Food Preservation - Let's be careful of food wastage and take steps to preserve food.

The foods we consume can be divided into three parts.

 

1. Foods that spoil quickly

2. Foods that can be kept for a while; foods that spoil very slowly

3. Stable food

Food is subject to spoilage; therefore, the methods for preserving foods are very important. Food preservation means processing foods to get rid of food deterioration so they can be kept for a long time.

Benefits of Food Preservation

1. Most foods are produced at specific times of the year. These products can be used for food in times of scarcity.

2. By processing the excess products for preservation, more income can be obtained throughout the year.

3. Foods of a variety of tastes and qualities can be produced.

4. When the production is increased, it becomes difficult to sell them. Wastage of production will occur. Therefore, the loss caused by it can be reduced, and you will be able to make a good income.

5. The damage caused to the environment and humans by throwing away excess production can be prevented.

Disadvantages of food preservation.

1. Destruction of nutrients in the food

2. Having to incur additional costs

Changes that are sensed when food is spoiled.

1. The physical nature of food changes.

Fruits become soft when they are ripe enough.

Stickiness occurs when cooked rice spoils.

When milk is spoiled, it becomes clotted.

2. Changes in the chemical nature of foods

The action of yeast on a sugar solution results in the formation of alcohol, and then, by the action of bacteria, acitic acid is formed. 

3. Food's Nutrient Deficiency

Nutrient-rich compounds in food are converted into other non-nutrient compounds.

4. Discoloration of food

When fruits are spoiled, the colour of the bark changes.

Fresh and spoiled fish can be identified by their colour.

Food odour.

Extrinsic enzymes, various excretory substances of microorganisms that cause food spoilage, can be toxic to humans.

There are two main ways to preserve food.

1. Preserving food without affecting its basic properties or texture

Ex. drying grain, vegetables, and fruits.

2. Preserving food by changing its basic properties and texture and producing new food productions

Ex: New products like yoghurt, milk toffee, ice cream, etc. are produced from milk.

The main ways in which food spoils

This can be divided into three main parts:

1. By microorganisms

Most foods are spoiled by microorganisms such as bacteria and fungi.

2. By the continuous occurrence of various biological activities in food.

Ex: When actions such as respiration occur, the temperature of production is increased and the food is boiled; therefore, the food is spoiled sooner.

3. By various enzymes present in food.

Methods to follow for preventing food spoilage caused by microorganisms

1. Preventing the entry of microorganisms into food

Prevent microbial entry into food through dirty dishes, dust, and flies.

protecting the food by covering it and using hygiene.

2. Controlling the growth of microorganisms on food

This can be achieved by changing the environmental conditions that are beneficial for microorganisms. (Microbial environment)

Ex: providing a lower temperature, changing the pH, and increasing the osmotic pressure

3. Eliminate microorganisms in food.

This method can be followed for liquid foods. This is an expensive method.

Finely filter the drinking water.

4. Destruction of microorganisms

This can be done by heating the solution and adding a chemical that is toxic to microorganisms. There are two main types of heating.

1. Sterilisation

All microorganisms are destroyed.

2. Pasteurisation.

In this case, the micro-growth cells are destroyed, but the spores are not. Also, spoilage enzymes are inactivated during pasteurization.

The factors that cause the growth of microorganisms

1. Microorganism growth depends on the amount of nutrition in food, such as proteins, carbohydrates, minerals, and vitamins.

Foods like milk and meat contain more nutrition, so they are prone to getting spoiled quickly.

2. Acidity is:

The specific microorganism group's growth is determined based on the medium's acidity. When it is neutral, bacterial growth is high. When it is acidic, fungus growth occurs.

3. The water in food:

When the amount of water is increased, microorganisms grow well. And growth is limited when there is a low amount of water. 

4. The temperature at which the food is stored

Microorganisms grow well at temperatures between 25 and 35°C.

When the temperature is lower than 7°C and higher than 80 °C, the growth is controlled.

5. Oxygen (O2) concentration in the media

Based on the amount of oxygen required by the microorganisms, they are divided into two groups.

1. aerobic

2. anaerobic

6. By the various compounds contained in food. Some foods contain compounds that reduce the growth of microorganisms. These compounds are found in some medical plants.

How foods are spoiled by microorganisms:

Food is spoiled by humans or by insects like flies, contaminated water, or dust falling on food. Uncleaned equipment, animals like cockroaches and rats, and not using proper hygiene methods can allow microorganisms to enter food. When considering foods such as meat, pollution can also be caused by eating sick animals' meat or by killing animals without using proper hygienic methods.

Actions to be taken to prevent food spoilage

The person consuming the food should be hygienic.

Use of clean containers.

Storage in clean places.

They should be closed properly so that animals cannot approach them.

Use of clean water.

Sick animals should not be consumed for food.

Basic strategies used for food preservation:

1. Drying (dehydration)

Drying food reduces the amount of water in which microbes can grow.

Ex: dry grain, milk powder, dried fish

2. Use of low temperatures

Storing in the refrigerator or freezer. Storage at temperatures below ambient is required for microbial growth.

3. Osmotic pressure control

In this case, the osmotic pressure of the external fluid increases. In this case, the epithelial cells of the microorganisms shrink, become inactive, or die.

Ex. salting, using sugar solvents

4. Controlling the pH

The pH of the medium adversely affects microbial growth.

Ex:

In pickles, vinegar is used. The HAC acid present in it lowers the pH of the medium.

5. Creating an airtight condition After sterilisation, food is stored, and bottles and cans are sealed. There, the microbes do not get the oxygen they need to breathe.

6. Use of various chemical compounds

Chemical compounds that are in use are divided into two categories:

1. Organic compounds

Sodium Benzoate

Bacteria coagulate milk (curdling). Yeast helps in the fermentation of toddy. Yeast is needed to bake bread. A fungus called Rysopas Oligus Porus helps in the making of soy tempeh.

2. Chemical Reactions

Mainly, chemical reactions in fruits and vegetables occur due to their natural enzymes. Fruits and vegetables are spoiled due to certain processes carried out by these enzymes.

3. Physical reasons

Changes in temperature and moisture will assist in speeding up the growth of microorganisms.

4. Rat and the Parasite

Fruits and vegetables are food for them, and because of them, the foods get infected. Moreover, their excretory fluid (excrement) creates an environment conducive to the growth of microorganisms.

 Fruit and vegetable preservation methods

1. Dehydration or drying

Not only for fruits and vegetables, but for many foods, the preservative method that is easiest and cheapest is drying. Also, there's no need for a lot of space to store these dried foods. Inexpensive packing methods can also be used to pack them. Drying in sunlight is the cheapest method. But at specific times, the oven or other fuel are used. The downside of drying is that it can cause a big change in the taste of the food.

After drying, the water content of vegetables should be about 10%, and that of grains could be 12%. Okra, beans, jackfruit, breadfruit, manioc, etc., and bitter gourd, egg plant, asparagus, tomatoes, etc. can also be used for drying. Okra, beans, etc. should have young shoots and be in good condition. Rinse with clean water, cut with a stainless steel knife, and put in a 2% salt mixture. After that, the chopped vegetables should be blanched. (boiling for a while). Or you need to put it in boiling water for 3–6 minutes. The reason for blanching is to deactivate the enzyme itself.

After blanching and dehydration, 25% of the sulfer-dioxide mixture should be applied. Sodium metabisulfite and potassium metabisulfite are suitable. To obtain the above concentration, it is necessary to dilute 2.5g of potassium metabisulfate in 1 litre of water and use it. (Fill 1 teaspoon with water and dissolve in 5 cups.) (And this way, the mixture can be made without a homemade scale.) Leave it in this mixture for about 15 minutes, then dry it in the sun for 8 hours while stirring occasionally. After that, the drying should be done gradually. Drying can also be done in an oven with a temperature of 56–60 °C. After drying, pile up and leave for about two hours; later storage is required. Sulfidation helps maintain the colour of food and preserve food. Fruits like rambutan can also be dried. Blanching is unnecessary. Add the extracted flesh of the fruit (pits removed) to the 25% sulphur dioxide mixture. Finally, strain the water and let it dry for a few days. They can be used as raisins.

2. Sterilisation in cans or bottles

The taste of vegetables and fruits packed in cans or bottles is largely the same. But the jars needed for packing are expensive. This is not a cheap preservation method. Special equipment, etc., is required.

3. Changing the osmotic pressure

Water is required for the growth of microorganisms. However, they usually do not absorb water when the sugar content of a solution exceeds 65%. Therefore, when making jams and jellies from fruits, they can be preserved by adding more than 65% sugar.

4. By applying chemicals and drugs

Fruits and vegetables can be preserved with chemicals and spices. Fruit drinks or cordials are preserved by adding potassium metabisulfite, sodium metabisulfite, or sodium benzoate, and by adding vinegar and spices to some vegetables (pickles).

1. Organic Compounds

Sodium Benzoate

Fomic Acid

Acitic Acid

Alcohol

2. Inorganic Compounds

Nitric

Nitrous

Sulfiuric Acid

Potassium Nitrate

Some of the above are toxic to microorganisms. Some change the pH, while others control the osmotic pressure and restrict microbial growth.

5. In addition to the main points mentioned above:

Store in sand. ex: jackfruit seeds, lime, lasia stalk

Store food in the soil (burial of food). Ex: Manioc

Smoking. Ex: Gambooge, meat, fish

Benefits of preserving vegetables and fruits.

The main reason for preserving fruits and vegetables is that they are in excess during the season and not available during the off-season. Another reason is that their cultivation is limited to certain climatic regions. Rambutan, for example, grows in areas around Colombo (Sri Lanka), while strawberries grow in areas such as the tea country hills in Sri Lanka. Some seasonal vegetables and fruits are available on the market in excess of consumer demand at that time. Due to this, it is difficult for the farmer who cultivates them to get a fair price. There are also times when it is wasted without being able to be sold. In an agricultural country like Sri Lanka, this is economically disadvantageous.

Causes of spoilage of vegetables and fruits:

1. Microorganisms' Actions

Bacteria: Payuserium bacteria causes potatoes to spoil.

Yeast: fermentation of alcoholic beverages due to yeast

Fungi: Bananas get a disease called "Aththaknose," which makes bananas turn black and spoil because of a fungus.

2. Chemical Reactions

The activation of enzymes causes the starch in the fruit to turn into sugar, and lipase causes the oil to (breakdown) go rancid.

Oxidation 

When ash plantain, or breadfruit, is cut, its colour changes. This can be prevented by soaking them in 2% concentrated salt water. enzyme-unactivated browning. (It can be seen as a grey ring on top of the cordial bottle when stored.)

3. Physical reasons

Temperature (in vegetables and dried fruits) helps increase microorganisms' actions.

Moisture: Vegetables tend to be spoiled quickly on rainy days.

Light: When cod liver oil is exposed to light, its quality decreases.

Osmotic Pressure: Spoiling of jam in jam bottles due to a lack of sugar.

4. Damage from parasites

Insects, rodents, weevils, and cockroaches

Microbial activity. (Bacteria, yeast, fungi) Vegetables and fruits are ideal media for the growth of microorganisms. In tropical countries like Sri Lanka, the temperature, the food and water contained in fruits and vegetables, and the secretions of microorganisms cause a chemical reaction in the food. These foods are then identified as spoiled. 

In some cases, yeast, fungi, and bacteria are useful. (in making lactic acid).

5. Cooling (freezing)

We know that fruits and vegetables spoil mainly due to microorganisms and enzymes. As the environment cools, their growth rate slows. It also reduces the activity of enzymes'. To cool and freeze, a refrigerator can also be used.

6. Deep freezing

Not only meat or fish but also vegetables and fruits can be frozen. But special methods have to be used for freezing. Unlike meat or fish, vegetables and fruits should be refrigerated quickly in small containers.

From this description, you got to know various information regarding the use and preservation of food, which directly leads to human existence.