Q20. Which of the following chemicals is commonly used for preserving tomato sauces?
[SSC Selection Post Matric Level, 5 August 2022, Shift 1]
(A) Sodium benzoate
(B) Sodium nitrite
(C) Sodium nitrate
(D) Sodium chloride
Answer: (A) Sodium benzoate
Explanation: Sodium benzoate is a commonly used preservative in acidic foods such as tomato sauces, fruit drinks and pickles. Its effectiveness increases under acidic conditions, where benzoic acid inhibits several spoilage microorganisms. Permitted levels are governed by food safety regulations.
Q19. At what temperature is milk boiled for 15 to 30 seconds in the pasteurisation process?
[SSC Selection Post Higher Secondary Level, 1 August 2022, Shift 3]
(A) 72°C
(B) 60°C
(C) 80°C
(D) 45°C
Answer: (A) 72°C
Explanation: High-temperature, short-time milk pasteurisation commonly uses about 72°C for at least 15 seconds. This heat treatment markedly reduces vegetative pathogens, after which rapid cooling helps maintain quality. Pasteurised milk is not necessarily sterile and normally requires appropriate refrigeration.
Q18. The phosphatase test is used for the analysis of:
[MPPSC State Service Prelims 2021, held 19 June 2022]
(A) Milk
(B) Tea
(C) Water
(D) All of the above
Answer: (A) Milk
Explanation: The alkaline phosphatase test is a quality-control method for milk. Sufficient pasteurisation inactivates the enzyme normally found in raw milk. Detection of active alkaline phosphatase may suggest inadequate heat treatment or post-pasteurisation contamination with unheated milk.
Q17. Which chemical is used as food preservative?
[MP Police Constable, 10 January 2022, memory-based paper]
(A) Sodium benzoate
(B) Glycerin
(C) Sodium carbonate
(D) Tartaric acid
Answer: (A) Sodium benzoate
Explanation: Sodium benzoate is the sodium salt of benzoic acid and is used to inhibit spoilage microorganisms in certain acidic foods and drinks. Food preservation depends on concentration, acidity and processing conditions; the additive must be used within applicable food-safety limits.
Q16. Which of the following chemicals is NOT used as a food preservative to check the growth of microorganisms?
[SSC GD Constable, 13 December 2021, Shift 2]
(A) Sodium metabisulphite
(B) Sodium hydrogen carbonate
(C) Benzoic acid
(D) Sodium benzoate
Answer: (B) Sodium hydrogen carbonate
Explanation: Sodium hydrogen carbonate is baking soda, better known for its leavening role and acid-neutralising properties. Benzoic acid, sodium benzoate and sodium metabisulphite are established preservatives used under appropriate conditions to help limit deterioration by microorganisms.
Q15. Intestinal bacteria are main source of which one of the following vitamins?
[UPSC NDA-II General Ability Test, 14 November 2021]
(A) Vitamin E
(B) Vitamin C
(C) Vitamin B12
(D) Vitamin A
Answer: (C) Vitamin B12
Explanation: Some intestinal microorganisms can synthesize vitamin B12, making it the answer among the choices in this examination. However, most B12 made in the human colon is not efficiently absorbed; dietary animal products and fortified foods remain important usable sources.
Q14. Which of the following vitamins are fat soluble?
[RPSC RAS Prelims, 27 October 2021]
(A) C and E
(B) A and C
(C) A and D
(D) B12 and D
Answer: (C) A and D
Explanation: Vitamins A and D are fat-soluble, along with vitamins E and K. They are absorbed with dietary lipids and may be stored in body tissues. Vitamins C and the B-complex group are water-soluble, making the other given pairs incorrect.
Q13. Which of the following is used as a preservative?
[SSC MTS 2020, held 26 October 2021, Shift 1]
(A) Magnesium silicate
(B) Sodium palmitate
(C) Dipropylene glycol
(D) Sodium chloride
Answer: (D) Sodium chloride
Explanation: Sodium chloride is ordinary table salt and has long been used to preserve foods. At sufficiently high concentrations, it lowers water availability and limits microbial growth. It is especially useful for curing and pickling, frequently with drying or acidity.
Q12. An antibiotic is not useful against a virus whereas a vaccine is. Which one of the following is the most appropriate reason for this?
[UPSC CDS General Knowledge, 7 February 2021]
(A) An antibiotic can break RNA only, whereas virus has DNA
(B) An antibiotic is a carbohydrate in its chemical nature, whereas a vaccine is a protein which works well to kill a virus
(C) Only a vaccine can break the genetic material of a virus
(D) A virus does not use biochemical pathways which can be blocked by an antibiotic, but a vaccine can boost an immune system to fight the virus
Answer: (D) A virus does not use biochemical pathways which can be blocked by an antibiotic, but a vaccine can boost an immune system to fight the virus
Explanation: Antibiotics act on bacterial targets such as cell-wall synthesis or ribosomes, which viruses lack. Vaccines instead prime immune responses against particular pathogens. They reduce the risk or severity of infection but do not directly destroy viral genetic material.
Q11. Antibiotic such as penicillin blocks _______.
[UPSC CDS General Knowledge, 8 November 2020]
(A) cell wall formation in bacteria
(B) RNA synthesis in bacteria
(C) DNA synthesis in bacteria
(D) division in bacteria
Answer: (A) cell wall formation in bacteria
Explanation: Penicillin belongs to the beta-lactam antibiotic class and interferes with bacterial peptidoglycan cross-linking. Weakening cell-wall construction can lead to bacterial death, particularly in actively growing susceptible bacteria. Human cells lack peptidoglycan walls, providing useful selective toxicity.
