"Slowing down the speed of food spoilage" Food PPT courseware

Description

"Slowing down the speed of food spoilage" Food PPT courseware

Causes of food spoilage

Food spoilage is caused by microorganisms. The growth and reproduction of microorganisms, like plants and animals, require certain conditions such as air, moisture, and temperature.

In the right environment, they can reproduce at an alarming rate. More and more microorganisms decompose and absorb the nutrients in the food, and at the same time eliminate waste, so that the food is no longer the same as it was before, and the food becomes spoiled.

Is the refrigerator universal?

Low-temperature storage is divided into refrigerated storage and frozen storage. Low-temperature refrigeration generally cannot kill microorganisms in food and is only suitable for short-term storage of food. Low-temperature freezing. The temperature of frozen food in household refrigerators is now between -12°C and -23°C. Generally, microorganisms can no longer reproduce or decompose food, but individual psychrophilic bacteria can still reproduce and cause food to slowly deteriorate.

Application:

Given a fish, how many ways can you store it?

Discuss in groups and take notes.

Tell us what you think.

Destroy the living environment

Temperature: roast, boil, bake, freeze

air seal vacuum immersion

Moisture Exposure Drying

Notice:

If I give you a package of well-packaged food, must it be healthy and safe food?

What information should we pay attention to on the packaging?

Invite students to go to the supermarket after class to conduct a food packaging information collection activity.

Things to note when observing spoiled food:

1. Do not touch spoiled food directly with your hands.

2. Wash hands with soap after observation.

3. Wear a mask and use tweezers to touch objects.

4. Do not directly smell harmful or unpleasant odors. You should fan them and smell them as little as possible.

Observe discipline:

1. The team leader came to the stage to receive various experimental supplies. Distribute observation sheets first, and then distribute a glove to each person.

2. Wear sanitary gloves with your left hand. Wear it when in contact with spoiled food. Do not touch good food. Use your right hand to touch good food.

3. Spoiled food is poisonous and should not be used to joke with classmates.

4. Each student chooses one kind of food for comparison and observation, and makes observation records.

5. After observing, hand the gloves to the group leader. The group leader collects the food and puts it in the trash can and returns all the food to the teacher.

summary:

Food spoilage is caused by microorganisms, which require air, moisture, and temperature to grow.

Controlling the conditions for microbial growth can slow down the rate at which food spoils.

Methods for storing food include: sun-drying, freezing, pickling, airtight packaging, sterilization, and the use of preservatives. Preservatives are harmful to the human body and should be used with caution.

1. Observe spoiled food

1. Have you ever eaten dried fish? How does it taste?

2. What are the differences between fresh dried fish and rotten fish, dry bread and rancid bread?

think about it

1. What are the similarities between rotten fish, sour noodles and moldy bread?

2. Why did Xiaoyu become corrupted in a short period of time? Why can dried fish keep a good smell for a long time?

2. Various methods of storing food

1. We already know that certain air, moisture, temperature and other conditions are required to cause food to spoil. If you want to store a fresh small fish, what method can be used?

2. Discuss in groups and explain the reasons for using this method to store food.

3. Why can food cans be used to store food in this way?

4. What other methods do you know about storing food? Why do these methods slow down food spoilage?

test you

True or False

1. Food spoilage is caused by the proliferation of microorganisms. ( )

2. The growth and reproduction of microorganisms require air, moisture and suitable temperature. ( )

3. When you smell spoiled food, fan it and try to smell it as little as possible. ( )

4. Freezing, drying, vacuum packaging and other methods can slow down the rate of food deterioration. The reason for this is the destruction of the conditions required for microbial growth. ( )

fill in the blank:

◆Food spoilage is caused by ( ). The mold that makes bread moldy is ( ), and there are many bacteria that are invisible to the naked eye and cannot be seen with a magnifying glass, also ( ).

◆The growth and reproduction of microorganisms, like plants and animals, require certain conditions. In ( ) environments, they can reproduce quickly. More and more microorganisms decompose and absorb the ( ) in the food, and at the same time excrete ( ), so that the food is no longer the original food ( ).

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"Slow down the speed of food spoilage" food PPT download:

"Slowing down the speed of food deterioration" Food PPT download Part 1: Introduction of new knowledge There are often some foods in the pantry and drawers at home. How can we preserve food for a long time without deteriorating? ... ... ... Slow down the speed of food spoilage PPT..

"Slow down the speed of food spoilage" Food PPT:

"Slowing down the speed of food spoilage" Food PPT Part 1: Observing spoiled food Observe a fresh dried fish and fresh dried noodles. What are the characteristics of fresh food? Observe a small fish that has begun to rot and noodles that have gone sour. spoiled food..

"Slowing down the speed of food spoilage" Food PPT courseware 3:

"Slowing down the speed of food spoilage" Food PPT Courseware 3 Scientific Concept Food spoilage is caused by the massive proliferation of microorganisms. Microbial growth and reproduction require conditions such as air, moisture and suitable temperature. Destroying the conditions for microbial growth and reproduction can slow down food spoilage.

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Update Time: 2024-11-22

This template belongs to science courseware Fourth Grade Science Volume 2, Textbook Edition industry PPT template

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