Everything you need to know about food and dairy microbiology. Some of the most frequently asked questions are as follows:-
Q.1. The prize announced by the French government was won by a confectioner Nicholas Appert in 1809. What was it for?
Ans: He showed that food could be preserved if it was sealed in tightly stoppered containers and boiled for a specific duration of time.
Q.2. Where are Central Food and Technological Research Institute situated in India?
Ans: At Mysore.
Q.3. What do you mean by C.F.T.R.I.?
Ans: Central Food and Technological Research Institute.
Q.4. What is 12 D treatment?
Ans: It comprises 12 decimal reductions by which theoretical populations of Clostridium botulinum endospores are decreased by 12 logarithmic cycles. In simple words if there were 1012 (1,000,000,000,000) endospores in a food can; only one of them should survive after treatment.
Q.5. Are obligate thermopiles a problem in storage at temperatures lower than 45°C? If not, why?
Ans: No. Because they generally remain dormant at temperatures lower than about 45°C.
Q.6. Thermopile anaerobic spoilage is very common in canned food. The can usually swells from gas and the contents have lowered pH and a sour odour. Which sort of microorganisms is responsible for this?
Ans: A number of thermopile species of Clostridium are responsible for the above.
Q.7. What is flat sour spoilage of canned foods?
Ans: When the thermopile spoilage occurs but the can is not swollen by gas production, it is called flat sour spoilage, which is caused by thermopile bacteria as Bacillus stearothermophilus which occur in the starch and sugars used in food preparation.
Q.8. In what conditions do mesophilic bacteria spoil canned foods?
Ans: If the food is unprocessed or if they can leaks.
Q.9. Give the steps involved in commercial sterilization process in industrial canning.
Ans: The steps involved in commercial sterilization are:
(1) Washing, sorting and blanching of the food material. In blanching, food is treated with hot water or live steam that softens the product to fill the can better. Blanching also destroys enzymes which may change the colour, flavour or texture of the product and also lowers the microbial count.
(2) The cans are filled to the extent leaving the least dead space.
(3) The cans are placed in a steam box to drive out the dissolved air.
(4) The cans are sealed.
(5) The cans are sterilized in large retorts with steam under pressure.
(6) The cans are copied by spraying or submerging in water.
(7) The cans are labeled, stored and delivered.
Q.10. Which are the important spoilage organisms of acid foods in cans?
Ans: They are moulds, yeasts, and occasionally species of acid tolerant, non-endospore forming bacteria.
Q.11. Which are the organisms that create problems due to being heat resistant and acid tolerant?
Ans: The heat resistant mould Byssochlamys fulva that produce heat resistant ascospores and Aspergillus. Bacillus coagulans can grow at a pH of 4.0.
Q.12. How is aseptic packaging done?
Ans: By feeding the rolls of packaging materials in hot hydrogen peroxide solution and sometimes aided by ultraviolet light. The metal containers can be sterilized with super-heated steam or other high temperature methods or high energy electronic beams.
Q.13. Pathogenic bacteria often do not grow under low temperature preservation of food. However, there are exceptions that some bacteria do. List them.
Ans: Clostridia which cause type E botulism, Yersinia enterocolitica and Listeria monocytogenes.
Q.14. How could pork be made free from parasitic worms which cause trichinosis, without heating?
Ans: By irradiating.
Q.15. What is irradiation logo?
Ans: The irradiation logo indicates that the food has received irradiation treatment.
Q.16. High energy electron accelerators are much faster and achieve sterilization within a few seconds, but they have low penetrating power. Therefore, for what sort of food preservation is they suitable?
Ans: Sliced meats, bacon and similar thin products.
Q.17. What are the common additives used to retard the spoilage of food?
Ans: Sodium benzoate, sorbic acid and calcium propionate are the common additives.
Q.18. What are the chemical additives often added to meat products like ham, bacon, hot dogs and sausage?
Ans: These are sodium nitrate and sodium nitrite.
Q.19. What are the two main functions of nitrites?
Ans: 1. To preserve the red colour of the meat by reacting with blood components.
2. To prevent the germination and growth of any botulism endospores, which may be present.
Q.20. What is the drawback of nitrites?
Ans: Nitrites with amino acids form certain carcinogenic products like nitrosamines. Therefore, the amount of nitrites added to food has been reduced these days.
Q.21. Which are the microorganisms responsible for the spoilage of bread?
Ans: Aspergillus, Neurospora sitophia, Mucor sp. and Rhizopus Nigerians cause bread mould.
Q.22. Name the organisms that turn raw milk sour.
Ans: Streptococcus lactis, S. cremoris and Lactobacillus bulgaricus.
Q.23. Which organism spoils pasteurized milk (turn into sour milk)?
Ans: Lactobacillus thermopiles.
Q.24. Which organisms spoil chicken (cause sliminess)?
Ans: Achromobacter sp, Pseudomonas, Alcaligenes sp. and Flavobacterium sp.
Q.25. Which organisms cause spoilage (fishy odour) offish?
Ans: Achromobacter sp, Flavobacterium, Micrococcus, Pseudomonas sp. and Serratia sp.