Food engineering in the industry

Course & Lecture Logistics

• One-off lecture titled “Food Engineering in the Industry”.
• Attendance: expected 5 students, 9 showed up (bad weather).
• Assessment:
  • • No formal exam.
  • • A short quiz will cover only the first half of today’s material (fundamentals & basic concepts).
  • • Do not worry about calculations—focus on concepts.
• Teaching style: heavy use of videos and industrial examples.

"Farm-to-Fork" & Rationale for Processing

• Food’s life-cycle: raw agricultural ingredients → multiple unit-operations → packaged product on the table.
• “Food engineering” ≈ “food processing engineering”: all steps between farm gate and fork.
• Major reasons we process food
  • • Extend shelf life (storage between seasons → civilisation).
  • • Create new flavours, colours, textures, aromas.
  • • Provide nutrition in convenient/healthy form.
  • • Add economic value (Australia exports >50 % of production, mostly raw; higher value added overseas).
  • • Enable large-scale, consistent, safe supply.

Core Engineering Knowledge Needed

• Material & energy balances.
• Fluid mechanics, heat & mass transfer.
• Separation & transport operations.
• Two red-flag areas: processing (unit-operations) & formulation (product design, nutrition, allergens, sensory, fortification).

A 3-Factor Mental Model of Processing

• All operations can be decomposed into:
  1. Temperature (heat input)
  2. Time (duration)
  3. Turbulence / mixing
• E.g. pasteurisation: 70\,^{\circ}C for 20\text{–}30\,\text{min}, mild turbulence; membrane filtration: high turbulence, little/no heat; sterilisation: 121\,^{\circ}C for \ge 1\,\text{h}.

Engineering Fundamentals (Thermal)

1. Specific Heat Capacity

• Definition: energy to raise 1\,\text{kg} by 1\,^{\circ}C at constant P.
• Formula c_p = \dfrac{q}{m\,\Delta T}.
• Rule of thumb: high‐moisture foods (apple) > dry (bread) > fat > ice.

2. Thermal Conductivity (k)

• Heat-flow rate through material: q = -kA\dfrac{\Delta T}{\Delta x}.
• Depends on water content, structure, temperature, pressure.

3. Thermal Diffusivity (α)

• \alpha = \dfrac{k}{\rho c_p} – ratio of ability to conduct vs store heat; dictates heating/cooling rate.

4. Heat-Transfer Modes

• Conduction: molecule-to-molecule (pan bottom → food).
• Convection: mass movement (boiling water, pumped fluids).
• Radiation: electromagnetic (microwave, infrared, induction).

Key Thermal Operations

Blanching

• Mild 70\text{–}100\,^{\circ}C, 1–15 min; inactivates enzymes in veg/fruit without full cooking.

Pasteurisation vs Sterilisation

Examples

• Milk: chilled pasteurised vs UHT long-life packs.
• Heinz baked beans: retort at 121\,^{\circ}C, shelf life years.

Evaporation & Distillation

• Evaporation: remove water (pre-concentrate milk before spray drying, cut transport cost).
• Distillation: separate volatile components (spirits, flavours).

Drying & Dehydration

• Spray drying: atomised mist + hot air → powder in seconds (milk, coffee, flavours).
• Fluid-bed, drum, conveyor, vacuum, freeze-dry.

Freeze-Drying (Lyophilisation)

• Steps: freeze product (≤-40\,^{\circ}C) → low P → sublimation of ice → minimal flavour loss.
• Used for premium instant coffee flakes, berries, astronaut food.

Non-Thermal / Minimal-Heat Technologies

Industrial-Scale Illustrations

Cheese Manufacture (Flow)

1. Raw milk → pasteurise
2. Standardise composition (protein/fat)
3. (Missing in slide) Homogenise
4. Cool; add starter culture (lactic acid bacteria)
5. Add rennet enzyme → coagulation (curd & whey)
6. Cut curd, drain whey → mold/press
7. Ripen (weeks–years)
8. Pack & distribute.

• By-product whey → spray-dried to \sim90\% protein (body-building powders).

Baked Beans (Heinz, Wigan UK)

• Plant makes 3{,}000{,}000 cans / day; towers hold >80{,}000 cans.
• Continuous retort: cradles cycle cans through steam zones (2.5 h).
• Achieves commercial sterility ⇒ theoretical shelf life “indefinite”; labelled 1–2 years for quality.

Dairy Processing & Spray Drying

• Australia: \approx13\, billion AUD industry; 80 % milk from VIC.
• Pilot dryer (US lab): 1 kg H₂O / h; industry tower (Fonterra NZ): 30\,\text{t h}^{-1} ⇒ >30{,}000 cows’ milk/day.

Fully Automated “Dark” Factories

• Mengniu (China) milk/Yoghurt plant: no operators on floor; visitors view via sky-walk.
• 2023 “black-light factory” (lights off) launched; end-to-end robotics, AGVs, vision QC.

Packaging & Supply-Chain Digitisation (Tetra Pak Vision)

• Smart cartons: full traceability, interactive AR labels.
• Predictive analytics: optimise production, reduce recalls, align expiry with demand.
• Connected bins to improve recycling rates.

Research Frontiers at UNSW (Presenter’s Lab)

1. Plant-Based Meat Challenges

• Impossible triangle: cannot maximise cheap + tasty + nutritious simultaneously.
• Beyond Meat case: share 181\,USD \to 3 USD (2019→24); high cost, flavour gaps, complex ingredient list.
• Extrusion (high T/P) forms fibrous protein; current work: non-extrusion texturisation via protein gels (layered structures → bacon, muscle fibres).

2. Plant-Based Bacon Fat-Mimic

• Problem: coconut oil droplets melt instantly, cause greasiness.
• Solution: protein gel tissue with slow-melting behaviour → browning & shrinkage like pork fat.

3. Plant-Based Cheese

• Commercial vegan cheeses: \le1\% protein (often 0 g).
• Lab prototype: 5–10 % protein, melts/stretch similar to Mozzarella; tested with digestion simulator.

4. 3-D Printing of Foods

• Modified desktop printer extrudes protein/fat pastes; prints UNSW logo, bespoke textures, future personalised nutrition.

5. Hand-Pulled Noodle Rheology (MIT collab)

• Advanced rheometer resolves non-linear extensional viscoelasticity during stretching; links microstructure ↔ chewiness.

Ethical, Economic & Practical Take-Aways

• Engineering choices balance safety, flavour, nutrition, environment, cost.
• Shift toward minimal-heat, data-driven, automated plants.
• Sustainability pressures: reduce water/energy (evaporation, powder), cut CO₂ (plant proteins), optimise supply (smart packaging).
• Skills blend required: chemical engineering principles + food science + digital/AI + sensory & consumer insight.

Numbers & Equations Recap

• Pasteurisation: T=60\text{–}85\,^{\circ}C,\;t=10\text{–}30\,\text{min}.
• Sterilisation benchmark: T=121\,^{\circ}C,\;t=\ge60\,\text{min} (or UHT 135\,^{\circ}C,\; 2\,\text{s}).
• HPP range: 400\text{–}600\,\text{MPa} (≈ 4{,}000\text{–}6{,}000 bar).
• Specific heat example ordering: cp(\text{apple}) > cp(\text{bread}) > cp(\text{milk powder}) > cp(\text{ice}).
• Thermal diffusivity: \alpha = \dfrac{k}{\rho c_p}.

Quick Glossary

• Rennet – calf stomach enzyme causing milk coagulation.
• Homogenisation – high-pressure size reduction of fat droplets.
• Retort – pressurised steam vessel for canned foods.
• Sublimation – solid → vapour without liquid phase (freeze-dry).
• Dark factory – fully automated, lights-off production.
• PEF / PL / HPP – non-thermal microbial inactivation methods.

Study Tips for Quiz

1. Memorise why we process food (shelf life #1).
2. Distinguish pasteurisation vs sterilisation (temperature, shelf life).
3. Understand three thermal properties (c_p,k,\alpha) & three heat-transfer modes.
4. Be able to name one thermal and one non-thermal technology + example product.
5. Recall flowchart of cheese (pasteurise → culture → rennet → curd/whey).