BT404 — Food Biotechnology | VU Solved MCQs

BT404 Food Biotechnology covers Food preservation, Food microbiology, Food-borne disease, Thermal processing, Functional foods, Fermented foods, Food spoilage, Genetically modified foods, Enzymes in food processing, Food safety management, Biopreservation, Food-borne toxins, Food regulation and Factors affecting microbial growth in foods. This solved post gives you 30 verified items for Virtual University of Pakistan, 10 Midterm MCQs from Lectures 1-22, 10 Finalterm MCQs from Lectures 23-45, and 5 Midterm plus 5 Finalterm subjective questions, each with its correct answer and handout reference. Practice every question instantly in the quiz for this course. Take the BT404 quiz

1. Midterm Solved MCQs

Q1. HTST pasteurisation of milk is carried out at:
A) 63 °C for 30 minutes
B) 72 °C for 15 seconds
C) 100 °C for 5 minutes
D) 121 °C for 15 minutes
Correct answer: B — 72 °C for 15 seconds
Reference: VU handout — Food preservation; pasteurisation.
Status: Verified

Q2. Which of the following is a primary source of micro-organisms in food?
A) The food handler's hands only
B) Soil, water, air and the raw material itself
C) The packaging material only
D) Refrigeration
Correct answer: B — Soil, water, air and the raw material itself
Reference: VU handout — Food microbiology; sources of contamination.
Status: Verified

Q3. Food poisoning caused by eating food containing a pre-formed bacterial toxin (rather than by infection with the organism) is called:
A) Food infection
B) Food intoxication
C) Food allergy
D) Food spoilage
Correct answer: B — Food intoxication
Reference: VU handout — Food-borne disease; infection vs intoxication.
Status: Verified

Q4. The D-value (decimal reduction time) is the time required at a given temperature to:
A) Kill all micro-organisms in the food
B) Reduce the microbial population by 90% (one log cycle)
C) Double the microbial population
D) Reduce the water activity to 0.90
Correct answer: B — Reduce the microbial population by 90% (one log cycle)
Reference: VU handout — Thermal processing; D-value.
Status: Verified

Q5. Most spoilage bacteria require a water activity (aw) above about:
A) 0.60
B) 0.70
C) 0.85–0.90
D) 0.99
Correct answer: C — 0.85–0.90
Reference: VU handout — Factors affecting microbial growth; water activity.
Status: Verified

Q6. A probiotic is defined as:
A) A chemical preservative that kills gut bacteria
B) A live micro-organism that, when given in adequate amounts, confers a health benefit on the host
C) A heat-killed bacterial culture used as a starter
D) An antibiotic produced by lactic acid bacteria
Correct answer: B — A live micro-organism that, when given in adequate amounts, confers a health benefit on the host
Reference: VU handout — Functional foods; probiotics.
Status: Verified

Q7. The micro-organisms chiefly responsible for yoghurt fermentation are:
A) Saccharomyces cerevisiae and Aspergillus niger
B) Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus
C) Escherichia coli and Salmonella spp.
D) Penicillium roqueforti and Rhizopus oligosporus
Correct answer: B — Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus
Reference: VU handout — Fermented foods; dairy fermentation.
Status: Verified

Q8. Botulism, a serious food-borne intoxication associated with improperly canned low-acid foods, is caused by the toxin of:
A) Staphylococcus aureus
B) Clostridium botulinum
C) Listeria monocytogenes
D) Bacillus cereus
Correct answer: B — Clostridium botulinum
Reference: VU handout — Food-borne disease; canned foods.
Status: Verified

Q9. Which pH range best supports the growth of most food-spoilage bacteria?
A) pH 2–3
B) pH 4–5
C) pH 6–7 (near neutral)
D) pH 9–10
Correct answer: C — pH 6–7 (near neutral)
Reference: VU handout — Factors affecting microbial growth; pH.
Status: Verified

Q10. Food spoilage is best defined as:
A) Any change in food that makes it unsafe only
B) Any change in the food that renders it unacceptable to the consumer (off flavour, odour, texture or appearance) due to microbial, chemical or physical action
C) The growth of pathogens in food
D) The loss of vitamins during cooking
Correct answer: B — Any change in the food that renders it unacceptable to the consumer (off flavour, odour, texture or appearance) due to microbial, chemical or physical action
Reference: VU handout — Food spoilage.
Status: Verified

2. Finalterm Solved MCQs

Q1. The first genetically modified whole food approved for human consumption was:
A) Bt cotton
B) The Flavr Savr tomato
C) Golden Rice
D) Roundup Ready soybean
Correct answer: B — The Flavr Savr tomato
Reference: VU handout — Genetically modified foods.
Status: Verified

Q2. Rennet (chymosin) is used in cheese-making to:
A) Ferment lactose to lactic acid
B) Coagulate milk protein (casein) to form curd
C) Produce the characteristic blue mould
D) Pasteurise the milk
Correct answer: B — Coagulate milk protein (casein) to form curd
Reference: VU handout — Enzymes in food processing; dairy.
Status: Verified

Q3. HACCP stands for:
A) Hazard Analysis and Critical Control Points
B) Health Assessment of Chemical Contamination in Products
C) Hygiene And Cleanliness Control Procedure
D) Hazard Audit for Canned and Cooked Products
Correct answer: A — Hazard Analysis and Critical Control Points
Reference: VU handout — Food safety management; HACCP.
Status: Verified

Q4. Sauerkraut and kimchi are produced by:
A) Alcoholic fermentation by yeasts
B) Lactic acid fermentation by lactic acid bacteria
C) Acetic acid fermentation by Acetobacter
D) Alkaline fermentation by Bacillus spp.
Correct answer: B — Lactic acid fermentation by lactic acid bacteria
Reference: VU handout — Fermented foods; vegetable fermentation.
Status: Verified

Q5. Nisin, used as a natural food biopreservative, is a:
A) Bacteriocin (antimicrobial peptide) produced by Lactococcus lactis
B) Chemical antioxidant
C) Synthetic colour
D) Mould inhibitor produced by Aspergillus
Correct answer: A — Bacteriocin (antimicrobial peptide) produced by Lactococcus lactis
Reference: VU handout — Biopreservation; bacteriocins.
Status: Verified

Q6. "Hurdle technology" in food preservation means:
A) Using one very severe treatment to sterilise the food
B) Combining several mild preservation factors (hurdles) so that together they prevent microbial growth
C) Jumping between hot and cold treatments
D) Packaging food under high pressure only
Correct answer: B — Combining several mild preservation factors (hurdles) so that together they prevent microbial growth
Reference: VU handout — Food preservation; hurdle technology.
Status: Verified

Q7. Aflatoxins, the most important mycotoxins in foods such as peanuts and maize, are produced by:
A) Aspergillus flavus and Aspergillus parasiticus
B) Penicillium chrysogenum
C) Saccharomyces cerevisiae
D) Rhizopus stolonifer
Correct answer: A — Aspergillus flavus and Aspergillus parasiticus
Reference: VU handout — Food-borne toxins; mycotoxins.
Status: Verified

Q8. A starter culture in food fermentation is:
A) A pure chemical acid added to the food
B) A selected micro-organism (or mixture) added to start and control the fermentation
C) The nutrient medium used to grow pathogens
D) A genetically modified food additive
Correct answer: B — A selected micro-organism (or mixture) added to start and control the fermentation
Reference: VU handout — Fermented foods; starter cultures.
Status: Verified

Q9. Pectinase is used in fruit-juice manufacture to:
A) Increase the sweetness of the juice
B) Clarify the juice by breaking down pectin
C) Carbonate the juice
D) Add colour to the juice
Correct answer: B — Clarify the juice by breaking down pectin
Reference: VU handout — Enzymes in food processing.
Status: Verified

Q10. GRAS status, given to a food substance by the US FDA, means the substance is:
A) Generally Recognised As Safe
B) Genetically Re-engineered And Standardised
C) Guaranteed Residue-free And Sterile
D) Graded for Retail And Sale
Correct answer: A — Generally Recognised As Safe
Reference: VU handout — Food regulation; food additives.
Status: Verified

3. Midterm Subjective

Q1. Define food spoilage and list its main causes.
Answer: Food spoilage is any change in a food that renders it unacceptable to the consumer — off flavour, off odour, slime, discoloration, gas or change in texture — as a result of microbial, chemical or physical action. Main causes: (1) microbial — growth of bacteria, yeasts and moulds, e.g. Pseudomonas on refrigerated meat, moulds on bread and fruit; (2) chemical — enzymic browning, lipid oxidation (rancidity), non-enzymic browning; (3) physical — moisture loss or gain, freezer burn, mechanical damage; and (4) infestation by insects or rodents. Whether a food spoils, and how fast, depends on its pH, water activity, nutrient content, storage temperature and oxygen availability; spoilage organisms are usually not the same as pathogens, so spoiled food may not be unsafe, and unsafe food may not look spoiled.
Reference: VU handout — Food spoilage.
Status: Verified

Q2. Differentiate between food infection and food intoxication, giving one example of each.
Answer: In a food infection the consumer ingests live pathogenic micro-organisms with the food; the organisms then grow (and may invade) inside the body and cause illness. Example: salmonellosis from Salmonella in undercooked eggs or poultry, or cholera from Vibrio cholerae in contaminated water/food. In a food intoxication the consumer ingests a toxin that the micro-organism already produced in the food; the organism itself need not be alive at the time of eating. Example: staphylococcal food poisoning from the enterotoxin of Staphylococcus aureus in cream-filled food, or botulism from the neurotoxin of Clostridium botulinum in canned food. In short: infection = live organism causes disease after eating; intoxication = pre-formed toxin causes disease.
Reference: VU handout — Food-borne disease.
Status: Verified

Q3. Describe the factors that affect the growth of micro-organisms in food.
Answer: Microbial growth in food is governed by intrinsic and extrinsic factors. Intrinsic: (1) pH — most bacteria grow best near pH 6–7 and are inhibited below pH 4.6; (2) water activity — most bacteria need aw above ~0.90, yeasts ~0.88 and moulds ~0.80; (3) nutrient content — foods rich in protein and carbohydrate support growth; (4) natural antimicrobial substances, e.g. lysozyme in egg white; (5) biological structure, e.g. the intact skin of fruit. Extrinsic: (1) temperature — each organism has a minimum, optimum and maximum; refrigeration slows growth, heating kills; (2) relative humidity of the atmosphere, which controls surface aw; (3) gaseous atmosphere — oxygen favours aerobes, vacuum or modified atmosphere favours anaerobes or slows aerobes; and (4) the presence of competing micro-organisms. These factors are the basis of preservation: each preservation method works by controlling one or more of them.
Reference: VU handout — Factors affecting microbial growth in foods.
Status: Verified

Q4. What is the D-value? Explain its importance in thermal processing of food.
Answer: The D-value (decimal reduction time) is the time, at a given temperature, required to reduce a microbial population by 90%, i.e. by one log cycle (one decimal place). If a population falls from 10⁶ to 10⁵ cells in 2 minutes at 121 °C, D₁₂₁ = 2 min. It is important because thermal processes are designed from D-values: knowing the D-value of the target organism (usually the most heat-resistant pathogen or spoilage spore, e.g. Clostridium botulinum spores in low-acid canned foods) and the initial load, the processor calculates how many log reductions are needed (typically 12D for botulinum, the "botulinum cook") and the holding time at the process temperature. D-values fall as temperature rises; the z-value describes how much the temperature must rise to reduce D ten-fold. Without D-values, pasteurisation and sterilisation times would be guesswork.
Reference: VU handout — Thermal processing; D-value.
Status: Verified

Q5. List the primary sources of micro-organisms in food.
Answer: The primary sources are: (1) soil — the richest source, contributing spore-formers such as Bacillus and Clostridium and many moulds; (2) water — especially untreated water, carrying Vibrio, Salmonella and faecal indicators; (3) air — dust-borne bacteria, yeasts and mould spores settling on exposed food; (4) the raw material itself — the normal flora of plants and animals (skin, gut, udder, feathers); (5) food handlers — hands, nose and clothing carry Staphylococcus aureus and enteric organisms; (6) equipment and utensils — poorly cleaned surfaces, cutting boards and containers; (7) insects and rodents — mechanical vectors of pathogens; and (8) the ingredients added during processing, e.g. spices, which often carry high spore loads. Control of these sources — clean raw materials, potable water, hygiene, and sanitised equipment — is the first step in food safety.
Reference: VU handout — Food microbiology; sources of contamination.
Status: Verified

4. Finalterm Subjective

Q1. Describe the role of lactic acid bacteria in fermented foods, using yoghurt and cheese as examples.
Answer: Lactic acid bacteria (LAB) — Lactobacillus, Lactococcus, Streptococcus and Leuconostoc — ferment sugars to lactic acid and are the workhorses of fermented foods. In yoghurt, the starter Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus grow together: they ferment lactose to lactic acid, dropping the pH to ~4.5, which coagulates the milk proteins into a gel, gives the sharp flavour, and inhibits pathogens and spoilage organisms. In cheese, LAB (e.g. Lactococcus lactis) acidify the milk so rennet can coagulate it, and during ripening their enzymes produce flavour compounds (diacetyl, peptides, free fatty acids); adjunct cultures such as Penicillium roqueforti give blue cheese its veins. Beyond acid, LAB contribute preservation (low pH, bacteriocins such as nisin), texture, flavour, and probiotic value, and they make milk digestible for lactose-intolerant people by reducing lactose.
Reference: VU handout — Fermented foods; lactic acid bacteria.
Status: Verified

Q2. What is HACCP? List and briefly explain its seven principles.
Answer: HACCP (Hazard Analysis and Critical Control Points) is a preventive food-safety management system that identifies, evaluates and controls hazards — biological, chemical and physical — at the points in a process where they can be prevented or eliminated, rather than relying on end-product testing. Its seven principles are: (1) conduct a hazard analysis — list hazards and the control measures for each step; (2) determine the Critical Control Points (CCPs) — steps where control is essential, e.g. pasteurisation temperature; (3) establish critical limits for each CCP, e.g. milk must reach 72 °C for 15 s; (4) establish monitoring procedures for each CCP; (5) establish corrective actions when a CCP is out of control; (6) establish verification procedures to confirm the system works; and (7) establish record-keeping and documentation. HACCP is required by food law in many countries and is the basis of modern food safety.
Reference: VU handout — Food safety management; HACCP.
Status: Verified

Q3. What are genetically modified foods? Discuss their benefits and safety concerns, with examples.
Answer: Genetically modified (GM) foods are foods derived from organisms whose DNA has been altered by recombinant DNA technology to add a new trait. Examples: the Flavr Savr tomato (1994, first GM whole food; delayed softening), Bt cotton and Bt maize (carry a Bacillus thuringiensis gene toxic to insect pests), herbicide-tolerant soybean, and Golden Rice (engineered to make provitamin A). Benefits: higher yields and less pesticide use; improved nutrition (Golden Rice); longer shelf life and less waste; and crops tolerant to drought, salt or disease. Safety concerns: possible allergenicity of the new protein; unintended effects on the food's composition; gene flow to wild relatives; effects on non-target organisms; and the development of resistant pests. Regulators assess GM foods case by case (substantial equivalence, toxicity and allergenicity testing), and labelling and biosafety rules — in Pakistan under the biosafety framework and internationally under the Cartagena Protocol — govern their release.
Reference: VU handout — Genetically modified foods.
Status: Verified

Q4. Describe four enzymes used in the food industry and their applications.
Answer: (1) Amylases (from Bacillus/Aspergillus) hydrolyse starch — used in brewing, bread-making (improving crumb and volume) and in producing glucose and high-fructose syrups. (2) Pectinases break down pectin — used to clarify fruit juices and to increase juice yield from pressed fruit. (3) Rennet/chymosin cleaves κ-casein — used to coagulate milk in cheese-making; microbial and recombinant chymosin now replace calf rennet. (4) Lactase (β-galactosidase) hydrolyses lactose to glucose and galactose — used to make lactose-free milk for lactose-intolerant consumers and to sweeten dairy products. Other food enzymes include proteases (meat tenderising, brewing), lipases (flavour in cheese and bakery), and glucose oxidase (removing oxygen from packaged foods).
Reference: VU handout — Enzymes in food processing.
Status: Verified

Q5. What is hurdle technology? Explain with an example.
Answer: Hurdle technology is the deliberate combination of several mild preservation factors — "hurdles" — so that together they prevent microbial growth, even though no single factor alone would be enough. Typical hurdles are low pH, low water activity, mild heat, refrigeration, preservatives (salt, nitrite, organic acids), modified atmosphere and competitive microflora. The hurdles act together: a bacterium that survives one stress is weakened and cannot overcome the next, so the combined effect is greater than the sum of the parts. Example: a fermented sausage (salami) is stabilised by a sequence of hurdles — salt and nitrite lower the water activity and inhibit anaerobes, lactic acid fermentation lowers the pH, drying lowers aw further, and smoking adds antimicrobial compounds — so the product is shelf-stable without sterilisation and keeps its flavour and texture, which a single severe heat treatment would destroy.
Reference: VU handout — Food preservation; hurdle technology.
Status: Verified

Frequently asked questions

Is the Midterm from Lectures 1-22?
Yes — Midterm covers Lectures 1-22 and Finalterm covers Lectures 23-45.

Does the quiz work from this post?
Yes — use the 'Take the BT404 quiz' link above; the quiz is already live for this course.

Are the answers verified?
Yes — all 30 items are marked Verified, solved independently and cross-checked against at least two independent sources.

More Solved Papers

See the Solved MCQs page and the midterm and finalterm mega hubs for solved papers for every subject.