Food Packaging: Shelf-Life, Materials & Sustainability

Course Context & Logistics

• Lecture part of Food Engineering course; current position: “Food Packaging Dilemma – Shelf-Life & Sustainability” (Week 7, Thu 17 July)

• Past weeks: Flexibility week ➔ Prof. Yong Wang ➔ 2 × Ernest (topics: preservation, industry-scale processing)

• Coming weeks: Food & Health (Dr Jayashree Arcott), Sensory Analysis & Nutrition (neuroscience focus), surprise VIP speaker on Food Security & Packaging Dilemma—networking opportunity for careers

• Lecturer encourages email questions; slides available on Moodle

Why Package Food?

(Contain & Protect)
• Two primary purposes

• Contain the product for handling, storage, transport, portioning

• Protect product from dirt, rodents, insects, microbes, oxygen, moisture, light, mechanical damage
  • Secondary purposes

• Marketing / consumer information

• Convenience & portion control (consumers pay extra)

• Enable global, non-uniform supply (strawberries in winter, shipping commodities)

• Tamper evidence, child resistance, traceability
  • Dilemma = shelf-life extension vs packaging waste (environmental burden)

Ideal Package? (No universal solution)

• Must balance opposing requirements: cost vs function, barrier vs visibility, strength vs light-weighting, sustainability vs convenience

• Desirable attributes:
  • Displays product attractively (e.g. transparent RTE meals)
  • High barrier to gases, moisture, aroma
  • Affordable / mass-producible
  • Stackable & strong
  • Non-toxic / inert
  • Reliable closure, re-closability when needed
  • Easy to decorate/print

Global & Historical Milestones

• 1990 Germany: all plastic pkg must be recyclable/combustible

• 1995 EU: 95\% of plastics to be recycled

• Ian Kiernan AO → “Clean Up Australia Day” (yachtsman noticing ocean trash)

• Dame Ellen MacArthur → Circular Economy concept after solo circumnavigation

• 2005: hottest year on record (climate link to petro-plastics)

• 2013: container-recycling directives tightened (Aus.)

3 R’s Symbol (Mobius Loop) & Waste Logic

• Reduce – use less material/weight

• Reuse – refillable, returnable, multi-trip

• Recycle – material recovery into new products

• Packaging both CREATES waste (physical litter, micro-plastics) and REDUCES food waste (spoilage drop from 20–50\% to <3\% in developed nations)

Food Groups & Specific Packaging Challenges

1. Bakery & Biscuits

• Brittle → individual trays, partitions, internal films; moisture barrier to keep crispness

2. RTE Cereals

• Hygroscopic; waxed/polythene liners inside cardboard

3. Chocolate / Confectionery

• Solid; primarily marketing wrapper (paper + alu foil) ; bloom avoided via light/oxygen barrier

4. Dairy (multiple sub-types)

• Butter/ice cream (high fat → rancidity barrier)

• Liquid milk (light & micro protection; UHT aseptic cartons)

• Fermented (yoghurt) – gas release; vented lidding films

• Powder – moisture strict; foil laminate bags

5. Meat / Fish

• Spoilage via microbes, oxidation, dehydration

• Modern solution: MAP/VP (modified-atmosphere or vacuum); CO₂/N₂ mix, CO to stabilise colour; absorbent pads

6. Savoury Snacks (potato chips)

• Mechanical breakage & rancidity

• Gas-flushed pillow bags act as cushion (N₂) – MAP variant

7. Fresh Fruit & Vegetables

• Continue respiration → need micro-perforated films; ethylene management; mushrooms “sweat” in closed bags

8. Coffee & Aroma-Sensitive Foods

• One-way valves, multilayer alu laminate to retain volatiles

9. Dried / Frozen Foods

• Dried: minimal barrier except moisture

• Frozen: cold-crack resistant polymers (LDPE blends)

10. Alcoholic Beverages & Sensitive / Hazardous Products

• Light & O₂ barriers (amber glass, alu cans, bag-in-box); tamper-proof & child-safe closures

Materials Overview

Plastics

• Consumption now > steel; short service life

• History:
  • Gutta-Percha (natural latex, 1840s)
  • Celluloid (ivory substitute)
  • Bakelite (1st fully synthetic, 1907)
  • Casein bioplastics, present PFAS etc.

• Additives: plasticisers, antioxidants, pigments, UV stabilisers, PFAS ("forever chemicals"), BPA (endocrine disruptor, now restricted; structure: two phenol rings)

• Forms/Processes:
  • Blow moulding (bottles)
  • Injection moulding
  • Extrusion → films, sheets (<0.1 in film; >0.1 in sheet)
  • Co-extrusion & lamination (multi-layer high-barrier)

• Resin Identification Codes (Mobius digits):
  1 = PET, 2 = HDPE, 3 = PVC, 4 = LDPE, 5 = PP, 6 = PS, 7 = Other

• Sustainability issues: difficult sorting; micro-/nanoplastics; wildlife harm (bags & turtles); Mount Everest & deep-sea contamination

• Ageing factors: molecular weight, crystallinity, UV, additives, temperature; breakdown ➔ micro/nano plastics

Metals

• Steel (tin-plated “tinplate”): sacrificial tin layer prevents corrosion; excellent barrier; requires sterilisation before sealing

• Aluminium: electrolytic from bauxite (energy-intensive); light weight, non-rusting, infinitely recyclable; beverage cans, foils

• Convenience closures: ring-pull, stay-tab, zip-top; consumers pay for convenience

Glass

• Composition: sand-based amorphous SiO₂; inert to nearly all foods (except HF acid)

• Pros: total barrier, flavour neutrality, transparency, endlessly recyclable

• Cons: heavy, brittle; lifecycle may surpass PET impact due to transport weight

• Light-weighting: 1986 beer bottle 260\,g \to 180\,g by 1995 (≈ 30\% reduction)

• Forms: bottles, jars, tumblers, ampoules

Paper / Paperboard

• Origin: China (Han dynasty); printable surface ideal for branding

• Pros: low cost, biodegradable, from renewable fibers

• Cons: weak to moisture, gases

• Evolutions:
  • 1850s machine-made paper bags
  • Gusseted, self-opening designs
  • Laminated cartons (e.g. Tetra Pak: paperboard + LDPE + alu foil + screw cap) provide long-life liquid packaging

• Corrugated board: fluting layer + liners → high stacking strength (secondary & tertiary packs)

Barrier Science & Migration

• Migration = movement of substances across packaging interface
  • Outside → food (O₂, odours)
  • Food → outside (water, volatiles)

• Leaching = packaging components (e.g. ink, BPA, styrene) entering food

• Real-world incidents: printing-ink transfer in EU cereals; styrene flavour in sour cream; glass chips/cyanide adulterations

Key Parameters

• WVTR (Water-Vapour Transmission Rate) / MVTR
  \text{WVTR} = \frac{Q}{A\,t}
  where Q = mass of water permeated (g), A = area (m²), t = time (day)
  → Often given as \text{g}\,\text{m}^{-2}\,\text{day}^{-1}

• OTR (Oxygen Transmission Rate) analogous

• Permeability constant Pm relates to film thickness x and partial-pressure difference \Delta p: \text{Rate} = \frac{Pm\,\Delta p}{x}

• Measurement: gravimetric (balance records weight change of test cell), coulometric O₂ analysers, GC for volatiles

Influence on Shelf-Life

• Moisture loss/gain, O₂ ingress, CO₂ loss determine spoilage kinetics

• Shelf-life evaluation methods
  • Direct storage trials (real-time)
  • Accelerated tests (elevated T, humidity; Arrhenius extrapolation)
  • Microbial challenge tests
  • Shelf turnover analysis (retail velocity)

Modified Atmosphere Packaging (MAP)

• Principle: replace ambient air with gas mix (commonly \text{N}2, \text{CO}2, trace \text{O}_2, sometimes \text{CO} for red meat colour)

• Goals: inhibit aerobic microbes, slow oxidation, maintain colour/texture, extend shelf-life without chemical preservatives

• Components: high-barrier tray/film + gas-impermeable seal + absorbent pad (scavenges drip, antimicrobial agents)

• Examples:
  • Fresh red meat (21 d refrigerated)
  • Salmon portions
  • Snack bags (chips) inflated with \text{N}_2 for cushioning = MAP variant

Closures & Sealability

• Functions: contain, allow access, enable re-seal, provide tamper evidence, be economical

• Types: screw caps, lug caps, press-on twist-off, crimped crowns, roll-on pilfer-proof (ROPP), heat seals, zippers, sliders

Tamper Evidence / Child Resistance

• Tamper-evident bands, induction foil seals, break-away tabs; driven by historical incidents (Tylenol cyanide 1982, Australian meat pie poisoning threats)

• Child-resistant designs: push-and-turn caps, blister packs (compliance with ISO 8317, US CPSC)

Printing & Design Dynamics

• Short product life cycles ⟹ frequent artwork changes; packaging = “silent salesman”

• Haze definition: % light deviated > 25° by forward scattering → clarity spec for films

• Need durable inks & coatings (immune to scratching during palletising)

Ethical, Environmental & Societal Connections

• Convenience often outweighs eco-concern in consumer choice

• Developed vs developing nations: packaging reduces spoilage to <3\% vs up to 50\% waste

• Large numbers: 200 billion food & beverage containers/year; AU food industry turnover > 11\text{ bn}

• Activism: Clean-Up Australia Day, Circular Economy Foundation

Numerical / Formula Summary

• WVTR unit: \text{g}\,\text{m}^{-2}\,\text{day}^{-1}

• 95\% EU plastics recycling target (1995)

• Micro vs nano-plastics: deteriorated fragments <5 mm & <100 nm

• Beer bottle lightweighting: 260 \rightarrow 180\,\text{g} (≈30\% mass cut)

• Extrusion film: film < 0.1\,\text{in} (≈0.25 mm); sheet > that

Real-World Examples & Metaphors

• Banana/Orange have “built-in packaging” (peel) → no extra needed

• Mushrooms in plastic bag “sweat” (water migration example)

• Bicycle/iPhone = indefinitely shelf-stable vs food (biologically active) → need preservation & packaging

• Turtles suffocated by plastic bags; Mt Everest litter; deepest ocean trenches polluted by micro-plastics

Key Terms Glossary

• Contain & Protect • Barrier Function • Migration / Leaching • WVTR / OTR • MAP / VP • Lamination • Extrusion / Blow Moulding / Injection Moulding • Tinplate • Lightweighting • Corrugation • Tamper-Evident vs Tamper-Proof • Child-Resistant • BPA • PFAS • Circular Economy • Three R’s • Shelf-Life