Methods of preserving food - class-VIII

Food products like fruits and vegetables are kept at low temperature to maintain its freshness, longevity and taste. Respiration uses stored starch and enhances ageing process. Low temperature minimizes the bacterial attack on food and also decreases respiration rate.

When green coloured apple are stored in low temperature the cellular proccess in the apples also gets reduced for conserving energy due to which the rate of respiration is reduced and the aging process is slowed down.

i) Canned foods are boiled in the can to kill all the bacteria and seal the can to prevent any new bacteria from getting in.

the correct answer is '-18ooC'

• The temperature range between 1 to 4 degrees Celsius is an ideal balance between the temperature required to stop/avoid microbial growth and not freeze the food that is to be preserved. 
• At 0 or -2 degrees Celsius the microbial growth is stopped but the food gets frozen whereas 10 degrees Celsius won't stop microbial growth. 
  Hence, correct option is B.

In the classic pasteurization treatment of milk, the milk was exposed to a temperature of about $63^{0}$C for 30 minutes. Most milk pasteurization today uses higher temperatures, at least $72^{0}$C, but for only 15 seconds. 

We can keep food for longer duration in cold storage than in ordinary cupboard because bacterial multiplication is greatly reduced. At room temperature, bacteria grow rapidly. When food is stored at cold temperature, bacteria enters a dormant stage. Also, water content of the food freezes in cold storage. This prevents bacteria from multiplying and food spoiling.

Food can be kept for longer duration and unspoiled at low temperature than in ordinary temperature because bacterial multiplication is greatly reduced. At room temperature, bacteria grow rapidly. When food is stored at cold temperature, bacteria enter a dormant stage. Also, the water content of the food freezes in cold storage. This prevents bacteria from multiplying and food spoiling.

Respiration uses stored starch and enhances ageing process. Food products like fruits and vegetables are kept in cold storage or refrigerator to maintain its freshness, longevity and taste. This is possible due to low respiration rate at low temperature. 

Respiration uses stored starch and enhances ageing process. Food products like fruits and vegetables are preserved by keeping them at low temperature to maintain its freshness, longevity and taste. This is possible due to low respiration rate at low temperature. 

Bacteria can grow in the cooked food from 5C to 60C. So, it is better to store cooked food at 3C whereas raw food at 5C.

The safe refrigeration period for most perishable foods is generally considered to be 3 to 6 days, depending on the specific food item and storage conditions.

Refrigeration slows down the growth of microorganisms but does not kill them. If food is kept for too long, the existing microorganisms eventually cause spoilage.

Food stored at or below −18 °C (0 °F) is safe to avoid bacterial growth. Most household freezers maintain temperatures from −23 to −18 °C.

Ultra-High Temperature (UHT) processing of milk typically involves heating it to approximately 132-140 degrees Celsius for a very short duration, usually 1 to 2 seconds, to ensure sterilization.

Blanching, which involves dipping vegetables in hot water or steam for a short time, is a standard pretreatment before deep freezing to inactivate enzymes and preserve quality.

Cryopreservation is a technique used to preserve organelles, cells, tissues, or embryos by cooling them to very low temperatures, typically using liquid nitrogen.

Drying food removes the moisture necessary for the growth of bacteria, yeast, and moulds, thereby inhibiting their ability to spoil the food.

The improved solar energy treatment (ISET), which consisted of soaking of seeds in water (1:1 w/v) in a galvanized tub tightly covered with a transparent polythene sheet during September for 6 h (08.00-14.00 h) and keeping the seeds under the sun, was most effective, providing more than 96% control of loose smut, 73.64% control of Karnal bunt, and complete control of flag smut. The treatment had no adverse effects on seed germination. 

There are various methods of preserving the food items. These methods include Pasterurisation (high temperature), Fridge (low temperature), dehydration (drying), etc. Fruit, meat and milk can be preserved at room temperature by the process of dehydration. This is the most easiest and oldest method of preservation. In this, the water or moisture is removed from the food. This inhibits the growth of microorganisms and increases the shelf life of food. Vernalisation is a process of induction of flowering process in plants by exposure to the prolonged cold temperature.