Class 5 Environmental Studies Chapter 3: The Mystery of Food

The forgotten lunch box

Monday morning is sunny. Disha finds the lunch box she left behind at school on Friday. Inside it sits the uttapam from three days ago. She opens the lid. A bad smell rushes out. Coloured patches have spread over her favourite food. What happened to it? Disha decides to find out.

Detective Disha takes the case

Disha loves a puzzle. She runs home to her Anna, who is in Grade 8. She holds out the box. "What are these patches? And why does it smell so bad?" Anna looks in and smiles. "That is mould," he says.

Meet the microbes

Mould is made of microbes. Microbes are living things that are far too small for our eyes. They are smaller than the tiniest insect. To see them at all you must look through a microscope. A patch of mould is a colony of thousands of them together.

They are everywhere

Disha opens her notebook and writes her first finding. Microbes live in the soil. They live in water and in the air. They live on plants and on animals. Some even live inside our own bodies. There is no corner without them.

Not all of them are our enemies

"Are they all bad?" Disha asks. Anna shakes his head. Some microbes turn milk into curd. Others live in our stomach and help us digest food. Only some spoil our meals. They feed on the food and change its colour, taste and smell.

A slice and a jar

That afternoon Disha sees a slice of bread on the balcony. She had left it there for a cat two days ago. It now carries coloured patches. Yet her Paati's mango pickle, made two months ago, is still tasty. The pickle sits under a layer of oil. Strange!

What microbes need to grow

Disha goes back to her Anna with the puzzle. His answer is short. Microbes need moisture, air and the right warmth. Take away even one of these, and they cannot grow. That is the key to the whole mystery.

Why bread lost and pickle won

Now the two cases make sense. The bread was soft, damp and open to the air. That is a perfect home for microbes. The pickle had oil over it, so no air could reach the mangoes. Without air, the microbes could not grow.

How to spot spoiled food

Your nose and eyes are good helpers. Spoiled food often smells bad. It may show coloured or fuzzy patches. It may look wet and slimy. Its taste changes too, but never taste food to test it.

If spoiled food is eaten

Eating spoiled food can upset your stomach. You may feel sick or have pain. Tell an adult at once. Drink safe water and rest. If the trouble does not settle, a doctor must be seen.

Disha's rule

Disha writes a rule at the end of her page. Do not scrape the patch off and eat the rest. When food looks or smells wrong, let it go. It is better to lose one uttapam than to fall ill.

Scenario:

A class leaves four pieces of bread in four places for five days. One is dry and open, one is damp and covered, one is in the fridge, and one is damp in a warm cupboard. The warm damp piece grows the biggest patch of mould. The fridge piece grows almost none. Ravi says mould comes from dirt. His teacher asks why the fridge piece stayed clean, since it was handled the same way. The class works it out. The mould needed warmth and damp to grow, not dirt. Nita adds that a patch is not one thing but thousands of microbes together.

Analysis:

Four pieces handled alike and four different results. What differed was warmth and damp, so those are what the mould needed.

Activity:

Leave bread in three places for four days. Draw the mould on each and write which conditions suited it best.

Title:

The damp slice and the dry slice

Safety:

Do not open the bowls or smell the slices. Ask an adult to throw both away at the end.

What You Notice:

The damp slice grows coloured patches much sooner. The dry slice stays clear for longer. Moisture helps microbes to grow.

Our country grows more millets than any other. Millets carry a lot of goodness for the body.

India also leads the world in growing pulses, the dals we eat almost every day.

What microbes need — MAW: Moisture, Air, Warmth — Take away any one of the three and microbes cannot grow.

Spoiled food — Smell it, see it, skip it — A bad smell or a coloured patch means the food goes in the bin.

The detective goes hunting

Disha now knows why food spoils. One question is still open. How do people keep food good for months? She takes her notebook and walks around her own home. Every room, she decides, may hold a clue.

Clue one: chillies in the sun

On the balcony, Amma and Appa are spreading red chillies on a mat. "Why?" asks Disha. "For chilli powder," says Amma. "It will last us the whole year." Disha writes her finding. Drying takes the moisture away, so microbes cannot grow.

Many foods are dried

Once she knows the trick, Disha sees it everywhere. Papads dry on the terrace. Fish is dried by the sea. Mango pulp is dried into aam papad. Roti is dried and crisped into khakhra. All of them keep for a long time.

Clue two: oil in the pickle jar

In the kitchen, Paati is pouring mustard oil over pickled green mangoes. "Why the oil?" Disha asks. "Oil keeps the air out," Paati says. "That keeps the pickle safe." Finding two goes into the notebook.

Clue three: salt, sugar and spices

Disha's grandfather has his own story. Long ago, people kept food from spoiling with salt, sugar and spices such as pepper. We still use those ways today. Jams are full of sugar. Pickles are full of salt.

Clue four: the cold shelf

Next morning Disha opens the fridge. Milk, butter, vegetables and a cake sit inside. "The fridge keeps things too cold for microbes," Appa explains. Cold does not kill them. It only slows them down, so the food stays good for longer.

The clay pot cooler

Not every home has a fridge for water. Many use a matka, a clay pot. The pot keeps drinking water pleasantly cool on the hottest day. It is a simple, old and clever idea.

Butter and ghee

Butter must sit in the fridge, but ghee does not. Disha finds out why. Butter is heated at home. The water in it separates and goes off into the air. What is left is ghee, with no water in it. No moisture means no microbes.

Clue five: tins and sealed packets

Anna tells her about food factories. There, food is packed in airtight cans and sealed packets. No air and no microbes can enter. That is how juice and other foods travel far and still stay good.

Good microbes at work

Some microbes are welcome in the kitchen. Amma keeps idli batter overnight. Microbes from the air make it rise and turn it fluffy. Curd is set by microbes too. Buttermilk after a heavy meal helps the stomach.

The detective's list

Disha closes her notebook with a list. Dry it, oil it, salt it, chill it or seal it. Each way removes moisture, air or warmth. Different homes use different ways. The idea behind all of them is the same.

Scenario:

Paati grows chillies in her backyard in a village near Madurai. Every summer she spreads them on mats to dry in the sun. This year the dried chillies are ground into chilli powder at the village mill. Paati fills the powder into glass jars. Each jar holds 500 grams, and she fills 20 jars in all. She wipes every jar dry and closes the lids tightly. Then she stores the jars on the top shelf, away from the steam of the stove. Her family uses about one jar of chilli powder every month. Paati tells Disha that a wet spoon in a jar can spoil the whole powder.

Analysis:

Weighing and counting show why drying is worth the work. One week of sunshine feeds a family for more than a year.

Activity:

Count the jars and packets in your kitchen that hold dried food. List how each one is kept safe.

Title:

Sun-dried tomato slices

Safety:

An adult must do the cutting. Keep the tray away from flies and from small children.

What You Notice:

The slices shrink and turn leathery as the water leaves them. Dry slices keep much longer than a fresh, juicy slice on the counter.

Black pepper was once prized across the world. Vasco da Gama sailed the oceans to fetch it from India.

In the North East, bamboo is used for houses and for cooking. Tender bamboo shoots become tasty curries.

Ways to preserve food — Dry, Oil, Salt, Chill, Seal — Five ways, one idea. Each takes away moisture, air or warmth.

Why ghee keeps without a fridge — No water, no worry — Heating butter drives the water off, and microbes cannot grow without moisture.

Aaaah! says the detective

Disha has solved the mystery of spoiling food. Now a new question arrives. Where does food go once it is eaten? She stands before the mirror, opens her mouth wide and says, "Aaaah!" Rows of teeth look back at her. Not one of them is the same shape.

Four kinds of teeth

Anna explains the shapes. The flat teeth in front are incisors, and they cut. The pointed ones at the corners are canines, and they tear. Behind them sit the premolars, which crush. Right at the back are the molars, which grind food fine.

A team at work

Bite an apple and the incisors do the cutting. The food then travels back. The premolars and molars work it into a soft mush. Each kind of tooth has its own job. Together they get the food ready to swallow.

Chewing calls for saliva

Something else happens while you chew. Your mouth fills with saliva. The longer you chew, the more saliva comes. Saliva mixes into the mush and begins the work of digestion. Chewing well is the first step of a good meal.

Do not gulp it down

Amma has a rule at dinner. Do not swallow food in a hurry. Big lumps can block the throat, and that is called choking. Take small mouthfuls. Chew them properly. Never talk or laugh with food in your mouth.

A hole in a tooth

One week Disha has a toothache. The dentist finds a cavity, a small hole in her tooth, and treats it. "Rinse your mouth after you eat," the dentist says. "Brush your teeth regularly, and cut down on sweets."

Good microbes at work inside us

Anna eats at a fair and gets an upset stomach. Amma gives him curd. Curd carries tiny helpers. Those microbes join the good microbes in our stomach and help with digestion. If the trouble is serious, a doctor must be seen and medicines taken.

Waiting for the lychees

One rainy evening Appa brings home lychees. Disha is delighted. "Lychee is a seasonal fruit," Appa says. "We must look forward to it all year." The waiting makes the taste even better. Amla comes in winter. Jamun comes in summer.

Food that has not travelled far

Appa says one more thing about the mangoes from their own district. They are fresh because they did not travel far to reach the house. Food from nearby fields spends less time on the road. Less travel means fresher food on the plate.

Choosing at the market

Thatha goes to the vegetable market every day. Disha watches him closely. He looks at each fruit and vegetable before buying it. He leaves the soft, bruised and dull ones. He picks the firm and fresh ones instead.

Mystery solved

Disha closes her notebook with a smile. Eat food that is fresh and in season. Store it the right way. Chew it slowly and well. Look after your teeth. And say thank you to the good microbes.

Scenario:

A class counts its own teeth with a mirror and sorts them by shape. The front ones are flat and sharp, the next are pointed, and the back ones are wide and bumpy. Each child writes the four numbers down. The totals match across the class. Their teacher asks why one mouth needs four shapes. The children test it on an apple. The front teeth cut a piece off, and the back teeth grind it. Meena sees that one shape could not do both jobs. The class notes which food each shape suits best and why chewing brings saliva into the work.

Analysis:

Four shapes because there are four jobs. Cutting and grinding need opposite tools, which is why no single tooth shape would serve.

Activity:

Count your teeth of each kind using a mirror. Eat an apple slowly and note which teeth do which job.

Title:

The thirty-chew test

Safety:

Take small pieces only. Sit up straight and do not talk while chewing.

What You Notice:

The longer you chew, the softer the food becomes. Your mouth fills with saliva and the taste turns slightly sweet. The back teeth do most of the grinding.

In India most people eat with their hands. Your fingers read the texture, and the stomach gets ready for the meal.

Most Indian thalis are planned so that one plate carries a rich, balanced meal.

What each tooth does — I Cut, C Tear, P Crush, M Grind — Incisor cuts, canine tears, premolar crushes, molar grinds.

Safe eating — Small bites, slow chews, quiet mouth — Small mouthfuls, chewed well, with no talking, keep you from choking.