Food Packaging Interactions

What are packaging interactions?

• Permeation —> through the packaging (gasses)

• Migration —> out of the packaging (monomers and additives)

• Absorption (scalping) —> into the packaging (Aroma compounds. fats, organic acids, pigments)

Which law governs migration from pastic into food?

Ficks second law (concentration changes vs time)

What are the mechanisms of Migration?

1. migrant must diffuse through the polymer matrix

2. partition across the polymer-food interface

3. diffuse through the food

How can you accelerate migration?

short-contact, high-temp. situations

What are they key influencing factors at the polymer side?

• crystallinity —> lower crystallinity diffusivity increases

• Molecular weight (Mw) —> high molecular weight makes it still lowers diffusivity

• additive content —> generally low Mw which gives flexibilty

• thickness —> increased thickness diffusivity decreases

• polarity (polyester higher than polyolefinic) —> affinity matters

• glass transition temperature (Tg)

What is the glass transition temperature?

Rubbery polymers —> high diffusion

glassy polymers —> low diffusion (stiff)

Why does retort processing matter in cans (Bisphenol A (BPA))?

BPA from can epoxy coatings only mobilizes when the can is heated above the Tg of resin (150 degrees)

What are the key influencing factors at the migrant side?

• molecular size (smaller —> faster)

• Polarity (lipophilic migrants go into fatty foods much faster)

• volatility

What are the key influencing factors at the food side?

• Antioxidant additives —> can migrate intentionally (active packagining) and unintentionally

  • BHT

Why does migration usually increase with temperature?

Diffusion coefficient increases

Which polymer property usually reduces migration?

High crystallinity

What are key migrants?

Glass packaging:

• silicates

• heavy metals

Metal packaging:

• tin dissolution from plain tinplate into tomato products

Paper and board:

• BP photoinitiator migrant from UV-cured inks

• printing inks

Plastics:

• risidual monomers

• plasticizers

• antioxidants

• risidual solvents

• low Mw compounds

• decomposition products

What is an example of residual monomers?

Vinyl chloride monomer (VCM) from PVC

• correlation between VCM inhalation and cancer

Styrene monomer from PS

• taste threshold in orange juice is as low as 0.2-0.3 ppm

What are plasticizers?

Phthalates (from PVC) are endocrine disruptors

What are EU directives?

The rules for plastics (specific and overall (10mg/dm2) migration limits) and simulants

Why are simulants measured and not food?

Real food is too complicated and is not standardized.

• assumed surface to volume ration is important (6dm2/kg)

Are there standard conditions for migration experiments?

Yes, there are standard conditions for contact during processing and shelf life experiments

Why is the surface to volume ration important in migration testing?

It standardizes exposure conditions

If contact time between food and packaging increases, migration will…

increase until the equilibrium is reached

which change definitely reduces migration?

Increasing film thickness

Why does orange juice in HDPE taste different after storage?

Scalping:

• d-limonene (main component of essential oils in citrus juices) —> lipophilic and non polar

What is scalping?

When food components (mainly flavor compounds) are absorbed on packaging materials with consequent severe reduction of quality.

Why does absorption and scalping occur?

• partition between food and polymer

• sorption into amorphous polymer regions