Meat Science & Food Safety
1. Most spoilage bacteria grow at:
a) acidic pH
b) alkaline pH
c) neutral pH d) any of the pH
Correct Answer: c) neutral pH
Explanation: Most bacteria, especially those responsible for food spoilage, are neutrophiles. They grow best at a pH range of 6.5 to 7.5. Since milk has a near-neutral pH (approx. 6.7), it is an ideal medium for these organisms.
2. Water activity ($a_w$) can act as:
a. an intrinsic factor determining the likelihood of microbial proliferation
b. a processing factor
c. an extrinsic factor
d. all of the above
Correct Answer: d) all of the above
Explanation: Water activity ($a_w$) is a measure of the available water for microbial growth. It is an intrinsic factor of the food itself, a processing factor (as in drying or adding salt/sugar), and interacts with extrinsic factors like humidity.
3. The time-temperature combination for HTST pasteurization of 71.1°C for 15 sec is selected on the basis of:
a. Coxiella burnetii
b. E. coli
c. B. subtilis
d. C. botulinum
Correct Answer: a. Coxiella burnetii
Explanation: Coxiella burnetii is the most heat-resistant non-spore-forming pathogen found in milk. Therefore, pasteurization standards (High Temperature Short Time) are specifically designed to ensure its total destruction.
4. Milk fermentation to produce cheese is done initially by inoculating with:1
a) Saccharomyces cerevisiae2
b) Streptococcus lactis and Lactobacillus spp.3
c) Acetobacter and Gluconobacter4
d) Lactobacillus bulgaricus and Streptococcus t5hermophiles
Correct Answer: b) Streptococcus lactis and Lactobacillus spp.
Explanation: These are common starter cultures for many cheeses. They ferment lactose into lactic acid, lowering the pH, which is the first step in curd formation. (Option D is specifically used for yogurt production).
5. ___________ is resistant to heat due to the presence of Mycolic acid:
a) Mycobacterium tuberculosis b) Clostridium tetani
c) Bacillus cereus
d) E. coli
Correct Answer: a) Mycobacterium tuberculosis
Explanation: Members of the genus Mycobacterium have a high concentration of mycolic acid in their cell walls. This waxy substance makes them resistant to chemical disinfectants and relatively resistant to environmental heat.
6. Water content of milk ranges from:
a) 20-30%
b) 40-50%
c) 85-90% d) None of the above
Correct Answer: c) 85-90%
Explanation: Cow’s milk is typically composed of approximately 87% water. The remaining 13% consists of milk solids (fat, protein, lactose, and minerals).
7. Bacillus cereus causes “sweet curdling” in milk by the release of the enzyme:
a) Lactase
b) Coagulase
c) Protease d) Amylase
Correct Answer: c) Protease
Explanation: In “sweet curdling,” milk coagulates without a significant drop in pH (no souring). This is caused by the proteolytic enzymes (proteases) produced by Bacillus cereus, which break down casein proteins to form a curd.
8. In the Low Temperature Long Time (LTLT) method of pasteurization, milk is heated at:
a) 90°C for 30 minutes
b) 85°C for 25 minutes
c) 63°C for 30 minutes (Note: Correcting option C)
d) None of the above
Correct Answer: d) None of the above
Explanation: The standard for LTLT (Batch) pasteurization is exactly 62.8°C (often rounded to 63°C) for 30 minutes. Since option C says 20 minutes, “None of the above” is technically the most accurate based on standard definitions.
[Image comparing LTLT and HTST pasteurization curves]
9. __________ are live microbial feed supplements that have beneficial effects on the host by improving its intestinal microbial balance:
a) Probiotics b) Prebiotics
c) Bacteriophages
d) Starter culture
Correct Answer: a) Probiotics
Explanation: Probiotics (e.g., Lactobacillus and Bifidobacterium) are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host by balancing the gut microbiota.
10. The first scientist to give the concept of probiotics was:
a) Metchnikoff b) Fleming
c) D’Herelle
d) Louis Pasteur
Correct Answer: a) Metchnikoff
Explanation: Élie Metchnikoff (a Nobel laureate) proposed that consuming lactic acid-producing bacteria (in fermented milk) could “honor” the gut and increase longevity, forming the foundation of probiotic science.
11. Green color in milk is caused by:
a) Bacillus cereus
b) Campylobacter jejuni
c) Clostridium perfingens
d) Pseudomonas aeruginosa
Correct Answer: d) Pseudomonas aeruginosa
Explanation: Pseudomonas aeruginosa produces a water-soluble fluorescent pigment called pyoverdin (fluorescein), which can impart a greenish-blue tint to contaminated milk.
12. Red color in milk is caused by:
a) E. coli
b) Brevibacterium erythrogenes
c) Serratia marcescens
d) Both b and c
Correct Answer: d) Both b and c
Explanation: Brevibacterium erythrogenes and Serratia marcescens (which produces the red pigment prodigiosin) are both associated with red discoloration in dairy products.
13. Yellow color in milk is caused by:
a) Brucella melitensis
b) Pseudomonas synxantha c) Alcaligenes
d) Aspergillus
Correct Answer: b) Pseudomonas synxantha
Explanation: Pseudomonas synxantha is a lipolytic bacterium that breaks down milk fat and produces a yellow pigment, leading to yellow discoloration, especially in the cream layer.
14. __________ comprises all the milk contents except milk fat and casein protein:
a) Butter milk
b) Milk whey c) Curd
d) Yogurt
Correct Answer: b) Milk whey
Explanation: Whey is the liquid remaining after milk has been curdled and strained. It contains water, lactose, minerals, and whey proteins (albumins/globulins), but lacks the casein and fat that stay in the curd.
15. Nestle Yogurt is obtained by monoculture of:
a) Lactococcus lactis
b) Streptococcus
c) Micrococcus
d) None of the above
Correct Answer: d) None of the above
Explanation: Yogurt is almost never a monoculture; it requires a symbiotic culture of Lactobacillus bulgaricus and Streptococcus thermophilus. Using only one would not result in the standard flavor and texture of yogurt.
16. Sharp sour flavour in milk is due to the environment of ________ species:
a) Bacillus
b) Mycobacterium
c) Clostridium
d) Streptococcus
Correct Answer: d) Streptococcus
Explanation: Lactic acid bacteria like Streptococcus lactis ferment lactose to produce lactic acid. High concentrations of this acid lead to a sharp sour flavour.
17. In Dry Milk, water activity ($a_w$) is reduced to:
a) 0.2 b) 0.5
c) 0.7
d) 0.8
Correct Answer: a) 0.2
Explanation: To ensure a long shelf life and stop all microbial growth, milk powder is dried until the water activity ($a_w$) is very low, typically around 0.2.
18. Oxidation of Unsaturated Fatty acids imparts _________ odor:
a) Stringent
b) tallowy c) pleasant
d) None of the above
Correct Answer: b) tallowy
Explanation: The oxidation of fats (oxidative rancidity) produces aldehydes and ketones that result in a distinctive tallowy or “cardboard” odor and taste.
19. The term ____________ is used widely particularly in fermented sausage manufacturing:
a) Front slopping
b) Back slopping c) Side slopping
d) None of the above
Correct Answer: b) Back slopping
Explanation: Back-slopping is the traditional practice of using a small portion of a successful previous batch (the “mother” or “starter”) to inoculate a new batch.
20. A typical flavour of fishiness is produced by:
a) Aeromonas hydrophila
b) Pseudomonas aeruginosa
c) Mycoplasma bovis
d) Both a and b
Correct Answer: d) Both a and b
Explanation: Microbial breakdown of lecithin in milk can result in the production of trimethylamine, which gives a fishy odor. Both Aeromonas and Pseudomonas species are capable of this spoilage.
21. ______________ spores are added to the curds just before the final cheese processing:
a) Penicillium notatum
b) Penicillium chrysogenum
c) Penicillium roquefortii d) All of these
Correct Answer: c) Penicillium roquefortii
Explanation: Penicillium roquefortii is the specific mold used to produce “blue-veined” cheeses (like Roquefort). The spores are added to create the characteristic blue/green veins and sharp flavor.
22. Infection by Coxiella results in a disease called:
a) Q fever b) Coxiellosis
c) Brucellosis
d) None of the above
Correct Answer: a) Q fever
Explanation: Coxiella burnetii is the causative agent of Q fever, a zoonotic disease that can be transmitted to humans through unpasteurized milk.
23. __________ an enzyme from calf stomachs, but now produced by genetically engineered microorganisms, can also be used to promote curd formation:
a) Amylase
b) Protease
c) Rennin d) Both a and c
Correct Answer: c) Rennin
Explanation: Rennin (or Chymosin) is the active enzyme in rennet. It specifically cleaves $\kappa$-casein, causing the milk to coagulate into curd.
24. Gas production by ______ contributes to final flavor development and hole or eye formation in this cheese:
a) Bifidobacterium
b) Propionibacterium c) Lactobacillus
d) Streptococcus
Correct Answer: b) Propionibacterium
Explanation: In Swiss-type cheeses, Propionibacterium species ferment lactic acid into propionic acid (for flavor) and Carbon dioxide ($CO_2$), which creates the characteristic eyes (holes).
25. ______________ is found in soft cheeses and unpasteurized milk; it can even survive below freezing temperatures and can therefore withstand refrigeration:
a) Listeria b) Brucella
c) Salmonella
d) Streptococcus
Correct Answer: a) Listeria
Explanation: Listeria monocytogenes is a psychrotroph, meaning it can grow at refrigeration temperatures ($4^{\circ}C$). This makes it a major concern in ready-to-eat soft cheeses.
26. Potato-like flavour in milk is caused by:
a) Pseudomonas mucidolens b) Pseudomonas aeruginosa
c) Bacillus subtilis
d) None of these
Correct Answer: a) Pseudomonas mucidolens
Explanation: Pseudomonas mucidolens is known to produce volatile compounds that impart a distinct potato-like off-flavor to milk.
27. ____________ strain of E. coli has been associated with a number of food-borne outbreaks and is the cause of Bloody Diarrhea:
a) O157:H7 b) O151:H8
c) O111:H8
d) All of these
Correct Answer: a) O157:H7
Explanation: E. coli O157:H7 is a Shiga toxin-producing strain (STEC) that causes severe foodborne illness, characterized by hemorrhagic colitis (bloody diarrhea).
28. pH of milk is about:
a) 3.2
b) 4.4
c) 6.8 d) 8.5
Correct Answer: c) 6.8
Explanation: Fresh cow’s milk is slightly acidic, with a pH typically ranging from 6.6 to 6.8.
29. Camembert cheese is inoculated with spores of:
a) Penicillium camemberti b) Aspergillus fumigatus
c) Mucor
d) All of these
Correct Answer: a) Penicillium camemberti
Explanation: Penicillium camemberti (or P. candidum) is used to create the white, bloomy rind characteristic of Camembert and Brie cheeses.
30. ______________ is an important food-borne intoxication:
a) Botulism b) Measles
c) Salmonellosis
d) None of the above
Correct Answer: a) Botulism
Explanation: Botulism is an intoxication, meaning the illness is caused by ingesting the pre-formed toxin (produced by Clostridium botulinum) already present in the food, rather than an infection by the bacteria themselves.