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How Salt Keeps Food From Spoiling

7th grade nonfiction passage about salt and food preservation: 222 words, six questions, an answer key and vocabulary.

7th grade nonfiction salt and food preservation 222 words

How Salt Keeps Food From Spoiling

Long before refrigerators, people kept food from spoiling by burying it in salt. Fish, pork, and even butter were preserved this way, and sailors and explorers depended on salted food for long trips. The method works because of how water moves through the thin walls of living cells.

Bacteria and molds that spoil food are living things, and they need water to grow. Salt is very good at attracting water. When food is packed in salt, or soaked in salty water called brine, a process called osmosis begins. Water moves through cell walls from the area where it is plentiful toward the area where salt is concentrated. The water inside the food is drawn out, and the food becomes drier.

The same thing happens to the microbes. When a bacterium lands on heavily salted food, the salt pulls water out of its cell. Without enough water, it cannot grow or multiply, and many kinds simply stop being a problem.

Salt cannot keep every food safe forever, and some tough microbes can survive it. But combined with drying, smoking, or cool storage, it greatly extends how long food lasts. Today, salt curing is still used for foods such as ham, anchovies, and some cheeses, although it is now often chosen for flavor and tradition rather than necessity, since most kitchens have a refrigerator.

Questions

  1. Why do bacteria and molds need water? in the text

  2. What is brine? in the text

  3. What does osmosis do when food is packed in salt? in the text

  4. What happens to a bacterium that lands on heavily salted food? in the text

  5. Why are heavily salted foods often dry? think about it

  6. Why do people still cure foods with salt when they own a refrigerator? think about it

Words to know

preserved
treated so that food lasts a long time
brine
water with a lot of salt dissolved in it
osmosis
the movement of water through a thin cell wall
microbes
living things too small to see without a microscope
concentrated
packed closely together in one place
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 186 words · Flesch-Kincaid grade 4

Before there were refrigerators, people kept food from spoiling with salt. They packed fish, pork, and even butter in salt. Sailors and explorers took salted food on long trips. It works because of how water moves through cell walls.

Bacteria and molds spoil food. They are alive, and they need water to grow. Salt pulls water toward itself. Food may be packed in salt or soaked in salty water called brine. Then osmosis starts. Water moves through cell walls toward the salt. The water in the food is pulled out. The food gets drier.

The same thing happens to the tiny microbes. When a bacterium lands on very salty food, the salt pulls water out of its cell. It cannot grow or make more bacteria. Many kinds stop being a problem.

Salt cannot keep every food safe forever. Some tough microbes can live with it. But salt plus drying, smoke, or cool storage helps food last a long time. Today, people still cure ham, anchovies, and some cheeses with salt. They often do it for the flavor and the tradition, since most kitchens have a refrigerator.

▲ This passage · 222 words · Flesch-Kincaid grade 7.7

Long before refrigerators, people kept food from spoiling by burying it in salt. Fish, pork, and even butter were preserved this way, and sailors and explorers depended on salted food for long trips. The method works because of how water moves through the thin walls of living cells.

Bacteria and molds that spoil food are living things, and they need water to grow. Salt is very good at attracting water. When food is packed in salt, or soaked in salty water called brine, a process called osmosis begins. Water moves through cell walls from the area where it is plentiful toward the area where salt is concentrated. The water inside the food is drawn out, and the food becomes drier.

The same thing happens to the microbes. When a bacterium lands on heavily salted food, the salt pulls water out of its cell. Without enough water, it cannot grow or multiply, and many kinds simply stop being a problem.

Salt cannot keep every food safe forever, and some tough microbes can survive it. But combined with drying, smoking, or cool storage, it greatly extends how long food lasts. Today, salt curing is still used for foods such as ham, anchovies, and some cheeses, although it is now often chosen for flavor and tradition rather than necessity, since most kitchens have a refrigerator.

■ Harder · 236 words · Flesch-Kincaid grade 10.4

Long before refrigerators existed, people prevented food from spoiling by burying it in salt. Fish, pork, and even butter were preserved in this manner, and sailors and explorers relied upon salted provisions during lengthy journeys. The technique succeeds because of the way water travels through the thin walls of living cells.

The bacteria and molds that spoil food are living organisms, and they require water in order to grow. Salt is exceptionally good at attracting water. When food is packed in salt, or soaked in a salty solution called brine, a process known as osmosis begins: water moves through cell walls from the region where it is plentiful toward the region where salt is concentrated. The moisture inside the food is drawn outward, and the food gradually becomes drier.

Microbes suffer the same fate. When a bacterium settles on heavily salted food, the salt draws water out of its cell, and without sufficient water it can neither grow nor multiply. Many kinds of microbes therefore cease to be a problem.

Salt cannot keep every food safe indefinitely, and certain hardy microbes are able to survive it. Combined with drying, smoking, or cool storage, however, it dramatically extends how long food will last. Salt curing is still used today for foods such as ham, anchovies, and some cheeses, although it is now frequently chosen for flavor and tradition rather than necessity, because most kitchens contain a refrigerator.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put preserved, brine, osmosis, microbes and concentrated on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 2 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 5 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "How Salt Keeps Food From Spoiling"?

It was written for 7th grade. It has 222 words and works out to a Flesch-Kincaid grade level of about 7.7. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 4 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 2 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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