5. FOOD PRESERVATION BY RADIATION
Radiation refers to a wave of energy that can have either a long or short wavelength. The radiation of most radioactive substances is similar to a wave of particles. This radiation comes from the smallest unit of matter which is called an atom. A particular chemical element commonly consists of various types of atoms which possess identical chemical properties but are different in terms of weight. Such atoms with the same chemical attributes are defined as isotopes.
The kinds of radiation used in food preservation may include:
1) Gamma is commonly used in preserving food. The gamma ray is emitted from cobalt 60 or Cesium 137.
2) X-radiation is emitted from a radiation-producing machine operated with the energy level of equal or less than 5 million electron volts.
3) Electron radiation is emitted from a radiation-producing machine operated with the energy level of equal or less than 10 million electron volts.
5.1 Principles of food preservation with radiation
The radiation emitted into the food will eliminate or slow the growth of microorganisms, or reduce its chemical attributes; as a result, food can be kept longer without becoming spoiled. However, this depends on the type of food and the amount of radiation received. The objectives of radiation can be summarized as follows:
1) To prevent the growth of the plant while being kept. The maximum amount of radiation allowed by the Ministry of Public Health on food is 0.15 Kilo grays; however, the common amount used to preserve crops such as garlics, onions, and potatoes is between 0.05 and 0.12 Kilo grays. This amount of radiation can control the growth and the loss of weight for more than 6 months.
2) To control insect breeding while the food is being stored, the amount of radiation typically used is around 0.2-0.7 Kilograys which is less than the maximum value allowed (1 Kilogray). This radiation will kill all insect eggs and control the spread of insects on stored food such as rice, peanuts, spices, and dried fish.
3) To keep various types of food longer. Irradiating sea food and meats with of 1-3 Kilograys will greatly reduce the number of bacteria, allowing them to be stored for longer periods but the food will have to be kept in containers in cold rooms. For fruits such as mangoes and bananas, an irradiation of 0.3-1 Kilograys will slow down their ripening and help control insects while being kept, allowing for a longer storage. Radiation of 3 Kilograys on strawberries will eliminate some microorganisms which cause decomposition and a radiation of 1-2 Kilograys will also slow down the bloom of mushrooms, thus lengthening the selling period.
4) To eliminate bacteria and parasites in food. Products made from meat may contain certain bacteria or parasites; for examples, opisthorchis found in raw fish can be eliminated by irradiating with 0.15 kilograys. Salmonella which is a species of bacteria that causes diarrhea found in fermented pork, a popular pork product among Thai people, can be terminated by irradiating with 2-3 kilograys.
5.2 Radiation process
In Thailand food irradiation is controlled and operated by the Office of Atoms for Peace, the Ministry of Science and Technology of Thailand. However, the standards of radiation in use and safety will depend on announcements from the Ministry of Public Health. Food processing with radiation includes agricultural products after harvesting, ready-made food and convenience food, so packaging for these products should be suitable; for instance, fermented pork and Moo-yor should be wrapped with banana leaves, while onions and potatoes need no wrapping. The products should first be enclosed in an appropriate package, then processed through the electromagnetic building which is located far away from the emission building which should be well designed in accordance with safety standards. Then this process will neither cause harm nor damage to surrounding communities.
5.3 The amount of radiation used to preserve food
A gray is a unit of radiation. 1 kilogram of food that is irradiated by 1 joule of radiation is called 1 gray. Furthermore, there is a unit called a rad. 100 rads are equal to 1 gray and 1,000 grays are equal to 1 kilogray. The World Health Organization and International Atomic Energy Agency conclude that less than 10 kilograys of irradiation on food is harmless and does not alter the nutrients in food. However, the amount of radiation irradiated must comply with the amount announced by the Ministry of Public Health and such amounts will vary depending on the types of food and the purpose of irradiation.
5.4 Labeling the product
Irradiated food should have a label indicating certain information important for purchasers. A label should contain:
1) The name and the location of the manufacturer including the company performing irradiation.
2) The purpose of irradiation such as: “This food has been irradiated in order to……..” (the blank should inform such a purpose).
3) Date and year of irradiation.
4) A sign showing that the food has been irradiated.
Source: https://www.proprofs.com/quiz-school/story.php?title=convenience-foods
Convenience food refers to a ready-made food that is able to be warmed and eaten immediately. A convenience food in this context also includes food that is ordered and cooked by a consumer. The following factors should be considered when buying convenience food; the cleanliness of the place of production, a container that is protected from insects and dust, and the cleanliness of the seller.
Instant food means a ready-made food packed in a container to be sold such as instant chili sauces (Nam Prik Phao, Nam Prik Sawan, Nam Prik Ta Dang, and Jaew Bong), confections (Rang Taen, Kao Taen, Krayasart, Rolled wafer, Tongtan, Tongphab, Krobkhem, Curry puff, fried crisp rice cake, Thong Yip, Thong Yod, Foi Thong, biscuit, cookie, éclair, wafer, and snacks), processed vegetables and fruits (dried bananas, sweet banana crisps, buttered bananas, banana jam, pineapple jam, preserved mangos, preserved guavas, pickled star gooseberries, pickled mangos, pickled guava, conserved garcinia, and conserved mango), and animal products (salted eggs, dried shredded pork, dried crispy pork, sweetened pork, dried crispy fish, sweetened beef etc.
Ready to cook is a set of readily prepared ingredients to be cooked by a consumer at home. It is necessary to observe its expiration date since raw ingredients are more likely to spoil.