marshall Brain with today's question, how

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Speaker 1: is it that lettuce stored in plastic bags at the

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Speaker 1: grocery store can stay fresh for so long? Many of

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Speaker 1: the foods that you buy wrapped in plastic today are

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Speaker 1: using what's called modified atmosphere packaging or MAP. The package

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Speaker 1: is filled with a mix of gases that are beneficial

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Speaker 1: to the food. Most foods do better if they're stored

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Speaker 1: away from oxygen. Also, many microorganisms have a hard time

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Speaker 1: with high concentrations of c O two, so eliminating oxygen

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Speaker 1: and adding c O two is very common in modified

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Speaker 1: atmosphere packaging. The amount of time that MAP can add

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Speaker 1: to shelf life can be amazing. The shelf life of

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Speaker 1: meat can go from three to twenty one days, cheese

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Speaker 1: from seven to a hundred and eighty days, and fresh

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Speaker 1: pasta from three to sixty days. That's not bad when

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Speaker 1: you consider that the cost of adding the gas is

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Speaker 1: practically nothing. Shelf life extension often lowers the cost of

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Speaker 1: a product by reducing spoilage, and also opens up long

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Speaker 1: distance import export options. It can also extend the seasons

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Speaker 1: of certain fruits and vegetables. In the case of lettuce

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Speaker 1: in a bag, the modified atmosphere does two things. First,

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Speaker 1: it changes the way that the green leaves behave The

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Speaker 1: green leaves are still alive even after you pick the lettuce,

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Speaker 1: and you want to keep them alive as long as

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Speaker 1: possible by changing their behavior. Second, it discourages bacteria. The

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Speaker 1: high c O two and low oxygen atmospheres can lead

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Speaker 1: the less discoloration, slower rotting action for the bacteria, and

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Speaker 1: it helps the lettuce stay crisp longer. Plus there are

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Speaker 1: no added chemicals. Do you have any ideas or suggestions

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Speaker 1: for this podcast? If so, please send me an email

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Speaker 1: at podcast at how stuff works dot com. For more

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Speaker 1: on this and thousands of other topics, go to how

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Speaker 1: stuff works dot com and be sure to check out

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Speaker 1: the brain stuff blog on the how stuff works dot

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Speaker 1: com home page.