Question

Heating a broth culture of microorganisms to 140∘∘C for three seconds would ___ the culture.

View Available Hint(s)

autoclave

pasteurize

pressurize

sterilize

Answer 1

Broth culture of microorganisms --- broth culture is a method of growing bacteria in a liquid medium. The liquid medium is rich in nutrients and consists of all the necessary nutrients required by bacteria to grow.

Heating a broth culture of microorganisms to 140°C for 3 seconds would STERILIZE the culture.

Answer to question is STERILIZE. Because heating broth culture at 140°C for 3 seconds make it STERILIZE. It is generally used for milk. This is an example of Moist Heat Method. The milk sterilize by this technique is sterilized and hence no bacterial growth can occur in it for a time. The flavour and quality of milk is not affected. This type of milk produced is also called " Shelf Milk". And this type of milk does not require to be refrigerated.

E.g. of this kind of milk is Amul milk in India which has a shelf life of about 180 days. This milk is widely used in hilly areas that lacks facilities to store milk for long days.

Pasteurisation ---- it is a technique of heating the culture at 145° for about 30 minutes. It prevent spoilage but do not STERILIZE. We oftenly use pasteurized milk in our daily life which have a life of 1-2 days maximally. After 1-2 days if milk is left it gets spoiled due to bacterial growth in it as it is not sterilized. So this is not the answer.

Autoclave ---- also called pressure chamber. It is used for sterilization of liquids, glassware, plasticware used in laboratories. It is a steam sterilization technique. In it the substrates i.e. liquids, glasswares are in direct contact with the steam at a temperature of about 121°C for 30 minutes at 15 psi pressure.

Pressurize --- it is a technique of applying pressure. Autoclave uses the pressure in sterilizing the equipments.

So the answer to the question is sterilize, as at 140°C for 3 seconds sterilization is done while the other options given uses different temperatures and for different time periods. Autoclave sterilize by pressurizing at a temperature for a time period while pasteurization prevent spoilage of products but do not sterilize them.

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