Basic Food Technology interview questions

150 questions with answers (FDT-001 to FDT-150). Try each one aloud before reading the answer.

Food Chemistry

FDT-001 · What are the major macronutrients in food?

Carbohydrates, proteins and lipids (fats and oils). Water is the most abundant food component and is often studied alongside them, while vitamins and minerals are micronutrients.

FDT-002 · What is the difference between amylose and amylopectin?

Both are glucose polymers in starch. Amylose is mainly linear with α-1,4 links; amylopectin is highly branched with α-1,4 chains and α-1,6 branch points. Most starches contain about 20–30% amylose.

FDT-003 · What is a reducing sugar?

A sugar with a free aldehyde or ketone group (open-chain form) that can reduce mild oxidising agents such as Fehling's or Benedict's solution. Glucose, fructose, lactose and maltose are reducing; sucrose is not.

FDT-004 · What is starch gelatinization?

The irreversible swelling and loss of crystalline order of starch granules when heated in excess water. Granules absorb water, amylose leaches out and viscosity rises sharply, as when thickening a sauce.

FDT-005 · What is caramelization?

Non-enzymatic browning caused by heating sugars alone, without amino acids, to high temperatures (roughly above 160 °C for sucrose). It yields brown colour and bitter-sweet caramel flavours.

FDT-006 · What is protein denaturation?

Loss of a protein's native secondary, tertiary or quaternary structure without breaking peptide bonds. Heat, acid, alkali, salts, shear and solvents cause it, as when egg white sets on cooking.

FDT-007 · What is rancidity in fats and oils?

Deterioration that produces off-odours and flavours. Hydrolytic rancidity releases free fatty acids via lipase or water; oxidative rancidity is a free-radical reaction of unsaturated fatty acids with oxygen.

FDT-008 · What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have no carbon–carbon double bonds and are usually solid at room temperature (e.g. palmitic). Unsaturated ones have one (MUFA) or more (PUFA) double bonds, are usually liquid and oxidise more easily.

FDT-009 · What is an emulsifier?

A surface-active molecule with hydrophilic and lipophilic parts that lowers interfacial tension and stabilises an oil–water mixture. Examples are lecithin, mono- and diglycerides and polysorbates.

FDT-010 · What are antioxidants in food?

Substances that delay lipid oxidation, mainly by scavenging free radicals or chelating metals. Examples are tocopherols, ascorbic acid, BHA, BHT and TBHQ.

FDT-011 · What is enzymatic browning?

Browning of cut fruits and vegetables when polyphenol oxidase oxidises phenolic compounds to quinones, which polymerise into brown melanins. Apple, banana and potato show it readily.

FDT-012 · Which vitamins are fat-soluble and which are water-soluble?

Fat-soluble: A, D, E and K. Water-soluble: vitamin C and the B-complex vitamins. Water-soluble vitamins leach more readily during washing and blanching.

FDT-013 · What is dietary fibre?

Edible plant carbohydrates and lignin that resist digestion in the human small intestine. Soluble fibre (pectin, β-glucan) forms gels; insoluble fibre (cellulose, lignin) adds bulk.

Food Microbiology

FDT-014 · What causes food spoilage?

Microbial growth, endogenous enzyme activity, chemical changes such as lipid oxidation, physical damage and moisture gain or loss, and pests such as insects and rodents.

FDT-015 · What are the phases of a bacterial growth curve?

Lag (adaptation), log or exponential (fastest division), stationary (growth equals death) and death or decline phase. Preservation aims to extend the lag phase.

FDT-016 · Classify microbes by temperature preference.

Psychrophiles grow best below about 15–20 °C, mesophiles around 20–45 °C (most pathogens near 37 °C) and thermophiles above about 45 °C. Psychrotrophs are mesophile-like organisms that can still grow at refrigeration temperatures.

FDT-017 · What is a bacterial endospore?

A dormant, highly resistant structure formed by genera such as *Bacillus* and *Clostridium*. Spores survive boiling, drying and many chemicals, which is why canning targets them.

FDT-018 · What is food poisoning?

Illness from eating food contaminated with pathogens or their toxins. Infection involves live organisms multiplying in the body (e.g. *Salmonella*); intoxication involves a preformed toxin (e.g. *Staphylococcus aureus*).

FDT-019 · What are indicator organisms?

Microbes whose presence signals poor hygiene or possible faecal contamination, such as coliforms, *E. coli* and Enterobacteriaceae. They are easier to test than specific pathogens.

FDT-020 · What is Total Plate Count (TPC)?

An estimate of viable aerobic mesophilic bacteria, reported as colony-forming units per gram or millilitre (CFU/g or CFU/mL), obtained by plating dilutions and incubating, typically at about 30–35 °C.

FDT-021 · What are mycotoxins?

Toxic secondary metabolites of moulds. Examples are aflatoxins from *Aspergillus flavus* (groundnuts, maize), ochratoxin A, patulin in apple products and fumonisins in maize.

FDT-022 · What is fermentation in food?

Controlled microbial or enzymatic conversion of food components into desirable products, such as lactic acid in curd, ethanol and CO₂ in bread and beer, or acetic acid in vinegar.

FDT-023 · What are probiotics?

Live microorganisms that, when given in adequate amounts, confer a health benefit on the host. Common genera are *Lactobacillus* and *Bifidobacterium*.

FDT-024 · What are prebiotics?

Non-digestible food ingredients selectively used by beneficial gut microbes, such as inulin, fructo-oligosaccharides and galacto-oligosaccharides.

FDT-025 · What is the difference between Gram-positive and Gram-negative bacteria?

Gram-positive cells have a thick peptidoglycan wall and stain purple; Gram-negative cells have a thin peptidoglycan layer plus an outer membrane and stain pink. *Listeria* is Gram-positive; *Salmonella* is Gram-negative.

FDT-026 · What is cross-contamination?

Transfer of microbes or allergens from one food, surface, utensil or person to another, for example from raw chicken to ready-to-eat salad via a shared cutting board.

Food Preservation

FDT-027 · What are the common methods of food preservation?

Heating, refrigeration, freezing, drying, salting, sugaring, smoking, fermentation, chemical preservatives, irradiation and modified-atmosphere or vacuum packaging.

FDT-028 · What is shelf life?

The period during which a food, stored under stated conditions, stays safe and retains acceptable sensory, chemical, physical and microbiological quality and any label claims.

FDT-029 · What is the basic principle of food preservation?

Prevent or delay microbial, enzymatic and chemical spoilage by killing microbes, inhibiting their growth, inactivating enzymes and protecting food from recontamination.

FDT-030 · What is refrigeration temperature for food storage?

Generally 0–5 °C (often stated as below 5 °C). It slows but does not stop microbial growth, so psychrotrophs like *Listeria* can still multiply.

FDT-031 · What is freezing as a preservation method?

Lowering food temperature so most water turns to ice, typically storing at −18 °C or below. Low temperature and reduced liquid water stop microbial growth and slow chemical reactions.

FDT-032 · What is dehydration?

Removing water, usually by heated air, to lower water activity so microbes cannot grow and enzymatic and chemical reactions slow down. Examples are dried fruit, milk powder and spices.

FDT-033 · What is a chemical preservative? Give examples.

An additive that inhibits microbes or chemical deterioration. Examples include sodium benzoate, potassium sorbate, sulphur dioxide and its salts, propionates, nitrites and natamycin.

FDT-034 · What is food irradiation?

Exposing food to controlled ionising radiation (gamma rays from Co-60, electron beams or X-rays) to kill microbes and insects, inhibit sprouting or delay ripening. The dose is measured in grays (Gy).

FDT-035 · What is pickling?

Preserving food in brine or vinegar, often with oil and spices, where acidity, salt and sometimes lactic fermentation inhibit spoilage organisms. Indian achar and sauerkraut are examples.

FDT-036 · What is smoking of food?

Exposing food to wood smoke, which deposits antimicrobial and antioxidant compounds (phenols, acids, carbonyls) and partially dries the surface. It is usually combined with salting.

FDT-037 · What is hurdle technology?

Combining several mild preservation factors (hurdles) such as low aw, low pH, mild heat, preservatives and packaging, so that together they inhibit microbes while preserving quality. The concept was developed by Lothar Leistner.

FDT-038 · What is the "danger zone" for food?

The temperature range, about 5–60 °C, where pathogens grow rapidly. Perishable food should spend minimal time in it; hot food is held above 60 °C and cold food below 5 °C.

FDT-039 · What is cold chain?

An unbroken temperature-controlled supply chain covering storage, transport, display and handling that keeps perishable foods at specified chilled or frozen temperatures from production to consumption.

Thermal Processing

FDT-040 · What is the difference between pasteurization and sterilization?

Pasteurization uses mild heat to kill vegetative pathogens and reduce spoilage organisms, so the product still needs refrigeration or another hurdle. Sterilization (commercial sterility) destroys pathogens and spores capable of growing under normal storage, giving shelf-stable food.

FDT-041 · What is blanching?

A brief heat treatment of vegetables or fruits in hot water or steam, mainly to inactivate enzymes before freezing, drying or canning. It also removes tissue gases, cleans and sets colour.

FDT-042 · What is canning?

Sealing food in hermetic containers and heating it to commercial sterility, then cooling. Nicolas Appert pioneered the process, and Louis Pasteur later explained why it works.

FDT-043 · What is commercial sterility?

A condition achieved by heat processing in which the food is free of microbes capable of growing under normal non-refrigerated storage and distribution, and free of viable microbes of public-health significance.

FDT-044 · What is a retort?

A pressure vessel that heats sealed containers above 100 °C, usually with saturated steam or pressurised water, for sterilization. Typical processing temperature is around 121 °C.

FDT-045 · What is the difference between low-acid and high-acid foods?

Low-acid foods have pH above 4.6 (and aw above 0.85) and need full sterilization against *C. botulinum*, e.g. vegetables, meat, milk. High-acid foods (pH ≤ 4.6), such as most fruits, need only milder heat.

FDT-046 · What is hot filling?

Filling a hot (typically about 85–95 °C) acidic product such as juice or sauce into containers, sealing and inverting so the hot product pasteurises the container and lid, then cooling.

FDT-047 · What is aseptic processing?

Sterilising the product and packaging separately and then filling and sealing in a sterile environment. It allows rapid heat treatment and gives shelf-stable products such as UHT milk in cartons.

FDT-048 · What is the cold point in a container?

The slowest-heating location in a container during thermal processing. It is near the geometric centre for conduction-heated foods and lower on the axis for convection-heated foods. Process design is based on it.

FDT-049 · What is the reference temperature for sterilization calculations?

121.1 °C (250 °F). F₀ is the equivalent time in minutes at 121.1 °C with z = 10 °C.

FDT-050 · Which microorganism is the target in canning low-acid foods?

*Clostridium botulinum*, a spore-forming anaerobe that can produce lethal neurotoxin in sealed, low-acid, high-aw foods.

FDT-051 · What is thermal death time (TDT)?

The time needed at a given temperature to destroy a stated microbial population or achieve a stated number of log reductions.

FDT-052 · What is the difference between conduction- and convection-heating foods?

Solid or viscous foods (e.g. corned beef, thick purées) heat slowly by conduction. Liquids and particles in brine (e.g. juices, peas in brine) heat faster by natural or forced convection currents.

Dairy Technology

FDT-053 · What is the approximate composition of cow milk?

About 87% water, 3.5–4.5% fat, 3.2–3.5% protein, 4.6–4.9% lactose and 0.7% ash. Buffalo milk is richer, with roughly 6–8% fat.

FDT-054 · What is HTST pasteurization?

High-temperature short-time pasteurization: heating milk to at least 72 °C for 15 seconds in a plate heat exchanger, followed by rapid cooling to below 5 °C.

FDT-055 · What is LTLT pasteurization?

Low-temperature long-time (batch or vat) pasteurization: heating milk to 63 °C and holding for 30 minutes, then cooling. It suits small-scale operations.

FDT-056 · What is homogenization of milk?

Forcing milk through a narrow valve at high pressure to break fat globules into smaller ones (about 1 µm or less). This prevents cream separation.

FDT-057 · What is SNF in milk?

Solids-not-fat: total solids minus fat, i.e. protein, lactose, minerals and vitamins. Cow milk typically has about 8.5–9% SNF.

FDT-058 · What is casein?

The main milk protein family (about 80% of cow milk protein), present as micelles with calcium phosphate. It precipitates at its isoelectric point, pH 4.6, or when rennet acts on it.

FDT-059 · What are whey proteins?

The milk proteins that stay soluble at pH 4.6, mainly β-lactoglobulin and α-lactalbumin, plus serum albumin and immunoglobulins. They make up about 20% of cow milk protein and are heat-sensitive.

FDT-060 · What is the difference between toned and double toned milk?

Toned milk is standardised to 3.0% fat and 8.5% SNF; double toned milk to 1.5% fat and 9.0% SNF. Both are made by mixing whole milk with skim milk or reconstituted skim milk powder.

FDT-061 · How is paneer made?

Hot milk (about 70–85 °C) is coagulated with an acid such as citric acid or lemon juice. The whey is drained, and the curd is pressed and chilled in cold water.

FDT-062 · What is ghee?

Clarified milk fat made by heating butter or cream to evaporate water and remove the solids. It has about 99.5% fat and typically under 0.5% moisture, giving a long shelf life and a characteristic cooked flavour.

FDT-063 · Which cultures are used to make yogurt?

*Streptococcus thermophilus* and *Lactobacillus delbrueckii* subsp. *bulgaricus*, which grow symbiotically at about 40–45 °C. Indian dahi uses mixed mesophilic lactic cultures.

FDT-064 · What is rennet?

An enzyme preparation, traditionally from calf stomach, whose key enzyme chymosin cleaves κ-casein and destabilises casein micelles to form curd in cheesemaking. Microbial and fermentation-produced chymosin are common alternatives.

FDT-065 · What is cream separation?

Using a centrifugal separator to split whole milk into cream (fat-rich, lighter) and skim milk (heavier). It works because fat and serum have different densities.

Cereal, Bakery & Confectionery

FDT-066 · What are the main parts of a cereal grain?

The bran (outer layers, rich in fibre and minerals), the germ or embryo (rich in fat, protein and vitamins) and the endosperm (mostly starch, with some protein).

FDT-067 · What is gluten?

A viscoelastic protein network formed when wheat flour is mixed with water. Its components are gliadins, which give extensibility, and glutenins, which give elasticity.

FDT-068 · What is the difference between atta and maida?

Atta is whole-wheat flour, traditionally stone-ground (chakki), containing bran and germ. Maida is refined flour milled from the endosperm only, so it is whiter, finer and lower in fibre.

FDT-069 · What is semolina (suji/rava)?

Coarse middlings of wheat endosperm. Durum semolina is the standard raw material for pasta.

FDT-070 · What is the role of yeast in bread?

*Saccharomyces cerevisiae* ferments sugars to CO₂ and ethanol. The CO₂ leavens the dough, and fermentation by-products add flavour.

FDT-071 · What is baking powder?

A chemical leavener combining sodium bicarbonate with one or more acid salts (e.g. sodium acid pyrophosphate, monocalcium phosphate) and a starch filler. It releases CO₂ when moistened and heated.

FDT-072 · What is parboiled rice?

Paddy that has been soaked, steamed and dried before milling. The process gelatinises starch, drives B-vitamins into the endosperm, reduces breakage and gives harder cooked grains.

FDT-073 · What is bread staling?

Firming of the crumb and loss of freshness over time, caused mainly by retrogradation (recrystallisation) of amylopectin and moisture redistribution, not simply by drying out.

FDT-074 · What is malting?

Controlled germination of cereal grains, typically barley: steeping, germinating, then kilning. It develops amylases and other enzymes and modifies the endosperm for brewing or malt foods.

FDT-075 · What is tempering of chocolate?

Controlled heating, cooling and reheating of chocolate to crystallise cocoa butter in the stable Form V polymorph. This gives gloss, snap, contraction for demoulding and resistance to bloom.

FDT-076 · What is a hard-boiled candy?

An amorphous glassy confection made by boiling sugar and glucose syrup to very low moisture (about 1–2%) and cooling quickly so the sugar does not crystallise.

FDT-077 · What is invert sugar?

An equimolar mixture of glucose and fructose made by hydrolysing sucrose with acid or the enzyme invertase. It is sweeter than sucrose, hygroscopic and resists crystallisation.

FDT-078 · What is the difference between a cake and a biscuit (cookie) batter or dough?

Cake batter is high in water, sugar and fat and is aerated to give a soft, open crumb. Biscuit dough is low in moisture and baked to low final moisture (about 1–5%) for a crisp texture.

Fruit & Vegetable Processing

FDT-079 · What are climacteric and non-climacteric fruits?

Climacteric fruits (banana, mango, tomato, apple, papaya) show a respiration and ethylene burst during ripening and can ripen after harvest. Non-climacteric fruits (citrus, grape, strawberry, pineapple) do not, so they must be picked ripe.

FDT-080 · What is ethylene's role in fruits?

Ethylene is a gaseous plant hormone that triggers and speeds ripening, softening, colour change and senescence. It is used for controlled ripening and removed from stores to extend storage life.

FDT-081 · What is jam?

A product made by boiling fruit pulp with sugar, pectin and acid until it reaches a high soluble-solids content (about 65–68 °Brix), so it sets into a gel on cooling.

FDT-082 · What is the difference between jam, jelly and marmalade?

Jam uses fruit pulp. Jelly uses clear fruit juice and is transparent. Marmalade is usually a citrus jelly with suspended peel shreds.

FDT-083 · What is pectin?

A plant cell-wall polysaccharide made mainly of galacturonic acid units. High-methoxyl pectin gels with high sugar at low pH (about 3); low-methoxyl pectin gels with calcium ions.

FDT-084 · What is °Brix?

A measure of soluble solids, mainly sugars, expressed as grams of sucrose per 100 g of solution. It is read with a refractometer or hydrometer.

FDT-085 · What is a squash?

A fruit beverage base with fruit juice or pulp, sugar and acid, plus permitted preservative, intended to be diluted before drinking. It typically has at least 25% fruit juice and about 40% or more TSS.

FDT-086 · What is the difference between fruit juice, nectar and fruit drink?

Juice is 100% fruit juice, possibly from concentrate. Nectar contains a substantial juice or pulp share with added water and sugar. Fruit drinks contain much less fruit and more water, sugar and acid.

FDT-087 · What is controlled atmosphere (CA) storage?

Storing produce in sealed rooms with regulated low O₂, elevated CO₂, temperature and humidity to slow respiration and ripening. It is widely used for apples.

FDT-088 · What is chilling injury?

Physiological damage in tropical and subtropical produce (banana, mango, cucumber, tomato) stored above freezing but below a critical temperature, often about 10–13 °C. It causes pitting, browning and failure to ripen.

FDT-089 · What is lye peeling?

Dipping fruits or vegetables (e.g. peaches, tomatoes) in hot dilute sodium hydroxide to loosen the skin, then washing it off with water sprays.

FDT-090 · What is tomato ketchup?

A seasoned tomato sauce made from tomato concentrate with sugar, vinegar, salt and spices, concentrated to a thick consistency. Its low pH and high solids aid preservation.

Meat, Fish & Poultry

FDT-091 · What is rigor mortis in meat?

Post-mortem stiffening of muscle as ATP is depleted and actin and myosin bind permanently into actomyosin. It later resolves during ageing as proteolysis tenderises the meat.

FDT-092 · What is meat ageing (conditioning)?

Holding carcasses or cuts at chill temperatures (about 0–4 °C) for days to weeks so endogenous enzymes, mainly calpains, tenderise muscle and develop flavour.

FDT-093 · What gives meat its red colour?

Myoglobin. Deoxymyoglobin is purple-red, oxymyoglobin (oxygenated) is bright cherry-red and metmyoglobin (oxidised Fe³⁺) is brown.

FDT-094 · What is curing of meat?

Treating meat with salt and nitrite or nitrate (plus sugar, spices and ascorbate). Nitrite gives the pink cured colour, characteristic flavour and protection against *C. botulinum*.

FDT-095 · What is the difference between red and white muscle?

Red muscle has more myoglobin, mitochondria and oxidative (slow-twitch) fibres. White muscle is mostly glycolytic, fast-twitch fibres with less myoglobin, as in chicken breast.

FDT-096 · What is surimi?

Minced fish flesh that is washed to remove fat, blood and sarcoplasmic proteins, then mixed with cryoprotectants (sugar, sorbitol) and frozen. It is the base for gel products such as imitation crab.

FDT-097 · Why is fish more perishable than meat?

Fish has high post-mortem pH, little glycogen, lipids rich in PUFA, active autolytic enzymes, psychrotrophic flora adapted to cold water, and non-protein nitrogen (e.g. TMAO) that bacteria use easily.

FDT-098 · What is stunning in slaughter?

Rendering an animal unconscious before bleeding, by electrical, captive-bolt or gas methods, for welfare and to improve bleeding and meat quality.

FDT-099 · What is a sausage?

Comminuted meat mixed with fat, salt, spices and sometimes curing agents, stuffed into natural or artificial casings. It may then be cooked, smoked, fermented or dried.

FDT-100 · Which pathogens are commonly associated with poultry?

*Salmonella* and *Campylobacter* are the major ones. *Clostridium perfringens*, *Listeria monocytogenes* and *Staphylococcus aureus* also occur.

FDT-101 · What is the role of salt in meat products?

Salt extracts myofibrillar proteins (myosin) for binding and water holding, adds flavour and lowers water activity. It also aids preservation together with nitrite.

FDT-102 · What is the iced storage method for fish?

Covering fish with crushed or flake ice, at about a 1:1 fish-to-ice ratio in tropical conditions, to hold them near 0 °C. This slows bacterial and enzymatic spoilage.

Food Packaging

FDT-103 · What are the functions of food packaging?

Containment, protection (physical, chemical, biological), preservation, convenience, and communication through labelling and information. It also supports traceability and marketing.

FDT-104 · What are primary, secondary and tertiary packaging?

Primary packaging touches the food (bottle, pouch). Secondary groups primary packs (carton, shrink-wrap). Tertiary packaging is for bulk handling and transport (pallets, stretch-wrap).

FDT-105 · What are common plastics used in food packaging?

PET (bottles), HDPE (milk jugs, caps), LDPE/LLDPE (films, pouches), PP (tubs, retortable trays), PS (cups, foam trays), PVC/PVDC (cling and barrier films) and EVOH (oxygen barrier layer).

FDT-106 · What is tinplate?

Low-carbon steel sheet coated thinly with tin on both sides, usually with an inner lacquer. It is used for cans because it is strong, hermetic and formable.

FDT-107 · What is OTR?

Oxygen transmission rate: the volume of O₂ passing through a unit area of packaging material per day under specified temperature and humidity, typically in cm³/(m²·day).

FDT-108 · What is WVTR?

Water vapour transmission rate: the mass of water vapour passing through a unit area of material per day under specified conditions, typically in g/(m²·day).

FDT-109 · What is vacuum packaging?

Removing air from a pack before sealing to reduce oxygen. This slows aerobic spoilage and oxidation and is used for cheese, cured meats and coffee.

FDT-110 · What is a retort pouch?

A flexible laminated pouch, typically PET/aluminium foil/cast polypropylene, that withstands sterilization at about 121 °C. It offers faster heat penetration than cans because it is thin.

FDT-111 · What is a Tetra Pak (aseptic carton)?

A multilayer carton of paperboard, polyethylene and aluminium foil, filled aseptically with UHT-treated liquids. The foil gives light and oxygen barrier, so the product is shelf-stable without refrigeration.

FDT-112 · What is active packaging?

Packaging that deliberately interacts with the food or headspace to extend shelf life, for example oxygen scavengers, ethylene absorbers, moisture absorbers, CO₂ emitters and antimicrobial films.

FDT-113 · What is intelligent (smart) packaging?

Packaging that monitors and communicates the product's condition, using time–temperature indicators, freshness indicators, gas indicators, RFID tags and QR codes.

FDT-114 · What is glass used for in food packaging, and what are its pros and cons?

Bottles and jars. Glass is inert, transparent, impermeable and recyclable. It is also heavy, brittle and sensitive to thermal shock.

Food Engineering Unit Operations

FDT-115 · What is a unit operation?

A basic physical step common to many processes, such as heat exchange, evaporation, drying, size reduction, mixing, separation, filtration, extraction and freezing.

FDT-116 · What is a plate heat exchanger?

A heat exchanger of thin corrugated stainless-steel plates clamped in a frame, with hot and cold fluids flowing in alternate channels. It gives high heat-transfer coefficients and is standard for milk pasteurization.

FDT-117 · What is evaporation in food processing?

Concentrating a liquid food by boiling off part of its water, often under vacuum to lower the boiling point. Examples are condensed milk, tomato paste and juice concentrates.

FDT-118 · What is spray drying?

Atomising a liquid into hot air so droplets dry in seconds into powder. Milk powder, instant coffee and encapsulated flavours are made this way.

FDT-119 · What is freeze drying (lyophilization)?

Freezing the food and then removing ice by sublimation under high vacuum, followed by secondary drying of bound water. It preserves structure, flavour and nutrients but is costly.

FDT-120 · What is size reduction?

Breaking solids into smaller pieces by compression, impact, shear or attrition, using crushers, hammer mills, roller mills or ball mills. Liquid size reduction is called homogenization or emulsification.

FDT-121 · What is centrifugation?

Separating phases of different density by spinning, producing centrifugal forces many times gravity. It is used for cream separation, clarification and juice and oil separation.

FDT-122 · What is membrane filtration? Name its types.

Pressure-driven separation through semi-permeable membranes. In order of decreasing pore size: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO).

FDT-123 · What is extrusion cooking?

Forcing moistened ingredients through a screw-barrel and die under high temperature, pressure and shear. This cooks, texturises and shapes products such as puffed snacks, breakfast cereals and pasta.

FDT-124 · What is a Newtonian fluid?

A fluid whose shear stress is proportional to shear rate, so viscosity is constant (τ = μγ̇). Water, milk and clear juices are close to Newtonian.

FDT-125 · What is CIP?

Clean-in-place: cleaning pipelines, tanks and equipment without dismantling by circulating rinse water, detergents (alkali, acid) and sanitiser at controlled time, temperature, concentration and flow.

FDT-126 · What is the difference between sensible and latent heat?

Sensible heat changes temperature without phase change (Q = m·cp·ΔT). Latent heat changes phase at constant temperature (Q = m·λ). Water's latent heat of vaporisation is about 2257 kJ/kg at 100 °C; its latent heat of fusion is about 334 kJ/kg.

Food Safety & Quality Systems

FDT-127 · What is HACCP?

Hazard Analysis and Critical Control Point: a preventive, science-based system that identifies biological, chemical and physical hazards and controls them at critical points. It was first developed for NASA's space food programme.

FDT-128 · What types of hazards does HACCP consider?

Biological (bacteria, viruses, parasites), chemical (pesticides, toxins, allergens, cleaning residues) and physical (glass, metal, stones, bone). Radiological hazards are sometimes added.

FDT-129 · What is a Critical Control Point (CCP)?

A step at which control can be applied and is essential to prevent, eliminate or reduce a food-safety hazard to an acceptable level, such as pasteurization or metal detection.

FDT-130 · What is GMP?

Good Manufacturing Practices: basic operational and environmental conditions such as premises, equipment, personnel hygiene, sanitation and process controls needed to produce safe food consistently.

FDT-131 · What are prerequisite programmes (PRPs)?

Basic conditions and activities that maintain a hygienic environment, such as cleaning, pest control, water quality, personnel hygiene, maintenance, supplier control and waste management. They are the foundation on which HACCP is built.

FDT-132 · What is ISO 22000?

An international standard for Food Safety Management Systems that combines HACCP principles, prerequisite programmes, interactive communication and ISO management-system elements. The current edition is ISO 22000:2018.

FDT-133 · What is traceability?

The ability to follow a food, ingredient or package through all stages of production, processing and distribution: one step back to suppliers and one step forward to customers.

FDT-134 · What is a food recall?

Removing an unsafe or non-compliant product from the distribution chain and from consumers. In India, FSSAI's Food Recall Procedure regulations govern it.

FDT-135 · What is a food allergen?

A food protein that triggers an immune (often IgE-mediated) reaction in sensitive people. Major allergens include milk, egg, peanut, tree nuts, soy, wheat (gluten), fish, crustaceans and sesame.

FDT-136 · What is sensory evaluation?

Scientific measurement and interpretation of food characteristics as perceived by sight, smell, taste, touch and hearing. It uses trained or consumer panels and tests such as hedonic scales and triangle tests.

FDT-137 · What is the 9-point hedonic scale?

A consumer acceptance scale from 1 = "dislike extremely" to 9 = "like extremely", with 5 = "neither like nor dislike".

FDT-138 · What is the difference between quality control and quality assurance?

Quality control is product-oriented and detects defects through inspection and testing. Quality assurance is process-oriented and prevents defects through systems, procedures and audits.

Food Regulations & Nutrition

FDT-139 · What is the Food Safety and Standards Act, 2006?

India's integrated food law. It consolidated earlier laws such as the Prevention of Food Adulteration Act, 1954 and the Fruit Products Order into one framework, and it created a single authority to set science-based standards for food.

FDT-140 · What is the Codex Alimentarius?

The international food code of standards, guidelines and codes of practice developed by the Codex Alimentarius Commission, set up in 1963 by FAO and WHO, to protect consumer health and ensure fair food trade.

FDT-141 · What is the role of the US FDA in food?

It regulates the safety and labelling of most foods in the USA, other than meat, poultry and some egg products, which USDA regulates. It enforces the Federal Food, Drug, and Cosmetic Act and the Food Safety Modernization Act (FSMA).

FDT-142 · What is an INS number?

A code from the International Numbering System for Food Additives, developed by Codex, used to identify additives on labels, e.g. INS 211 for sodium benzoate. EU E-numbers follow the same system.

FDT-143 · What are the veg and non-veg symbols on Indian food labels?

A green filled circle inside a green-outlined square marks vegetarian food. A brown filled circle (earlier a triangle) inside a brown-outlined square marks non-vegetarian food. Both are mandatory under FSSAI labelling rules.

FDT-144 · What is the energy value of carbohydrate, protein, fat and alcohol?

About 4 kcal/g for carbohydrate and protein, 9 kcal/g for fat and 7 kcal/g for alcohol (Atwater factors). 1 kcal = 4.184 kJ.

FDT-145 · What is the difference between "Best Before" and "Use By"?

"Best Before" relates to quality: the food may still be safe after it but may have lost freshness. "Use By" (expiry) relates to safety for highly perishable foods and should not be exceeded.

FDT-146 · What is food fortification?

Deliberately adding micronutrients to commonly eaten foods to improve public nutrition, such as iodised salt, rice with iron, folic acid and vitamin B12, and oil and milk with vitamins A and D. FSSAI marks such foods with the "+F" logo.

FDT-147 · What is RDA?

Recommended Dietary Allowance: the daily intake of a nutrient that meets the needs of nearly all healthy individuals in a group. In India, ICMR-NIN sets RDAs.

FDT-148 · What is food adulteration?

Adding, substituting or removing substances so that food quality falls below standards or becomes unsafe, such as water in milk, starch in khoa, Metanil Yellow in turmeric or papaya seeds in black pepper.

FDT-149 · What is BMI?

Body Mass Index = weight (kg) ÷ height² (m²). The WHO adult categories are underweight < 18.5, normal 18.5–24.9, overweight 25–29.9 and obese ≥ 30; lower cut-offs are often recommended for Asian Indians.

FDT-150 · What is the difference between FSSAI registration and FSSAI licence?

Registration is for petty food businesses with small annual turnover (up to ₹12 lakh). Larger businesses need a State or Central licence, depending on turnover, capacity and type of activity, applied for through the FoSCoS portal.

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