In the high-temperature short-time (HTST) method of pasteurisation, milk is heated to about:
- A.63 degrees Celsius for 30 minutes
- B.72 degrees Celsius for 15 seconds
- C.100 degrees Celsius for 10 minutes
- D.150 degrees Celsius for 2 seconds
Correct answer
Explanation
The correct answer is B, about 72 degrees Celsius for 15 seconds, followed by rapid cooling to about 4 degrees Celsius. Pasteurisation is not sterilisation: it is a mild heating that kills disease-causing organisms such as Mycobacterium tuberculosis, Salmonella and Brucella and most spoilage bacteria, while leaving the taste and nutritive value of milk largely unchanged. The flash or HTST method is what large dairies use because it is continuous and quick. Option A is wrong only as the HTST figure; 63 degrees Celsius for 30 minutes is the older low-temperature long-time or holding method, done in batches. Option C is wrong because heating milk at 100 degrees Celsius is boiling or sterilisation, which alters the flavour and destroys part of the vitamin content. Option D is wrong because treatment at about 135 to 150 degrees Celsius for a few seconds is ultra-high temperature processing, which gives long-life packaged milk rather than ordinary pasteurised milk.
Read the full article: Food Preservation, Adulteration and Food Safety Notes
Practice Questions
View allFruits stored in a cold chamber exhibit longer storage life because
- A.exposure to sunlight is prevented
- B.concentration of carbon dioxide in the environment is increased
- C.rate of respiration is decreased
- D.there is an increase in humidity
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A harvested fruit is still a living tissue that keeps respiring, using up its own sugars and acids and giving off heat, carbon dioxide and ethylene.
Read the full explanation →The adulteration of mustard oil with argemone oil causes which disease?
- A.Lathyrism
- B.Epidemic dropsy
- C.Fluorosis
- D.Minamata disease
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Argemone mexicana, the prickly poppy known in India as satyanashi, has seeds that look very like mustard seeds, so its oil is a classic adulterant of mustard oil.
Read the full explanation →Lathyrism in human beings is caused by the prolonged consumption of which of the following?
- A.Khesari dal
- B.Argemone seeds
- C.Metanil yellow
- D.Chicory
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Khesari dal, botanically Lathyrus sativus and also called grass pea, is a hardy pulse that survives drought and is therefore sometimes mixed with arhar dal or besan.
Read the full explanation →Lyophilisation, used to make instant coffee and to preserve vaccines, is the technical name for which process?
- A.Pasteurisation
- B.Freeze-drying
- C.Canning
- D.Irradiation
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In lyophilisation the material is first frozen and then placed under a strong vacuum, so that the ice changes directly into vapour without passing through the liquid state.
Read the full explanation →Which of the following is a Class I preservative under Indian food standards?
- A.Sodium benzoate
- B.Sulphur dioxide
- C.Common salt
- D.Potassium sorbate
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Indian food standards divide preservatives into two classes. Class I preservatives are the natural ones that cooks have always used, and no limit is placed on the quantity: common salt, sugar, dextrose, spices, vinegar or acetic acid, honey and edible vegetable oils.
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