Food Packaging

Course Road-Map & Context

  • Position in course: "Food Packaging Dilemma – Shelf Life & Sustainability" (Week 7, Thu 17 July)
    • Preceded by preservation modules from Yong Wang and Ernest.
    • Upcoming: Week 8 “Food & Health” (Jayashree Arkod), Week 9 “Sensory Analysis & Nutrition”, surprise VIP speaker on food security & packaging.
  • Lecturer stresses attendance, cross-modular links (food processing, neuroscience, consumer health).
  • Exam/quiz hint: lecturer often asks for definitions & formulas.

Why Package? – Dual Perspective

  • Two headline functions (quiz cue):
    • Contain the product for transport, portioning, storage.
    • Protect the product from rodents, insects, dirt, oxygen, moisture, light, microbes.
  • Additional business/consumer drivers:
    • Marketing & brand communication (printability, shelf appeal).
    • Convenience (willingness to “pay an extra dollar” for easy use, resealability, single-serve).
    • Enable global/non-seasonal supply (e.g., strawberries in winter).
    • Non-uniform distribution/portion control.
  • Fundamental dilemma = Protection vs. Environmental waste ➜ “Packaging Dilemma”.

Industry Scale & Milestones

  • Australia: > 11\,000\,000\,000 AU$ annual food industry turnover (figure likely higher today).
  • Worldwide: ~200\,000\,000\,000 food & beverage containers per year.
  • Selected regulatory / sustainability milestones:
    • 1990 DE (Germany): all plastic packaging must be recyclable or combustible.
    • 1995 EU: target 95\% plastic recycling.
    • 1989 Ian Kiernan (AUS yachtsman) launches “Clean Up Australia Day”.
    • Early 2000s: Ellen MacArthur champions Circular Economy.
    • 2005: hottest year on record ➜ climate linkage.
    • 2013: global push that all packaging become recyclable.

Three R’s (Quiz Favourite)

  • Reduce (minimise material usage, lightweighting).
  • Reuse (returnable bottles, refill systems).
  • Recycle (mechanical, chemical, energy recovery).
  • Symbol: Möbius loop ♻ — presence ≠ guarantee; depends on consumer compliance & local infrastructure.

Food Groups & Their Specific Packaging Needs

Bakery Goods

  • Brittle → require cushioning trays, inner plastic seals to stay crispy (moisture barrier).

Ready-To-Eat (RTE) Breakfast Cereals

  • Hygroscopic → waxed or LDPE paper liners inside cardboard; focus on mild moisture & oxygen barrier.

Chocolate & Confectionery

  • Solid & fat-rich → paper + aluminium foil to block fat bloom, light & odour.

Dairy

  • Sub-types: liquid milk, butter, ice cream, cheese, powders, fermented.
  • Hazards: rancidity, bacterial growth, light-induced flavour loss, moisture pickup (powders).
  • Solutions: high-barrier laminates, UHT aseptic packs for infant formulas, light-opaque bottles.

Meat & Fish

  • Risks: microbial spoilage, oxidation (colour loss), dehydration.
  • Solutions: MAP (modified atmosphere), oxygen scavengers, absorbent pads, high-barrier trays.

Savoury Snacks (e.g., potato chips)

  • Critical: structural integrity + oxidation of fats.
  • Nitrogen flush + cushion space, metallised films.

Fresh Produce

  • Continue to respire → semi-permeable films, micro-perforation, breathable clamshells.

Coffee, Dried, Frozen, Alcoholic, Airline Meals

  • Coffee: one-way degassing valves, aluminium laminates.
  • Frozen: materials must resist -40^\circ\text{C} without embrittlement.
  • Alcohol: child-safe, tamper-evident closures, UV barrier for wine/beer.

Core Science: Migration & Barrier Concepts

  • Terminology
    • Migration: net movement across package wall (in → out or out → in).
    • Leaching: contaminants leaving package into food (e.g., ink, BPA).
  • Typical migrants
    • Water vapour, O2, CO2, ethylene (plant hormone), aroma volatiles, oils.
  • Measurement via gravimetric method
    • Place filled pack on ultra-sensitive balance; plot weight Δ vs. time.
    • Regions: adsorption → steady diffusion → saturation.
  • Key equation (memorise): \text{WVTR}=\frac{Q}{A\,t}=\frac{P_M\,\Delta P}{d} \quad\left[\frac{\text{g}}{\text{m}^2\,\text{day}}\right]
    • Q = mass of water transferred.
    • A = area; t = time.
    • P_M = permeability constant of film; d = thickness; \Delta P = vapour-pressure diff.
  • Higher thickness \uparrow → lower WVTR; laminates can approach near-zero permeability.

Shelf-Life Determination

  • Direct storage study (gold standard) – monitor quality until failure.
  • Comparative / inferential – benchmark vs. competitor or historical data.
  • Shelf Turnover Time – if product sells fast, shorter technical shelf life acceptable.
  • Accelerated tests: elevate temperature, humidity or microbial load (“Arrhenius approach”).

Major Packaging Materials

Plastics

  • Dominant: consumption > steel; low energy per unit, excellent barriers.
  • Common resins: PET (1), HDPE (2), PVC (3), LDPE (4), PP (5), PS (6), “other” (7) – recycling codes inside Möbius loop.
  • Manufacturing
    • Extrusion → Blow Molding (hollow bottles; air inflates parison).
    • Extrusion → Injection Molding (tubs, caps; plastic injected into cooled mold cavity).
    • Films & sheets: < 0.1 inch = film; > 0.1 inch = sheet. Used for liners, wrap-around bags.
  • Additives & Concerns
    • Plasticisers, antioxidants, colourants → can migrate.
    • Bisphenol A (BPA): endocrine disruptor, binds estrogen receptor; now restricted.
    • PFAS (Per- & Polyfluoroalkyl Substances) “forever chemicals” – persistent, bio-accumulative.
  • Environmental fate: fragmentation to micro- (<5 mm) & nano-plastics – detected from ocean trenches to Mt. Everest.

Metals

  • Steel/Tinplate
    • Tin layer = sacrificial corrosion barrier & acid protection.
    • Requires prior thermal sterilisation (no survival of microbes in sealed can).
  • Aluminium
    • Produced from bauxite electrolytically (energy-intensive; site often chosen by cheap electricity).
    • Virtually non-corrosive, light-weight, infinite recyclability – yet relies on consumer collection.
  • Closures: ring-pull, pop-top, stay-on tabs for convenience (consumer pays premium).

Glass

  • Chemically inert (except to HF). Historical mass production since \sim350 CE.
  • Pros: barrier perfection, quality perception, high-temperature tolerance, endless recyclability.
  • Cons: weight, fragility, higher transport emissions; strong PET competition except niche (restaurants want glass).
  • Lightweighting: Australian stubby reduced from 260 g (1986) → 170 g (1995).

Paper & Paperboard

  • Invented in China (1st century CE). Earliest use for wrapping, sacks \sim17th century.
  • Pros: low cost, high print quality, compostable.
  • Cons: poor moisture/grease resistance ➜ laminated solutions e.g., Tetra Pak (paper + polymer + Al foil).
  • Structural designs: gusseted bags, corrugated (fluted) board, cartons—important for secondary (& tertiary) packaging.

Printing, Design & Marketing

  • Product life-cycle ≈ <1 year for “new” design → agility crucial.
  • Damage to graphics during palletising can deter consumers.
  • Paper easiest to decorate; metals/glass require specialised inks/coatings.

Safety: Tamper Evident / Tamper Proof / Child-Safe

  • Historic incidents: Tylenol cyanide poisoning (USA), glass shards in baby food, K pies with cyanide → drove regulation.
  • Tamper-evident: irreversible visual damage when opened (heat shrink bands, induction seals).
  • Tamper-proof: prevents opening by force (pharma blister packs, break-rings).
  • Child-resistant closures: push-down-and-twist, lock-lids.

Closures & Access Systems

  • Functions (5-point list): contain, enable first access, allow repeated access, provide evidence of opening, be economical.
  • Screw caps, snap-fits, zipper profiles, peelable heat seals.
  • Barcode / QR code integration for traceability (computer-readable ID).

Modified Atmosphere Packaging (MAP)

  • Goal: inhibit microbial catabolism & oxidative reactions without chemical preservatives.
  • Typical gas mixes: CO2 (antimicrobial), N2 (filler, replaces O2), low O2 (<1\%) for fresh meat.
  • Components: high-barrier tray + lidding film + absorbent pad (captures purge, may contain antimicrobial agents).
  • Shelf-life extension: e.g., fresh steak from ~1 week → ≥3 weeks at 4^\circ\text{C}.
  • Snack example: potato-chip bags inflated with N_2 to both cushion & retard oxidation.

Manufacturing Equipment Snapshot

  • Extruder parts: hopper (feed), heated barrel, screw, die plate.
  • Downstream: cooling rolls, laminators, slitting, pouch form-fill-seal lines.
  • Machines must avoid static build-up, crystal breakage in sensitive films.

End-of-Life & Degradation Timelines

  • “Plastic and Time”: persists for centuries; UV, heat, abrasion → micro/nano-plastics.
  • Intrinsic factors: molecular weight, crystallinity, hydrophobicity, additives.
  • Extrinsic: UV exposure, temperature, mechanical stress (e.g., ocean waves).

Ethical & Practical Implications

  • Consumers share responsibility: recycling only works if segregation bins used (yellow/red in AU; bottle returns in EU).
  • Life-Cycle Assessment (LCA): transport weight of glass vs. PET can shift sustainability ranking.
  • Health: migration leads to endocrine disruption (BPA) or PFAS accumulation – driving bans & material innovation.
  • Global equity: developing regions lose more food to spoilage (lack of packaging) vs. developed regions lose more to package waste.

Potential Quiz / Exam Prompts (as hinted by lecturer)

  • State the two primary functions of food packaging.
  • List and explain the 3 R’s.
  • Provide the definition and formula for WVTR.
  • Compare pros/cons of glass vs. PET for bottled water.
  • Outline MAP principle and give two examples (meat, potato chips).
  • Identify recycling code for HDPE and give one typical application.
  • Explain why BPA is considered an endocrine disruptor.
  • Describe blow molding vs. injection molding.
  • Name one tamper-evident and one child-safe feature.

Quick Reference Figures & Equations

  • Global container usage: 2\times10^{11} units yr$^{-1}$.
  • Australian food sector: > 1.1\times10^{10} AU$ per yr.
  • WVTR: \text{g}\;\text{H}_2\text{O}\,/\,(\text{m}^2\cdot \text{day}).
  • Film classification: film
  • Lightweight beer bottle: 260\;\text{g} \rightarrow 170\;\text{g} (1986–1995).

Key Take-Aways

  • No “ideal” package: always a trade-off between barrier, cost, weight, recyclability, consumer expectations.
  • Understanding migration & barrier science is central to shelf-life design.
  • Plastics dominate volume; metals & glass dominate barrier perfection; paper dominates communication & secondary packs.
  • Sustainability solutions must pair industry design with consumer behaviour (3 R’s + circular economy).