Why food has to be preserved
Mangoes are sweet and cheap in summer, but in winter there are none in the market. Yet your grandmother's mango pickle is on the table all year. That is food preservation.
Preserving food (अन्न टिकवणे) means keeping food from spoiling so that it can be eaten after its season too.
Rule 1: Why we preserve food — Crops get ready only in some months, so wheat, rice and pulses must be stored till the next crop. Fruits and vegetables are plentiful and tasty in their season, so we preserve them for the whole year.
In the figure : In the figure food is preserved so that we can eat it after its season too.
- Easy : Easy: Wheat is stored for the whole year.
- Medium : Medium: Mangoes become pickle to be eaten in winter.
- Exam-type : Exam: Crops come only at certain times, so we must store them.
Rule 2: Preserving at home — Papads, jams, pickles, onions, fish and masalas are made for the year. Eggs, milk and milk products must stay good during transport. Grains are dried in the sun before storing, onions and potatoes are dried in the open air, and boiled milk does not spoil at once.
- Easy : Easy: Pickles are kept for the year.
- Medium : Medium: Boiled milk lasts longer than raw milk.
- Exam-type : Exam: Milk and mango pulp spoil quickly.
We preserve food to eat it after its season.
Thinking fresh food never spoils. All food can spoil.
Memory clue: "हंगामाचे अन्न वर्षभर".
Spot the difference
| Food | How kept |
|---|---|
| Grains | Dried in sun |
| Onion, potato | Dried in open air |
| Milk | Boiled |
Practice questions
- 1Why do we preserve food?
- 2Name two foods preserved at home.
- 3Why are grains dried before storing?
- 4Which spoils quickly: milk or dry wheat?
- 5Why must milk be kept good in transport?
- 6Why does winter keep food longer?
- 7A farmer harvests wheat in March. Why store it till next March?
- 8Why do we store provisions for several days at home?
Show answers (try them yourself first)
- 1To eat it after its season too.
- 2Pickle and papad.
- 3Dry grain does not spoil easily.
- 4Milk.
- 5So it reaches users fresh.
- 6It is cold, so spoiling is slow.
- 7There is no new crop till then.
- 8To avoid going to the market again and again.
Spoiling of food and micro-organisms
A piece of bread forgotten in a bag during the rainy season grows green and fluffy spots in a few days. Something living is growing on it.
A micro-organism (सूक्ष्मजीव) is a living thing too small to see. A fungus (बुरशी) is one type; it spoils food.
Rule 1: The chapati experiment — Divide a chapati into three pieces: one in a closed box, one roasted crisp, one in the fridge. After two to three days, only the closed-box piece grows white, black or greenish cottonwool-like fibres and smells.
In the figure : In the figure food kept in a closed box gets fungus within a few days.
- Easy : Easy: Only the closed-box piece spoiled.
- Medium : Medium: The crisp and fridge pieces stayed good.
- Exam-type : Exam: In three days, a piece shows fungus; if the experiment runs 6 days, the fungus will keep growing.
Rule 2: What micro-organisms need — Spores of fungus are in air and water. They need food, water, air and warmth. The closed box gave all four. Spoiled food can cause stomachache, diarrhoea and vomiting, and it loses nutrition.
In the figure : In the figure, take away any one of these and micro-organisms cannot grow easily.
- Easy : Easy: Fungus needs food.
- Medium : Medium: Without water it cannot grow.
- Exam-type : Exam: The crisp roasted piece had no water.
Micro-organisms need food, water, air and warmth. Remove one and they stop.
Thinking the white fluff is dust. It is a living fungus.
Memory clue: "अन्न-पाणी-हवा-उब".
Spot the difference
| Piece | Result |
|---|---|
| Closed box | Fungus grows |
| Roasted crisp | No growth (dry) |
| Fridge | No growth (cold) |
Practice questions
- 1What is a micro-organism?
- 2Which micro-organism grew on the chapati?
- 3Name two things fungus needs.
- 4Where are spores of fungus found?
- 5Which chapati piece spoiled?
- 6Why did the fridge piece not spoil?
- 7Name two harms of eating spoiled food.
- 8How many things do micro-organisms need? Name them.
Show answers (try them yourself first)
- 1A living thing too small to see.
- 2Fungus.
- 3Water and warmth.
- 4In air and water.
- 5The one in the closed box.
- 6It was cold, so no warmth for growth.
- 7Stomachache and vomiting.
- 8Four: food, water, air, warmth.
Drying, cooling and boiling
Wet clothes kept in a bag smell musty, but dry clothes do not. The water in them lets germs grow. Remove the water, and the problem goes away.
To preserve food, we destroy micro-organisms in it or put it where they cannot grow again.
Rule 1: Three simple methods — Drying (वाळवणे): the water is lost, as in papad, kurdai, sandage, wheat and daals. Cooling (थंड करणे): in a fridge the micro-organisms do not get warmth. Boiling (उकळणे): the micro-organisms get destroyed.
In the figure : In the figure drying, cooling and boiling each stop micro-organisms in a different way.
- Easy : Easy: Papad is dried.
- Medium : Medium: Cooling in a fridge removes warmth.
- Exam-type : Exam: Boiling destroys micro-organisms.
Rule 2: Which method for which food — Wheat and daals are dried, vegetables and leftover curry are cooled, and milk is boiled. A dried food must stay dry or water will let micro-organisms grow again.
- Easy : Easy: Milk is boiled.
- Medium : Medium: Dry papads must not get wet.
- Exam-type : Exam: Dried food gets spoiled if water enters again.
Drying removes water; cooling removes warmth; boiling kills micro-organisms.
Thinking boiled food can never spoil again. It can if micro-organisms enter again.
Memory clue: "वाळव-पाणी, फ्रिज-उब, उकळ-मार".
Spot the difference
| Method | Effect |
|---|---|
| Drying | Water lost |
| Cooling | No warmth |
| Boiling | Micro-organisms destroyed |
Practice questions
- 1Name three simple methods of preserving food.
- 2Which method removes water?
- 3Which method takes away warmth?
- 4Which method destroys micro-organisms?
- 5Name two dried foods.
- 6Why should dried papads be kept in a dry tin?
- 7Leftover curry is kept in a fridge. Which need is removed?
- 8Milk is boiled at 6 pm and kept open till morning. Can it spoil?
Show answers (try them yourself first)
- 1Drying, cooling and boiling.
- 2Drying.
- 3Cooling.
- 4Boiling.
- 5Papad and sandage.
- 6Water would let micro-organisms grow.
- 7Warmth.
- 8Yes, micro-organisms may enter and grow again.
Airtight cans, preservatives and pickle
A sealed jar of jam stays good for months, but once the lid is opened and left, it grows fungus. The seal and the sugar were protecting it.
Preservatives (परिरक्षके) are substances added to food to keep it good for a long time.
Rule 1: Airtight cans — In canning, the micro-organisms are destroyed first and then the food is sealed so that no air or water can enter.
In the figure : In the figure canned food stays safe because nothing can get in.
- Easy : Easy: Cans are airtight.
- Medium : Medium: Micro-organisms are destroyed before sealing.
- Exam-type : Exam: A dented, leaking can is unsafe.
Rule 2: Preservatives — Sugar, salt, asafoetida (hing), mustard, oil and vinegar are preservatives used in jams and pickles.
In the figure : In the figure preservatives keep jams and pickles good for a long time.
- Easy : Easy: Salt is a preservative.
- Medium : Medium: Jam has sugar; pickle has salt and oil.
- Exam-type : Exam: Name three preservatives.
Rule 3: Making lemon pickle — Take a clean, dry glass jar. Cut 7–8 lemons into 8 pieces each. Add salt, sugar and red chilli powder, mix with a dry spoon, tie a clean cloth over the mouth and keep in the sun for about 10 days, stirring daily with a clean, dry spoon. Hands must be clean and dry.
In the figure : In the figure use a clean, dry jar, a dry spoon and clean, dry hands.
- Easy : Easy: Use a dry jar.
- Medium : Medium: 8 lemons × 8 pieces = 64 pieces.
- Exam-type : Exam: Water must not enter, or the pickle spoils.
Canning: seal after killing germs. Preservatives: sugar, salt, hing, mustard, oil, vinegar.
Using a wet spoon for pickle. Water spoils it.
Memory clue: "लोणचे = कोरडे, स्वच्छ".
Spot the difference
| Food | Preservative |
|---|---|
| Jam | Sugar |
| Pickle | Salt, oil, mustard, hing |
| Sauce | Vinegar |
Practice questions
- 1What is a preservative?
- 2Name two preservatives.
- 3How is canned food made safe?
- 4Which preservative is used in jam?
- 5How long is lemon pickle kept in the sun?
- 6Why use a dry spoon for pickle?
- 76 lemons are cut into 8 pieces each. How many pieces?
- 8A jam jar was opened and left for a week. Why did fungus grow?
Show answers (try them yourself first)
- 1A substance added to keep food good for long.
- 2Salt and sugar.
- 3Germs are destroyed and the can is sealed.
- 4Sugar.
- 5About 10 days.
- 6Water would spoil it.
- 76 × 8 = 48.
- 8Air and micro-organisms entered the open jar.
Spices and safe use of food
The taste of dal changes with a pinch of cumin or a drop of turmeric. A tiny amount of spice makes a big difference.
Spices (मसाले) give food its flavour and are used in very small quantities.
Rule 1: About spices — Much of the variety of taste in food comes from spices. Each has its own flavour. They are strong, so only a little is used. They can be dried, stored for a long time, mixed and powdered to make different masalas. They come from different parts of different plants.
In the figure : In the figure always check the use-before date on packed food.
- Easy : Easy: Turmeric is a spice.
- Medium : Medium: Only a little spice is used.
- Exam-type : Exam: Spices come from different parts of plants.
Rule 2: Safe use of packed food — When buying food in sealed bags or boxes, check the expiry date (मुदत संपण्याची तारीख, "use before"). If micro-organisms get air, water and warmth they grow, so use food before the date.
- Easy : Easy: Check the date before buying.
- Medium : Medium: A packet marked "use before 30 June" must not be used on 5 July.
- Exam-type : Exam: Expired food can make us sick.
Spices: small amount, strong. Check the expiry date.
Eating packed food without checking the date.
Memory clue: "घेण्यापूर्वी तारीख पाहा".
Spot the difference
| Item | Point |
|---|---|
| Spices | Strong, used little |
| Masala | Mixed and powdered spices |
| Expiry date | Use before this date |
Practice questions
- 1What are spices?
- 2Why are only small amounts of spice used?
- 3Name two spices.
- 4How can spices be stored long?
- 5What should we check on packed food?
- 6Why check the date?
- 7A packet says "use before 15 March". Today is 20 March. May we use it?
- 8List the five methods of preserving food.
Show answers (try them yourself first)
- 1Plant parts that give food its taste.
- 2They are strong.
- 3Turmeric and cumin.
- 4By drying them.
- 5The expiry (use before) date.
- 6Old food may be spoiled and make us sick.
- 7No, the date has passed.
- 8Drying, cooling, boiling, canning, adding preservatives.
Quick revision
- Fungus is a micro-organism; it grows where there is food, water, air and warmth.
- Methods: drying, cooling, boiling, airtight cans, preservatives.
- Preservatives: sugar, salt, hing, mustard, oil, vinegar.