Semester 1, 2018/2019
AMY YONG KUI WEI BP18110147 CHOO YUN YAO BS18110462 CHOO MING HUI BP18110250 ELIZABETH HARRY BB18110314 List of Content
1.0 Introduction
2.0 Main Content
2.1 Traditional Method of Food Preservations
2.1.1 Drying
2.1.2 Salting
2.1.3 Fermentation
2.1.4 Pickling
2.1.5 Smoking
2.1.6 Freezing
2.2 Modern Method of Food Preservations
2.2.1 Cooling / Freezing
2.2.2 Bio-preservation
2.2.3 Vacuum Packing
2.2.4 Pasteurization
2.2.5 Artificial Food Additives
2.2.6 Irradiation
2.2.7 Waxing
2.2.8 Canning
3.0 Conclusion
4.0 References
Food preservation is invented by a man, named Nicholas Appert. He found out that food can be preserved by heating it and keeping in a sealed container. The method is canning. Canning method only be prioritized since year 1790. Although Nicholas Appert invented canning method, but he did not fully understand. He thought that exclusion of air was responsible for preservations. At year 1864, Louis Pasteur discovered the relationship between microorganisms and food spoilage. Since that time, food preservation method is getting advance. From last time, frozen climate, they froze meat on the ice; in tropical climate, they dried food under the sun and also with method smoking, to now presence of refrigerator, artificial food addictive, vacuum packing, pasteurization and others. After food preservation have invented, people in early time no longer had to consume the food after they harvested. See how technologies improved and helped in our life.
What is food preservation? Food preservation is the method of treating and handling food to prevent the food contaminated so that it can be stored for a long period. Food preservation is said to prolong the shelf life of food, because it emphasized on the inhibition, and inactivation of microorganisms. Due to the growth of bacteria, microorganisms and also the enzyme that make the taste change, so we need to preserve our food. If we did not preserve in a good way, we might get food poisoning. This is why food preservation is important in our life. There are many methods for us to preserve our food to prevent it spoiled. Preservation of food normally can use traditional method and modern method. In this 21st century, people normally prefer modern method to preserve their food, but there are still a few people using traditional method. Traditional method includes, drying, salting, fermentation, pickling, smoking and freezing whereas modern method included cooling / freezing, bio-preservation, vacuum packing, pasteurization, artificial food addictive, irradiation, waxing and canning.
The benefits of preserve food are that people can avoid wasting of money. For example, supermarket normally preserve their food after the food is produced to save their cost. At the same time, preservation method can help them to prolong the shelf life of food. They can produce many foods in a same batch and preserve it by using different method of preservation until the expiry date. Food can still be consumed before the expiry date, as long as the flavour, colour and taste does not have any changes. For milk, they used pasteurization method; for meat, they used cooling/ freezing method; for prickled food, they used canning method. Not only supermarket, but in our daily life, we also used it to preserve our food to prevent wasting of food. For instance, a family went to a restaurant to have their lunch or dinner, when they cannot finish the food, they will ask for take away the food. So, the family can still eat the food by preserve it in refrigerator and heat it again for the next day when they want to eat. Now you know the importance of food preservation in our life.
Conversely, food preservation also has its disadvantages. If people who do not know the proper way of preserve their food, the quality of the food might have changed. For example, cooling method. People will just directly put their leftover food inside the fridge, without closing the container in which they place their food. They should have close the container tightly with the lid before they put inside the fridge for preservation. Although adding salt has its advantage, like people use to preserve food, but it can cause excessive salt content in the food preserved. This excessive salt in the food will bring damage to human health, so it will lead to disease such as kidney failure.
Food preservation has many method, which consist of both traditional and modern ways. Although it can help us to prolong the lifespan of food, but we should use the right technique to do so.
2.2 Modern Method of Food Preservation
2.2.1 Cooling / Freezing
Clarence Birdseye, a man that invented quick freezing method, which is the method that we are widely use today. Cooling and freezing method can be counted as traditional method and also modern method to preserve food. As time passed, people are improving and so technology are getting advance. So, technology – refrigerator has been invented. The temperature in refrigerator is about 1? to 6?, whereas in freezer, the temperature is about -18? or below than that. As we keep our food in refrigerator, the growth of mould and bacteria can be stopped or slowed down by the low temperature. When in low temperature, mould and bacteria hardly grow in it, unlike room temperature, there are more easily for mould and bacteria to grow on it. Furthermore, the rate of chemical reaction for enzyme to change is very low. That is why we keep our food in refrigerator to preserve it. Freezing delays spoilage and keeps foods safe by preventing microorganisms from growing and by slowing down the enzyme activity that causes food to spoil. For instance, as the water in the food freezes into ice crystals, microorganisms cannot grow due to the temperature is unfavorable.
The advantages of freezing preservation are it requires less time and the temperature in freezer is sufficient to freeze food for few days or weeks. In addition, it does not requires large amount of food to freeze, just follow your individual needs. Freezing can also still remain the nature colour and the taste of the food even if you freeze for weeks. There are also disadvantages if we use freezing as food preservation. Due to the low temperature inside the freezer, the cells expands when it is frozen and breaks the cell walls, which make the food turn mushy, hence some texture of the food might have undesirably changed. For example, strawberries retain flavor, color, and nutritive value of the fresh strawberries but the textual changed to make it more suitable for smoothies or sauces. By freezing, vitamin B and vitamin C are easily lost, due to both of them are water soluble vitamin. In addition, disadvantage of freezing is that frozen food that is not packed closely might contain the smell of other food that is also in freezer.

For a good freezing tips, you need to know about the appropriate equipment. For instances, food in freezer need to have proper packaging to protect their flavour, colour, and nutritive value. In other words, packaging materials must be durable, easy to seal, and resistant to moisture vapour. The good example of the packaging materials are rigid containers and flexible bags or wrappings. Other than that, you need to know the period of the product that can be kept in the freezer, because after the period, the products might be changing of its quality. So, it is better to use masking tape or permanent pen to make a label for the frozen products. The label should include the name of the product, freezing date especially for the syrup type. Many fruits still maintain high quality for 8 – 10 months if store below -18?, citrus fruits keep for 4 – 6 months. For vegetables, they can remain the quality up to 12 months. After the period, the quality of the food will become poor. Diagram 1 will show the process of freezing drying in order to preserve food.

Diagram 1 – freeze drying is also a method to preserve the freshness of food.
2.2.2 Bio-preservation
Bio-preservation, defined as the use of natural or controlled microbiota to enhance food safety and extend shelf life. Any agent that used for bio-preservation can be termed as bio-preservatives. There are few instances of bio-preservatives, which are benzoate, nitrites and sulphites. The fermentation products as well as beneficial bacteria, lactic acid bacteria are generally selected in this process to control the spoilage of food. Some lactic acid bacteria produce antimicrobial proteins, bacteriocin which inhibit spoilage and pathogenic bacteria without changing the physicochemical nature of the food. The bacteriocin that produced by lactic acid bacteria can be added directly to the food to inhibit pathogenic bacteria.
Lactic acid bacteria are used for the process of fermentation. Lactic acid bacteria make the fermentation of sour dough bread successfully because it is an anaerobic fermentation, which do not need oxygen, hence it will not cause extreme changes in food. Lactic acid bacteria will produce bacteriocins and other compounds like ethanol, hydrogen peroxide which inhibit non-desirable, pathogenic and food spoilage microorganisms to grow in the food during fermentation. This mechanism is known as bio-preservation method. This method of preserve food is easy because it does not required refrigerator. Other than that, bio-preservation also used in dairy products, and meat product. For instance, in dairy products like blue vein cheese, the vein like structure is made by using bacteria penicillium. For meat products, Lactobacillus is used to fermentate, whereas Staphylococcus carnosus used to ensure the meat quality and coloration as lactic acid cannot ensure the proper quality of meat. Besides that, Staphylococcus carnosus also used for sausage fermentation. The uses of bacteria helped to enhance the taste of meat items and also helped in longer preservation period. Not only meat can be preserved, but vegetables product also can be preserved. Example is Kimchi, a well-known Korean vegetables also used the bio-preservation method to prolong the shelf life. In addition, in wine industry, bio-preservation is also used in wine industry, like lactic bacteria stabilize unstable malic acid to stable lactic acid. This conversion can preserve the taste of wine and quality. Thus, wine is become more expensive if they are stored for longer time.
The advantages of using lactic acid bacteria in fermentation will lower its pH due to the production of the acid. The lower the pH, the slower the bacteria growth. Diagram 2 shows how the pH affect the microorganisms.

Diagram 2 – In the lowest pH, which is pH 4 and below, all microorganisms died.

Other than that, using bio-preservation can enhance our immune system. This is because some probiotics can help in digestion, strengthen immune system. Although bio-preservation brings many advantages, but it also bring disadvantages like people who have asthma not encourage to eat food that used bio-preservatives because some preservatives will cause allergic reactions. Furthermore, bio-preservatives are also the caused of cancer. Sodium nitrate that used to preserve meat have found out that it will produce cancer causing chemicals called nitrosamines. It is also harmful to children. It might linked to behavioral changed and also increase the risk of headache. Bio-preservation is a good method to preserve our food from spoilage.

2.2.3 Vacuum Packing
Vacuum packing is the process that removes air for prior sealing. Without air, or in an air-tight container, the growth of microorganisms can be prevented. It is also a modern way to preserve food because the air inside the container will be sucked out. How does vacuum packing preserve food better? Vacuum packing, without oxygen, the growth of bacteria or fungi are terminated, and also the prevention for volatile components to evaporate. It is normally use to store dry food, for example, nuts, potato chips, cereals and cheese. The process of removing air, which is vacuum packing can be done by automatically or manually. With machine, you just need to clean your food that you wished to seal, then put it in a plastic bag. After that, put that plastic bag in the sealing machine, and you’ll see the plastic bag shrinked. Lastly, just put the plastic bag inside the fridge to preserve it. Another way, which is manual, using nozzle pump to suck out the air in the container or plastic bag that you have store food inside. Lastly, just put inside the fridge to preserve it. Diagram below shows how vacuum packing can be done. In diagram 3 shows that vacuum packing done by machine whereas diagram 4 shows vacuum packing done manually.

Diagram 3 – Using machine to suck the air out from the plastic.

Diagram 4 – Using nozzle pump in order to suck the air out from the plastic.

Vacuum packing has its own advantages, which are sealed food last 3 – 5 times longer to conventional storage method. It also conserves spaces for food storage. This is because after you vacuum packing, the size of the food will be shrinked, so it will use up small spaces compare with non-vacuum packing food. Lastly, it is more hygiene when we are handling or moving the products. Vacuum packing also has disadvantages like the vacuum packaging machine can be expensive, the safety of the consumers can be affected and the misconceptions towards vacuum packing by people. The vacuum packing machine can be expensive depends on the size and the quality. Other than vacuum packing machine, you need to buy for the plastics, it is normally cheaper if you buy in a bulk. But, if you do not need that much, it is another way of wasting money. Secondly, is the safety of consumers. Removing oxygen to extend their lifespan is the main advantage of vacuum packing, but also can be a disadvantage because certain bacteria that cause spoilage need oxygen to grow and reproduce. There are types of bacteria that caused diseases which prefer low oxygen environments and grow well in vacuum packed foods. So, check carefully whether the food is suitable for vacuum packing, if not you would just be creating a perfect breeding place for bacteria, such as botulism.
2.2.4 Pasteurization
Pasteurization is the process of heat treatment on a liquid or a food to kill pathogenic bacteria to prolong the storage of the food. There are 3 processes used to pasteurized foods, which is flash pasteurization, steam pasteurization and irradiation pasteurization. Flash pasteurization involves a high temperature, short time treatment in which pourable products, such as juices, heated for 3 to 15 seconds to a temperature that destroys harmful microorganisms. After heating, the product is cooled and packaged. Most drink boxes and pouches use this pasteurization method as it allows extended unrefrigerated storage and also in the same time providing safe product meanwhile for steam pasteurization, is mainly used for beef. It uses heat to control or reduce harmful microorganisms in it. This system passes freshly-slaughtered beef carcasses that are already inspected, washed, and trimmed, through a chamber that exposes the beef to pressurized steam for approximately 6 – 8 seconds. The steam raises the surface temperature of the carcasses to 88? – 93?. The carcasses are then cooled with a cold-water spray. This process has proven to be successful in reducing pathogenic bacteria, such as E. coli without using any chemicals. Lastly is the irradiation pasteurization. For example, poultry, red meat, spices, fruits and vegetables are subjected to small amounts of gamma rays. This process not only controls vegetative bacteria and parasitic foodborne pathogens, it also increases the storage time of foods.
Another example for using pasteurization is milk. The method to preserve milk by using method pasteurization is widely known. There are two methods to pasteurize milk, which is ultra-pasteurization and ultra-high temperature pasteurization. This involves the heating of milk and cream to at least 138? for at least 2 seconds, but they must be refrigerated. The shelf life of milk is extended 60 to 90 days. Ultra-high temperature pasteurization typically involves heating milk or cream to 138?to 150? for 1 or 2 seconds. The milk is then packaged in sterile, airtight containers. It can be stored without refrigeration for up to 90 days. After opening, spoilage times for ultra-pasteurization and ultra-high temperature pasteurization products are similar to those of conventionally pasteurized products. However, you can do pasteurization on yourself as it requires only sudden drop temperature from a high temperature. First, you need to pour the raw milk into the stainless-steel pot. Then heat the milk gently. Slowly heat the milk around 63?, and stirring occasionally to avoid scalding the milk. Try to keep the temperature constant at around 63? for 30 – 45 minutes. During that duration, you may need to increase and decrease the heat so it will remain at around 63?. After that, remove the pot of milk from the heat and place it in a sink or large bowl that is filled with ice water. Stir constantly until the temperature drops to around 5?. Lastly, you can store the pasteurized milk in the refrigerator. Diagram 1.3 shows how pasteurization of milk can be done.

Diagram 1.3 – Pasteurization of raw milk need to pass by heating and cooling process.

The advantages of using pasteurization as a method of preservation is that high temperature can kill bacteria and so the duration of food that is still edible can be extended. It is also cost saving method as you can do it yourself. Pasteurization method won’t experience too much changes in flavor and color of food. However, the disadvantages of pasteurization are, this method might also destroy beneficial bacteria found in raw milk. It kills the natural enzyme and destroy the chemical make up calcium, which is needed on formation of bone and also growth of children. It also a wasting time because you need to monitor the temperature and maintain it.