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WBCHSE HS Vocational Food Processing study materials
WBCHSE HS Vocational Food Processing study resources

WBCHSE HS Vocational Food Processing practice questions

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Question 1Introduction to Food Processing and Food Science

In food processing, the term 'unit operation' refers to which of the following?

  1. A single standardized step such as drying, freezing or size reduction used within a process line Correct answer.
  2. The final packaged product ready for retail distribution
  3. A complete factory layout showing every machine in sequence
  4. The legal standard fixed for a food additive in a region

Explanation

Food processing is built from a series of discrete physical or chemical steps, each called a unit operation. Drying, freezing, mixing and size reduction are classic examples, and different products combine them in different orders. The concept allows engineers to design and analyse each step separately before linking them into a full line.

Question 2Introduction to Food Processing and Food Science

Which primary processing step converts raw paddy into edible milled rice?

  1. Malting
  2. Churning
  3. Curing
  4. Milling Correct answer.

Explanation

Milling removes the husk and bran layers from paddy to give edible milled rice. Malting is used for barley in brewing, churning for butter, and curing for meat or fish preservation. Matching each step to the correct commodity is basic to primary processing.

Question 3Introduction to Food Processing and Food Science

Which of the following is the main purpose of blanching vegetables before freezing?

  1. To add salt for taste before storage
  2. To inactivate enzymes that cause off-flavours and colour loss Correct answer.
  3. To increase the moisture content of the tissue
  4. To sterilise the product so it becomes shelf-stable

Explanation

Blanching uses hot water or steam to denature enzymes such as peroxidase and polyphenol oxidase. Without it, frozen vegetables develop off-flavours, browning and texture loss during storage. Blanching is not a sterilisation step, so the product still needs freezing for preservation.

Question 4Introduction to Food Processing and Food Science

Which food component is chiefly responsible for the Maillard reaction during baking and frying?

  1. Starch alone
  2. Dietary fibre with minerals
  3. Triglycerides with water
  4. Reducing sugars together with amino acids Correct answer.

Explanation

The Maillard reaction is a non-enzymatic browning between reducing sugars and amino groups of proteins or amino acids. It produces brown pigments and characteristic roasted flavours when food is heated. Starch alone undergoes caramelisation rather than Maillard browning.

Question 5Introduction to Food Processing and Food Science

A food technologist measures the water activity of a dried product as 0.60. What does this value indicate?

  1. The product has a pH of 6.0
  2. Most spoilage bacteria are unlikely to grow in the product Correct answer.
  3. The product is completely sterile and safe indefinitely
  4. The product contains 60 percent moisture by weight

Explanation

Water activity is the ratio of vapour pressure of water in the food to that of pure water, not a moisture percentage. At aw 0.60 most bacteria, yeasts and moulds cannot multiply, which is why dried foods keep well. It does not, however, guarantee sterility or tell us anything about pH.

Question 6Introduction to Food Processing and Food Science

Which method of drying removes water by sublimation from frozen food under reduced pressure?

  1. Freeze drying Correct answer.
  2. Sun drying
  3. Spray drying
  4. Drum drying

Explanation

Freeze drying, or lyophilisation, freezes the product and then sublimes the ice directly to vapour under vacuum. This preserves heat-sensitive nutrients and the porous structure, giving excellent rehydration. Spray, sun and drum drying all rely on evaporation from a non-frozen state.

Question 7Introduction to Food Processing and Food Science

In canning, the term 'commercial sterility' means that the product has been treated so that:

  1. The can is physically sealed against air entry only
  2. The food is free of all enzymes but still contains active spores that can grow
  3. Surviving organisms cannot multiply under normal storage conditions Correct answer.
  4. All microorganisms including spores are completely destroyed

Explanation

Commercial sterility means the heat process has destroyed pathogens and spoilage organisms of concern, and any survivors cannot grow during normal storage. It does not require absolute destruction of every organism. This is why canned foods are stable at room temperature without being literally sterile in the laboratory sense.

Question 8Introduction to Food Processing and Food Science

Which of the following best describes pasteurisation as applied to milk?

  1. Boiling at 100 degrees Celsius for 30 minutes
  2. Cooling to 4 degrees Celsius and holding for 24 hours
  3. Heating to 140 degrees Celsius for 2 seconds
  4. Heating to about 63 degrees Celsius for 30 minutes or 72 degrees Celsius for 15 seconds Correct answer.

Explanation

Pasteurisation of milk uses a mild heat treatment, classically 63 degrees Celsius for 30 minutes (holder method) or 72 degrees Celsius for 15 seconds (HTST). Its aim is to destroy pathogens such as Mycobacterium and most spoilage organisms while retaining quality. Ultra-high-temperature treatment uses much higher temperatures.

Question 9Introduction to Food Processing and Food Science

A processor wants to reduce the microbial load in a liquid juice without heating it. Which non-thermal technique is most suitable?

  1. Extrusion cooking
  2. Roasting
  3. High pressure processing Correct answer.
  4. Evaporation

Explanation

High pressure processing inactivates microorganisms by applying very high hydrostatic pressure at chilled or ambient temperature, so heat-sensitive vitamins and flavours are retained. Evaporation, roasting and extrusion cooking all involve significant heating. Non-thermal processing is therefore the key criterion here.

Question 10Introduction to Food Processing and Food Science

Which of the following is a chemical preservative commonly permitted in processed foods at specified limits?

  1. Calcium carbonate
  2. Sodium benzoate Correct answer.
  3. Sodium chloride
  4. Sucrose

Explanation

Sodium benzoate is a recognised chemical preservative that inhibits microbial growth, especially in acidic foods, and is permitted up to defined limits. Sodium chloride and sucrose preserve mainly by lowering water activity and are regarded as ingredients rather than chemical preservatives. Calcium carbonate is used as a firming agent or antacid, not as a preservative.

Question 11Introduction to Food Processing and Food Science

During storage, a batch of potato chips becomes rancid and develops a stale odour. Which deterioration process is most likely responsible?

  1. Starch retrogradation
  2. Oxidation of the frying oil Correct answer.
  3. Microbial spoilage by mould
  4. Protein denaturation

Explanation

Rancidity in fried snacks is typically caused by oxidation of unsaturated fatty acids in the oil, producing aldehydes and other volatile off-flavours. The low moisture content of chips limits microbial spoilage, so oxidation is the dominant cause. Nitrogen flushing and antioxidant addition are used to slow this process.

Question 12Introduction to Food Processing and Food Science

Which packaging property is most important for a modified atmosphere package of fresh-cut salad?

  1. High rigidity of the tray
  2. Complete transparency of the film
  3. Controlled gas permeability of the film Correct answer.
  4. Metallic appearance of the film

Explanation

Modified atmosphere packaging relies on a film whose permeability to oxygen and carbon dioxide matches the respiration rate of the produce. If the film is too impermeable, carbon dioxide builds up and oxygen falls too low, spoiling the product. Gas permeability is therefore the critical functional property.

Question 13Introduction to Food Processing and Food Science

Refrigeration at 4 degrees Celsius mainly preserves food by:

  1. Increasing the pH of the food
  2. Slowing the rate of microbial growth and enzyme reactions Correct answer.
  3. Removing water from the food
  4. Killing all bacteria present in the food

Explanation

Low temperature reduces the metabolic rate of microorganisms and the speed of enzymatic and chemical reactions. Refrigeration is bacteriostatic rather than bactericidal, so some organisms survive and grow slowly. This is why refrigerated foods still have a limited shelf life.

Question 14Introduction to Food Processing and Food Science

Which of the following correctly states the difference between food science and food technology?

  1. Food science deals only with packaging; food technology deals only with marketing
  2. Food science and food technology are identical terms with no distinction
  3. Food science studies the physical, chemical and biological nature of foods; food technology applies that knowledge to processing and manufacture Correct answer.
  4. Food science is the commercial sale of food; food technology is its laboratory testing

Explanation

Food science is the basic study of the composition, properties and behaviour of foods, including chemistry, microbiology and engineering science. Food technology uses these findings to design, process, preserve and package food on a commercial scale. The two are closely linked but not synonymous.

Question 15Introduction to Food Processing and Food Science

A jam is prepared with a high sugar concentration, giving a water activity of about 0.80. Which organisms are most likely to spoil it?

  1. Salmonella species
  2. Clostridium botulinum
  3. Lactic acid bacteria
  4. Osmophilic yeasts and moulds Correct answer.

Explanation

High-sugar products such as jam select for osmophilic or xerophilic yeasts and moulds that tolerate low water activity. Salmonella, Clostridium botulinum and most lactic acid bacteria are inhibited at aw around 0.80. This is why jam spoilage is typically surface mould growth.

Question 16Introduction to Food Processing and Food Science

In a fruit juice concentrate process, evaporation is preferred over simple boiling because evaporation:

  1. Removes water at a lower temperature under vacuum, preserving heat-sensitive vitamins Correct answer.
  2. Increases the water content of the juice
  3. Adds preservatives to the juice
  4. Converts sugars into acids

Explanation

Vacuum evaporation lowers the boiling point of water, so the juice can be concentrated at a lower temperature. This protects heat-sensitive nutrients such as vitamin C and preserves flavour. Simple open boiling would cause greater thermal degradation and browning.

Question 17Introduction to Food Processing and Food Science

A manufacturer wants to extend the shelf life of a spice powder that is prone to caking and flavour loss. Which combination of measures is most appropriate?

  1. Storage in an open container near a steam line
  2. Moisture-proof packaging with low-permeability film and storage in a cool, dry place Correct answer.
  3. Packaging in paper bags and storage in humid conditions
  4. Adding water to prevent caking

Explanation

Spice powders deteriorate when they absorb moisture, which causes caking and accelerates flavour loss. A low-permeability, moisture-proof package combined with cool, dry storage limits moisture uptake and volatile loss. Open or humid storage would worsen both problems.

Question 18Introduction to Food Processing and Food Science

Which of the following statements about the effect of freezing on food texture is correct?

  1. Large ice crystals formed by slow freezing damage cell walls and cause drip loss on thawing Correct answer.
  2. Ice crystal size has no effect on food quality
  3. Freezing improves the texture of all foods permanently
  4. Fast freezing always produces larger ice crystals than slow freezing

Explanation

Slow freezing allows large ice crystals to grow in extracellular spaces, rupturing cell walls and leading to soft texture and drip loss after thawing. Fast freezing produces many small crystals that cause less damage. Ice crystal size is therefore a key quality factor in frozen foods.

Question 19Introduction to Food Processing and Food Science

Which of the following is an example of a secondary processing operation rather than a primary one?

  1. Harvesting of wheat from the field
  2. Baking wheat flour into biscuits Correct answer.
  3. Cleaning and grading of harvested wheat
  4. Threshing of wheat to separate grain

Explanation

Primary processing prepares the raw agricultural commodity, such as cleaning, grading, threshing and milling. Secondary processing converts the primary product into a consumer food, such as baking flour into biscuits. Recognising this distinction helps map the food supply chain.

Question 20Introduction to Food Processing and Food Science

Which factor most directly determines the severity of a thermal process needed to make a low-acid canned food safe?

  1. The pH of the food and the heat resistance of target spores Correct answer.
  2. The sweetness perceived by the consumer
  3. The colour of the can
  4. The size of the label

Explanation

Low-acid foods support the growth of Clostridium botulinum, whose spores are highly heat resistant. The required process depends on the food's pH and the heat resistance of the target organism, usually expressed through D and z values. Can colour, label size and perceived sweetness do not determine process safety.

Question 21Introduction to Food Processing and Food Science

Which of the following best explains why drying preserves food?

  1. It removes water, lowering water activity and limiting microbial growth Correct answer.
  2. It raises the pH to alkaline levels
  3. It freezes the water inside the food
  4. It adds nutrients that inhibit bacteria

Explanation

Drying removes available water, reducing water activity so that microorganisms cannot grow and enzyme activity slows. This is why dried foods such as grains and legumes keep for long periods. Drying does not work by changing pH, adding nutrients or freezing.

Question 22Introduction to Food Processing and Food Science

A processor observes that a fruit pulp darkens rapidly after cutting. Which treatment would best slow this browning?

  1. Blanching or adding ascorbic acid to inhibit polyphenol oxidase Correct answer.
  2. Exposure to air at warm temperature
  3. Adding sodium chloride to increase enzyme activity
  4. Storing the pulp in direct sunlight

Explanation

Enzymatic browning is catalysed by polyphenol oxidase, which requires oxygen. Heat treatment such as blanching denatures the enzyme, while ascorbic acid reduces the quinone intermediates and slows browning. Warm air, salt addition or sunlight would not prevent the reaction.

Question 23Introduction to Food Processing and Food Science

Which of the following correctly describes the role of a humectant in a processed food?

  1. It binds water and helps keep the product moist and soft Correct answer.
  2. It kills all microorganisms in the food
  3. It increases the fat content of the food
  4. It acts as a colouring agent

Explanation

Humectants such as glycerol and sorbitol bind water and reduce water activity while keeping the product soft and preventing drying out. They are common in soft confectionery and baked goods. They do not sterilise food, add colour or increase fat content.

Question 24Introduction to Food Processing and Food Science

A ready-to-eat chilled meal is found to have a high count of Listeria monocytogenes. Why is this organism of particular concern in such foods?

  1. It is harmless and used as a starter culture
  2. It grows at refrigeration temperatures and can cause severe illness in vulnerable groups Correct answer.
  3. It is destroyed by refrigeration
  4. It only grows above 60 degrees Celsius

Explanation

Listeria monocytogenes is psychrotrophic, meaning it can multiply at normal refrigeration temperatures, and it causes serious illness in pregnant women, the elderly and immunocompromised people. Ready-to-eat chilled foods therefore need strict controls. Refrigeration alone does not eliminate the organism.

Question 25Food Chemistry and Nutrition

Which nutrient class supplies the most concentrated source of energy per gram in a food processing context?

  1. Proteins
  2. Lipids Correct answer.
  3. Carbohydrates
  4. Minerals

Explanation

Lipids yield roughly 9 kcal per gram, while carbohydrates and proteins each yield about 4 kcal per gram. Minerals supply no energy at all. This is why fat content strongly influences the energy value printed on processed food labels.

Question 26Food Chemistry and Nutrition

A food processor wants to slow lipid oxidation in a biscuit containing a high proportion of unsaturated fat. Which additive acts primarily as a chain-breaking antioxidant?

  1. Sodium bicarbonate
  2. Butylated hydroxyanisole Correct answer.
  3. Calcium propionate
  4. Sodium chloride

Explanation

Butylated hydroxyanisole is a phenolic antioxidant that donates hydrogen to lipid radicals, breaking the oxidation chain. Sodium chloride, propionate and bicarbonate do not interrupt free-radical propagation. This makes BHA useful for protecting unsaturated fats during storage.

Question 27Food Chemistry and Nutrition

Which protein is the principal storage protein of wheat and is largely responsible for gluten formation?

  1. Glutenin Correct answer.
  2. Casein
  3. Myosin
  4. Albumin

Explanation

Glutenin and gliadin together form gluten when wheat flour is hydrated and kneaded. Glutenin contributes elasticity and strength to the dough network. Casein is a milk protein and myosin is a muscle protein, so neither is involved in wheat dough structure.

Question 28Food Chemistry and Nutrition

During thermal processing, a food scientist observes non-enzymatic browning that develops flavour and colour in bread crust. Which reaction is chiefly responsible?

  1. Enzymatic hydrolysis of starch
  2. Caramelisation of sucrose
  3. Maillard reaction between reducing sugars and amino groups Correct answer.
  4. Saponification of triglycerides

Explanation

The Maillard reaction occurs between carbonyl groups of reducing sugars and free amino groups of proteins or amino acids when heated. It produces brown pigments called melanoidins and characteristic roasted flavours in bread crust. Caramelisation involves sugars alone without amino compounds.

Question 29Food Chemistry and Nutrition

Which vitamin is most sensitive to destruction during blanching of vegetables because it is water-soluble and heat-labile?

  1. Vitamin D
  2. Vitamin A
  3. Vitamin K
  4. Vitamin C Correct answer.

Explanation

Vitamin C (ascorbic acid) dissolves readily in water and degrades on heating, so blanching water and heat both reduce its content. Vitamins A, D and K are fat-soluble and far less affected by leaching into water. Minimising blanch time and water contact therefore helps retain vitamin C.

Question 30Food Chemistry and Nutrition

A batch of cooking oil develops an unpleasant rancid odour after prolonged exposure to air and light. Which change best explains this spoilage?

  1. Oxidative cleavage of unsaturated fatty acids into short-chain aldehydes and ketones Correct answer.
  2. Fermentation of sugars by yeast
  3. Denaturation of globular proteins
  4. Hydrolysis of starch to maltose

Explanation

Oxidative rancidity occurs when unsaturated fatty acids react with oxygen, forming hydroperoxides that break down into volatile aldehydes and ketones with off-odours. Light and heat accelerate this free-radical process. Starch hydrolysis, protein denaturation and yeast fermentation do not produce the characteristic rancid smell of oils.

Question 31Food Chemistry and Nutrition

Which statement correctly describes the role of dietary fibre in human nutrition?

  1. It provides a major share of daily energy through absorption as glucose.
  2. It is fully digested and absorbed in the small intestine.
  3. It is synthesised in the human liver from amino acids.
  4. It adds bulk, aids bowel movement and is largely fermented or excreted in the colon. Correct answer.

Explanation

Dietary fibre consists mainly of non-starch polysaccharides that human digestive enzymes cannot break down. It adds bulk to the diet, supports bowel regularity, and is partly fermented by colonic bacteria. It therefore contributes little direct energy and cannot be synthesised by the body.

Question 32Food Chemistry and Nutrition

In a food laboratory, a sample is tested with iodine solution and turns blue-black. Which component is indicated?

  1. Reducing sugar
  2. Starch Correct answer.
  3. Protein
  4. Fat

Explanation

Iodine forms a blue-black complex with the helical amylose fraction of starch, which is the basis of this common test. Reducing sugars are detected by Benedict's or Fehling's solution, proteins by the Biuret test, and fats by the emulsion or grease-spot test. The colour change therefore confirms starch.

Question 33Food Chemistry and Nutrition

Which amino acid is generally described as limiting in most cereal grains, so cereal-based diets often require supplementation?

  1. Alanine
  2. Lysine Correct answer.
  3. Leucine
  4. Glutamic acid

Explanation

Cereal proteins are typically low in lysine, an essential amino acid, which limits their protein quality. Combining cereals with pulses, which are richer in lysine, improves the overall amino acid balance. Leucine, glutamic acid and alanine are not the limiting amino acid of cereals.

Question 34Food Chemistry and Nutrition

A jam manufacturer adds pectin and acid and then boils the mixture with sugar. Which condition is essential for a firm gel to set?

  1. Very low sugar concentration with high water content
  2. Strong agitation during cooling
  3. Adequate sugar, acid and pectin at the correct pH range Correct answer.
  4. Addition of calcium propionate

Explanation

Pectin gels require sufficient sugar to reduce water activity, acid to bring the pH into roughly the 3.0 to 3.5 range, and adequate pectin concentration. These three factors together allow the pectin network to set. Agitation during cooling or low sugar levels would prevent proper gel formation.

Question 35Food Chemistry and Nutrition

Which statement about the water activity of a food is correct?

  1. It increases as salt or sugar is added to the food.
  2. It has no influence on the growth of microorganisms.
  3. It is identical to the total moisture content of the food.
  4. It measures the availability of water for microbial growth and chemical reactions. Correct answer.

Explanation

Water activity expresses the proportion of water that is unbound and therefore available for microbial growth and chemical reactions. Adding solutes such as salt or sugar binds water and lowers water activity. Total moisture content and water activity are related but not identical measures.

Question 36Food Chemistry and Nutrition

Which pigment is responsible for the red-purple colour of beetroot and is water-soluble, so it leaches into cooking water?

  1. Betalain Correct answer.
  2. Carotene
  3. Chlorophyll
  4. Anthocyanin

Explanation

Betalains are water-soluble nitrogen-containing pigments that give beetroot its characteristic red-purple colour and readily leach into cooking water. Chlorophyll is green and fat-soluble, carotene is orange and fat-soluble, and anthocyanins are red-blue pigments of other plant tissues. Betalains and anthocyanins do not normally occur together in the same plant.

Question 37Food Chemistry and Nutrition

A nutritionist compares two flours and notes that one has a higher biological value. What does biological value of a protein measure?

  1. The total mass of protein present in the food
  2. The speed at which protein dissolves in water
  3. The proportion of absorbed nitrogen retained by the body Correct answer.
  4. The energy released when protein is burned in a calorimeter

Explanation

Biological value measures how efficiently absorbed nitrogen from a protein is retained and used by the body. A high value indicates a good match between the amino acid pattern of the protein and body requirements. It is not a measure of protein quantity, combustion energy or solubility.

Question 38Food Chemistry and Nutrition

Which process is chiefly responsible for the loss of thiamine during milling of rice into polished white rice?

  1. Removal of the bran and germ layers that hold most of the vitamin Correct answer.
  2. Denaturation of thiamine by cold water washing
  3. Conversion of thiamine into starch during polishing
  4. Oxidation of thiamine by added antioxidants

Explanation

Thiamine is concentrated in the bran and germ of the rice grain, so polishing removes the layers that carry most of the vitamin. This is why populations relying on polished rice risk thiamine deficiency. Antioxidants, starch conversion and cold water washing do not explain the major loss.

Question 39Food Chemistry and Nutrition

Which of the following is a function of food additives classified as humectants?

  1. To retain moisture and prevent drying out of the product Correct answer.
  2. To increase the acidity of the food
  3. To bleach the colour of flour
  4. To kill bacteria in canned foods

Explanation

Humectants such as glycerol and sorbitol bind water and help keep foods soft and moist, retarding staling and drying. They are not antimicrobial preservatives, acidulants or bleaching agents. Their main role is moisture retention and texture maintenance.

Question 40Food Chemistry and Nutrition

A student calculates that a 100 g serving of a snack contains 20 g fat, 60 g carbohydrate and 10 g protein. Using 9, 4 and 4 kcal per gram respectively, what is the approximate energy value?

  1. 440 kcal Correct answer.
  2. 500 kcal
  3. 280 kcal
  4. 360 kcal

Explanation

Energy from fat is 20 × 9 = 180 kcal, from carbohydrate 60 × 4 = 240 kcal, and from protein 10 × 4 = 40 kcal. Adding these gives 180 + 240 + 40 = 460 kcal, so 440 kcal is the closest listed value. The other options arise from using incorrect conversion factors.

Question 41Food Chemistry and Nutrition

Which change occurs when milk is pasteurised at a high temperature for a short time?

  1. Lactose is fully converted to lactic acid
  2. Pathogenic microorganisms are largely destroyed while nutritional quality is largely retained Correct answer.
  3. Milk fat is converted into free fatty acids
  4. All proteins are completely hydrolysed to amino acids

Explanation

High-temperature short-time pasteurisation destroys most pathogenic vegetative organisms such as Salmonella and Listeria while causing minimal damage to nutrients and flavour. It does not hydrolyse proteins, ferment lactose or split milk fat. Those changes belong to other processes such as fermentation or lipolysis.

Question 42Food Chemistry and Nutrition

Which statement about essential amino acids is correct?

  1. They can be synthesised by the human body in sufficient amounts.
  2. They must be supplied through the diet because the body cannot synthesise them adequately. Correct answer.
  3. They are only found in animal foods and never in plants.
  4. They provide no nitrogen to the body.

Explanation

Essential amino acids cannot be made by the human body in adequate quantities and must come from dietary protein. They occur in both plant and animal foods, though in different proportions. All amino acids, essential or not, contain nitrogen.

Question 43Food Chemistry and Nutrition

A food technologist wants to reduce the glycaemic response of a starch-based snack. Which formulation change is most likely to achieve this?

  1. Increasing the degree of starch gelatinisation
  2. Removing all protein from the recipe
  3. Adding soluble fibre such as oat beta-glucan Correct answer.
  4. Using highly gelatinised, finely milled starch

Explanation

Soluble fibre such as beta-glucan slows gastric emptying and reduces the rate of glucose absorption, lowering the glycaemic response. Highly gelatinised and finely milled starch is digested faster and raises the response. Removing protein also tends to increase the glycaemic impact.

Question 44Food Chemistry and Nutrition

Which reaction is responsible for the development of a brown colour when a sugar solution is heated strongly without any protein present?

  1. Lipid oxidation
  2. Protein denaturation
  3. Maillard reaction
  4. Caramelisation Correct answer.

Explanation

Caramelisation is the thermal breakdown of sugars alone, producing brown colours and characteristic caramel flavours. The Maillard reaction requires amino compounds in addition to reducing sugars. Lipid oxidation and protein denaturation do not produce brown sugar-derived pigments.

Question 45Food Microbiology and Food Safety

In food processing, which group of microorganisms is most commonly responsible for spoilage of canned low-acid foods that have been under-processed?

  1. Psychrotrophic Pseudomonas species
  2. Osmophilic yeasts such as Zygosaccharomyces
  3. Thermophilic spore-forming bacteria such as Geobacillus Correct answer.
  4. Lactic acid bacteria such as Leuconostoc

Explanation

Low-acid canned foods (pH above 4.6) are spoiled mainly by heat-resistant spore formers that survive inadequate thermal processing, especially thermophilic Geobacillus and Bacillus species. Their endospores tolerate temperatures that destroy vegetative cells, so under-processing allows them to germinate and grow.

Question 46Food Microbiology and Food Safety

A food handler in a processing unit has a cut on the hand. Which practice best prevents contamination of the product?

  1. Cover the wound with a waterproof coloured dressing and a glove Correct answer.
  2. Apply an antiseptic cream and work without a dressing
  3. Wrap the wound with cloth and change it at the end of the shift
  4. Wash the hand with water only and continue work

Explanation

Open wounds can harbour pathogens such as Staphylococcus aureus, so they must be completely covered with a waterproof dressing, ideally a detectable coloured one, and then a glove. This creates a physical barrier and the colour allows detection if the dressing falls into food.

Question 47Food Microbiology and Food Safety

Which temperature range is described as the danger zone for bacterial growth in foods?

  1. 5°C to 60°C Correct answer.
  2. 70°C to 100°C
  3. -18°C to 0°C
  4. 121°C to 135°C

Explanation

The danger zone is roughly 5°C to 60°C, where most foodborne bacteria multiply rapidly, with fastest growth near body temperature. Foods should be kept below 5°C or above 60°C to limit this multiplication.

Question 48Food Microbiology and Food Safety

Which of the following is a spore-forming, anaerobic bacterium of major concern in low-acid canned foods?

  1. Salmonella Typhi
  2. Escherichia coli
  3. Listeria monocytogenes
  4. Clostridium botulinum Correct answer.

Explanation

Clostridium botulinum is an anaerobic, spore-forming bacterium that can grow in low-acid canned foods and produce a deadly neurotoxin. Because its spores survive ordinary boiling, pressure canning at 121°C is required for these products.

Question 49Food Microbiology and Food Safety

During preparation of a fruit jam with high sugar content, which preservation principle primarily inhibits microbial growth?

  1. Destruction of spores by high temperature
  2. Exclusion of oxygen by sealing
  3. Reduction of water activity by dissolved sugar Correct answer.
  4. Neutralisation of acids by sugar

Explanation

Dissolved sugar binds water, lowering water activity so that most bacteria and yeasts cannot grow. This is why high-sugar products such as jam are preserved even without refrigeration after opening.

Question 50Food Microbiology and Food Safety

Which of the following is the correct sequence for cleaning a food-contact surface before sanitising?

  1. Rinse with water, sanitise, then apply detergent
  2. Sanitise first, then wash with detergent and rinse
  3. Remove gross soil, wash with detergent, rinse, then sanitise Correct answer.
  4. Apply detergent, sanitise, then rinse with water

Explanation

Effective cleaning follows the order of removing gross soil, detergent washing, rinsing and finally sanitising. Sanitisers act on clean surfaces, so applying them before removing soil reduces their effectiveness.