Ms. Ajita Tiwari, HoD (i/c), Department of Agricultural Engineering, Assam University, Silchar, Assam, talks about food preservation techniques.
The purpose of processing and preserving foods is to prevent spoiling of food material by reducing the growth of microorganisms and to extend the shelf life of food products, thereby reducing health hazards. We have to work on how to extend the shelf life by retaining the nutrition and making it safe to consume. Most of the fruits, vegetables, and animal products get spoilt quickly due to the high water percentage which makes it easy for microorganisms to get into the food products and grow easily. Effective preserving techniques are using salt, sugar, vinegar, and brine. These preserving gents basically prevent bacteria, mold and other potentially harmful organism to grow on the food. There are two drying techniques – one is dry preservation which involves mixing salt in foo which draws water out of the food and make it impossible for the microorganisms to grow. The next one is wet preservation where the food undergoes heat processing to kill microorganisms and vacuum seal created by proper canning that prevents life sustaining oxygen entering into containers.
Most bacteria and fungal spores cannot live without oxygen or manage prolonged immersion in boiling water. When we remove the oxygen out, it may not have microorganisms, but they may have some chances. When we use boiling water, immerse food products directly, there are chances of microorganisms not surviving. Clostridium botulinum is a dangerous bacteria that causes food poisoning. Clostridium botulinum is a dangerous bacteria which is the main reason for the food poisoning. This is hard and usually survives in anoxic environment where oxygen is toxic to it. it cannot survive acidic environment as brine. If the pH value is low and acidic, it kills the bacteria. Even in autoclaving, due to high pressure, the bacteria get killed. So food preservation is a process that stops rotting of fruits and vegetables, retaining colour, taste, and nutritional value. Due to the microorganisms, food gets spoilt when there is high moisture content or air. When food is kept for long time at room temperature, the skin of fruits and vegetables get spoilt, as also during transportation, or when they have less salt, sugar, and acid content. Presence of insects, worms, and rats also spoil the food.
There are many methods and principles to delay the decomposition. We have to keep out microorganisms by creating aseptic environments with zero microbial load. Nature also gives some food products protective covering as in ground nut which prevents decay. Food industries have adopted aseptic methods to prevent contamination during processing. In canning industries, the load of microorganisms determine the heat process necessary for preservation of food. Here the channels are getting through sterilisation process which offer no chance for microorganisms to grow. In dairy industry, the quality of milk is judged by bacterial content. There are so many packaging materials through which the products are getting saved and shelf life gets enhanced.
We try to prevent microorganisms inside the food products by using filtration techniques. Industries use many bacterial proof materials in products such as juices, soft drinks, beer, and other materials. We will try to ensure that the growth of microorganisms is curtailed and activity hindered. This can be done by using low temperature or drying or providing anaerobic conditions inside the packaging material. In such a condition, there is no chance of oxygen to be there leading to microorganisms dying, and the spores may survive but cannot multiply in absence of oxygen. Using low temperature, drying, and use of chemicals are the other techniques. Cold storage comes in here which slows down and prevents bacterial activity. Drying is a popular and effective method of avoiding food getting spoilt as the microorganisms cannot flourish without the presence of moisture. Some chemicals like sodium benzoate and potassium metabisulfite are used in preservation and to increase the shelf life. Heat and radiation help in extending the shelf life by more days.
Yet another technique is prevention of self-decomposition by destruction and inactivation of food enzymes present in fruits which accelerates their decomposition. Blanching is a solution for this to inactivate the enzymes. Plant and animal tissues containing enzymes are highly active in the room temperature, and chemical changes double. Rancidity of fat is a major issue in products that have oxidation that leads to deterioration. Oil seeds are examples. Fungal growth is seen in plants and animal tissue fibre. To prevent the growth of bacteria, fruits and vegetables are blanched to inactivate the oxidative enzymes. Blanching is done with hot water, steam. It is a process where vegetables are exposed to boiling water or steam for some time and then quickly placed in ice water to prevent getting cooked. The basic preservation of foods is divided into three stages to prevent insects, mishandling leading to damage, such as effective packing, transportation, and storage facility.
The main methods of preservation of food are canning, bottling, salting, and sugaring, and these involve osmotic dehydration, drying, fermentation, cooling, and freezing. During canning, the product is transported to another place and after the complete preservation practices it is canned as it is a fully aseptic method. Jars and containers are used here, heating them to a temperature that destroys microorganisms which cause food to spoil. Air is removed to create vacuum. Boiling water bath method and pressure canning method are the safe canning methods. Jars of food are placed in a special pressure cooker heated up to 240 degree Fahrenheit. The microorganisms are removed as the moisture content is removed. We must ensure to use food products which have stipulated shelf life mentioned within the time. Products such as meat, seafood, poultry, dairy, and vegetables with pH of 4.6 undergo this process. We can add lemon and citric acid to solve the acidity problem. Salting where osmotic dehydration is applied as salt removes water moisture, and very few bacteria grow in high salt solution. We have another method of using sugar where we first desiccate food by dehydrating and packing with sugar. Instead of sugar, we can use honey syrup also. Sugaring creates a hostile environment for microbial life and prevents food spoiling. This is mainly used in fruits and vegetables. We call it mummification process, but sugar also attracts moisture. It must be controlled. Drying is an old method where moisture is removed using solar drying, microwave drying, and spray drying. In this way molds are not able to grow on the food, and products become smaller and lighter in weight as water content is removed which helps in easy transportation. Fermentation is another method when applied in the correct way as done in sauerkraut and kimchi and bread. Widely consumed fermented foods are vinegar, olives, and cheese apart from beans, grains, vegetable, fruits, honey, and dairy products.
Cooling and freezing are some more techniques adopted. Refrigerators and modified atmospheric packaging using combination of CO2, Nitrogen, and Oxygen and additives come under this category. Chilling slows down the rate of decay. Smoking is another method used especially in processing fish. In fluidised bed drying, the liquified products get warm air blown upward to remove moisture. Many more methods such as plate freezing, blast freezing, fluidised bed freezing, cryogenic freezing, batch pasteurisation, high temperature and short time pasteurisation, sterilization, and ultra heat treatment are the other methods to preserve food products.
What are the food preservation techniques approved by APEDA?
All the techniques such as drying and freezing are methods approved by APEDA as they are safe to use.
What are the most common challenges farmers face when it comes to food preservation, and how can they be overcome?
Majorly, in India, farmers are small and marginal landholders, and very few farmers come under large land holding ones. These small and marginal farmers do not know techniques and face lot of problems. They are not tech savvy. They have post-harvest losses from their own products which cost them high. They do not know which technique is suitable for a particular products.
Are there any innovative and emerging food preserving technologies that the farmers should be aware of?
When we talk about modern preservation techniques, there are ultra-high temperature and other technologies which are based on high pressure processing. There are many more techniques. But the question is if we are trying to educate them about these techniques, it will not work out as these machineries are very expensive, and they are available only in a few labs in big cities. To take the farmers to those places to get skilled in using those machines is very difficult. Theoretically, if we want to teach them about the advantages, it has no meaning. So nowadays, APEDA is conducting trainings in traditional methods also. These are economical ones which they can use and get benefited out of them.
How can farmers ensure the safety and hygiene of preserved foods throughout the preservation process? What role education and awareness play in effective food preservation techniques among farming communities?
There are certain protocols set by FSSAI and other regulatory authorities. Food Safety centres are set up in every district and panchayat level. So it is their duty to educate the farmers about the necessary protocols and other details where they can go through them and follow. Education is a vital weapon to solve all these things because we find in rural areas people are not acquainted with latest techniques and using only open products which are contaminated with flies and other insects. They do not know the safety precautions to be taken and how such unhealthy practices will affect the health. Only with training and education, we can solve these issues.
Are there any region specific considerations that farmers should take into account when selecting a food preservation method?
I cannot say it will be region specific, but the crops are region specific. Some crops cannot be grown in some regions. So the demand for preservation is different here. For example, fruits like strawberries cannot be grown in dry land areas but can be cultivated in Western ghat side. Here the demand for preservation is different. We need to think of fruits and vegetables compositions and requirements that can be cultivated in the regions to adopt only such techniques. We need to think of fruits and vegetables preservation as per requirement and not region specific and follow only such techniques that are useful in those areas.
How can farmers strike a balance between traditional and modern food preservation methods for optimum results?
Farmers can do it if we provide good skill trainings and other facilities on hiring basis which are being provided to the farmers now. There are also credit facilities through which they can adopt preservation techniques and enhance the shelf life of products. They can thus get benefited by their own traditional knowledge and by following modern techniques.
Are there community based initiatives or success stories related to food preservation that you find particularly inspiring?
Yes. We can explore about the persons who have achieved very good success in preserving food products using techniques such as fermenting. In India, there are so many startup companies that are doing very well in these things. We can google to find out the details on companies that are highly successful in India.
The purpose of processing and preserving foods is to prevent spoiling of food material by reducing the growth of microorganisms and to extend the shelf life of food products, thereby reducing health hazards. We have to work on how to extend the shelf life by retaining the nutrition and making it safe to consume. Most of the fruits, vegetables, and animal products get spoilt quickly due to the high water percentage which makes it easy for microorganisms to get into the food products and grow easily. Effective preserving techniques are using salt, sugar, vinegar, and brine. These preserving gents basically prevent bacteria, mold and other potentially harmful organism to grow on the food. There are two drying techniques – one is dry preservation which involves mixing salt in foo which draws water out of the food and make it impossible for the microorganisms to grow. The next one is wet preservation where the food undergoes heat processing to kill microorganisms and vacuum seal created by proper canning that prevents life sustaining oxygen entering into containers.
Most bacteria and fungal spores cannot live without oxygen or manage prolonged immersion in boiling water. When we remove the oxygen out, it may not have microorganisms, but they may have some chances. When we use boiling water, immerse food products directly, there are chances of microorganisms not surviving. Clostridium botulinum is a dangerous bacteria that causes food poisoning. Clostridium botulinum is a dangerous bacteria which is the main reason for the food poisoning. This is hard and usually survives in anoxic environment where oxygen is toxic to it. it cannot survive acidic environment as brine. If the pH value is low and acidic, it kills the bacteria. Even in autoclaving, due to high pressure, the bacteria get killed. So food preservation is a process that stops rotting of fruits and vegetables, retaining colour, taste, and nutritional value. Due to the microorganisms, food gets spoilt when there is high moisture content or air. When food is kept for long time at room temperature, the skin of fruits and vegetables get spoilt, as also during transportation, or when they have less salt, sugar, and acid content. Presence of insects, worms, and rats also spoil the food.
There are many methods and principles to delay the decomposition. We have to keep out microorganisms by creating aseptic environments with zero microbial load. Nature also gives some food products protective covering as in ground nut which prevents decay. Food industries have adopted aseptic methods to prevent contamination during processing. In canning industries, the load of microorganisms determine the heat process necessary for preservation of food. Here the channels are getting through sterilisation process which offer no chance for microorganisms to grow. In dairy industry, the quality of milk is judged by bacterial content. There are so many packaging materials through which the products are getting saved and shelf life gets enhanced.
We try to prevent microorganisms inside the food products by using filtration techniques. Industries use many bacterial proof materials in products such as juices, soft drinks, beer, and other materials. We will try to ensure that the growth of microorganisms is curtailed and activity hindered. This can be done by using low temperature or drying or providing anaerobic conditions inside the packaging material. In such a condition, there is no chance of oxygen to be there leading to microorganisms dying, and the spores may survive but cannot multiply in absence of oxygen. Using low temperature, drying, and use of chemicals are the other techniques. Cold storage comes in here which slows down and prevents bacterial activity. Drying is a popular and effective method of avoiding food getting spoilt as the microorganisms cannot flourish without the presence of moisture. Some chemicals like sodium benzoate and potassium metabisulfite are used in preservation and to increase the shelf life. Heat and radiation help in extending the shelf life by more days.
Yet another technique is prevention of self-decomposition by destruction and inactivation of food enzymes present in fruits which accelerates their decomposition. Blanching is a solution for this to inactivate the enzymes. Plant and animal tissues containing enzymes are highly active in the room temperature, and chemical changes double. Rancidity of fat is a major issue in products that have oxidation that leads to deterioration. Oil seeds are examples. Fungal growth is seen in plants and animal tissue fibre. To prevent the growth of bacteria, fruits and vegetables are blanched to inactivate the oxidative enzymes. Blanching is done with hot water, steam. It is a process where vegetables are exposed to boiling water or steam for some time and then quickly placed in ice water to prevent getting cooked. The basic preservation of foods is divided into three stages to prevent insects, mishandling leading to damage, such as effective packing, transportation, and storage facility.
The main methods of preservation of food are canning, bottling, salting, and sugaring, and these involve osmotic dehydration, drying, fermentation, cooling, and freezing. During canning, the product is transported to another place and after the complete preservation practices it is canned as it is a fully aseptic method. Jars and containers are used here, heating them to a temperature that destroys microorganisms which cause food to spoil. Air is removed to create vacuum. Boiling water bath method and pressure canning method are the safe canning methods. Jars of food are placed in a special pressure cooker heated up to 240 degree Fahrenheit. The microorganisms are removed as the moisture content is removed. We must ensure to use food products which have stipulated shelf life mentioned within the time. Products such as meat, seafood, poultry, dairy, and vegetables with pH of 4.6 undergo this process. We can add lemon and citric acid to solve the acidity problem. Salting where osmotic dehydration is applied as salt removes water moisture, and very few bacteria grow in high salt solution. We have another method of using sugar where we first desiccate food by dehydrating and packing with sugar. Instead of sugar, we can use honey syrup also. Sugaring creates a hostile environment for microbial life and prevents food spoiling. This is mainly used in fruits and vegetables. We call it mummification process, but sugar also attracts moisture. It must be controlled. Drying is an old method where moisture is removed using solar drying, microwave drying, and spray drying. In this way molds are not able to grow on the food, and products become smaller and lighter in weight as water content is removed which helps in easy transportation. Fermentation is another method when applied in the correct way as done in sauerkraut and kimchi and bread. Widely consumed fermented foods are vinegar, olives, and cheese apart from beans, grains, vegetable, fruits, honey, and dairy products.
Cooling and freezing are some more techniques adopted. Refrigerators and modified atmospheric packaging using combination of CO2, Nitrogen, and Oxygen and additives come under this category. Chilling slows down the rate of decay. Smoking is another method used especially in processing fish. In fluidised bed drying, the liquified products get warm air blown upward to remove moisture. Many more methods such as plate freezing, blast freezing, fluidised bed freezing, cryogenic freezing, batch pasteurisation, high temperature and short time pasteurisation, sterilization, and ultra heat treatment are the other methods to preserve food products.
What are the food preservation techniques approved by APEDA?
All the techniques such as drying and freezing are methods approved by APEDA as they are safe to use.
What are the most common challenges farmers face when it comes to food preservation, and how can they be overcome?
Majorly, in India, farmers are small and marginal landholders, and very few farmers come under large land holding ones. These small and marginal farmers do not know techniques and face lot of problems. They are not tech savvy. They have post-harvest losses from their own products which cost them high. They do not know which technique is suitable for a particular products.
Are there any innovative and emerging food preserving technologies that the farmers should be aware of?
When we talk about modern preservation techniques, there are ultra-high temperature and other technologies which are based on high pressure processing. There are many more techniques. But the question is if we are trying to educate them about these techniques, it will not work out as these machineries are very expensive, and they are available only in a few labs in big cities. To take the farmers to those places to get skilled in using those machines is very difficult. Theoretically, if we want to teach them about the advantages, it has no meaning. So nowadays, APEDA is conducting trainings in traditional methods also. These are economical ones which they can use and get benefited out of them.
How can farmers ensure the safety and hygiene of preserved foods throughout the preservation process? What role education and awareness play in effective food preservation techniques among farming communities?
There are certain protocols set by FSSAI and other regulatory authorities. Food Safety centres are set up in every district and panchayat level. So it is their duty to educate the farmers about the necessary protocols and other details where they can go through them and follow. Education is a vital weapon to solve all these things because we find in rural areas people are not acquainted with latest techniques and using only open products which are contaminated with flies and other insects. They do not know the safety precautions to be taken and how such unhealthy practices will affect the health. Only with training and education, we can solve these issues.
Are there any region specific considerations that farmers should take into account when selecting a food preservation method?
I cannot say it will be region specific, but the crops are region specific. Some crops cannot be grown in some regions. So the demand for preservation is different here. For example, fruits like strawberries cannot be grown in dry land areas but can be cultivated in Western ghat side. Here the demand for preservation is different. We need to think of fruits and vegetables compositions and requirements that can be cultivated in the regions to adopt only such techniques. We need to think of fruits and vegetables preservation as per requirement and not region specific and follow only such techniques that are useful in those areas.
How can farmers strike a balance between traditional and modern food preservation methods for optimum results?
Farmers can do it if we provide good skill trainings and other facilities on hiring basis which are being provided to the farmers now. There are also credit facilities through which they can adopt preservation techniques and enhance the shelf life of products. They can thus get benefited by their own traditional knowledge and by following modern techniques.
Are there community based initiatives or success stories related to food preservation that you find particularly inspiring?
Yes. We can explore about the persons who have achieved very good success in preserving food products using techniques such as fermenting. In India, there are so many startup companies that are doing very well in these things. We can google to find out the details on companies that are highly successful in India.