Advanced Food Technology interview questions

125 questions with answers (FDT-301 to FDT-425). Try each one aloud before reading the answer.

Food Chemistry

FDT-301 · A potato chip line shows high acrylamide. What changes would you make?

Choose potato varieties and storage temperatures (above about 8 °C) that keep reducing sugars low, blanch slices to leach sugars and asparagine, consider asparaginase enzyme, and fry at lower temperature to a lighter colour. Monitor colour as a quick proxy and acrylamide by LC-MS.

FDT-302 · How would you extend the shelf life of a cookie that turns rancid in two months?

Measure peroxide value and hexanal over time to confirm oxidation, switch to a more stable fat (high-oleic or fractionated), add antioxidants such as tocopherols or rosemary extract, cut oxygen and light with barrier packaging or nitrogen flushing, and remove pro-oxidant metals.

FDT-303 · How do you choose an emulsifier system for a low-fat mayonnaise?

Fat reduction needs extra stabilisation: use egg yolk or a high-HLB emulsifier for oil-in-water droplets, add hydrocolloids such as xanthan or modified starch to build viscosity, and control droplet size by homogenisation. Check stability by centrifuge and storage tests.

FDT-304 · How would you prevent colour loss in a strawberry jam?

Anthocyanins degrade with heat, oxygen, light and high pH. Use short, low-temperature (vacuum) cooking, keep pH around 3.0–3.3, remove oxygen, use light-protective packaging and store cool. Ascorbic acid can accelerate loss, so its addition must be tested.

FDT-305 · How do you control the texture of a starch-thickened sauce that thins after freezing?

Freeze-thaw causes retrogradation and syneresis. Use cross-linked and stabilised (acetylated or hydroxypropylated) modified starches or waxy starches, add hydrocolloids such as xanthan, and control water activity and freezing rate.

FDT-306 · How would you design a sugar-reduced beverage that keeps the same taste?

Replace sugar with blends of high-intensity sweeteners (stevia, sucralose) and bulk or flavour modifiers, rebalance acidity, and add body with fibres or polyols where needed. Validate with sensory panels (difference and preference tests).

FDT-307 · How do you determine the oxidative stability of an oil?

Run accelerated tests such as the Rancimat (induction time at elevated temperature) or oven storage, measuring peroxide value, anisidine value and totox. Results guide antioxidant choice and shelf-life estimates.

FDT-308 · How would you reduce trans fat in a bakery shortening?

Replace partially hydrogenated fats with interesterified blends, fully hydrogenated fat blended with liquid oil, or palm fractions, adjusting solid fat content profile to keep creaming and texture. Check crystallisation behaviour (β′ form preferred).

FDT-309 · How do Maillard reactions affect nutritional quality?

They reduce available lysine and other essential amino acids, can form undesirable compounds such as acrylamide and AGEs, but also produce desirable flavour and colour. Processing is optimised to get flavour without excessive nutrient loss.

FDT-310 · How do you stabilise a protein beverage against sedimentation at neutral pH?

Use homogenisation to reduce particle size, add stabilisers such as carrageenan or gellan, control mineral levels and heat treatment to avoid aggregation, and check viscosity and sedimentation over shelf life.

FDT-311 · How would you design an analytical plan for food composition labelling?

Use validated methods: proximate analysis (moisture, ash, protein by Kjeldahl/Dumas, fat by Soxhlet or acid hydrolysis, carbohydrate by difference, dietary fibre), plus sugars, sodium and others required. Use representative samples and accredited labs.

Food Microbiology

FDT-312 · A ready-to-eat salad plant has recurring Listeria positives. How do you investigate?

Map environmental swab results by zone and time, use subtyping to see if one strain persists, inspect equipment for harbourage sites (hollow rollers, seals, drains), review cleaning and sanitation, traffic flow and cold-water handling, and intensify verification after corrective actions.

FDT-313 · How do you design a challenge study for a new chilled product?

Inoculate the product with relevant pathogens (e.g. Listeria) at realistic levels, store under intended and abuse temperatures, sample over shelf life and measure growth. Results show whether the product supports growth and support shelf-life decisions.

FDT-314 · How do you use predictive microbiology in product development?

Models such as ComBase predict growth or inactivation under different temperatures, pH, aw and preservatives. They screen formulations and storage conditions quickly before confirming with challenge tests.

FDT-315 · How do you calculate the number of log reductions needed for a pasteurisation step?

Compare the initial pathogen load with the target maximum level: log reduction = log(N₀) − log(N_target). For example, reducing from 10⁴ CFU/g to below 1 CFU in 100 g (10⁻² CFU/g) needs a 6-log reduction.

FDT-316 · A batch of yogurt shows slow acidification. What could be wrong?

Check starter culture viability and dose, milk quality (antibiotic residues, bacteriophage, inhibitory substances), incubation temperature and milk composition. Phage infection is a common cause; culture rotation and hygiene help.

FDT-317 · How do you validate a sanitiser in a food plant?

Test against relevant organisms on representative surfaces at the intended concentration and contact time, with organic load, and verify effectiveness with ATP and microbiological swabs after cleaning.

FDT-318 · How would you control spore-formers in a dairy powder?

Control raw milk quality, avoid biofilms in evaporators (limit run times, effective CIP), and design heat treatments that inactivate vegetative cells, while monitoring thermophilic spore counts.

FDT-319 · How do you set microbiological specifications for a product?

Use risk-based sampling plans (e.g. ICMSF 2-class or 3-class plans with n, c, m and M), based on intended use, consumer risk and regulatory requirements.

FDT-320 · How would you investigate a food poisoning outbreak traced to a restaurant?

Collect case information, food histories and samples, test leftovers and staff, review food handling practices (temperature abuse, cross-contamination), and use subtyping to link cases. Implement controls and staff training.

FDT-321 · How do you control mould growth on bread?

Use good hygiene and filtered air after baking, add preservatives (calcium propionate or natural alternatives), control water activity, use packaging under clean conditions and consider MAP.

FDT-322 · How do you choose between culture-based and rapid methods for testing?

Culture methods are reference methods with longer turnaround; rapid methods (PCR, immunoassays) give faster results for release decisions. Methods must be validated and confirmed positives handled correctly.

Food Preservation

FDT-323 · How would you apply hurdle technology to a shelf-stable sauce?

Combine moderate pH (below 4.6), reduced aw, preservatives and mild heat so no single hurdle has to be extreme. Each hurdle is chosen to inhibit target organisms while keeping quality.

FDT-324 · How do you choose between HPP and thermal pasteurisation for a juice?

HPP retains fresh flavour and nutrients but costs more and does not inactivate spores, so products need refrigeration. Thermal pasteurisation is cheaper and established but affects flavour and colour.

FDT-325 · How would you determine the shelf life of a new snack product?

Identify the failure mode (rancidity, moisture uptake, texture loss), store samples under real and accelerated conditions, measure key indicators and sensory acceptance, and use kinetics (e.g. Arrhenius) to predict shelf life.

FDT-326 · How does water activity control help preserve intermediate moisture foods?

Lowering aw to about 0.6–0.85 limits most bacteria; humectants such as sugar, salt and glycerol bind water. Combined with pH and preservatives, aw control gives shelf stability without full drying.

FDT-327 · How do you design a freezing process for good texture?

Fast freezing gives small ice crystals and less cell damage. Choose blast or IQF freezers, control product size and packaging, avoid temperature fluctuations in storage to limit recrystallisation.

FDT-328 · How would you reduce the use of chemical preservatives in a product?

Use natural antimicrobials (e.g. vinegar, cultured dextrose), improved hygiene, packaging, mild processing and refrigeration. Validate safety and shelf life after changes.

FDT-329 · How do you evaluate the effectiveness of irradiation for spices?

Measure microbial reduction at different doses, verify dose delivery with dosimeters, and check sensory and chemical quality. Labelling rules must be followed.

FDT-330 · How do you control temperature abuse in a cold chain?

Use temperature loggers, time–temperature indicators, alarms and monitoring, train staff and set corrective actions for excursions.

FDT-331 · How do you design a drying process for vegetables?

Pre-treat (blanching), choose drying method and temperature to balance quality and drying time, and determine final moisture and aw for stability.

FDT-332 · How would you assess the impact of preservation on nutrients?

Measure vitamins (e.g. vitamin C) before and after processing and during storage, and compare processing options.

FDT-333 · How do you choose packaging to extend a product's shelf life?

Start from the failure mode: oxygen-sensitive products need high-barrier films (EVOH, metallised layers) and nitrogen flushing; moisture-sensitive snacks need low WVTR; fresh produce needs films matched to respiration (EMAP). Seal integrity and light protection complete the design.

Thermal Processing

FDT-334 · How do you calculate the F₀ value of a canning process?

F₀ = ∫ 10^((T − 121.1)/z) dt with z = 10 °C, integrated over the time–temperature profile at the cold point (General Method). It gives equivalent minutes at 121.1 °C; low-acid foods typically need F₀ ≥ 3 min for botulinum safety.

FDT-335 · A retort heat penetration test shows a slower-heating container. What do you do?

Find the cause (fill weight, headspace, product viscosity, container orientation), re-establish the process using the worst-case container, and adjust process time or temperature so the cold point achieves the required F₀.

FDT-336 · How do D and z values help design a process?

D is the time for a 1-log reduction at a given temperature; z is the temperature change that changes D by tenfold. Together they calculate lethality at different temperatures and the time needed for a target log reduction.

FDT-337 · How do you choose between retort pouches and cans?

Pouches heat faster (thinner profile) giving better quality and lower energy, and are lighter, but need overpressure retorts and careful handling; cans are robust and established.

FDT-338 · How do you validate an aseptic processing system?

Validate heat treatment of product (hold tube residence time and temperature), sterilisation of packaging material, equipment sterilisation and sterile zone integrity, with media fills and incubation tests.

FDT-339 · How do you calculate holding tube length for a given flow rate?

Length = velocity of fastest particle × required hold time. For laminar flow, fastest velocity is about twice the mean.

FDT-340 · How do you reduce quality damage during sterilisation?

Use HTST principles, thin profiles, rotating retorts, and aseptic processing to reduce time at high temperature, since quality factors have higher z-values than microbes.

FDT-341 · How do you handle a process deviation in a canning plant?

Hold affected product, evaluate the deviation's impact on lethality, consult process authority, and decide whether to reprocess or destroy. Document corrective action.

FDT-342 · How does product viscosity affect a thermal process?

Thin liquids heat mainly by convection and reach the cold point quickly; thick or particulate products heat by conduction, so the cold point lags and process time rises sharply. Agitating (rotary) retorts or thinner packs restore faster heating.

FDT-343 · How do you design the heat treatment for an acidified vegetable product?

Confirm the equilibrium pH stays at or below 4.6 so C. botulinum cannot grow, then target acid-tolerant spoilage organisms (yeasts, moulds, lactobacilli) with a mild pasteurisation, often hot fill at 85–95 °C. pH control is a critical control point and the process is filed with the authority where required.

FDT-344 · Why is thermal process modelling software useful, and what are its limits?

It predicts cold-point temperatures and lethality from product properties and retort conditions, letting you test options and handle deviations quickly. Results must be validated by heat penetration tests because real products vary in fill, viscosity and headspace.

Dairy Technology

FDT-345 · How do you control the texture of set yogurt?

Increase milk solids (skim milk powder, protein), apply high heat treatment to whey proteins, control incubation and cooling.

FDT-346 · Cheese yield is lower than expected. What would you check?

Check milk fat and casein levels and standardisation, coagulation conditions (rennet dose, temperature, setting time), curd cutting and stirring (shattering causes fines), whey fat losses and moisture in the cheese. Measuring fat and fines in whey usually pinpoints the loss.

FDT-347 · How do you standardise milk to 3.0% fat using cream of 40% fat and skim milk of 0.05% fat?

By Pearson's square: parts of cream = 3.0 − 0.05 = 2.95 and parts of skim = 40 − 3.0 = 37. So mix 2.95 parts cream with 37 parts skim, about 7.4 kg cream per 100 kg of standardised milk.

FDT-348 · How do you reduce fouling in a UHT plant?

Preheat and hold milk to denature whey proteins before the hottest section, control milk quality (acidity, heat stability), keep calcium balance in check, design heat exchangers with suitable velocities and temperature differences, and schedule intermediate cleans. Fouling cuts run time and heat transfer.

FDT-349 · How would you develop a lactose-free milk without a sweet off-taste?

Add lactase to hydrolyse lactose to glucose and galactose, which taste sweeter, then reduce perceived sweetness by partially removing lactose first using ultrafiltration. Control residual lactose (below 0.1% for lactose-free claims) and apply the enzyme aseptically after UHT to avoid Maillard browning.

FDT-350 · Which parameters do you control for milk powder quality, and why?

Moisture (shelf life and caking), solubility index and wettability (reconstitution), bulk density (packing), scorched particles, and microbiological counts including thermophilic spores. Spray dryer inlet and outlet temperatures, feed concentration and agglomeration set most of these.

FDT-351 · How do you keep ice crystals small in ice cream during storage?

Freeze quickly in the continuous freezer, harden fast, use stabilisers that limit water mobility, and avoid temperature fluctuations in storage and distribution that cause recrystallisation. Large crystals give an icy, coarse texture.

FDT-352 · How would you set up screening for milk adulteration at a collection centre?

Use rapid tests for water (lactometer and freezing point), urea, detergents, starch, neutralisers, hydrogen peroxide and glucose, plus instrumental milk analysers for fat, SNF and protein. Suspicious samples go to an accredited laboratory for confirmation.

FDT-353 · How can a dairy plant handle whey instead of discharging it?

Whey has very high BOD, so discharge is costly and polluting. Concentrate and dry it into whey powder, recover protein by ultrafiltration (WPC), crystallise lactose, use it in beverages or bakery, or digest it for biogas.

FDT-354 · How do you extend the shelf life of paneer?

Use good hygiene and heat treatment of milk, avoid post-process contamination during pressing and cutting, chill quickly, vacuum or MAP pack, and consider mild post-pack heat treatment. These can extend shelf life from a few days to several weeks under refrigeration.

FDT-355 · What are the key principles of a hygienic dairy plant layout?

Product flows one way from raw milk reception to finished goods without crossing back, raw and processed areas are separated, high-care zones have controlled access and air, and equipment is placed for cleaning and CIP access. Drains, floors and personnel routes are designed to prevent recontamination.

Cereal, Bakery & Confectionery

FDT-356 · Bread from a new flour lot has low volume. How would you troubleshoot?

Check flour protein and gluten quality (farinograph, extensograph), falling number for amylase activity, water absorption and dough development time, then adjust water, mixing, improvers (enzymes, ascorbic acid) or blend with stronger flour. Bake test against the previous lot.

FDT-357 · How would you extend the soft shelf life of packaged bread?

Slow staling with anti-staling amylases and emulsifiers (DATEM, mono- and diglycerides), keep moisture with good packaging, and prevent mould with hygiene, preservatives or clean-label cultured ingredients. Avoid refrigerating bread, which accelerates staling.

FDT-358 · How do you reformulate a biscuit to cut sugar by 30%?

Sugar affects sweetness, spread, colour and texture, so replace it with a mix of fibres (inulin, polydextrose), polyols where allowed and high-intensity sweeteners, adjust leavening and baking profile, and re-check texture, colour and shelf life.

FDT-359 · How do you control fat bloom in chocolate?

Temper correctly to form stable form V crystals, use compatible fats, avoid temperature fluctuations in storage, and add bloom-retarding fats where allowed. Fat migration from fillings is a common cause in pralines.

FDT-360 · How do you design a gluten-free bread formulation?

Replace gluten's network with hydrocolloids (psyllium, HPMC, xanthan), use rice, maize, sorghum or pseudocereal flours with starches, add proteins (egg, dairy, pulse) for structure, and adjust water and processing. Prevent cross-contact with gluten in production.

FDT-361 · How do you optimise an extruded breakfast cereal's expansion?

Control moisture (lower moisture increases expansion), barrel temperature, screw speed and configuration, die design and starch content. Measure expansion ratio and bulk density and adjust for target crunch.

FDT-362 · How would you prevent hard-candy stickiness during storage?

Keep final moisture very low (about 1–3%), use glucose syrup to prevent crystallisation, control humidity in packing rooms and use moisture-barrier wrappers. Candy is hygroscopic and absorbs moisture quickly.

FDT-363 · How do you reduce breakage in biscuit production?

Control dough consistency, baking profile and moisture gradient (checking due to uneven moisture), cooling rate and handling. Checking often appears days after baking, so moisture distribution must be uniform.

FDT-364 · How do you assess wheat flour quality for different products?

Measure protein, gluten strength, water absorption, falling number, damaged starch and ash. Bread needs strong, high-protein flour; biscuits and cakes need weaker, low-protein flour.

FDT-365 · How do you scale up a bakery formulation from pilot to factory?

Account for mixer energy input, dough temperatures, fermentation and proving times, oven heat transfer differences and handling. Run trial batches and adjust to maintain product specs.

Fruit & Vegetable Processing

FDT-366 · How do you design a juice processing line that keeps fresh flavour?

Minimise heat exposure (HTST pasteurisation or HPP), deaerate to remove oxygen, recover aroma during concentration, use enzymatic clarification only where needed, and fill aseptically or chill.

FDT-367 · How would you prevent cloud loss in orange juice?

Inactivate pectin methylesterase by adequate pasteurisation (about 90 °C for a short time), which prevents pectin demethylation and calcium pectate precipitation that causes clarification.

FDT-368 · How do you reduce browning in fresh-cut apples?

Use anti-browning dips (ascorbic acid, calcium ascorbate), choose low-browning varieties, use MAP with low oxygen, and keep products cold.

FDT-369 · How much sugar is needed for 100 kg of fruit pulp at 10 °Brix to make jam at 68 °Brix with a 45:55 fruit-to-sugar ratio?

Sugar = 100 × 55/45 ≈ 122 kg. Total soluble solids = 10 (from fruit) + 122 = 132 kg, so the batch must be concentrated to 132/0.68 ≈ 194 kg, evaporating about 28 kg of water from the 222 kg mix.

FDT-370 · How would you design storage for mangoes destined for export?

Store around 10–13 °C to avoid chilling injury, at 85–90% relative humidity, with ethylene control and good air circulation. Pre-cool after harvest, use hot-water or vapour heat treatment for quarantine, and ripen with controlled ethylene exposure near the market.

FDT-371 · How do you choose blanching conditions for vegetables to be frozen?

Find the shortest time–temperature combination that inactivates the indicator enzyme (peroxidase or lipoxygenase), then check texture, colour and vitamin C retention. Steam blanching reduces leaching losses; over-blanching softens and wastes energy.

FDT-372 · How would you reduce post-harvest losses of tomatoes between farm and market?

Harvest at the right maturity, pre-cool to remove field heat, pack in ventilated plastic crates instead of sacks, avoid over-stacking and rough handling, keep a cold chain, and shorten time to market. Each of these cuts bruising, decay and weight loss.

FDT-373 · How do you produce a tomato paste with high consistency?

Use hot break: heat crushed tomatoes rapidly to about 90–95 °C to inactivate pectin methylesterase and polygalacturonase before they degrade pectin. Then concentrate under vacuum at low temperature to keep colour and flavour.

FDT-374 · How do you extend the shelf life of fresh-cut salad mixes?

Wash with chlorinated or peracetic acid water to cut microbial load, remove surface water by spin-drying, pack in films with low oxygen and moderate CO₂ (EMAP) matched to respiration, and keep at 1–4 °C throughout distribution.

FDT-375 · How do you evaluate a new fruit or vegetable variety for processing?

Run trials for yield, soluble solids and acidity, colour, texture after processing, enzymatic browning, peel and seed ratio and flavour after heat treatment. A variety good for fresh market can perform poorly when processed.

Meat, Fish & Poultry

FDT-376 · A sausage line produces products that release fat and water on cooking. What would you check?

Check the meat-to-fat-to-water ratio, salt and phosphate levels (which extract myofibrillar protein), chopping temperature (it should stay below about 12 °C so the emulsion does not break), chopping time, and fillers. Unstable emulsions show fat caps and jelly pockets after cooking.

FDT-377 · How do you validate a cooking step for ready-to-eat chicken?

Measure core temperature at the slowest-heating point across product sizes and oven positions, confirm a 7-log Salmonella reduction (for example 74 °C instantly or equivalent time–temperature combinations), and set the critical limit with margin. Monitor every batch.

FDT-378 · How would you reduce Salmonella and Campylobacter on poultry carcasses?

Control at farm level, then apply processing interventions: counter-current scalding, careful evisceration to avoid gut rupture, antimicrobial washes (peracetic acid), rapid chilling and hygienic design. Verify with carcass sampling against performance standards.

FDT-379 · How do you extend the shelf life of fresh fish for export?

Ice immediately and keep at 0 °C, gut and bleed quickly, use hygienic handling and slurry ice or superchilling, and pack in MAP with high CO₂ for some species. Monitor freshness with sensory scores, TVB-N and temperature logs.

FDT-380 · How do you control histamine risk in tuna?

Chill the fish rapidly after catch and keep it below about 4 °C throughout, because histamine forms from bacterial decarboxylation of histidine and is not destroyed by cooking. Test lots for histamine and reject temperature-abused fish.

FDT-381 · How would you formulate a reduced-sodium ham?

Replace part of the salt with potassium chloride and flavour enhancers, use phosphates or alternative binders to maintain water-holding and texture, and check microbial safety because salt contributes to preservation. Sensory testing guides acceptable reduction.

FDT-382 · How do you choose the stunning and chilling methods to protect meat quality?

Effective stunning reduces stress and PSE risk; rapid but not excessive chilling avoids cold shortening (especially in beef and lamb) while controlling bacteria. Electrical stimulation can speed rigor to allow faster chilling without toughness.

FDT-383 · How would you set up a cold chain for frozen seafood?

Freeze rapidly (plate or blast freezers), glaze to prevent dehydration, store at −18 °C or below without fluctuations, and monitor temperatures through transport and retail. Thawing practices at the end also matter.

FDT-384 · How do you assess meat tenderness objectively?

Use Warner-Bratzler shear force or texture analysers on cooked samples, together with measurements of sarcomere length, collagen content and ageing time, plus sensory panels.

FDT-385 · How do you design a HACCP plan for a meat processing plant?

Identify hazards from slaughter to packing (pathogens, residues, foreign bodies), determine CCPs such as carcass chilling, cooking and metal detection, set critical limits, monitoring and corrective actions, and verify through testing and audits.

Food Packaging

FDT-386 · How do you select a packaging material for a coffee pouch?

Coffee needs very low oxygen and moisture transmission and protection from aroma loss, so use a multilayer laminate with an aluminium or metallised barrier, plus a one-way degassing valve to let CO₂ escape from freshly roasted beans.

FDT-387 · How do you calculate the shelf life of a moisture-sensitive product in a given film?

Use the product's moisture sorption isotherm to find the moisture gain allowed before quality fails, the film's WVTR at storage conditions and package area. Shelf life ≈ allowed moisture gain/(WVTR × area × driving force correction).

FDT-388 · How do you test package seal integrity?

Use dye penetration, bubble (leak) tests in water, seal strength (peel) tests, burst tests and vacuum decay or pressure decay methods. Seal problems are a leading cause of spoilage in flexible packaging.

FDT-389 · How would you design MAP for fresh meat?

For red meat, use high O₂ (about 70–80%) with CO₂ (20–30%) to keep the red oxymyoglobin colour and inhibit bacteria; or vacuum or low-O₂ packs with CO for colour where permitted. Choose barrier trays and films and maintain refrigeration.

FDT-390 · How do you assess migration from plastic packaging into food?

Run migration tests with food simulants under specified time and temperature conditions, measuring overall migration and specific migration of substances against regulatory limits. Consider worst-case uses such as heating.

FDT-391 · How would you reduce plastic use in snack packaging?

Down-gauge films, switch to mono-material recyclable structures (all-polyolefin), use paper-based laminates where barrier allows, and optimise pack size and headspace. Barrier and shelf life must still be met.

FDT-392 · How do you select packaging for retort sterilisation?

Material must withstand about 121–130 °C with pressure, maintain seal and barrier, and resist delamination. Retort pouches use PET/aluminium/cast polypropylene laminates; rigid trays use PP with EVOH.

FDT-393 · How do you choose an oxygen scavenger size for a package?

Calculate oxygen in the headspace and ingress through the package over shelf life (OTR × area × time), then select a scavenger capacity with a safety margin. Scavenger activation and moisture conditions must match the product.

FDT-394 · How do you evaluate a compostable packaging claim?

Check certification to standards such as EN 13432 or ASTM D6400, test disintegration and biodegradation under industrial composting conditions, and confirm local composting infrastructure exists.

FDT-395 · How would you troubleshoot bloated cans on the market?

Bloating can come from under-processing, post-process contamination through seams, or chemical hydrogen swell. Inspect double seams, review processing and cooling water records, and culture the contents to identify the cause.

Food Engineering Unit Operations

FDT-396 · How do you design a spray dryer for milk powder?

Set inlet and outlet temperatures to dry the product without heat damage (typically 180–200 °C inlet, 80–90 °C outlet), size the chamber for droplet residence time, choose an atomiser for particle size, and add fines recovery and agglomeration.

FDT-397 · How do you calculate the evaporation required to concentrate juice from 12 to 65 °Brix?

Solids balance: 1000 kg × 0.12 = 120 kg solids; final mass = 120/0.65 ≈ 185 kg. Water evaporated = 1000 − 185 ≈ 815 kg per 1000 kg of feed.

FDT-398 · How would you improve the steam economy of an evaporator?

Add more effects, use thermal vapour recompression or mechanical vapour recompression, preheat feed with condensate and vapour, and reduce fouling with good cleaning.

FDT-399 · How do you size a plate heat exchanger for milk cooling?

Calculate heat load Q = m·cp·ΔT, choose the cooling medium and its temperatures, find log-mean temperature difference, and determine area A = Q/(U·LMTD). Check pressure drop and cleaning needs.

FDT-400 · How do you choose a pump for viscous food products?

Use positive displacement pumps (lobe, progressive cavity) for viscous or particulate products to avoid shear damage, with sanitary design and CIP ability.

FDT-401 · How do you estimate the freezing time of a meat block?

Use Plank's equation, t = (ρ·L/(Tf − Ta))·(P·a/h + R·a²/k), with latent heat L, freezing point Tf, air temperature Ta, thickness a, surface coefficient h, thermal conductivity k and shape factors P and R (1/2 and 1/8 for a slab). It underestimates slightly, so add a margin or use refined methods.

FDT-402 · How would you select membrane filtration for whey processing?

Use ultrafiltration (about 1–100 kDa cut-off) to concentrate whey protein while lactose and minerals pass, nanofiltration to partly demineralise, and reverse osmosis to concentrate total solids. Diafiltration raises protein purity in WPC80 and isolates.

FDT-403 · How do you scale up a mixing process from pilot to production?

Keep the same mixing mechanism and match a key criterion such as power per unit volume, tip speed or blend time, depending on whether the product is shear-sensitive or needs good dispersion. Confirm product quality in production trials.

FDT-404 · How would you reduce energy use in a food dryer?

Recover heat from exhaust air, recirculate part of the air, pre-dewater mechanically before thermal drying, optimise air temperature and flow, insulate the dryer and avoid over-drying below target moisture.

FDT-405 · How do you design a CIP system for a juice plant?

Map circuits, set sequences (pre-rinse, hot caustic wash, rinse, acid wash, rinse, sanitise) with the right temperature, concentration, time and turbulent velocity (about 1.5 m/s), recover and reuse solutions where possible, and verify cleanliness with ATP and micro swabs.

Food Safety & Quality Systems

FDT-406 · How do you conduct a hazard analysis for a new product?

Map the process flow, list biological, chemical, physical and allergen hazards at each step, assess severity and likelihood, and decide which are significant. Identify control measures and use the decision tree to determine CCPs.

FDT-407 · How would you validate a metal detector as a CCP?

Define test piece sizes (ferrous, non-ferrous, stainless) based on risk and product effect, test at the worst-case position in the aperture, verify rejection to a secure bin, and set test frequency and corrective action for failures.

FDT-408 · How do you manage allergens in a shared production line?

Assess allergens in all ingredients, schedule allergen-containing products after allergen-free runs, validate cleaning between runs, segregate storage and utensils, use correct labelling and precautionary labels only based on risk assessment.

FDT-409 · How do you perform a mock recall?

Select a lot, trace ingredients one step back and products one step forward within a set time (usually a few hours), and check record accuracy. Gaps found are fixed before a real recall happens.

FDT-410 · How do you set up an environmental monitoring programme for Listeria?

Define zones (1 to 4) by distance from product contact, set sampling sites and frequencies, use "seek and destroy" to find harbourage, trend results, and take corrective action for positives.

FDT-411 · How do you handle a customer complaint about a foreign body?

Log details and retain the sample, identify the material, trace the lot and process, review controls (sieves, magnets, detectors), take corrective action and respond to the customer.

FDT-412 · How do you select suppliers in a food safety system?

Assess risk by ingredient, require certifications (GFSI), audit high-risk suppliers, set specifications and certificates of analysis, and monitor performance.

FDT-413 · How is statistical process control used in food manufacturing?

Critical variables such as fill weight, cooking temperature, pH or seal strength are plotted on control charts so drift and unusual variation are seen before limits are breached. Operators react to special causes, and capability indices (Cpk) show whether the process can meet specifications.

FDT-414 · How do you prepare a plant for a third-party food safety audit?

Run internal audits against the standard, close open corrective actions, check that records (monitoring, calibration, training, cleaning) are complete and signed, walk the plant for hygiene and maintenance issues, and brief staff to explain their own tasks and controls.

FDT-415 · How do you strengthen food safety culture in a factory?

Leaders show commitment and resources, staff are trained and understand why controls matter, reporting near-misses is encouraged without blame, and food safety performance is measured and discussed like production targets. Surveys and observations track progress.

Food Regulations & Nutrition

FDT-416 · How do you calculate the nutrition facts panel for a new product?

Use validated analysis or databases for each ingredient, adjust for processing losses and moisture changes, calculate per 100 g and per serving, and round according to regulatory rules.

FDT-417 · How do you decide whether a product can carry a "high protein" claim?

Check the regulatory criteria (for example a minimum percentage of energy from protein or grams per 100 g), confirm by analysis, and ensure the label wording follows the rules.

FDT-418 · How do you get approval for a novel ingredient?

Compile a dossier on safety (toxicology, history of use), specifications, manufacturing process and intended use, and submit to the authority (such as FSSAI non-specified food approval or EFSA novel food).

FDT-419 · How do you design a fortified food to address iron deficiency?

Choose an iron form that is bioavailable but doesn't cause off-colours or flavours (such as ferric pyrophosphate or NaFeEDTA), add enhancers like vitamin C, test stability and bioavailability, and meet fortification standards.

FDT-420 · What do you check before finalising front-of-pack nutrition labelling?

Follow the local regulation's format and thresholds, ensure values match the back-of-pack nutrition panel and lab or calculated data, check that any colour or interpretive scheme is applied correctly, and make sure no claims conflict with the nutrient levels shown.

FDT-421 · How do you choose between a use-by and a best-before date, and set the date?

Use-by applies when safety can be compromised (such as chilled ready-to-eat foods supporting Listeria growth); best-before applies when only quality declines. The date comes from shelf-life studies and challenge tests, with a safety margin for distribution and consumer storage.

FDT-422 · How do you comply with export regulations for a food product?

Check the importing country's standards for additives, contaminants, labelling, certificates and registration, and adapt formulation and labels.

FDT-423 · How do you evaluate whether a proposed health claim is supported?

Check whether the claim is on the authorised list for the market, review human intervention studies for consistency, effect size and relevance to the target population, confirm the product contains an effective amount, and make sure wording matches the approved claim.

FDT-424 · How would you cut sodium in a packaged soup by 25% while keeping consumers?

Reduce salt gradually in steps below detection thresholds, use potassium chloride blends, yeast extracts, herbs and umami ingredients to keep taste, and check microbial safety and shelf life because salt contributes to preservation. Sensory testing at each step confirms acceptance.

FDT-425 · How would you design a snack suitable for people managing diabetes?

Lower the glycemic load by using whole grains, pulses, fibre and protein, replace sugar with non-nutritive sweeteners or polyols where allowed, and keep portion sizes controlled. Measure glycemic index in a clinical test before making claims, and avoid wording that implies treatment.

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